Niagara Power Project FERC No. 2216

 

DESCRIBE NIAGARA RIVER AQUATIC AND TERRESTRIAL HABITAT BETWEEN THE NYPA INTAKES AND THE NYPA TAILRACE (U.S. SIDE)  

 

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Prepared for: New York Power Authority

Prepared by: Aquatic Science Associates, Inc. and E/PRO Engineering & Environmental Consulting, LLC

 

August 2005

 

 

Copyright © 2005 New York Power Authority

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EXECUTIVE SUMMARY

The New York Power Authority (NYPA) is engaged in the relicensing of the Niagara Power Project (NPP) in Lewiston, Niagara County, New York.  This study was conducted as part of the relicensing process.  The objectives were to: 1) Describe the aquatic and riparian habitats on the U.S. side of the Niagara River in the area between the NYPA intakes and the NYPA tailrace at flows of 50,000 and 100,000 cfs to assess the effects of water level and flow fluctuations, and 2) identify and describe factors that influence these habitats. 

The Treaty Between Canada and the United States of America Concerning the Diversion of the Niagara River, Oct. 10 1950, 1 U.S.T. 694 (Treaty) specifies the seasonal flow regime over the Niagara Falls and through the Niagara Gorge.  The Treaty establishes a seven-month tourist season from April through October, and a five-month non-tourist season from November through March.  The Treaty requires a minimum flow of at least 100,000 cfs over the falls during tourist season hours from 8:00 AM to 10:00 PM EDST during the period April 1 to September 15, and 8:00 AM to 8:00 PM from September 16 to October 31.  At all other times during the tourist season, as well as during the entire non-tourist season, the minimum flow requirement is 50,000 cfs.  Flows are sometimes greater due to storm surges from Lake Erie, ice management, wind conditions, and regional precipitation patterns that affect lake levels (URS et al. 2005).

The study methodology involved compiling and reviewing existing information about aquatic and terrestrial habitats in the investigation area and collecting additional information during field surveys.  The field surveys included aerial surveys that were conducted at approximately 50,000 and 100,000 cfs, and documented with video.  Ground surveys were also conducted throughout the entire gorge to delineate habitat reaches, measure areas affected by flow changes, document terrestrial communities, locate and assess waste discharges, and observe the effect of mist and ice at the falls.  In addition, ground surveys were documented with video.

Two major reaches were delineated to characterize the aquatic habitats of the upper Niagara River from the intakes to the Niagara Falls.  These are the Chippawa-Grass Island Pool (reach 1) and the Cascade Rapids (reach 2).  The Chippawa-Grass Island Pool is up to 12 feet deep, with water velocity up to two feet per second and a man-made shoreline composed of fill and rip-rap.  The Cascade Rapids are a shallow, high-energy habitat with boulder and ledge substrates.  Since these two reaches are extremely wide, increasing flows cause relatively small increases in water levels.  The Cascade Rapids have a median daily water level change of 1.0 feet during the tourist season, and 0.3 feet during the non-tourist season, as measured just upstream of the American Falls.  This daily flow change has relatively little effect on near shore aquatic habitats, with the exception of the Three Sisters Islands where the channel adjacent to Goat Island is dewatered when the flow drops to 50,000 cfs.  In the Chippawa-Grass Island Pool, the daily median water level change is 1.5 feet in the tourist season and 0.5 during the non-tourist season as measured at the Material Dock Gauge.  Water level changes in the Chippawa-Grass Island Pool, although relatively small, are quite frequent due to water level management for hydroelectric water withdrawals and compliance with the Treaty and IJC directives.  Near shore habitats in the Chippawa-Grass Island Pool are composed of fill areas with rip-rap or cobble substrates.

Five aquatic habitat reaches were delineated in the Niagara Gorge: Maid of the Mist Pool (reach 3), Whirlpool Gorge (reach 4), Lower Gorge Run (reach 5), Foster Rapids (reach 6), and Tailrace Run (reach 7).  These five aquatic habitat reaches include pools, runs and rapids.  Pools are deep and slow moving with very little gradient while rapids are relatively shallow and fast moving with a steep gradient and runs have intermediate characteristics.  In addition to these inherent hydraulic differences, there are four hydraulic controls in the Niagara Gorge that also affect how these reaches respond to flow changes.  The Maid of the Mist Pool is a very deep (maximum depth over 200 feet) pool, with low water velocity, steep shorelines, and ledge/boulder substrates.  Water levels in the Maid of the Mist Pool are affected by a hydraulic control just downstream of the Whirlpool Bridge.  As a result of this constriction, the flow change from 50,000 to 100,000 increases the water height about 11 feet.  This is documented by data from the Ashland Avenue gauge, which is located in the Maid of the Mist Pool – the median daily water level change in the tourist season is about 11.1 feet.  During the non-tourist season, when flows are more stable, the daily median water level change is 2.9 feet.  Although tourist season daily water level changes are much greater than daily changes in the non-tourist season, the seasonal fluctuation range is actually greater during the non-tourist season due to storm surges from Lake Erie.  Winter storms on Lake Erie cause surges through the Niagara River that can significantly increase flow over Niagara Falls and through the Niagara Gorge. 

The Lower Gorge Run (reach 5) is a wide reach with moderate water velocity and steep shorelines composed of cobbles and boulders.  Water level fluctuations appear to be similar in the Lower Gorge Run, as in the Maid of the Mist Pool because there is also a hydraulic control at the end of the Lower Gorge Run.  When the flow increases from 50,000 to 100,000, this hydraulic control creates a large standing wave that backs up the water in the Lower Gorge Run. 

The Whirlpool Gorge (reach 4) includes four features that were formed by the St. David Gorge, which is thought to have been eroded during the middle of the Wisconsinian Glaciation and filled at the end of the Wisconsinian Glaciation (Wachtmeister 1997).  These sub-reaches are known as the Whirlpool Rapids (4A), the Eddy (4B), Little Niagara Falls (4C) and the Whirlpool (4D).  Hydraulic controls affect water level fluctuations in the Eddy (reach 4B) and the Whirlpool (reach 4D).  The sandstone layer that is exposed at the downstream end of the Eddy constricts the flow and creates Little Niagara Falls.  The same sandstone layer also affects flow from the Whirlpool, although this is a much smaller hydraulic control.  As a result, there are large water level changes in the Eddy and the Whirlpool.  Flow changes also affect the direction of flow in the Whirlpool – at low flows (about 50,000 cfs) the direction of flow is clockwise around the margin of the pool, while at high flows (about 100,000 cfs) there is a counterclockwise flow and a powerful whirlpool.  The two rapids reaches, Whirlpool Rapids (reach 4A) and Foster Rapids (reach 6), respond to increased flows with less of an increase in water level than the other Niagara Gorge habitats since the steeper gradient of these reaches increases the water velocity, more than water height, relative to the other reaches.

Potential fish spawning was evaluated at sites that could be dewatered when water levels are low.  One of those sites is a large rocky peninsula that extends out into the lower portion of Fosters Rapids (reach 6).  This area was identified by NYSDEC.  This site is not suitable for spawning by salmonids or sturgeon since it lacks the gravel required by salmonids and is too shallow for sturgeon, even at high flows.  However, gravel was present along the shoreline just downstream of this peninsula in backwater and this small gravel deposit was used by spawning steelhead in the spring of 2003.  This area has a shallow slope and a portion of it could become unusable to fish at low water levels.  Fosters Rapids appears to have abundant sturgeon spawning habitat, particularly at the downstream end where numerous boulders and rubble substrates are found in depths of about 6-15 feet.  Hughes (2002) studied the movements of sturgeon in the lower Niagara River, however, the Niagara Gorge was not included in the study so it is not known whether sturgeon actually spawn in Foster Rapids. 

Eight major terrestrial habitat types were observed and mapped in the investigation area.  These were mapped and classified at the natural community and land-use covertype levels.  These habitat types occur throughout the investigation area and are composed of a variety of native, non-native, invasive, and horticultural plant species. 

As determined through literature review and observations while conducting fieldwork for this study, these habitats are influenced by a number of factors.  These include water level and flow fluctuations, ice formation and accumulation, groundwater seepage, surface runoff, and sewer and storm drains, recreational activities, and the introduction of invasive and horticultural plants.  The influence of water level and flow fluctuations on terrestrial habitat is minimal because most of this habitat is located above the influence of fluctuating water levels.  Small, fringe areas of riparian wetland vegetation associated with the calcareous talus slope woodland and limestone woodland community type experience daily water level fluctuations during the growing season.  However, these areas appear to be relatively unaffected by water level and flow fluctuations as they are composed of species that are tolerant of daily root zone saturation and/or inundation, and discernible changes in species composition and shifting of vegetation zones either landward or waterward does not occur from year to year.  At the time of the field surveys, the observed difference between the amount of falls-generated mist produced at the 50,000 and 100,000 cfs flows was minimal.  Factors that may influence the size and distribution of mist clouds at both flow regimes include temperature, weather conditions, relative humidity, dew point, and wind speed and direction.  Ice formation and accumulation, and ice loading on vegetation appear to be factors that influence terrestrial habitat from the southern end of Goat Island to the Whirlpool Rapids.  Mist freezes on vegetation and ice accumulates in the Maid of the Mist Pool causing large ice dams.  The ice scours nearshore areas preventing soil formation and accumulation and removing vegetation.  This is an annual natural event that affects the growth and distribution of plants in near shore areas in the vicinity of the falls.  Prior to utilization of an ice boom, ice accumulation in the Niagara Gorge was much more severe.  The ice boom mitigates these effects by preventing large ice floes from entering the upper river and reducing ice accumulation in the lower river.

Observations during the field surveys and information from literature suggest that groundwater seeps, surface runoff, and sewer drains can influence terrestrial habitat by introducing salt-laden runoff (from winter road maintenance) into the gorge.  Stormwater runoff from city streets and parking lots may introduce various chemicals and petroleum products into the gorge as well.  Salt-laden runoff can encourage the growth of salt-tolerant invasive plant species, while salt and chemicals in runoff can stress and possibly kill vegetation.

Recreation is thought to be a major factor that influences terrestrial habitat.  Hikers and bikers traveling on both authorized and unauthorized trails can trample plants, cause soils erosion and loss, and cause soil compaction (Riveredge 2005).  The collection of plant specimens can lead to the eradication of some species while encouraging the growth of others.

Invasive plants and planting of horticultural species can influence vegetation in the investigation area.  The planting of non-native trees and shrubs on the edges or rim of both sides of the Niagara gorge influence the plant composition of natural communities.  Specifically, it is thought that the planting of alien invasive trees and shrubs to landscape public parks on both sides of the gorge can influence natural communities in the gorge itself.  However, the planting of introduced Eurasian species in Buffalo occurred as early as 1886 and many non-native plant species were introduced into western New York and adjacent Canada by European settlers and occur throughout this region today.  Some of these alien invasive species have displaced or have the potential to displace native plant species.

 

1.0     INTRODUCTION

The New York Power Authority (NYPA) is engaged in the relicensing of the Niagara Power Project (NPP) in Lewiston, Niagara County, New York.  The present operating license of the plant expires in August 2007.  In preparation for the relicensing of the Niagara Project, NYPA is assembling information related to the ecological, engineering, recreational, cultural, and socioeconomic aspects of the Project.  As part of this effort, Aquatic Science Associates, Inc. (ASA) and E/PRO Engineering and Environmental Consulting, LLC (E/PRO) investigated habitats and environmental conditions from the intakes to the tailrace of the NPP.  The investigation area for this study includes U.S. waters of the mainstem Niagara River and associated terrestrial habitats between the Niagara Power Project twin intakes upstream of Niagara Falls to the Robert Moses Power Plant tailrace in the lower river, and Artpark (Figure 1.0-1).

1.1         Background

The 1,880-MW (firm power output) NPP is one of the largest non-federal hydroelectric facilities in North America.  The Project was licensed to the Power Authority of the State of New York (now the New York Power Authority) in 1957.  Construction of the Project began in 1958, and electricity was first produced in 1961.

The Project has several components.  Twin intakes are located approximately 2.6 miles above Niagara Falls.  Water entering these intakes is routed around the Falls via two large underground conduits to a forebay, lying on an east-west axis about 4 miles downstream of the Falls. The forebay is located on the east bank of the Niagara River.  At the west end of the forebay, between the forebay itself and the river, is the Robert Moses Niagara Power Plant, NYPA’s main generating plant at Niagara.  This plant has 13 turbines that generate electricity from water stored in the forebay.  Head is approximately 300 feet.  At the east end of the forebay is the Lewiston Pump Generating Plant.  Under non-peak-usage conditions (i.e., at night and on weekends), water is pumped from the forebay via the plant’s 12 pumps/generators into the Lewiston Reservoir, which lies east of the plant.  During peak usage conditions (i.e., daytime Monday through Friday), the pumps are reversed for use as generators, and water is allowed to flow back through the plant, producing electricity.  The forebay, therefore, serves as headwater for the Robert Moses plant and tailwater for the Lewiston Plant.  South of the forebay is a switchyard, which serves as the electrical interface between the Project and the interstate transmission grid operated by the New York Independent System Operator.

1.2         Objectives

The objectives of the study were derived from issues raised by various stakeholders.  The objectives listed in the scope of services are as follows:

·        Describe the aquatic and riparian habitats on the U.S. side of the Niagara River in the area between the NYPA intakes and the NYPA tailrace at flows of 50,000 and 100,000 cfs to assess the effects of water level and flow fluctuations; and

·        Describe the past and present terrestrial habitat in the context of cumulative effects.

1.3         Description of the Study Area

The Niagara River drainage area includes four of the five Great Lakes, an area of approximately 263,700 square miles. The difference in surface elevations between Lake Erie and Lake Ontario is about 326 feet, half of this occurring at Niagara Falls.  The Niagara River consists of two major reaches; the upper Niagara River and the lower Niagara River. This report covers the upper Niagara River from the NPP water intakes to Niagara Falls, and the lower Niagara River from Niagara Falls to the end of the Niagara Gorge, just downstream of the tailrace of the NPP.

The upper Niagara River extends about 22 miles from Lake Erie to the Cascades Rapids, which begin 0.6 miles upstream of the Horseshoe Falls (Canadian side of river).  From Lake Erie to Strawberry Island, a distance of approximately 5 miles, the channel width is greatest at the river’s head (9,000 feet.) and least at Squaw Island, just downstream of the Peace Bridge (1,500 feet.).  Average channel velocities are approximately 5 to 9 feet per second (fps) in the vicinity of the Peace Bridge.  Between Squaw and Strawberry Islands, the river width is approximately 2,000 feet, with average channel velocities on the order of 4 to 5 fps.

