their own time and resources to remove the over grown invasive plants, such as Knot Weed.” The village and town also mowed and graded the land to the correct elevation and slope to allow water to spread out onto the floodplain, instead of overtopping the banks and flooding nearby businesses. Afterwards, grass was planted on the floodplain and native vegetation and shrubs were planted along the river including a mix of Maple and Ash trees. Dutcher said, “Now flood waters will drain from the town’s streets, building rooftops, and parking lots and filter through the vegetation before entering the river.” The vegetation traps and absorbs sediment and pollutants, like harmful phosphorus and nitrogen particles, from entering the river. The plant’s roots also stabilize the soil and prevent it from running into the river. An added benefit of this project is that it will lessen the damages of flooding. It will provide flood reductions for a 100-year storm event. This is a flood whose strength and water height is predicted to occur, on aver- age, about once in 100 years. The project will also be useful for storms that happen more frequently. Dutcher said, “The village is ecstatic. We have a clean slate here.” He said that the village’s plans for the land are to create a small pocket park for the community that will include trails, walkways, athletic fields, and a boat launch. South Street Bank Restoration Project, Town of Walton If you’re standing on the restored Walton floodplain that was just dis- cussed, and look across to the other side of the West Branch Delaware River, you’ll see South Street. The street sits high up on a bank that overlooks the river. This is where the South Street Bank Restoration Project is located. Over the years, South Street, which is lined with a few houses, has been slowly eroding down into the river. This has caused the river’s edge to erode, causing trees and soil to fall into the water and has created tension cracks in the street’s asphalt. “Under South Street there are water, sewer and gas lines,” said Dutch- er. “Under a flood condition, if the street continues to crack and shift down into the river, it could break the sewer line and the sewer would discharge into the river underground, contaminating the water and we wouldn’t even know it.” To stabilize the river’s banks and prevent the street from continuing to shift down, 40-foot steel sheet pile was installed along the bank that extends 30 feet below ground.
Dutcher said, “If we didn’t perform the sheet pile work, this whole area would have cleaved off. We really had to stabilize this bank using hard armoring, which is something we don’t typically do, but in this case it was really needed.” To further stabilize the bank and control streambank erosion, loose stone was placed at the edge of the river. The stones slow down the stream along the sheet pile and reduce potential damages downstream. Before: Stone wall sliding down into the West Branch Delaware River at South Street. Photo: DCSWCD. New York City Watershed System The New York City watershed region encompasses approximately 2,000 square miles of land north of New York City. The land includes three watershed systems - The Catskill, Delaware, and Croton Systems - that are located in the counties of Greene, Schoharie, Ulster, Sullivan, Westchester, Putnam, Dutchess and Delaware. A watershed is an area of land that catches rain and snow that drains or seeps into a marsh, stream, river, lake or groundwater. This water eventually gets stored in reservoirs, a place where water is collected and kept for use when wanted, such as to supply a city. The New York City Watershed System provides more than 90 percent of New York City's water supply. This comes to approximately 9.5 million people. New York City makes sure that this water is safe by treating it at the source rather than building a costly filtration plant. The source is the land that surrounds the streams, rivers, lakes and reservoirs. In 1996, all of the municipalities in the New York City watershed region came to an agreement. They wanted to avoid the creation of a huge filtration plant. Instead of a plant they agreed to have small projects throughout the region to provide the public with clean water with minimal filtration. "This is how our New York City Watershed Environmental Assistance Program came about," said Rifat Salim, project manager, U.S. Army Corps of Engineers, New York District.
csengineermag.com april 2020
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