Last Revised 7/02/01

Stormwater Management and Erosion Control

Introduction

Stormwater runoff is a major pathway for transporting sediment and other materials from the watershed to the surface water network. The porous and varied terrain of natural landscapes like forests, wetlands, and grasslands trap rainwater and snowmelt and allow it to slowly filter into the ground. Runoff tends to reach receiving waters gradually. In contrast, nonporous developed landscapes like roads, bridges, parking lots, and buildings don't let runoff slowly percolate into the ground. Water remains above the surface, accumulates, and runs off in large amounts.

Municipalities install storm sewer systems designed to quickly channel runoff from roads and other impervious surfaces. These engineered solutions are important to control high flows that may be a threat to public safety. Unfortunately, there are adverse ecological consequences to traditional stormwater management.

Runoff gathers speed once it enters the storm sewer system. When the water leaves the sewer system and empties into a stream, large volumes of high velocity runoff can erode streambanks, damage streamside vegetation, and widen stream channels. In turn, this will result in lower water depths during non-storm periods, higher than normal water levels during wet weather periods, increased sediment loads, and higher water temperatures.

Runoff from roads can contribute to water quality and habitat degradation of streams and lakes. Sediment and chemicals originate from winter deicing agents, shoulder ditching practices to maintain swales, and storm drains with inadequate provision for sediment removal.

Development activities can also increase the variety and amount of pollutants transported to receiving waters. Sediment from development and new construction; oil, grease, and toxic chemicals from automobiles; nutrients and pesticides from turf management and gardening; viruses and bacteria from failing septic systems and pet waste; road salts; and heavy metals are examples of pollutants generated in urban areas. Sediments and solids constitute the largest volume of pollutant loads to receiving waters in urban areas.

Conditions in the Cayuga Watershed

As discussed in Chapter II, sedimentation is the major water quality issue in Cayuga Lake.  New York State considers urban runoff and/or streambank erosion to be the primary cause of water quality and habitat degradation in the southern basin of Cayuga Lake and three southern tributaries (Fall Creek, Six Mile Creek and Cascadilla Creek). These stream and lake segments are included on the State’s Priority Waterbodies List (PWL). Streambank erosion is considered a secondary source of water quality impairment in three other streams: Salmon Creek, Yawger Creek, and Cayuga Inlet.

As part of the RPP process, Streambank & Roadbank Inventory was conducted in the summer of 2000.   Stream segments and roadbank/road ditch sites were ranked by severity based on erosion potential.  Very severe streambank segments and roadbank/road ditch sites are now being recommended as the highest priority for implementation.

The initial construction phase when land is cleared of vegetation and graded to create a proper surface for construction is one of the largest potential sources of erosion and sedimentation. When natural vegetation and topsoil are removed, the exposed area is particularly susceptible to erosion, causing transformation of existing drainage areas and disturbance of sensitive areas. Sediment loss from developed areas is potentially significant in the Cayuga watershed.

Deicing material, primarily sodium chloride, is used by area highway departments to help de-ice road surfaces during the colder months of the year. Each highway department has individual policies and procedures regarding salt application, salt/sand mixtures and storage.

There are several environmental concerns regarding the use of deicing salts. After application, salts are highly soluble in water. They easily wash off pavement into surface waters and leach into soil and groundwater. High concentrations of salt can damage and kill vegetation, disrupt fish spawning in streams, reduce oxygen solubility in surface water, interfere with the chemical and physical characteristics of a lake, pollute groundwater making well water undrinkable, disintegrate pavement, and cause metal corrosion of bridges, cars and plumbing.

As part of the RPP, a road deicing and storage survey was conducted throughout the Cayuga Lake watershed.  This dataset shows that there are 49 state, county and municipal salt storage pile sites within the Cayuga Lake Watershed. Twenty-one (42%) are exposed directly to the weather and many are significantly close to a stream or the lake itself.  The average total amount of deicing material spread in the watershed exceeds 30,000 tons per year.

Goals

• Protect or restore natural hydrology of streams in the Cayuga Lake watershed (see Wetlands, Shoreline, & Riparian Corridor Management Section)
• Reduce frequency of bank-full or flood stages of streams
• Keep baseflow conditions as close to natural as possible
• Prevent or reverse habitat and water quality degradation in streams
• Reduce transport of sediment, nutrients, pathogens and other pollutants to Cayuga Lake

Existing measures

A. Compendia of Technical Solutions

Federal guidance: EPA has published a "Handbook on Urban Runoff Pollution Prevention and Control Planning" (see http://www.epa.gov/ttbnrmrl/625/R-93/004.htm   (exit this site))

The Natural Resources Conservation Service has developed manuals for stream restoration at  http://www.usda.gov/stream_restoration/ (exit this site)

State guidance: New York DEC has recently issued a compilation of Best Management Practices (BMPs) for urban and stormwater management (NYSDEC Urban/Stormwater Runoff Management Practices Catalogue for Nonpoint Source Pollution Prevention in New York State, June 2000). NYSDEC also published Reducing the Impacts of Stormwater Runoff from New Development in 1992. NYSDEC has issued a compendium of BMPs for preventing nonpoint source pollution during construction (NYSDEC Construction Management Practices Catalogue for Nonpoint Source Pollution Prevention in New York State, June 2000).

Other resources: There are many university and private organizations focused on technical and regulatory approaches to stormwater management. One example is the Center for Watershed Protection. This organization maintains a highly informative web site of technical information and educational resources <http://www.cwp.org> and <http://www.stormwatercenter.net> (exit this site).

B. Regulatory Approaches

Federal: The Clean Water Act includes provisions for regulating stormwater discharges from urban and developing areas.

State: New York administers provisions of the Federal Clean Water Act through the State Pollution Discharge Elimination System (SPDES). Planning and permitting of stormwater falls under this state program.

Local: Several municipalities have created committees or boards to address stormwater issues within their local land use regulation and control structure.  The City of Ithaca has taken an active role in stream restoration along Six Mile Creek, the City’s drinking water supply.

Recommendations

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CLW IO 2004