At Grand Island, just downstream of Strawberry Island, the river divides into the west channel, known as the Canadian or Chippawa Channel, and the east channel, known as the American or Tonawanda Channel.  The Chippawa Channel, approximately 11 miles long, varies in width from 2,000 to 4,000 feet.  Average channel velocity is 2-3 fps.  The Chippawa Channel carries approximately 58% of total river flow. The 15-mile-long Tonawanda Channel varies in width from 1,500 to 2,000 feet upstream of Tonawanda Island.  Downstream of this island the channel varies in width from 1,500 to 4,000 feet, with average channel velocities of 2-3 fps.  At the downstream end of Grand Island (i.e., the north end), the channels unite to form the 3 mile-long Chippawa-Grass Island Pool, at the lower end of which is the International Niagara Control Structure.  This linear structure, with 18 sluice gates for control of flow over Niagara Falls, extends perpendicularly from the Canadian shoreline to the approximate midpoint of the river.  The Falls is located about 4,500 feet downstream of the International Niagara Control Structure.

The fall (i.e., change in elevation) from Lake Erie to the Chippawa-Grass Island Pool is approximately 9 feet.  Below the International Niagara Control Structure, the river falls 50 feet through the Cascade Rapids, which are divided into two channels by Goat Island.  These channels convey the flow to the brink of the Canadian Falls (also known as the Horseshoe Falls) on one side and the American Falls on the other. At this point the river drops approximately 167 feet, on the American side falling on a sizable volume of talus, or rock debris, that has accumulated at the foot of the precipice.

Below Niagara Falls (i.e., in the lower Niagara River), the river runs through the narrow and spectacular Niagara gorge seven miles from the Falls to the foot of the Niagara escarpment at Lewiston, New York.  The upper portion of this reach, which is navigable, extends from the base of the Falls to the Whirlpool Rapids, which are not navigable.  The fall through this upper reach, known as the Maid of the Mist Pool, is approximately 5 feet.  In the Whirlpool Rapids, the water surface elevation drops approximately 50 feet over the course of a mile, and velocities can reach 30 fps.  At the Whirlpool, a 1,700-foot-long, 1,200-foot-wide, 125-foot-deep basin downstream of the rapids, the river bends nearly 90 degrees to the northeast.  Below this point the river drops another 40 feet through the Foster Rapids.  It emerges from the gorge at Lewiston, New York, subsequently dropping another 5 feet to Lake Ontario, and widening to 2,000 feet.  The Niagara River is navigable from the mouth at Lake Ontario to just upstream of the NPP tailrace by conventional watercraft, and upstream to the Whirlpool by specialized watercraft (Stantec et al. 2005).

Figure 1.0-1

Investigation Area

[NIP – General Location Maps]

 

2.0     FORMATION OF THE NIAGARA GORGE

The Niagara River is somewhat unusual in that is has no valley.  The Niagara River was not formed through the typical geological process whereby a river erodes a valley within the landform.  Rather, the Niagara River was formed almost catastrophically in a short period of geologic time by very large volumes of water flowing over the flat plain of the Niagara escarpment and falling from its edge.  The erosive force of this falling water, and the characteristics of the stone that was eroded, have determined the basic character of the aquatic and terrestrial habitats of the gorge.  Water falling over the edge of the hard dolostone cap rock of the escarpment has undercut and eroded the escarpment, forming seven miles of gorge in less than 15,000 years.  The erosion of the gorge has not been a steady, uniform process.  It has changed over time, with five different stages of gorge formation recognized (Tiplin 1988). 

The most important forces shaping the formation of the gorge are the volume of falling water and the height of the falls.  Lakes formed at the margins of the retreating Pleistocene glaciers, roughly in the locations of the current Great Lakes.  Known as pro-glacial lakes, they were very dynamic in terms of their size, shape, drainage basins, elevations, and outlet locations.  They were sometimes much larger than the Great Lakes and at other times, much smaller.  The total volume of flow through the Niagara region was initially much larger than present, however, there were several outlets over the escarpment and only a portion of the water flowed at the current location of the Niagara River.  Even after the location of the gorge was fixed at the Niagara River, the drainage patterns of the Great Lakes were still in a state of flux.  There were two periods when a much smaller discharge from Lake Erie waters alone cut the gorge. 

Changes in the height of the falls have occurred as a result of changes in the elevation of the receiving waters.  For thousands of years, the outlet of Lake Iroquois, the precursor to Lake Ontario, was through the Mohawk River valley and on to the Hudson River.  As a result, Lake Iroquois was much higher and the shoreline abutted the north edge of the escarpment.  The first three stages of the gorge were formed when glacial Lake Iroquois was up to 125 feet higher than the present elevation of Lake Ontario.  The higher elevation of Lake Iroquois inundated the base of the falls.  Not only did this reduce the erosive force of the falling water, it also protected lower rock strata from erosion during the first three stages of gorge formation. 

During Stage I of the formation of the Niagara Gorge, the reduced fall of water stopped the erosion at a higher stratum of the escarpment.  Ancient terraces from the location of the base of the falls are still visible in Lewiston (e.g., Eldridge Terrace).  This was the first stage of the formation of the Niagara Gorge, known as the “Lewiston Branch Gorge” or “Lewiston Spillway” (Tiplin 1988).  It was created by a falls with a much smaller vertical drop and a much lower flow since the Lake Erie precursor had four outlets over the edge of the escarpment during this period (Tiplin 1988).  The Stage I gorge is relatively short, extending from the edge of the escarpment upstream less than halfway to the RMNPP tailrace (Figure 2.0-1).

Stage II of the Niagara Gorge formation is called the “Old Narrow Gorge” or “Erie Gorge” (Tiplin 1988).  This reach extends form the end of the Stage I gorge to a point just upstream of the current location of the RMNPP tailrace (Figure 2.0-1).  During the second stage of gorge formation, the height of the falls was still much reduced as a result of the higher water level of Lake Iroquois.  More importantly, the discharge of the river was much reduced since a large pro-glacial lake at the margin of the retreating glaciers had found an outlet further east through the Trent Valley in Ontario.  Most of the flow from the retreating glaciers passed through this channel in the Trent Valley – the river flowing through the gorge only drained the relatively small basin of Lake Erie that existed at that time.  The erosive force of this smaller river cut a much narrower and shallower channel.  The smaller flow of the river also required a long time to erode the Stage II portion of the gorge, much longer than other sections of comparable length.  This section of the gorge was further modified by erosion when the lake level dropped.  This subsequent channel erosion was carried out by the flowing waters of the river, as opposed to falling water, since the falls had cut its way further upstream.  This erosion also impacted the gorge walls – both the Stage I and Stage II portions of the gorge are choked with wide talus slopes of eroded and weathered rock, particularly the softer shales that are exposed in these reaches.

The continental land mass under the glaciers was depressed by the weight of ice.  The land mass rebounded as the glaciers melted and as a result, the Trent Valley outlet of the pro-glacial lakes was eventually abandoned.  This change in the outlet flow pattern began Stage III of the Niagara Gorge formation.  During this period, the orientation and flow patterns of the Great Lakes were similar to the current conditions.  The full flow of the melting glaciers passed through the gorge.  However, Lake Iroquois was still at a high elevation since the outlet was still via the Mohawk and Hudson valleys.  The St. Lawrence valley was blocked by glaciers during the third stage of gorge formation, preventing flow through this potential outlet.  Lake Iroquois reached its highest elevation during Stage III – estimated to be as much as 125 feet higher than present Lake Ontario (Tiplin 1988).  Thus, the fall of water was much less, although the volume of water was large.  During this stage, the falls spread out over a wide arc of the escarpment and cut a wide channel, similar to the current configuration of Niagara Falls, but with a much smaller vertical drop.  Stage III created the area known as Niagara Glen on the Canadian side of the gorge.  On the U.S. side of the gorge, all that remains of the large terraces below the falls are the numerous small terraces perched along the gorge wall.  The upper end of the Stage III gorge is marked by several features; a pronounced widening of the channel, the upstream margin of the Niagara Glen, and a river feature on the Canadian shore known as Cripps Eddy.  Subsequent lowering of Lake Iroquois resulted in erosion by the river channel through the Stage III section of the gorge.  This later period of erosion created a long stretch of rapids, known variously as Foster Rapids, Bloody Run, or Devils Hole (Figure 2.0-1).

Stage IV of gorge formation includes several striking changes that altered the character of the gorge.  The level of Lake Iroquois dropped, either due to rebound of the land mass or deepening of the outlet channel in the Mohawk valley (Tiplin 1988).  Lake Ontario became much smaller when the outlet eventually moved to the lower elevation of the St. Lawrence River – the shoreline at the mouth of the Niagara River may have been as much as 12 miles north of the current location.  It was during this period that the riverine erosion noted earlier further excavated the downstream portions of the gorge (Stages I through III).  At least two small falls were created downstream when the river encountered the softer sandstone and shale strata (Tiplin 1988).  The lower water level increased the height of the falls, which excavated a larger channel up to the location of the Whirlpool.  At the Whirlpool, the river intercepted the buried St. David Gorge (Figure 2.0-1).  The St. David Gorge was excavated during the previous interglacial period and then buried by glacial debris and sedimentation.  Since the material that filled the St. David Gorge was unconsolidated, the falls moved rapidly upstream through this material until it reached the location where the falls of the St. David Gorge had previously existed.  Intercepting the St. David Gorge turned the river ninety degrees to the southeast and rapidly excavated areas now known as the Whirlpool and the Eddy Basin, two features that were originally formed by the St. David Gorge.  These two deep basin features are separated by a lip of harder sandstone.  The upstream end of the Eddy Basin was most likely where the old falls was encountered, although Tiplin (1988) offers the opinion that the older falls of the St. David Gorge may have been located further upstream, near the Whirlpool Bridge.  The final event of the fourth stage of the formation of the gorge was another reduction in flow.  The reduced flow slowed the rate of erosion, creating a narrower gorge through the Whirlpool Rapids.  Alternatively, the Whirlpool Rapids were formed by low flows in the St. David Gorge and then excavated during Stage IV gorge formation.

The fifth, and final, stage of gorge formation resulted from what are essentially contemporary conditions.  The continued melting of the glaciers completely opened the St. Lawrence valley outlet from Lake Ontario.  Uplift of the land mass shut off the alternate outlet from the upper Great Lakes.  Thus, the entire discharge of the Great Lakes once again flowed through the gorge.  This large volume of falling water, and the great height of the Niagara Falls, excavated the widest and deepest part of the gorge – the Maid of the Mist Pool, which extends from the Whirlpool Bridge up to the present location of the Falls (Figure 2.0-1).

Figure 2.0-1

1913 Geological Map of the Niagara Gorge

 

3.0     NIAGARA RIVER HYDROLOGY

The hydrology of the Niagara River between the intakes and tailrace is controlled by natural features of the channel (primarily cross sectional area and gradient), and the diversion of water for the U.S. and Canadian hydroelectric projects.  The natural features of the channel are described in Section  5.0, as they relate to particular reaches delineated as part of this study.  This section describes the regulatory restrictions on water levels and flows, the operation of the hydroelectric projects, and presents data on flows and water levels in the study area.  All elevations in this report are referenced to U.S. Lake Survey Datum 1935 (USLSD).  Values for other data, such as International Great Lakes Datum 1985 (IGLD 1985), are identified when used. 

3.1         Regulatory Constraints on Water Levels and Flows

There are two regulatory constraints on flow and water level fluctuations; the Treaty Between Canada and the United States of America Concerning the Diversion of the Niagara River, Oct. 10 1950, 1 U.S.T. 694 (Treaty), and the 1993 Directive of the International Niagara Board of Control (Directive).  Article IV of the Treaty establishes a seven-month tourist season from April through October, and a five-month non-tourist season from November through March.  The Treaty requires a minimum flow of at least 100,000 cfs over the falls during tourist hours from 8:00 AM to 10:00 PM EDST during the period April 1 to September 15, and 8:00 AM to 8:00 PM from September 16 to October 31.  At all other times during the tourist season, as well as during the entire non-tourist season, the minimum flow requirement is 50,000 cfs.  The Directive requires that the International Niagara Control Structure be operated within certain water level restrictions that are monitored at the Material Dock Gauge in the Chippawa-Grass Island Pool.  Additional information on the Treaty, the Directive, and water levels, are contained in URS et al. (2005).

3.2         Hydroelectric Operations

Under Article V of the Treaty, Niagara River water flows in excess of flows used and necessary for domestic, sanitary and navigation under Article III of the Treaty, as well as mandated flows over the Falls under Article IV, may be diverted for hydroelectric generation purposes.  Article VI provides further that waters made available for power purposes must be shared equally between the U.S. and Canada.  Water for the U.S. and Canadian hydroelectric projects is withdrawn from the Chippawa-Grass Island Pool.  Together, the hydraulic control provided by the International Niagara Control Structure, and the withdrawal of water for hydroelectric operations, determine the flow over Niagara Falls.  When Chippawa-Grass Island Pool levels are normal, NYPA has the capacity withdraws up to 102,000 cfs of water from the upper river using two underground conduits that transport water to the Project forebay where it is used for generation in either the Robert Moses Niagara Power Plant, or the Lewiston Pump Generating Plant.  Ontario Power Generation (OPG) withdraws up to 65,000 cfs of water from an intake structure located close to the International Niagara Control Structure.  OPG uses this water at the Sir Adam Beck Generating Stations located across the river from the RMNPP tailrace in Queenston, Ontario.  Like the NPP, the Sir Adam Beck Stations include a pump storage facility and conventional hydroelectric generation.  Up to 10,000 cfs can also be diverted from just upstream of the Horseshoe Falls to the Canadian Niagara Power Rankin Plant.  This plant discharges to the Maid of the Mist Pool and is only operated when the water cannot be used at the Sir Adam Beck Stations.

3.3         Hydrology

Information on the hydrology of the reach from the NPP intakes to the tailrace is limited.  Just upstream of the Falls, very little information has been collected on the channel morphology or flows due to the hazard presented by the Falls.  A similar situation exists in the Niagara Gorge, where rapids preclude data collection in large sections of the Gorge.  Nonetheless, some physical data have been collected in navigable portions of the Chippawa-Grass Island Pool in the upper river, and the Maid of the Mist Pool in the lower river.  Water level data have been collected from several gauges that have been established for the purpose of monitoring flows in the Chippawa-Grass Island Pool and downstream of the Falls.  The following discussions of water levels and flows rely on data from gauges at Material Dock and Ashland Avenue.  The former is located in the Upper Niagara River near the downstream end of the Chippawa-Grass Island Pool, while the latter is located in the Niagara Gorge several miles downstream of the Falls in the Maid of the Mist Pool.

