Stream Reconnected to Historical Floodplain in Nanticoke Watershed
Top: Berm is removed and geotextile installed; lower left, small American eels, and lower right, Prothonotary warbler. USFWS photos.
Gravely Branch, flowing alongside Redden State Forest in Sussex County Delaware, was once a low gradient, meandering stream. During the 1960s it was channelized to increase flow and provide drainage for agriculture fields. The resulting lower stream bed disconnected the channel from the historic floodplain.
Soils and sediments removed from the stream channel as it was straightened were placed in wind rows parallel to the channel. These wind rows inadvertently act as a levee, preventing flood water from being dispersed on the floodplain.
Delaware currently has over 2,000 miles of channelized perennial streams that are part of organized drainage associations called Tax Ditch Associations. Taxes are levied by the Associations on adjacent landowners who receive drainage benefits. Taxes pay for the maintenance of the channels and spoil disposal areas. A right-of-way allows the tax ditch association to keep the ditch clear of sediment bars and woody debris.
Working with the Gravelly Branch Tax Ditch Association, Delaware Forest Service and Delaware Department of Natural Resources and Environmental Control, the Chesapeake Bay Field Office designed and implemented a project to reconnect this stream to its floodplain.
Six areas were chosen to breach the wind row along the eastern side of the tax ditch. Each area lowers the wind row by 1 foot to 2 ½ feet along a 25-foot section. The "dips" were then reinforced with a geotextile to allow maintenance equipment to continue to traverse the right-of-way.
The project restored over 5 acres of forested wetland. The resulting reconnected floodplain will provide habitat for a variety of fish, including the American eel, and forest interior birds like the prothonotary warbler. Temporary pools formed in the floodplain backwater will also provide much needed breeding habitat for many amphibians, including Cope's grey tree frog.
Reconnected floodplains trap sediment and nutrients and restored wetlands and forests capture carbon. This improves local water quality and ultimately the Chesapeake Bay as this technique is replicated throughout the headwaters of the Nanticoke River.