New Book: Floodplain Restoration Improves Water Quality, Reduces Flood Damage
Science and history have combined to find another tool—floodplain restoration-- to help solve stream bank erosion, nutrient runoff and stormwater problems, according to Mark Gutshall, LandStudies, Inc., publisher of a new book outlining the technique.
“Floodplain Restoration” describes how a previously undocumented source of watershed pollution was discovered by an unusual combination of history and science and how the technique provides a variety of benefits to communities and the environment.
“We developed the floodplain restoration technique based on studies we conducted in numerous watersheds over the last several years,” said Gutshall. “These studies pointed to a previously unrecognized major source of pollution – stream banks – but it wasn’t until we talked to colleagues at Franklin & Marshall College that we put our science and their understanding of land-use history together.”
Watershed assessments in the Susquehanna River Watershed demonstrated that 50 to 80 percent of the sediment loads in certain watersheds were coming from streambanks, along with the nutrient pollution they carry. Measured rates of bank erosion in the field were often exponentially greater than the commonly used models show.
“Drs. Dorothy Merritts and Robert Walter at F&M showed us their research that identified hundreds of mill dams built in the 18th and 19th centuries and behind each dam was up to 20 feet of sediment sometimes stretching hundreds of yards,” said Gutshall. “When the dams collapsed or were removed, the sediment was still there, but the stream began cutting its way down through that legacy sediment to the original floodplain and in the process carried away huge amounts of soil.
“Our floodplain restoration technique is designed to restore a stream to its original floodplain by removing the legacy sediment that would otherwise find its way downstream,” explained Gutshall. “Once we knew to look for old mill dams, we could accurately locate the old stream bed level and essentially put the stream back the way it was, with natural meanders but without the eroded stream banks.”
The book describes the multiple benefits of floodplain restoration, including:
· eliminating a major source of sediment and nutrients;
· reducing downstream nuisance flooding;
· providing an area for groundwater recharge and stormwater filtration;
· generating water quality credits for nutrient and sediment reduction to help wastewater plants comply with nutrient reduction requirements; and
· providing opportunities for carbon sequestration through the planting of riparian corridors.
“Looking for legacy sediments as part of a watershed assessment is critical because time and money invested in planting riparian buffers, for example, could be completely wasted if they are planted on top of these sediments, high above local groundwater and streambeds,” said Gutshall. “The discovery of legacy sediments has dramatically changed the way we look at water quality problems in our watersheds.”
Since the documentation of legacy sediments as a pollution source, the floodplain restoration technique has been recognized by the Pennsylvania Department of Environmental Protection in its Stormwater Best Practices Manual and as part of its Nutrient Trading Program for the Chesapeake Bay Tributary Strategy.
The agency is also in the process of developing a formal floodplain restoration Best Management Practice and is studying how to incorporate this technique into local sewage facilities planning.
The 11 x 17, 30-page “Floodplain Restoration” guide is available for $30 (tax and shipping included) by sending your request to LandStudies, Inc., 315 North St., Lititz, PA 17543, by contacting LandStudies at 717-27-4440 or by sending email to: firstname.lastname@example.org for an order form.
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