3.3.1        Water Level

Like any stream channel, the Niagara River between the NPP intakes and tailrace has certain hydraulic characteristics that cause water levels to change with changes in flow.  These hydraulic characteristics include the longitudinal profile (gradient), the horizontal pattern (e.g., sinuosity), and the cross sectional area at particular points in the river.  The broad, shallow, channel upstream of the Falls responds to a given flow change with much smaller vertical changes than the much narrower, confined, channel downstream of the Falls.  In addition, both reaches have natural and artificial hydraulic controls (obstructions to flow) that cause localized changes in water levels.  However, the most pronounced effect upon water levels in the study area is the distinct seasonal flow pattern resulting from the Niagara Falls flow requirements.    

Changes in Falls flows between 50,000 and 100,000 cfs contribute to fluctuating water levels in both the upper and lower Niagara River.  These changes are most pronounced in the Lower Niagara River between the Falls and the NPP tailrace.  The Ashland Avenue gauge, located 1.7 miles downstream from the Canadian Falls in the Maid of the Mist Pool, measures water height and these data are used to calculate flows through the Niagara Gorge.  (Note: Flow measurements are actually made just upstream of the RMNPP tailrace, and not at the gauge.)  During the tourist season, daily changes in the Falls flow cause Ashland Avenue gauge water levels to fluctuate about 11 feet daily (Table 3.3.1-1).  In contrast, the median daily water level changes in the non-tourist season, when the falls flow requirement is 50,000 cfs at all times, are about three feet.  The same pattern is evident at the first five gauges upstream of the Falls, where median daily water level changes are 1.0-1.5 feet in the tourist season, but only 0.5 feet or less during the non-tourist season (Table 3.3.1-1).  The pattern is reversed close to Lake Erie – the gauges at Buffalo, Fort Erie and the Peace Bridge have greater median water level fluctuations in the non-tourist season than in the tourist season (Table 3.3.1-1).  This is a result of strong westerly winds during winter storms that create surges in eastern Lake Erie.  These higher water levels during storms result in higher water levels all the way through to the lower river.  Of the ten highest water levels recorded at the Ashland Avenue gauge since 1991, nine were associated with storm surges from Lake Erie (URS et al. 2005).

The differences between tourist season and non-tourist season water levels are graphically illustrated with several of the water level duration exceedance graphs presented in URS et al. (2005).  Figure 3.3.1-1 shows the tourist season and non-tourist season water level duration exceedance curves at Material Dock, upstream of the falls.  The curves show that the frequency of occurrence of various water levels is nearly identical between the two seasons.  However, these seasonal water level frequency distributions mask the fact that tourist season water level fluctuations occur daily, while non-tourist season water level fluctuations occur more randomly throughout the season – Figure 3.3.1-2 shows that daily fluctuations in the non-tourist season are typically less than 0.5 feet, but fluctuations in the tourist season are typically close to 1.5 feet.  In summary, managing water in the Chippawa-Grass Island Pool to meet the Falls flow requirements and provide water for the hydroelectric generation is accomplished within similar water levels in each season, despite the fact that daily fluctuations are greater during the tourist season.  From a habitat perspective, this means that the same near shore habitats are affected in the tourist and non-tourist seasons.

The water level fluctuation situation is different in the Niagara River gorge.  Tourist season water levels at the Ashland Avenue gauge are much higher than non-tourist season water levels because of the higher tourist season flow requirement.  For example, an elevation of 320 feet is exceed about 40% of the time in the non-tourist season, but it is exceeded closer to 70% of the time in the tourist season (Figure 3.3.1-3).  Elevations below about 320 feet have a similar distribution in both seasons since these elevations correspond to the lower flows that occur during the night in the tourist season and all the time in the non-tourist season (Figure 3.3.1-3).  The daily flow change in the tourist season results in a much larger change in daily water surface elevations during the tourist season, compared to the non-tourist season (Figure 3.3.1-4).  This is similar to the pattern of daily changes at the Material Dock gauge, however, the magnitude of the daily change is much greater at Ashland Avenue (Table 3.3.1-1).  The highest water levels in the Niagara Gorge occur during the non-tourist season as a result of storm surges from Lake Erie.  From 1991 through 2002, the non-tourist season range of water level fluctuation was 12.7 to 25.9 feet, with an average of 20.6 feet of fluctuation during the non-tourist season (Table 3.3.1-2).  Tourist season fluctuations ranged from 13.1 to 23.8 feet, with an average of 17.2 feet (Table 3.3.1-2).  The habitat ramifications of these Ashland Avenue gauge water level data are similar to those for upstream habitats.  That is, the area of the gorge that is affected by water level fluctuations is similar in both seasons (slightly greater in the non-tourist season), but these fluctuations occur daily in the tourist season.  

3.3.2        Flow

Flow duration curves for tourist and non-tourist seasons were developed for the Fort Erie and Ashland Avenue gauges (URS et al. 2005).  Flows at the Ft. Erie gauge are usually higher during the tourist season, with the exception of severe winter storms that cause high flow events during the non-tourist season.  Flows in the tourist season range between 190,000 to 245,000 cfs in the upper Niagara River at Fort Erie (URS et al. 2005).  Flows at the Ashland Avenue gauge are always higher in the tourist season due to the higher tourist season scenic flow requirement for the Falls.

3.3.3        Water Velocity

Discharge measurements have been made in the Niagara River as part of a regular program by the U.S. Army Corps of Engineers (USACE) for the INBC to verify stage-discharge relationships for the Ashland Avenue gauge.  The flow measurements have been made at the cableway just upstream of the Sir Adam Beck and Robert Moses tailraces.  USACE has collected velocity data – which are used to calculate cellular flows and total discharge – using an Acoustic Doppler Current Profiler (ADCP).  The details of the ADCP methods, and complete data sets, are provided in URS et al. 2005.  In summary, very little flow occurs in the top ten feet of the water column, most of the flow (87%) occurs at 30-60 feet deep, where velocities ranged from 3.0 to 7.0 fps (Table 3.3.3-1).  This flow pattern was consistent at discharges of 49,000 and 112,000 cfs.  Less than 17% of the flow occurred in the top 30 feet at either flow and very high water velocities persist in the lower half of the water column at all flows.  However, the water surface elevation was about five feet lower at the lower flow. 

Table 3.3.1-1

Comparison of Daily Median Water Level Fluctuations at Locations in the Niagara River

Gauge

Tourist Season (ft.)

Non-Tourist Season (ft.)

Difference (ft.)

Buffalo

0.6

0.8

-0.2

Fort Erie

0.6

0.8

-0.2

Peace Bridge

0.5

0.7

-0.1

Frenchman's Creek

0.5

0.5

0.1

Huntley

0.5

0.5

<0.1

Black Creek

0.6

0.4

0.2

Tonawanda Island

0.6

0.4

0.1

LaSalle

1.2

0.5

0.8

Slater's Point

1.4

0.5

1.0

NYPA Intake

1.5

0.5

1.0

Material Dock

1.3

0.5

0.9

American Falls

1.0

0.3

0.7

Ashland Avenue

11.1

2.9

8.2

Data are from URS et al 2005.  The period of record is from 1991 to 2002.  The gauge locations are arranged from upstream at the top of the table, to downstream at the bottom.  Not all gauges are shown.  Median values are used to describe central tendency since these data are not normally distributed.

 

Table 3.3.1-2

Ashland Avenue Gauge Annual Water Level Statistics

Year

Tourist Season

Non-Tourist Season

Max

Min

Delta

Average

Max

Min

Delta

Average

1991

330.05

315.74

14.31

323.07

339.86

315.66

24.20

319.66

 

1992

329.85

315.78

14.07

323.42

341.22

315.07

26.15

319.72

 

1993

334.52

315.85

18.67

324.56

335.99

315.75

20.24

321.22

 

1994

331.84

315.76

16.08

323.98

336.19

315.69

20.50

319.71

 

1995

330.58

314.50

16.08

323.35

332.65

315.78

16.87

319.55

 

1996

339.42

315.83

23.59

323.89

336.43

315.87

20.56

320.25

 

1997

340.11

316.29

23.82

327.57

341.22

315.93

25.29

323.97

 

1998

335.58

315.78

19.80

325.64

336.24

315.84

20.40

321.91

 

1999

328.97

315.84

13.13

323.25

328.39

315.62

12.77

318.53

 

2000

330.40

315.84

14.56

323.52

337.70

315.67

22.03

317.91

 

2001

332.24

315.76

16.48

323.26

328.33

315.63

12.70

318.09

 

2002

331.77

315.76

16.01

323.76

341.39

315.54

25.85

318.95

 

Average

332.94

315.73

17.22

324.11

336.30

315.67

20.63

319.96

 

Data are from URS et al. 2005.  Vertical datum is USLSD 1935.

 

Table 3.3.3-1

Average Flow Distribution at the Robert Moses Cableway

Velocity Range

(feet/sec)

Depth Range (feet)

0 to 10

10 to 20

20 to 30

30 to 40

40 to 50

50 to 60

Total

0 to 1

0.14%

0.91%

0.00%

0.00%

0.00%

0.00%

1.05%

1 to 2

0.75%

4.04%

1.27%

0.28%

0.54%

0.00%

6.89%

2 to 3

0.42%

0.77%

4.82%

3.07%

0.70%

0.00%

9.78%

3 to 4

0.18%

1.49%

2.55%

5.69%

6.42%

0.00%

16.32%

4 to 5

0.00%

0.00%

0.58%

2.98%

12.43%

4.20%

19.56%

5 to 6

0.00%

0.00%

0.00%

0.49%

12.51%

13.90%

26.13%

6 to 7

0.00%

0.00%

0.00%

0.00%

12.64%

16.47%

27.93%

7 to 8

0.00%

0.00%

0.00%

0.00%

4.47%

4.45%

8.37%

Total

1.49%

7.20%

9.22%

12.46%

41.98%

32.52%

100.00%

Note: Each cell indicates the percentage of the total flow that occurs at that combination of depth and velocity.  The flow distribution is the average from 20 different flow data sets measured by USACE.  The 20 flow data sets range from approximately 49,000 to 112,000 cfs.  See URS et al. 2005 for additional details.

 

Figure 3.3.1-1

Material Dock – Water Level Duration Analysis for Tourist and Non-Tourist Period (1991 – 2002)

 

Figure 3.3.1-2

Material Dock – Duration Analysis of Daily Water Level Fluctuations for Tourist and Non-Tourist Period (1991-2002)

 

 

Figure 3.3.1-3

Ashland Avenue Water Level Duration Exceedance

From URS et al. 2005.  The period of record is 1991 to 2002

Figure 3.3.1-4

Ashland Ave. (GN-Ashland) – Duration Analysis of Daily Water Level Fluctuations for Tourist and Non-Tourist Period (1991-2002)

 

4.0     METHODS

4.1         Aquatic Habitat Mapping and Description

Aquatic habitats of the Niagara River Corridor from the NYPA intake to the downstream end of the Niagara Gorge were investigated, described, and delineated based on available information and field surveys.  Available information included U.S. and Canadian reference material related to aquatic and terrestrial habitats, river flows, water levels, geology, and aquatic communities.  Sources of information reviewed for the study included, maps, state/federal/provincial agency reports, scientific literature, popular literature, books, data and personal knowledge.  All sources that contained relevant information were listed in the references.  Any sources that were reviewed and not used in the report were not listed in the NPP database or references.

Field surveys were conducted at river flows of approximately 50,000 and 100,000 cfs.  The field surveys covered the Niagara River Corridor from the NYPA intake to the downstream end of the Niagara Gorge.  Field surveys were conducted in 2003 during the non-tourist season from March 26 through March 28, and in the tourist season on April 3 and June 16 through June 19.  Field surveys included ground surveys and helicopter flights.   Ground surveys were conducted by a minimum of two senior scientists with expertise in terrestrial and aquatics habitats.  The ground surveys included a complete shoreline reconnaissance from the NPP tailrace to the intakes (U.S. shoreline), as well as spot checks at Artpark in Lewiston, throughout Goat Island, and various locations at the rim of the Niagara Gorge in the U.S. and Canada.  Data recorded during the field surveys included the presence of discharges (e.g., storm drains, combined sewer overflows, and licensed discharges), flow conditions such as surface turbulence and eddies, wetted width, exposed shoreline substrates, and riparian habitats.  Conditions were recorded with video and still photography.  Helicopter flights were conducted by the aquatic scientist, accompanied by a professional videographer who recorded flow, water level and habitat conditions on video.  

4.2         Terrestrial Habitat Mapping and Description

Literature and map data with information regarding existing plant species and habitat types in the investigation area were examined before any fieldwork was conducted.  Ground surveys were conducted in March and June 2003 to supplement and verify the terrestrial habitat information derived from the aerial reconnaissance effort, video taken during the flight, and existing information.  Data collected during this reconnaissance effort included dominant plant species, areas of human development, invasive and/or non-native plant species populations, average slopes and substrate/soil conditions, locations of combined sewer overflows (CSOs), permitted wastewater discharges (PWDs) and sewer drain outfalls, and the locations of habitat types on the U.S. side of the Niagara River corridor.  Documentation of the CSOs, PWDs, and sewer drain outfalls involved noting the relative size (pipe diameter) of these discharges, the proximity of these areas to the river, the areal extent of terrestrial vegetation exposed to effluent, and the physical condition of the vegetation (i.e., appeared stressed, healthy, etc.).  The purpose was to evaluate whether the discharge of pollutants affects terrestrial habitat.  In addition, mist produced during the 50,000 and 100,000 cfs flow regimes was also documented. 

The entire U.S. shoreline from the NYPA intakes to the NYPA tailrace (including the Goat Island complex), and Artpark was visited.  Documentation included taking field notes, still photographs, and video, and sketching habitat types on aerial photographs.  Habitats were classified and described based on Reschke (1990) Ecological Communities of New York State and the Cornell University (1970) Land Use and Natural Resources (LUNR) Classification Manual.  Although the Reschke system is a widely accepted system for classifying the majority of the ecological communities in New York State, the LUNR system was also used because some of the habitats in the investigation area are on lands managed for recreation or are highly altered and were better described using LUNR.  In addition, this approach was consistent with other NPP reports associated with the relicensing effort.  Terrestrial habitat locations and supporting data were subsequently mapped on GIS base maps. 

5.0     RESULTS

5.1         Aquatic Habitat Description

Two aquatic habitat reaches were delineated in the upper Niagara River: the Chippawa-Grass Island Pool and the Cascade Rapids.  Five aquatic habitat reaches were delineated in the Niagara Gorge: Maid of the Mist Pool, Whirlpool Gorge, Lower Gorge Run, Foster Rapids, and Tailrace Run.  Most of these aquatic habitat reaches were broken down into sub-reaches.  These habitat reaches are described based on the existing information that was reviewed for this study and the data that were collected.

5.1.1        Chippawa-Grass Island Pool

The Chippawa-Grass Island Pool (reach 1) is one of two major habitat reaches in the upper Niagara River between the NPP Intakes and the Niagara Falls.  This reach extends from the upstream end of the study area (the NPP intake structures) to the rapids at the upstream end of Goat Island, a distance of about 15,000 feet.  The Chippawa-Grass Island Pool is the largest habitat in the study area with an estimated area of 1,345 acres (Table 5.1-1).  The upstream end of the Chippawa-Grass Island Pool was defined for this study by the location of the NPP intakes.  However, the same physical habitat characteristics appear to continue immediately upstream of the NPP intakes, although the flow characteristics may be different due to the water withdrawal for the NPP.  Water is also withdrawn from the Canadian shoreline of the Chippawa-Grass Island Pool for the Sir Adam Beck Stations, as well as further downstream on the Canadian shoreline.

The Chippawa-Grass Island Pool was classified as pool habitat due to the depth, unbroken water surface, and the moderate surface water velocity observed near the shorelines.  Water depth data were available from two sources, USGS navigation maps and a survey conducted for NYPA by Oceans Survey (1991).  The USGS data show depths of five to twelve feet in most of the Chippawa-Grass Island Pool (except the Carborundum Reef, as described below).  Water depth is significantly greater in the vicinity of the NYPA intakes.  According to Oceans Survey (1991):

Within the (intake) area, bottom depths in excess of 40 feet were found from the face of the concrete wall at the water intakes to approximately 150 feet into the river.  Depths in excess of 30 feet continue to approximately 350 feet into the river.  The western delimitation of the modified bottom is clearly evident by the closely spaced contour lines…To the west of the (intake area) the average bottom depth is approximately 12 feet out to approximately 750 feet into the river where the depths average about 9 feet.  

Oceans Survey (1991) also described the substrate character of the bottom.  Near the NYPA intakes their survey documented a generally flat bottom with isolated rocks less than two feet in diameter.  Downstream of the intakes, the report states that the “…the natural bottom is generally rough and believed to be composed of gravel, cobbles and rock.”  These observations are consistent with the substrates adjacent to the shoreline, and with the helicopter observations conducted for this study.  That is, the substrates in the Chippawa-Grass Island Pool appear to be a mixture of hard, non-erodable material (i.e., gravel, cobble and boulders) closer to the Cascade Rapids changing to smaller substrates and a flat bottom in the majority of the Chippawa-Grass Island Pool. 

No extensive areas of submerged aquatic vegetation were observed in the Chippawa-Grass Island Pool, either from the shorelines, during the helicopter survey, or on the aerial photos.  Shorelines were composed of fairly uniform cobble riprap placed in the fill areas that were constructed along the U.S. shoreline.  The drawdown zone exposes approximately three to eight linear feet (measured perpendicular to the shoreline) of this riprap material, depending on shoreline slope.  Shoreline substrate exposure results from the regular water level fluctuations of approximately two feet (see URS et al. 2005 for details).  Water levels are slightly lower in the non-tourist season (i.e., winter) than in the tourist season (URS et al. 2005).

There are about 8-10 concrete culverts along the shoreline of the Chippawa-Grass Island Pool.    Only one of these was marked with a sign required for PWDs that have been assigned a State Pollutant Discharge Elimination System permit number (Figure 5.1-1).  The others were assumed to be storm water outfalls.  However, some of these culverts may have been PWDs since NYSDEC lists three additional PWDs (Niagara Falls Treatment Plant, Olin Corporation, and Washington Mills Electra) that were not located during this survey (NYSDEC 2004).  The condition of the substrate along the shoreline proximal to the marked outfall was not different from areas immediately adjacent to it.  The substrate downstream of one of the unmarked concrete culverts was a lighter color than the surrounding rocks.  The cause of this difference was not determined.  In addition to the outfalls, Gill Creek enters the Niagara River in the Chippawa-Grass Island Pool. 

The Chippawa-Grass Island Pool includes two sub-reaches: a 19-acre area known as Caborundum Reef and a 253-acre area just downstream of the control structure.  Carborundum Reef (sub-reach 1B) is more shallow than sounding portions of the Chippawa-Grass Island Pool, includes portions that are less than five feet deep, appeared to have more boulders than the rest of the Chippawa-Grass Island Pool, and a small amount of submerged aquatic vegetation (during the helicopter overflight, it appeared that this may have been algal growth on the bottom and not rooted macrophytes).  The 253-acre area just downstream of the control structure – the Goat Island Transition (sub-reach 1C) – is a transitional reach with habitat characteristics that are intermediate between the Chippawa-Grass Island Pool and the Cascade Rapids.  Although it has an unbroken water surface, it is shallower than the upstream portions of the Chippawa-Grass Island Pool, has higher water velocities and coarser substrates.         

5.1.2        Cascade Rapids

The Cascade Rapids is a shallow fast moving reach of the upper Niagara River between the upstream end of Goat Island and Niagara Falls (Figure 5.1-1).  The rapids are divided into two sub-reaches (2A and 2B) by Goat Island.  The channel on the U.S. side of Goat Island, which flows to the American Falls, is approximately 2,800 feet long with an average channel width of about 450 feet (Table 5.1-1).  The channel on the Canadian side of Goat Island, which flows to the Horseshoe Falls, is about 2,600 feet long with an average channel width of about 2,300 feet (Table 5.1-1).  Although the Canadian channel is much wider than the U.S. channel, these sub-reaches have very similar habitat characteristics and no further discrimination is made between the characteristics of the two channels.

Water velocity information is not available for the Cascade Rapids; however, water velocities are very high throughout this reach.  There are numerous standing waves and white water was observed throughout the channel.  The only water level data available come from a water level gauge located near the American Falls.  Average daily water level change at the American Falls is 1.0 feet during the tourist season and 0.3 feet during the non-tourist season (see Table 3.3.1-1).  The greater daily water fluctuation during the tourist season is due to the daily minimum flow change from 50,000 to 100,000 cfs.  In comparison, the same tourist season flow regime at the NPP intakes results in a daily average water level change of 1.5 feet.  The smaller change at the American Falls is due to the fact that flow changes in rapids result in greater changes in velocity, whereas flow changes in pool habitats such as the Chippawa-Grass Island Pool create more of a change in water level than in water velocity. 

The upstream end of the Cascade Rapids begins at a ridge of rock that crosses the river near the upstream end of Goat Island.  This ridge extends across the Canadian channel just upstream of the Three Sisters Islands.  At low flows of approximately 50,000 cfs, this ridge blocks water flow though the Three Sisters Islands and dewaters the northernmost channel, between Goat Island and the first of the Three Sisters Islands.  The channels between the other islands are not dewatered during the daily tourist season flow changes, although the water velocity and depth are noticeably reduced when the flow is reduced at night.

5.1.3        Maid of the Mist Pool

The part of the gorge from Niagara Falls to the Whirlpool and Railroad bridges is known as the Upper Great Gorge, since it was formed by a prolonged period of high flows that left a wide gorge.  This reach is also known as the Maid of the Mist Pool.  The Maid of the Mist Pool (reach 3) is over 200 acres in size, the largest single habitat reach in the Niagara Gorge (Figure 5.1-2).  It is about 13,000 feet long with an average width of approximately 760 feet (Table 5.1-1).  The downstream end of the Maid of the Mist Pool is defined by a hydraulic control point where the gorge narrows at the beginning of the Whirlpool Rapids.  This hydraulic control impounds water in the Maid of the Mist Pool and determines the stage/discharge relationship for this reach.  The Maid of the Mist Pool corresponds to Tiplin’s (1988) Stage V of the formation of the gorge, as described in Section 2.0.  The geological evidence indicates that the Maid of the Mist Pool was formed by a large volume water flowing over a wide shelf of the escarpment, excavating a deep plunge pool and leaving a deep channel as the falls moved upstream. 

The Maid of the Mist Pool was classified as pool habitat in this study due to the depth, unbroken water surface, and low to moderate water velocity.  The Maid of the Mist Pool is the only location in the Niagara Gorge where comprehensive bathymetric data have been collected, although there are no data in close proximity to the Canadian Falls.  Based on the bathymetric data shown in the AFIB (1974) maps, most of the Maid of the Mist Pool is in excess of 100 feet deep.  The maximum depth is just over 200 feet, at a point in the downstream part of the Maid of the Mist Pool where an ice bridge typically forms in the winter.  The shallowest part of the Maid of the Mist Pool is just upstream of the base of the American Falls, adjacent to the downstream face of Goat Island, where a large area is 45 to 70 feet deep.  A smaller area of similar depth is found just upstream of the location of the Ashland Avenue gauge.  These shallow locations appear to be related to debris accumulation in the channel, possibly due to material that has fallen from the face of the gorge wall since large pieces of cap rock can been seen in the water and near the shoreline.  The shorelines throughout the Maid of the Mist Pool are very steep with large boulder and ledge substrates throughout. 

There are very large, and frequent, water level changes in the Maid of the Mist Pool, as described in Section 3.3.  The Ashland Avenue gauge is located in the Maid of the Mist Pool.  During the tourist season, which includes all of the growing season, water levels at the gauge fluctuate about 11 feet each day as a result of the daily change in flow from the 100,000 cfs scenic flow to the 50,000 minimum flow.  The magnitude of water level changes in the non-tourist season (i.e., winter) are similar, however, they do not occur on a daily basis.  Very high water levels sometimes occur in winter in response to occasional storm surges on Lake Erie.  Thus, the range of water level fluctuations is actually greater in winter, but winter water levels are more stable, with a daily median water level change of less than three feet.

Water velocities are extremely variable throughout the Maid of the Mist Pool.  Most locations have low to moderate velocity with numerous eddy currents along the shorelines.  A change in flow from 50,000 to 100,000 did not produce any obvious visible changes in water velocity although some of the eddy currents appeared to be more substantial at 100,000 cfs.  There was no emergent aquatic vegetation on the shorelines.  There was no evidence of any submerged aquatic vegetation in the river.  Recent beaver activity (large trees felled after leaf-out) was noted during the reconnaissance survey in June, although a bank lodge was not found.  Anglers encountered during the field survey reported very successful smallmouth bass fishing in this reach.

Three combined sewer overflows (CSO) and two permitted wastewater discharges (PWD) were noted in this reach during the field surveys (Figure 5.1-2).  NYSDEC (2003) has listed the presence of an additional CSO in this reach.  However, extensive ground surveys conducted during this study did not document the presence of this CSO.  Therefore, it is not discussed in this report in terms of potential effects and is not depicted on any of the report figures.  PWD-1 is located just upstream of the Rainbow Bridge and had a very high discharge during field surveys in March and again in June.  Similar high flows from PWD-1 were seen on a 1958 photo.  This discharge actually flows upstream due to a large eddy current at this location.  Although this is, at times, a large discharge, it is small in comparison to the flow of the river.  Therefore, it is rapidly mixed and does not appear to have any affect upon adjacent habitats.  A large CSO located about 50 yards downstream did not have any flow during either field survey.  Another CSO noted during the field surveys is found just upstream of the Whirlpool Bridge.  There was no flow during the observations, and no apparent effect on aquatic habitats.  The Niagara Falls Sewage Treatment Plant (PWD-2) discharge is located in the Maid of the Mist Pool just upstream of the Ashland Avenue gauge.

Two sub-reaches were delineated in the Maid of the Mist Pool.  The area at the base of the American Falls (sub-reach 3A) was broken out since it is a cascade over the large dolomite cap stone pieces that have fallen to the base of the American Falls.  The transitional reach at the interface of the Maid of the Mist Pool and the Whirlpool Rapids was delineated as a sub-reach (sub-reach 3C) since this area narrows and the water velocity increases.  Aside from the smaller cross-section, this reach of the gorge is physically similar to the upstream portions of the Maid of the Mist Pool.

5.1.4        Whirlpool Gorge

This reach includes four features that are commonly known as the Whirlpool Rapids, the Eddy, Little Niagara Falls, and the Whirlpool.  Although distinct features, they are united by their origin in the St. David Gorge, a gorge that was carved by an earlier river of the Pleistocene geologic epoch.  In light of this common geologic origin, they are labeled as sub-reaches 4A, 4B, 4C and 4D, respectively.  The Saint David Gorge is thought to have been eroded during the middle of the Wisconsinian Glaciation and filled with glacial debris and fluvial deposits at the end of the Wisconsinian Glaciation (Wachtmeister 1997).  The Whirlpool formed when the post-glacial Niagara River Gorge intersected the buried Saint David Gorge.  The less resistant Pleistocene deposits in the buried gorge were rapidly removed leaving a large wide pool.  The Niagara River followed the same path as the Saint David Gorge through the Whirlpool and upstream through the Eddy and into the Whirlpool Rapids.  From the Whirlpool, the buried portion of the St. David Gorge diverges and continues to the northwest (see Figure 2.0-1).  Although no CSOs or PWDs were observed in this reach during the field surveys conducted for this study, NYSDEC (2003) has listed the presence of two CSOs.  However, the potential effects of these CSOs on habitats are not discussed in this report and they are not depicted on any report figures.  Only CSOs that were identified and documented during the field survey effort are discussed in terms of potential effects and depicted on report figures.      

The Whirlpool Rapids (sub-reach 4A) is a high-energy habitat with very fast-flowing water and shallow water depth (Figure 5.1-2).  This reach extends from the end of the Maid of the Mist Pool to the Eddy, a distance of about 2,600 feet (Table 5.1-1).  The Whirlpool Rapids are 17 acres in size with an average width of 280 feet.  The depth of the river here is estimated to be 35 feet with a velocity of more than 32 feet per second (Tiplin 1988).  The Whirlpool Rapids were created during a period of reduced flow through the gorge.  Only the Lake Erie portion of the Great Lakes drainage flowed through the Niagara River.  This reduced flow over the falls may have been less than one quarter of the contemporary discharge of the Niagara River (Tiplin 1988).  The falls may have appeared more like the contemporary American Falls, as opposed to the Horseshoe Falls, with a boulder cascade at the base of the falls.  Compared to other parts of the gorge, this stage of gorge formation left a narrower gorge and a smaller channel.  The Whirlpool Rapids have the shortest distance across the top of the gorge.  Although the channel was later modified by the higher flows that created the Maid of the Mist Pool, it retains its original character.  For example, the Whirlpool Rapids are just over one third the width of the Maid of the Mist Pool.  Low flows observed in this study (approximately 50,000 cfs) were confined within the solid sandstone banks of this channel.  Flows of 100,000 and higher come out of this channel and flow over the sandstone shelf on the U.S. shore.  Measurements of the wetted width of this shelf (the drawdown zone) varied from 23 to 56 feet.   

The Eddy (sub-reach 4B) is located between the Whirlpool Rapids and Little Niagara Falls (Figure 5.1-2).  This reach is roughly ovate, about 17 acres in size, with a length of about 1,200 feet and an average width of 650 feet.  The width of the Eddy is similar to the Maid of the Mist Pool and other areas formed by a large flow over the falls.  Although there are no depth data for this reach, presumably the maximum depth is similar to the other wide and deep reaches of the Niagara Gorge.  Water enters the Eddy as a fast moving plume that dissipates somewhat as it moves through the reach.  At a low flow of 50,000 cfs there are strong eddy currents along both shorelines.  At 100,000 cfs, the plume of water moves further through the pool and prevents the eddy from forming on the U.S. shoreline – there is a very strong eddy on the Canadian shore at flows of 100,000 cfs.  Shorelines in the Eddy are steep, composed of broken ledge and boulders, with about 9.5 linear feet of these shoreline substrates exposed with the change from 100,000 to 50,000 cfs. 

Little Niagara Falls (sub-reach 4C) is a short transitional reach located between the Eddy and the Whirlpool (Figure 5.1-2).  It is about 300 feet wide and about 290 feet long and about 2 acres in size (Table 5.1-1).  This hydraulic control is created by a constriction between almost vertical walls of sandstone.  The same shelf of sandstone that borders the Whirlpool Rapids also creates Little Niagara Falls.  This sandstone layer is exposed as a wide shelf bordering Little Niagara Falls.  Flows from 50,000 to more than 100,000 cfs are confined within the ledge walls of the channel and thus, there is no drawdown zone over the normal range of flows.  This hydraulic control impounds water in the Eddy and has a steep drop into the Whirlpool.

The Whirlpool (sub-reach 4C) is a massive eddy located downstream of Little Niagara Falls (Figure 5.1-2).  The Whirlpool is roughly oval, about 45 acres in size, with a length of about 1,700 feet along the long axis and a width of 1,150 feet on the short axis (Table 5.1-1).  Soundings taken in the early 20th century show a maximum depth of about 125 feet near the middle of the Whirlpool (Spencer 1907).  The Whirlpool formed at the intersection of the present Niagara Gorge and the ancient Saint David Gorge.  The glacial debris that fills the St. David Gorge is evident along the northern shoreline of the Whirlpool, where cobble and gravel are the dominant substrates along the shoreline.  In contrast, the remaining shorelines of the Whirlpool are boulders and ledge.  The Whirlpool also has a hydraulic control at the outlet, although not as dramatic as the drop into the Whirlpool from Little Niagara Falls.  Flows of approximately 50,000 cfs and more move slowly clockwise around the Whirlpool.  That is, the current simply flows around the margin of the pool with no eddy current at low flows.  However, high flows of approximately 100,000 cfs or more move counterclockwise through the Whirlpool, with a powerful eddy flow and whirlpools where the eddy dives under the inflow from Little Niagara Falls.  During the tourist season, there are daily reversals of the direction of flow in the Whirlpool.

5.1.5        Lower Gorge Run

The part of the gorge from the Whirlpool to just upstream of the NPP tailrace is known as the Lower Great Gorge since it was formed by a prolonged period of high flows that left a wide gorge (Tiplin 1988, see Figure 2.0-1).  This is similar to the process that formed the Upper Great Gorge (a.k.a., Maid of the Mist Pool), however, the level of Lake Iroquois and the river varied during the formation of the Lower Great Gorge whereas the water levels were relatively stable during the formation of the Upper Great Gorge.  Glacial Lake Iroquois inundated the gorge for a prolonged period – only the part of the gorge from the Whirlpool to Cripps Eddy was created by the full height of the falls.  This reach is called the Lower Gorge Run (reach 5) for the purposes of this study.  It is 3,450 feet long with an average width of about 550 feet and a size of about 44 acres (Table 5.1-1).  This reach is classified as run habitat since it is deep with moderately high water velocity and an unbroken water surface.  The substrates along the U.S. shoreline are a mixture of cobble and boulders, similar to the material on the northern shoreline of the Whirlpool.  There are no water depth data for the Lower Gorge Run, however, it appears to be shallower than the Maid of the Mist Pool since the water velocity is much higher.  The water level of the Lower Gorge Run is controlled by a hydraulic control point at the downstream end.  This hydraulic control point is a constriction of the channel where a large standing wave forms.  At 50,000 cfs, there is a small constriction of flow and a small standing wave, however, flows of 100,000 cfs or more back up in the Lower Gorge Run and drop through this constriction where they form a standing wave that appears to be about 20 feet high.  The difference in the water level between 50,000 and 100,000 cfs appears to be similar to the Maid of the Mist Pool, where the daily median water level change is about 11 feet.  Although no CSOs or PWDs were observed in this reach during the field surveys conducted for this study, NYSDEC (2003) has listed the presence of one CSO.  However, the potential effects of this CSO on habitats are not discussed in this report and it is not depicted on any report figures.  Only CSOs that were identified and documented during the field survey effort are discussed in terms of potential effects and depicted on report figures. 

5.1.6        Foster Rapids

The Foster Rapids are the downstream part of the Lower Great Gorge, as shown on the 1907 map of the Geological Survey of Canada (Figure 2.0-1).  The Foster Rapids reach is a shallow, fast moving stretch of water that includes areas known as Bloody Run and Devils Hole.  Since the water level was as much as 125 feet higher when the falls were found here, the river channel created by the falls is evident in the higher elevation terraces found throughout this reach.  The largest remaining terrace is the area known as the Niagara Glen on the Canadian shore.  When the river water level dropped, the Falls were located further upstream.  Thus, the extant channel characteristics are a result of the erosive force of the river, as opposed to the falls.  The Foster Rapids extend from the end of the Lower Gorge Run to the Tailrace reach, a distance of 6,200 feet (Figure 5.1-2, Table 5.1-1).  The upstream end of this reach is marked by the narrowing of the channel described in the previous section.  This narrowing marks the location where the height of the falls changed and a different type of channel was formed.

Two sub-reaches were delineated for the Fosters Rapids, these are Devils Hole (sub-reach 6A) and Bloody Run (sub-reach 6B).  Fosters Rapids was divided into these two sub-reaches as a result of a change in channel width – Devils Hole has an average width of 310 feet while Bloody Run has an average channel width of 620 feet.  Although these names are commonly used in relation to this part of the Niagara Gorge, the references reviewed for this study provided neither a clear definition of the boundaries, nor the character, of either “Bloody Run” or “Devils Hole”.  In fact, both names may relate to terrestrial areas, rather than anything in the river (e.g., Bloody Run is also the name of a small creek that flows into this reach).  For the purposes of this study, Devils Hole refers to a 2,830-foot riffle reach beginning at the Lower Gorge Run.  The name is taken from its usage in reference to the hydraulic control point that begins this reach.  Bloody Run is used to identify the next 3,370 feet of the river, which includes the region where the creek of the same names enters the gorge.  Both reaches were classified as riffle habitats due to the broken water surface (i.e., white water), high water velocity, and apparent shallow water depth.

Substrates along the shoreline of these two sub-reaches were predominantly boulders, that is, large material eroded from the gorge walls.  The narrower Devils Hole sub-reach also had greater amounts of ledge along the shoreline, relative to Bloody Run.  In contrast, the wider Bloody Run sub-reach had greater amounts of cobble along with the dominant boulder substrates.  As a result of the high water velocity in these two sub-reaches, it is unlikely that the wetted portions of the channel have significant amounts of smaller substrate material such as cobbles or gravel.  

A large CSO is located where the two sub-reaches meet (Figure 5.1-2).  There was no discharge from this CSO during the surveys conducted in late April or mid-June.  There was no apparent difference between the habitat immediately downstream of the CSO and other near shore habitats in this reach.

Areas of potential sturgeon or salmonid spawning habitat were observed in the Bloody Run sub-reach.  Hughes (2002) studied sturgeon movements in the lower Niagara River using sonic telemetry, however, that study did not include the Niagara Gorge thus, it is unknown whether sturgeon use the habitats found in the Bloody Run sub-reach.  During the scoping of this study, NYSDEC requested more information on the characteristics of a rocky peninsula that extends out into the river in the Bloody Run sub-reach.  This peninsula is exposed at low flows but inundated at high flows.  A transect was established across this peninsula to document conditions at high and low flows.  The transect crossed the backwater area behind the peninsula and then crossed the peninsula itself, ending at the main channel.  The horizontal distance between the high and low water marks on shore was about 69 feet, with cobble and gravel substrates.  The wetted width of the backwater area behind the peninsula was 40 feet wide, with gravel and sand substrates and a maximum water depth of about two feet.  The exposed peninsula was 133 feet wide with large boulder substrates.  Steelhead spawning activity was observed in the gravel substrates of the backwater area, behind the peninsula.  The peninsula itself does not have the gravel substrates needed to support salmonid spawning and no steelhead spawning activity was observed in that area.  At 100,000 cfs, water depths on the peninsula were several feet with numerous exposed boulders.  With respect to lake sturgeon spawning, potentially suitable water depths and substrates were found in several portions of the Bloody Run sub-reach.  In particular, a large area at the end of the Bloody Run sub-reach, just downstream of the rocky peninsula, had very large boulders and rubble, with moderate to high water velocity and water depths of 6-15 feet. 

5.1.7        Tailrace Run

The area immediately upstream and downstream of the NPP tailrace was classified as run habitat since this reach is deep, with an unbroken water surface and moderate to high water velocity.  However, the flow regime upstream of the tailrace is much different than the flow regime downstream of the tailrace.  The reason is that the reach downstream of the tailrace is subjected to backwater effects from Lake Ontario, while the reach upstream of the tailrace is isolated from this backwater effect by a section of riffles that act as a hydraulic control.  Thus, two sub-reaches were delineated, the Upper Tailrace (sub-reach 7A) and the Lower Tailrace (sub-reach 7B). 

The Upper Tailrace extends from the end of the Bloody Run reach to the upstream end of the NPP tailrace.  This reach is 23 acres in size, about 1,550 feet long, and has an average width of 660 feet (Table 5.1-1).  Substrates along the shoreline are boulders and cobbles.  Water depths increase moving towards the tailrace, where the water is very deep.  The USACE has established a hydraulic measurement transect by anchoring a cable across the river just upstream of the tailrace.  Measurements of water depth and velocity are taken from the cable and used to calculate the stage/discharge relationship of the Ashland Avenue gauge.  Several hydraulic data sets have also been collected at this location by boat using ADCP methods, as described in Section 3.3.3.  The USACE data document that the maximum water depth at this transect is nearly 60 feet, at flows of about 112,000 cfs.  The hydraulic measurements also document that a reduction to about 50,000 cfs decreases the water level by up to eight feet, depending on the backwater effects from the hydroelectric projects and Lake Ontario (URS et al. 2005).  Data from the USACE transect show that water velocities are quite high at depths of 30 to 60 feet – based on an average of the hydraulic data, 87% of the water flows at depths of 30 to 60 feet.  Water velocities of 4-8 fps were measured in the bottom 10 feet of the water column. 

The Lower Tailrace reach extends from the RMNPP tailrace to the end of the Niagara Gorge, at the edge of the Niagara escarpment.  This reach is about 7,100 feet long with an average width of 500 feet, slightly narrower than the Upper Tailrace reach (Table 5.1-1).  The shoreline is generally very steep with boulder substrates.  Water depths are uniformly deep throughout this reach, particularly immediately downstream of the tailrace.  The water level and water velocity in this reach vary in response to changes in the discharge of the RMNPP and Sir Adam Beck Generating Stations.  The greatest changes occur in the tourist season, when the daily flow may include discharges from the U.S. and Canadian generating stations, as well as the 100,000 cfs minimum flow through the gorge.  Water levels may change by up to 12 feet daily in response to the flow changes.  However, water level changes attenuate rapidly downstream of the tailrace – water level changes at a temporary gauge located 1.3 miles downstream of the tailrace in 2002 ranged from 1.1 to 2.1 feet (URS et al 2005).  Water velocity also changes, although no water velocity data have been collected in this reach.

5.2         Terrestrial Habitat Description

Eight distinct terrestrial habitat types were identified during this investigation.  These were mapped at the habitat community level and are consistent with the habitats described by Beak (2002) in Wildlife Resource Inventory and Description (Table 5.2-1).  This community level provides good habitat mapping resolution while ensuring the proper depiction of dominant habitat features.  The various habitats were delineated through aerial photography interpretation and field investigations (Figures 5.2-1 through 5.2-5).  These habitat classifications and descriptions are based on Reschke (1990) Ecological Communities of New York State, and the Cornell University (1970) Land Use and Natural Resources (LUNR) Classification Manual.  Common plant species that have been documented within each of the community types are listed. 

5.2.1        Calcareous Cliff Community

The calcareous cliff community occurs on vertical exposures of erosion resistant, calcareous bedrock such as limestone or dolomite (Reschke 1990, Edinger et al. 2002).  The cliffs often include ledges and small areas of talus.  There are numerous groundwater discharge sites (seeps) associated with this community type.  Very little soil is present and vegetation is sparse.  Reschke (1990) describes characteristic species as Pellaea atropurpurea (purple cliff brake), Cystopteris bulbifera (bulblet fern), Saxifraga virginiensis (early saxifrage), Juniperus virginiana (eastern red cedar), and Thuja occidentalis (northern white cedar).  The calcareous cliff community is recognized by the New York State Natural Areas Program as a significant occurrence of a natural community.  In the investigation area this community type occurs from Goat Island to Artpark (Figures 5.2-2 through 5.2-5).

The calcareous cliff community of the Niagara gorge includes a number of stunted, mature northern white cedar trees.  These cedars are an important and unique component of this community.  Stunted cedars from the Ontario portion of the Niagara gorge were included in a global study of ancient trees and cliff ecosystems.  Cores extracted from trees growing on cliffs in Europe, Great Britain, New Zealand, and North America revealed that cliffs generally support slow-growing trees up to and exceeding 1,000 years old.  In the Niagara gorge, tree core data indicate that some white cedars are over 1,500 years old, and are likely among the oldest trees on the continent (Larson et al. 2000).

Recognition of the unique plants, natural communities, watersheds and geological formations found along the Niagara gorge in Ontario resulted in Canada’s first large-scale environmental land-use plan in the 1985 Niagara Escarpment Act (McKibbon et al. 1987, Tovell 1992).  In 1990, the United Nations named Canada’s portion of the Niagara escarpment a World Biosphere Reserve. 

5.2.2        Calcareous Talus Slope Woodland

The calcareous talus slope woodland occurs downslope of the cliffs of the calcareous cliff community.  The community type occurs from the American Falls to Artpark and is recognized by the New York State Natural Areas Program as a significant occurrence of a natural community (Figures 5.2-1 through 5.2-5).  Reschke (1990) describes these woodlands as having either a closed or open canopy and occurring on talus slopes of calcareous rock such as limestone or dolomite.  The slopes may contain numerous outcrops of exposed bedrock.  Soils are usually moist and loamy.  Characteristic trees include Acer saccharum (sugar maple), Fraxinus americana (white ash), Ostrya virginiana (eastern hop hornbeam), Quercus alba (white oak), Juniperus virginiana (eastern red cedar), and Thuja occidentalis (northern white cedar).  Shrubs may be abundant if the canopy is open and may include Cornus rugosa (round-leaf dogwood), Viburnum rafinesquianum (downy arrowwood), Zanthoxylum americanum (prickly-ash), and Staphylea trifolia (bladdernut).  Herbaceous vegetation may be quite diverse, including such characteristic species as Cystopteris bulbifera (bulblet fern), Athyrium filix-femina (=A. asplenioides, lady fern), Elymus hystrix (bottlebrush grass), Polygonatum pubescens (downy Solomon’s-seal), Asarum canadense (wild ginger), Actaea pachypoda (white baneberry), Thalictrum dioicum (early meadow-rue), Sanguinaria canadensis (bloodroot), Solidago caesia (blue-stem goldenrod), and Aster divaricatus (white wood aster).  Rock outcrops may have ferns such as Asplenium rhizophyllus (=Camptosorus rhizophyllus, walking fern) and Asplenium trichomanes (maidenhair spleenwort) (Reschke 1990). 

In addition to the descriptions and species presented above, Eckel (2002) documented that many other plant species are common to this community type.  Also, many examples of this community type are best described as replacement forest of the original forest that was cut.  As observed during the fieldwork portion of this investigation, many areas in this community type are dominated by a combination of native and non-native plant species.  Other documented common trees, saplings, and shrubs included Acer negundo (box elder), Acer platanoides (Norway maple), Aeculus hippocastanum (horse chestnut), Tilia americana (basswood), Ulmus rubra (slippery elm), Prunus avium (bird cherry), Populus deltoides (eastern cottonwood), Tsuga canadensis (eastern hemlock), Salix babylonica (weeping willow), Rhus typhina (staghorn sumac), Lonicera tatarica (tartarian honeysuckle), Physocarpus opulifolius (ninebark), Prunus virginiana (choke cherry), Sambucus pubens (red-berried elder), Rhamnus cathartica (common buckthorn), and Crataegus spp. (hawthorns).  Vines and herbaceous plants included Parthenocissus quinquefolia (Virginia creeper), Vitis riparia (river grape), Toxicodendron radicans (poison ivy), Solidago flexicaulis (zig zag goldenrod), Dryopteris marginalis (marginal wood fern), Arisaema triphyllum (Jack-in-the-pulpit), Geranium robertianum (herb Robert), Solanum dulcamara (bittersweet nightshade), Allaria officinalis (garlic mustard), Rubus odoratus (purple flowering raspberry), and Eupatorium rugosum (white snakeroot).  There are also narrow strips of wetland found along the shorline.  These were not mapped separately but were treated as inclusions within the calcareous talus slope woodland habitat type.  Common plant species included Populus deltoides (eastern cottonwood), Salix babylonica (weeping willow), Ulmus americana, U. rubra (American and slippery elm), Morus alba and  M. rubra (white and red mulberry), and Betula alleghaniensis (yellow birch) trees and saplings, and Cornus stolonifera (red-osier dogwood) and Sambucus canadensis (common elderberry) shrubs.  Common herbaceous plants included Carex spp. (sedges), Equisetum spp. (scouring rushes), and Impatiens capensis (spotted touch-me-not).  In addition, the invasive plant Lythrum salicaria (purple loosestrife) was common in these narrow wetland areas. 

This habitat type in the vicinity of the whirlpool rapids is much drier and narrow than in other areas of the gorge.  There is relatively little soil accumulation, vegetation is sparse, and substrates are composed of recent talus, old rubble from the bed of the former Gorge Railroad.  The large talus and rubble may account for the lack of heavy vegetation cover in this area.  The dryness of this section may be a result of the direct exposure of the talus and rubble to wind and sun

5.2.3        Commercial

LUNR (1970) describes this land-use community type as areas primarily associated with the sale of products and services.  This broad category includes central business sections of cities, shopping centers, resorts, and strip developments.  This land-use covertype occurs in the City of Niagara Falls in the vicinity of the American Falls and Goat Island (Figures 5.2-1 through 5.2-3).  Common plant species observed in the land-use covertype included naturally occurring and horticultural trees and shrubs, and typical species of lawns and disturbed areas.  Species included Tilia americana (basswood), Quercus rubra (red oak), Platanus occidentalis (sycamore), Viburnum recognitum (arrowwood), Ambrosia artemisiifolia (common ragweed), Bromus inermis (smooth bromegrass), Verbascum thapsus (common mullein), Hypericum perforatum (common St. Johnswort), Poa compressa (Canada bluegrass), Dactylis glomerata (orchard grass), and Taraxacum officinale (common dandelion).       

5.2.4        Limestone Woodland

Limestone woodlands occur over limestone bedrock and can include numerous rock outcrops (Reschke 1990).  Forest stands that develop on these substrates are composed primarily of conifers, hardwoods, or a mixture of the two.  Dominant tree species can include Thuja occidentalis (northern white cedar), Pinus strobus (white pine), Picea glauca (white spruce), Abies balsamea (balsam fir), Ostrya virginiana (hop hornbeam), Acer saccharum (sugar maple), Carya ovata (shagbark hickory), Quercus alba (white oak), Quercus macrocarpa (bur oak), Quercus rubra (red oak), and Tilia Americana (basswood).  The shrub stratum can be variable and generally becomes denser where canopy is open and soils are deeper.  Shrub species can include Cornus racemosa (gray dogwood), Lonicera dioica (wild honeysuckle), Rhamnus alnifolia (alder-leaf buckthorn), Ribes cynosbati (prickly gooseberry), Rubus spp. (raspberries), Staphylea trifolia (bladdernut), Amelanchier spp. (juneberry), and Toxidendren radicans (poison ivy).  The herb layer can include Carex eburnea, C. pensylvanica, C. platyphylla (Sedges), Dryopteris marginalis (marginal wood fern), Botrychium virgianum (rattlesnake fern), Pteridium aquilinum (bracken fern), Waldsteinia fragarioides (barren strawberry), Aster macrophyllus (big-leaf aster), Fragaria virginiana (wild strawberry), Sanicula marilandica (black snakeroot), Geranium robertianum (herb-robert), Maianthemum canadense (Canada mayflower), Smilacina racemosa (false Solomon’s-seal), Thalictrum dioicum (early meadow-rue), Trillium grandiflorum (white trillium), and Solidaga caesia (blue-stem goldenrod).  In addition, Polypodium virginianum (rock polypody), and Asplenium trichomanes (maidenhair spleenwort) can often by found growing on shaded rock surfaces and in crevices (Reschke 1990). 

In the investigation area limestone woodland communities occur at Goat Island and the northern portion of Artpark (Figures 5.2-2 and 5.2-5).  Ground surveys at the limestone woodland community at Artpark revealed assemblages of vegetation similar to those described by Reschke (1990).  Other common species observed in this community type at Goat Island included Fraxinus americana (white ash), Ulmus americana (American elm), Acer platanoides (Norway maple), Acer negundo (box elder), Salix alba-fragilis (white willow), and Populus deltoides (cottonwood) trees and saplings.  Shrubs, vines, and herbaceous plants included Cornus alternifolia (alternate-leaved dogwood), Rubus odoratus (purple-flowering raspberry), Sambucus pubens (elder), Rhamnus cathartica (common buckthorn), Parthenocissus quinquefolia (Virginia creeper), Morus alba (white mulberry), Lindera benzoin (spicebush), Prunus virginiana (choke cherry), Sambucus canadensis (common elderberry), Rhus typhina (staghorn sumac), Vitis riparia (riverbank grape), Allaria officinalis (garlic mustard), Arisaema triphyllum (jack-in-the-pulpit), Eupatorium rugosum (white snakeroot), Geum canadense (white avens).  In addition, patches of Lythrum salicaria (purple loosestrife) and various species of sedges and grasses were observed in areas subject to inundation by river water.          

5.2.5        Oak-Hickory Forest

One oak-hickory forest community occurs in the vicinity of the investigation area (Figure 5.2-3).  This community is located east of the whirlpool and Robert Moses Parkway and was the only community type not investigated during the ground surveys as this area had been previously documented by Beak (2002).  This area is included in this investigation because it is a natural community in close proximity to the Niagara River gorge.  The plant species composition of this natural community matches closely the Appalachian oak-hickory forest described in Reschke (1990), but the edaphic conditions do not (Beak 2002).  The Appalachian oak-hickory forest occurs on well-drained soils, usually ridge tops, upper slopes, or south and west-facing slopes.  In contrast, the oak-hickory forests in the investigation area are frequently found on relatively flat, somewhat poorly drained to moderately well drained soils (Beak 2002).  Therefore, for this report this natural community type is defined generically as oak-hickory forest.  Dominant tree species can include Quercus rubra (red oak), Quercus alba (white oak), Quercus velutina (black oak), Carya glabra (pignut hickory), Carya ovata (shagbark hickory), and Carya ovalis (sweet pignut).  Common associated tree species include Fraxinus Americana (white ash), Acer rubrum (red maple), and Ostrya virginiana (eastern hop hornbeam).  The shrub stratum can be quite variable and can include Cornus florida (flowering dogwood), Hamamelis virginiana (witch hazel), Amelanchier arborea (shadbush), Prunus virginiana (choke cherry), Viburnum acerifolium (maple-leaf virburnum), Vaccinium angustifolium, V. pallidum (blueberries), Rubus idaeus (red raspberry), Cornus racemosa (gray dogwood), and Corylus cornuta (beaked hazelnut).  Common herbaceous plants include Aralia nudicaulis (wild sarsaparilla), Smilacina racemosa (false Solomon’s seal), Carex pensylvanica (Pennsylvania sedge), Desmodium glutinosum, D. paniculatum (tick-trefoil), Cimicifuga racemosa (black cohosh), Prenanthes alba (rattlesnake root), Solidago bicolor (white goldenrod), and Hepatica americana (hepatica) (Reschke 1990).      

5.2.6        Outdoor Recreation

LUNR (1970) describes this land-use covertype as areas that constitute the predominant use of land and that have been developed primarily for outdoor recreation activities.  This broad category includes golf courses, ski areas and other winter sports, swimming pools and developed beaches, marinas, yacht clubs, and boat launches, public and private campgrounds, stadiums, race tracks, amusement parks, drive-in theaters, go-cart racing, fairgrounds, public parks, rifle and skeet shooting, and other private and community recreational developments such as baseball diamonds and playing fields.  This land-use covertype occurs throughout the investigation area and includes public parks and other lands with trails/paths for hiking, walking and bicycling, scenic areas and overlooks, and picnic areas (Figures 5.2-1 through 5.2-5).  Much of the land within this land-use type along the upper river (including the eastern third of Goat Island) is fill material populated with various native and non-native pioneer species and horticultural varieties.

Some of the common plant species observed within this land-use type included Tilia americana (basswood), Quercus rubra (red oak), Viburnum recognitum (arrowwood), Cornus amomum (silky dogwood), Amelanchier spp. (shadbush), Picea glauca (white spruce), Ambrosia artemisiifolia (common ragweed), Bromus inermis (brome grass), Verbascum thapsus (common mullein), Hypericum perforatum (common St. Johnswort), Poa compressa (Canada bluegrass), Dactylis glomerata (orchard grass), and Taraxacum officinale (common dandelion).  Most of these plant species were also documented in this land-use covertype on the western end of Goat Island, the gorge rim, and Artpark.                     

5.2.7        Successional Shrubland

This plant community type typically occurs on sites that have been cleared for farming, logging, development, etc., or have been otherwise disturbed.  The covertype is composed of at least 50% areal coverage of shrubs.  Typical shrub species include Cornus racemosa (gray dogwood), Juniperus virginiana (eastern red cedar), Rubus spp. (raspberries), Crataegus spp. (hawthorne), Amelanchier spp. (serviceberries), Prunus virginiana (choke cherry), Prunus americana (wild plum), Rhus glabra, R. typhina (sumac), Viburnum lentago (nanny-berry), Viburnum recognitum (arrowwood), and Rosa multiflora (multiflora rose) (Reschke 1990).  In the investigation area this habitat type occurs upslope of the calcareous cliff communities along the lower Niagara River (Figures 5.2-2 through 5.2-5).  Shrub species documented during fieldwork were consistent with those listed above.     

5.2.8        Transportation

This category includes the area encompassed by highways, railways, airports, barge/shipping canals, marine shipping, and communications and utilities.  In addition, for this investigation large, paved parking lots such as those found at Goat Island are included in this category.  This land-use covertype is found throughout the investigation area (Figures 5.2-1 through 5.2-5).  The plant species composition in the vicinity of transportation infrastructure is similar to that of the outdoor recreation land-use covertype.

 

Table 5.1-1

Niagara River Aquatic Habitat Reach Characteristics

 

 

 

Classification

 

 

 

 

 

Cover Characteristics

 

 

 

Habitat ID and Description

Type

Depth

Velocity

Average Width (feet)

Length (feet)

Size (acres)

Shoreline Substrates

Average Exposed Width (ft.)

Shoreline

Instream

Eddy Currents

UPPER RIVER

1. Chippawa-Grass Island Pool

 

 

 

 

 

 

 

 

 

 

 

 

1a. Grass Island Pool

Pool

5-12'

Low

5,400

11,000

1,345

Riprap/Cobble

5.0

Sparse Veg.

Boulders

Few

 

1b. Carborundum Reef

Run

<5'

Low

550

1,500

19

NA

NA

NA

Boulders

None

 

1c. Goat Island Transition

Run

3-9'

Moderate

2,750

4,000

253

Riprap/Cobble

3.0

Sparse Veg.

Boulders

None

 

 

 

 

 

Subtotal

16,500

1,616

 

 

 

 

 

2. Cascade Rapids

 

 

 

 

 

 

 

 

 

 

 

 

2a. Cascade Rapids (US)

Rapids

Shallow

Very High

450

2,800

29

Ledge/Riprap

1.0

Sparse Veg.

Ledge

None

 

2b. Cascade Rapids (Canada)

Rapids

Shallow

Very High

2,300

2,600

137

Ledge/Riprap

1.0

Sparse Veg.

Ledge

None

 

 

 

 

 

Subtotal

5,400

166

 

 

 

 

 

NIAGARA GORGE

3. Maid of the Mist Pool

 

 

 

 

 

 

 

 

 

 

 

 

3a. U.S. Falls Base

Cascade

Shallow

Very High

830

360

7

Ledge/Boulder

NA

NA

NA

None

 

3b. Maid of the Mist Pool

Pool

Deep

Moderate

760

11,400

199

Boulder/Ledge

14.6

Trees

Boulders

Many

 

3c. Whirlpool Bridge Transition

Run

Deep

High

320

1,280

9

Boulder/Ledge

32.1

Trees

Boulders

Some

 

 

 

 

 

Subtotal

13,040

215

 

 

 

 

 


 

Table 5.1-1 (CONT.)

Niagara River Aquatic Habitat Reach Characteristics

 

 

 

Classification

 

 

 

 

 

Cover Characteristics

 

 

 

Habitat ID and Description

Type

Depth

Velocity

Average Width (feet)

Length (feet)

Size (acres)

Shoreline Substrates

Average Exposed Width (ft.)

Shoreline

Instream

Eddy Currents

NIAGARA GORGE

4. Whirlpool Gorge

 

 

 

 

 

 

 

 

 

 

 

 

4a. The Whirpool Rapids

Chute

35' max.

Very High

280

2,620

17

Ledge/Boulder

39.5

None

None

None

 

4b. The Eddy

Pool

Deep

High

650

1,160

17

Boulder/Ledge

9.5

Trees

Boulders

Dominant

 

4c. Little Niagara Falls

Rapids

Shallow

Very High

300

290

2

Ledge/Boulder

0.0

None

None

None

 

4d. The Whirlpool

Pool

125' max.

Medium

1,150

1,700

45

Cobble/Ledge

10.5

Sparse Veg.

Boulders

Dominant

 

 

 

 

 

Subtotal

5,770

81

 

 

 

 

 

5. Lower Gorge 

Run

Deep

Moderate

550

3,450

44

Boulder/Cobble

23.3

Trees

Boulders

Some

6. Foster Rapids

 

 

 

 

 

 

 

 

 

 

 

 

6a. Devils Hole

Riffle

Medium

High

310

2,830

20

Boulder/Ledge

14.6

Trees

Boulders

Few

 

6b. Bloody Run

Riffle

Medium

High

620

3,370

48

Boulder/Cobble

15.3

Trees

Boulders

Few

 

 

 

 

 

Subtotal

6,200

68

 

 

 

 

 

7. Tailrace

 

 

 

 

 

 

 

 

 

 

 

 

7a. Upper Tailrace

Run

Deep

High

660

1,550

23

Boulder/Cobble

13.9

Trees

Boulders

Some

 

7c. Lower Tailrace

Run

Very Deep

High

500

7,100

81

Boulder/Cobble

 

Trees

Boulders

Few

 

 

 

 

 

Subtotal

8,650

105

 

 

 

 

 

 

Table 5.2-1

Terrestrial Habitats and Land Use Covertypes within the Investigation Area

System

Subsystem

Community/Land-use

Terrestrial

Open Uplands

Calcareous Cliff Community

Successional Shrubland

Barrens and Woodlands

Calcareous Talus Slope Woodland

Limestone Woodland

Forested Uplands

Oak-Hickory Forest

Terrestrial Cultural

Commercial

Outdoor Recreation

Transportation

Terrestrial Cultural habitat classifications were based on the Land Use and Natural Resources (LUNR) Manual (CLEARS 1988).  All other habitat classifications were based on Ecological Communities of New York State (Reschke 1990).

Figure 5.1-1

Aquatic Habitat Upstream of Falls

[NIP – General Location Maps]

Figure 5.1-2

Aquatic Habitat Downstream of Falls

[NIP – General Location Maps]

Figure 5.2-1

Natural Community and Land-use Covertype

[NIP – General Location Maps]

Figure 5.2-2

Natural Community and Land-use Covertype

Figure 5.2-3

Natural Community and Land-use Covertype

Figure 5.2-4

Natural Community and Land-use Covertype

Figure 5.2-5

Natural Community and Land-use Covertype

 

6.0     DISCUSSION

6.1         Aquatic Habitat

Seven major aquatic habitat reaches were delineated, with a total of 17 sub-reaches.  The boundaries of the major habitat reaches are dictated by the underlying geology of the gorge and the hydrology and erosion processes that formed the different stages of the Niagara Gorge.  That is, some parts of the gorge are wide and deep as a result of the large volume of flow and great height of the falls that eroded these areas.  Other reaches are narrower and shallower, either as a result of a smaller volume of flow over the falls, secondary erosion by riverine forces, or both. 

Different channel forms react differently to flow changes.  A wide channel will pass increased flow with a smaller increase in height, relative to a narrower channel.  Similarly, a steep gradient channel will pass increased flow with a greater increase in velocity, relative to a lower gradient channel.  In addition to the interaction of hydrology and channel morphology, the erosion of the gorge left hydraulic controls that restrict the flow from four reaches: the Maid of the Mist Pool, the Eddy, the Whirlpool, and the Lower Gorge Run.  The presence of these hydraulic controls, combined with the channel morphology of these reaches, result in very large water level changes with changes in flow.  For example, the water surface elevation of the Maid of the Mist Pool increases about 11 feet in response to the change from 50,000 to 100,000 cfs (URS et al. 2005).  This response is documented by more than a decade of data from the Ashland Avenue gauge, located in the Maid of the Mist Pool.  The Lower Gorge run reacts to increased flow in a similar manner – although it is not as deep as the Maid of the Mist Pool, it is relatively wide and is also affected by a hydraulic control.  The Eddy and the Whirlpool have similar hydraulics and as a result, the water height in these habitats also increases when flows change from 50,000 to 100,000 cfs.  At the other extreme, some reaches move increased flows with a combination of increased velocity and increased water height.  Thus, the Whirlpool Rapids and Foster Rapids (Devils Hole and Bloody Run) react to the change in flow with greater water velocity and a smaller change in water level.  In the Cascades Rapids upstream of the Falls, the water level increases only one foot with a change to 100,000 cfs.  This is because the channel is extremely wide and the drop in elevation in this reach moves water efficiently by increasing water velocity.

Three PWDs and four CSOs were observed and documented in the field as part of this study.  The PWDs included the City of Niagara municipal waste treatment plant discharge, which discharges continuously.  The large CSO at the rainbow bridge was also discharging during all the field observations.  The remaining PWDs and CSOs only discharge intermittently.  All of these discharges are rapidly mixed as a result of the moderate to high velocity of the river.  In addition, the large volume of flow of the Niagara River dilutes these discharges.  As a result, the aquatic habitats in the area adjacent to the discharges showed no obvious effects from sewage effluent (either treated, or mixed with storm water) or permitted industrial wastes.  In addition to the PWDs and CSOs identified during the field survey effort, NYSDEC has listed the occurrence of three additional PWDs (NYSDEC 2004) in the upper river and four CSOs (NYSDEC 2003) in the lower river.  These PWDs and CSOs were looked for, but not found, during the field surveys.  Of the additional CSOs listed by NYSDEC, three are listed as occurring upstream of the whirlpool and one is listed as occurring downstream.  Because they were not found during the field surveys, the potential effects of these PWDs and CSOs on aquatic and terrestrial habitats in the investigation area are not discussed in this report and they are not depicted on any report figures.

Potential fish spawning areas were of concern to several stakeholders.  In particular, areas upstream of the tailrace were identified as a concern due to dewatering by flow changes.  The large rocky peninsula that extends out into the lower portion of the Bloody Run reach was evaluated.  The substrates on this rocky peninsula are much too large to be suitable for salmonid spawning and the water depth is too shallow to be suitable for sturgeon spawning.  However, there are gravel substrates along the shoreline just downstream of this peninsula and steelhead spawning activity was observed there during this study.  This area is protected from high flows and has a shallow slope, so a large area is affected by water level fluctuations and some steelhead eggs may have been exposed during low flows.  The Bloody Run reach seems to have large areas of suitable habitat for sturgeon spawning, particularly at the downstream end.  In addition, suitable juvenile sturgeon habitat appears to be available immediately downstream of these potential sturgeon spawning areas.  Although Hughes (2002) studied juvenile and adult sturgeon movements in the lower Niagara River, he did not investigate habitat use in the Niagara Gorge.  Thus, use of these habitats by sturgeon is speculative. 

6.2         Terrestrial Habitat

Eight terrestrial community/land-use covertypes were identified and mapped in the investigation area.  This section presents a discussion of how ecological communities may be cumulatively influenced by various factors.

6.2.1        Water Level and Flow Fluctuations

Field observations of the terrestrial communities and land-use covertypes during the 50,000 and 100,000 cfs flows revealed that water level and flow fluctuations have relatively little direct influence on these areas.  The majority of terrestrial vegetation in the riparian zone is above the influence of water level fluctuations in the investigation area.  The exceptions are narrow strips of riparian wetland vegetation on the smaller islands near Goat Island, portions of the northern and southern shores of Goat Island, and small areas of the gorge in the vicinity of Devil’s Hole.  These riparian areas are relatively minor components of the calcareous talus slope woodland and limestone woodland natural community types.  Some of the root zones in these areas are inundated at the 100,000 cfs flow and dewatered or slightly dewatered at the 50,000 cfs flow.  These areas range in width from several to 20 feet and are composed of shrubs and herbaceous plants tolerant of saturated soils and short periods of inundation.  Common plant species included Populus deltoides (eastern cottonwood), Salix babylonica (weeping willow), Ulmus americana, U. rubra (American and slippery elm), Morus alba and  M. rubra (white and red mulberry), and Betula alleghaniensis (yellow birch) trees and saplings, and Cornus stolonifera (red-osier dogwood) and Sambucus canadensis (common elderberry) shrubs.  Common herbaceous plants included Carex spp. (sedges), Equisetum spp. (scouring rushes), and Impatiens capensis (spotted touch-me-not).  In addition, the invasive plant Lythrum salicaria (purple loosestrife) was common along the lower river in these narrow wetland areas.  These areas appeared to be relatively unaffected by water level and flow fluctuations.  The plant community structure and waterward or landward extent does not change extensively from year to year, and no stressed or dying vegetation was observed.  This is likely due to the adaptation of the wetland vegetation to the cyclical and generally consistent extent and frequency of water level changes in these areas.  The further development of these wetland areas in the lower river and in the vicinity of Goat Island is restricted by the lack of areas with little or no water velocity, the presence of coarse substrates (sand, gravel, cobble, ledge), and steep slopes.          

Mist from the falls during the vegetation growing season, ice formation, and floes, and ice loading on vegetation are factors that could influence terrestrial plant communities.  A literature search was conducted, but no references were found specific to the effects on plant communities (during the growing season) resulting from changes in falls-generated mist in climates similar to the Niagara region.  Therefore, qualitative observations of the amount of mist produced at 50,000 and 100,000 cfs flows were made over two consecutive days.  No major qualitative difference in size and distribution of the mist clouds was observed (Figures 6.2.1-1 through 6.2.1-6).  Although, at the time of field surveys the mist clouds produced during the 50,000 cfs flow seemed slightly larger than the ones created during the 100,000 cfs flow.  These observations could be attributable to temperature and weather conditions.  It was raining sporadically and temperatures were lower during the 50,000 cfs flows (early mornings) than during the 100,000 cfs flows (middle of the afternoon) when temperatures were higher and skies were clear.  This suggests that although there was a slight observed difference in the amount of mist produced by the two flows, other factors that help influence the size and distribution of the mist clouds may also be involved.  These factors include temperature, weather (raining, sunny, etc.), relative humidity, dew point, and wind speed and direction.  The potential effect of changes in falls-generated mist on plant community structure and diversity was not quantitatively assessed.  However, one species that is known to occur in the spray zone of the falls, Gentianopsis procera (smaller fringed gentian), also occurs in the gorge at Whirlpool state park (Riveredge 2005).  Based on this information and observations of mist at the 50,000 cfs and 100,000 cfs flow regimes, differences in the amount of mist produced at the two flows during the plant growing season are likely dependant on a number factors are expected to have minimal influence on terrestrial habitat        

Ice appears to influence terrestrial habitat in the vicinity of the falls and a section of riparian zone at Artpark.  Falls-generated mist freezes on vegetation in the vicinity of the falls.  Freezing mist and spray accumulate on all surfaces, including all vegetation (AFIB 1974).  Ice loads on plants can cause substantial mortality (Abell 1934, Bruederle and Stearns 1985, Lemon 1961, Siccama et al 1976, Boerner et al 1988).  Clinging ice stresses vegetation and can have a profound effect on natural community plant composition and structure, particularly next to the falls where ice loading on plants is more prevalent due to the abundance of mist.  Ice loading on vegetation is a natural process that has likely occurred since vegetation became established in the gorge after the Wisconsinian glacier receded.    

This formation and accumulation of ice in the vicinity of the falls has been well documented.  It is thought the accumulation of ice has always been a natural annual event.  When the ice from broad expanses of the upper river is dumped into the confinement of the plunge pool, the accumulation can be six to 15 times the volume that the lower channel can carry away (AFIB 1974).  The effect of this ice build up may be somewhat mitigated by the ice boom which prevents large ice floes from entering the Niagara and subsequently going over the falls.  The terrestrial habitats in the remainder of the investigation area are located upslope of ice floes at both the 50,000 and 100,000 cfs flows.  Therefore, ice does not appear to be a direct influencing factor on these areas.

6.2.2        CSOs

Four CSOs and three PWDs were identified and mapped during the ground surveys.  None of the discharges are situated such that effluent comes into contact with terrestrial vegetation.  All of these are very close to the river and either drain directly into the river or over short stretches of coarse substrates such as cobble in narrow (three to four feet wide) drainage swales.  The largest effect from these CSOs and PWDs is not the discharge of effluents that potentially contain pollutants, but is related to their physical conditions (i.e., concrete and plastic pipes, coarse substrates at the pipe outlets and drainage channels that preclude the growth of terrestrial vegetation).  

6.2.3        Groundwater Seepage, Surface Runoff, and Sewer Drains

There were many seeps found along the cliff face of the lower river gorge from which groundwater discharge was observed.  Many of these seeps were discharging onto “shelves” in the calcareous cliff community and appeared to be supporting small patches of Phragmites australis (common reed).  Salt runoff from the Robert Moses Parkway and runoff from storm sewers and discharge pipes along the gorge walls and in the talus slope may have contributed to the development of common reed Phragmites australis in the rubble associated with seeps, often high up on the cliff face, especially in the poorer shale exposures in the northern part of the gorge, where highway interchanges occur as noted by Eckel 2003.  NYNHP (Evans et al. 2001) also noted that stormwater runoff from city streets and parking lots may introduce various types of chemicals and petroleum products into the calcareous talus slope woodland community at the base of the cliff.

It is documented that at least one area of the gorge is drier than it once was.  The area around the access road to Devil’s Hole has been highly modified due to development, road construction, and the remediation of the Hooker Hyde Park landfill.  Hooker Hyde Park is a 15-acre site that was used to dispose of approximately 80,000 tons of waste, from 1953 to 1975 (USEPA 2002).  Contaminants from the landfill flowed into Bloody Run Creek and down the Niagara gorge face into the river (USEPA 2002).  The remediation plan involved the excavation of Bloody Run and the use of extraction wells to maintain an inward groundwater hydraulic regime at the site (USEPA 2002). Remediation activities have altered surface water and groundwater flow, and have dried up the seeps on the face of the cliff (NYWEA 2000).  The cliff face and the talus slope woodland in the vicinity of Devil’s Hole are now drier than they once were, and this likely has changed the plant species composition of the community (Eckel 1990).

Due to the area’s extensive development, channelization of surface water runoff has occurred along the entire length of the gorge.  The presence of roads and highways changes drainage patterns and contributes road salt and sand to surface water runoff.  Specific to the NPP is the access road that descends from Hyde Park Boulevard across the gorge rim down to the Project tailrace north of Devil’s Hole.  This road is maintained by NYPA, may divert water from the adjacent cliff areas, and possibly contributes some winter road salt and sand to the river shoreline through surface water runoff.  While the portion of the Niagara gorge near Devil’s Hole has a reduced moisture regime, other areas experience high amounts of runoff from melting snow or rain.  These changes have likely contributed to the modification of the plant species composition of some areas.

An area of particular focus during this investigation was Artpark.  Of interest was groundwater discharge through spoil piles and the potential effects of this discharge on plants.  Artpark has a variety of native and invasive plants.  This area has been highly modified and was once a quarry that was later used as a refuse and chemical dump site  (NYSOPR 1974).  The refuse dump was opened in 1937 and was later closed in 1944 to general dumping of refuse (doing so without a permit).  The chemical dump was opened in 1944 and was closed in 1965.  The site has since been remediated and is a public park.  Spoil piles and groundwater discharge sites were examined for the presence of stressed or dead vegetation, and plant species were noted.  Many of the discharge sites were dominated by plants that can tolerate wet or saturated conditions.  Small populations of the invasive plant species common reed and purple loosestrife were observed.  The growth of common reed may be enhanced by road salt in runoff.  Both of these plant species occur extensively in the region and watershed draining into the gorge.  Tufa-forming mosses can be found in many of the groundwater seepage areas.  No other discernible indications that groundwater discharge influences terrestrial habitat were observed.        

6.2.4        Recreation

All of the mapped communities/land-use cover types in the investigation area are likely influenced by recreational activities such as hiking, site seeing, biking, and fishing (accessing fishing areas) due to the urban nature of the area, the tourist attractions, high population density, and accessibility.  There may be areas of native vegetation at Artpark that are affected by recreational users.  People walking in these areas can trample vegetation and repeated foot traffic can eventually lead to soil erosion. 

According to Gayler (1994), since the end of the twentieth century over 12 million people per year visit the Niagara Falls area.  This is understandable given that Niagara Falls is one of the first natural features in North America to become a world-renowned tourist attraction (Berton 1992).  The two greatest threats to the rare plants and natural communities of the Niagara gorge are human disturbance and the introduction of alien invasive species (Evans et al. 2001, Eckel 1990).  Specific to rare, threatened, and endangered (RTE) plants of the Niagara gorge, NYNHP (Evans et al. 2001) noted that the single greatest is the impact of recreational users.  The soils of the Niagara gorge are thin and easily disturbed, and rare native plants may be trampled.  Recreational users have contributed to soil erosion and compaction both on and off designated trails throughout the investigation area.  In some areas the soils have been completely lost and only bare rock remains.  This scenario exists on an unauthorized trail that appears to be heavily used and extends from the rim of the gorge down to the whirlpool.  Larson et al. (2000) reported that recreational activities on the Niagara escarpment affected the recruitment, productivity, and survival of cedars along the gorge, some of which are over 1,500 years old.  Recreational users or collectors will sometimes collect both common and rare plants and people can be seen taking part in a number of different recreational activities. 

6.2.5        Invasive and Horticultural Plants

One of the primary influences on vegetation in the investigation area is the presence of invasive plants and planting of horticultural species.  Planting of non-native trees and shrubs on the edges or rim of both sides of the Niagara gorge can influence the species composition of the gorge’s natural communities (Evans et al. 2001;  Eckel 2003).   Eckel (2003) noted that the planting of introduced Eurasian species in Buffalo occurred as early as 1886.  Alien species such as marsh Sonchus uliginosus sow-thistle, bitter nightshade (Solanum dulcamara), garlic mustard (Alliaria petiolata), and other weeds and shrubs such as buckthorn (Rhamnus cathartica) have been expanding into the gorge for quite some time (Eckel 1990).  Horticultural material planted on the gorge crest in both New York and Ontario helps contribute to this flora, such as lilac (Syringa vulgaris) at Devil’s Hole State Park.  Seeds of horticultural plants may be spread from the Canadian side of the gorge on the prevailing winds.  One such example is Catalpa speciosa (catalpa), which was once limited to the Canadian gorge crest, but is now established on the U.S. side of the gorge and at Goat Island. Alien invasive species, which are prominent in the gorge (and western New York and adjacent Canada as well), have the potential to displace native species.  Alien species that pose the greatest threat to the integrity of these communities are Rhamnus cathartica (common buckthorn), Lonicera tatarica (Tartarian honeysuckle), Alliaria petiolata (garlic mustard), Robinia pseudo-acacia (black locust) and Acer platanoides (Norway maple).  NYNHP noted that these species can effect the natural environments in which they become established, and recommended that the spread of exotic species in the gorge be monitored and controlled (Evans et al. 2001).  Many plants alien to the Niagara region were introduced by the European settlers and have grown throughout the region ever since.  Non-native or alien invasive plants can readily be seen throughout western New York and are not limited to the investigation area. 

 

Figure 6.2.1-1

American Falls at 100,000 cfs

 

Figure 6.2.1-2

American Falls at 50,000 cfs

 

Figure 6.2.1-3

Horseshoe Falls at 50,000 cfs

 

Figure 6.2.1-4

Horseshoe Falls at 100,000 cfs

 

Figure 6.2.1-5

Horseshoe Falls at 50,000 cfs

 

Figure 6.2.1-6

Horseshoe Falls at 100,000 cfs

 

7.0     CONCLUSIONS

7.1         Aquatic Habitats

·        Flow fluctuations in the upper Niagara River portion of the study area (aquatic habitat reaches 1 and 2) create daily water level fluctuations of up to 1.5 feet during the tourist season and up to 0.5 feet during the non-tourist season.  These fluctuations dewater very small bands of rocky shoreline that consist of constructed sheet pile, rip-rap and other fill material.  The only significant shoreline area of the upper river that is affected by water level fluctuations is the western shore of Goat Island, particularly the channel adjacent to the first of the Three Sisters Islands.

·        Flow fluctuations in the Niagara Gorge (aquatic habitat reaches 3 through 7) create daily water level fluctuations of up to 11.1 feet that expose narrow bands of steep boulder shoreline, with the exception of a wide flat shelf of sandstone bordering the Whirlpool Rapids.  This shelf retains shallow pools of water after each reduction to 50,000 cfs and has the potential to strand fish.  However, it is unlikely that many fish inhabit the Whirlpool Rapids since velocities are up to 32 feet per second.

·        Steelhead spawning was observed in the Niagara Gorge near the downstream end of Foster Rapids in a near shore area that is protected from the main channel by a shallow peninsula of large boulders.  Gravel has accumulated behind this rocky area and was used by steelhead in the spring of 2003.  The area is partially dewatered by low flows and it is unlikely that any spawning in the exposed area was successful.  It is not known if any steelhead spawned in permanently wetted portions of this area.

·        Discharge from the NPP and Sir Adam Beck Stations appear to have a backwater effect that increases water level fluctuations immediately upstream.  Water levels at the USACE cableway, just upstream of the NPP tailrace, change up to eight feet with a flow increase of about 65,000 cfs and operation of the hydroelectric projects.  Changes in the level of Lake Ontario create a backwater effect in the Lower Niagara River that also contributes to water level changes downstream of the tailrace.

·        The tourist season flow regime reverses the direction of flow in the Whirlpool each time the flow changes between 50,000 and 100,000 cfs.  This may affect the behavior or movement of some aquatic organisms (e.g., the orientation of caddis fly nets spun to capture prey).

·        Three PWDs and four CSOs discharge to the study area.  All discharge to high velocity, high flow, parts of the river and rapidly mix with ambient water.  The aquatic habitats in close proximity to these discharges showed no obvious changes or effects from the discharges.

7.2         Terrestrial Habitats

·        Water level and flow fluctuations have relatively little direct influence on these areas as the majority of terrestrial vegetation in the riparian zone is above the influence of water level fluctuations in the investigation area.  The exceptions are narrow strips of riparian wetland vegetation that are relatively minor components of the calcareous talus slope woodland and limestone woodland natural community types and occur on the smaller islands near Goat Island, portions of the northern and southern shores of Goat Island, and small areas of the gorge in the vicinity of Devil’s Hole.  These areas appeared to be relatively unaffected by water level and flow fluctuations.  The plant community structure and waterward or landward extent does not change extensively from year to year, and no stressed or dying vegetation was observed.  This is likely due to the wetland vegetation being adapted to the cyclical and generally consistent extent and frequency of water level changes in these areas. 

·        Extensive development of wetland areas in the lower river and in the vicinity of Goat Island is restricted by the lack of areas with little or no water velocity, the presence of coarse substrates (sand, gravel, cobble, ledge), and steep slopes. 

·        No major qualitative difference in size and distribution of the mist clouds was observed between the 100,000 and 50,000 cfs flow regimes.  Other factors that help influence the size and distribution of the mist clouds may include temperature, weather (raining, sunny, etc.), relative humidity, dew point, and wind speed and direction.

·        Clinging ice stresses vegetation and has a profound effect on natural community plant composition and structure, particularly next to the falls where ice loading on plants is more prevalent due to the abundance of mist.  Ice loading on vegetation is a natural process that has likely occurred since vegetation became established in the gorge after the Wisconsinian glacier receded.    

·        Ice scour resulting from ice formation, accumulation, and floes influences the growth of vegetation, and plant species composition and distribution around the Goat Island complex and in the Maid-of-the-mist pool.  This is thought to be a natural annual event that is somewhat mitigated by the ice boom which prevents large ice floes from entering the Niagara and subsequently going over the falls.  The terrestrial habitats in the remainder of the investigation area are located upslope of ice floes at both the 50,000 and 100,000 cfs flows and the influence of ice scour in these areas is likely minimal.       

·        Four CSOs and three PWDs were identified and mapped in the investigation area.  None of the discharges are situated such that effluent comes into contact with terrestrial vegetation.  All of these are very close to the river and either drain directly into the river or over short stretches of coarse substrates such as cobble in narrow (three to four feet wide) drainage swales.  These have little to no influence on terrestrial habitats.

·        A number of groundwater seeps are found along the cliff face of the lower river gorge.  Many of these seeps discharge onto “shelves” in the calcareous cliff community and appear to be supporting small patches of Phragmites australis (common reed).  Salt runoff from the Robert Moses Parkway and runoff from storm sewers and discharge pipes along the gorge walls and in the talus slope may have contributed to the development of common reed in the rubble associated with seeps, often high up on the cliff face, especially in the poorer shale exposures in the northern part of the gorge, where highway interchanges occur as noted by Eckel 2003.  NYNHP (Evans et al. 2001) also noted that stormwater runoff from city streets and parking lots may introduce various types of chemicals and petroleum products into the calcareous talus slope woodland community at the base of the cliff.

·        The area around the access road to Devil’s Hole has been highly modified due to development, road construction, and the remediation of the Hooker Hyde Park landfill.  Contaminants from Hooker Hyde Park landfill flowed into Bloody Run Creek and down the Niagara gorge face into the river (USEPA 2002).  The site was remediation and these activities altered surface water and groundwater flow, and dried up the seeps on the face of the cliff (NYWEA 2000).  This likely has changed the plant species composition of the community (Eckel 1990).

·        Due to the area’s extensive development and increase in impervious area, channelization of surface water runoff has occurred along the entire length of the gorge.  The presence of roads and highways changes drainage patterns and contributes road salt and sand to surface water runoff.  While the portion of the Niagara gorge near Devil’s Hole has a reduced moisture regime, other areas experience high amounts of runoff from melting snow or rain.  These changes have likely contributed to the modification of the plant species composition of some areas.

·        Groundwater discharge through spoil piles at Artpark influences vegetation by making conditions more conducive to the growth of plants that can tolerate wet or saturated conditions.  Also, the growth of common reed may be enhanced by road salt in runoff. 

·        All of the mapped communities/land-use covertypes in the investigation area are likely influenced by recreational activities such as hiking, site seeing, biking, and fishing (accessing fishing areas) due to the urban nature of the area, the tourist attractions, high population density, and accessibility.  People walking in these areas can trample vegetation, repeated foot traffic can eventually lead to soil compaction and erosion, and rare plants are subject to collection. 

·        One of the primary influences on vegetation in the investigation area is the presence of invasive plants and planting of horticultural species.  Planting of non-native trees and shrubs on the edges or rim of both sides of the Niagara gorge can influence the species composition of the gorge’s natural communities (Evans et al. 2001;  Eckel 2003).   Eckel (2003) noted that the planting of introduced Eurasian species in Buffalo occurred as early as 1886.  Alien invasive species, which are prominent in the gorge (and western New York and adjacent Canada as well), have the potential to displace native species.  Alien species that pose the greatest threat to the integrity of these communities are Rhamnus cathartica (common buckthorn), Lonicera tatarica (Tartarian honeysuckle), Alliaria petiolata (garlic mustard), Robinia pseudo-acacia (black locust) and Acer platanoides (Norway maple).  Many plants alien to the Niagara region were introduced by European settlers and have grown throughout the region ever since.  Non-native or alien invasive plants can readily be seen throughout western New York and are not limited to the investigation area. 

 

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