Sediment and Small Habitats

One in a series of periodic stories related to the Delaware River Watershed Initiative, a project funded by the William Penn Foundation to protect and restore the basin’s water quality and overall ecological health.

By Alissa Falcone

The biggest threat to water quality isn’t what’s inside the stream, it’s what’s next to it. Sediment created by erosion or runoff from farm fields can cause a horrible “domino effect” on the ecosystem, according to David Keller, project coordinator within the Fisheries Department at the Academy.

Not only does the sediment affect the light penetration and water quality, but it can also change the substrate composition already in the river. Runoff sediment can fill in pore spaces, or spaces in between the substrate, which can transform the stream bottom from something more coarse to something more fine.

“Some animals use that substrate and pore space for habitat. So when you introduce sediment into a stream, it fills in the pore space and alters the habitat for the animals that live in the stream, like fish, salamanders and macroinvertebrates,” says Keller.

Though sediment runoff is a common problem throughout the Delaware River watershed, special circumstances have caused Keller and other Academy scientists to focus on a very specific part of land along Barrett’s Run, in the Cohansey River watershed in New Jersey. There, the American Littorial Society, an environmental nonprofit, is restoring a seven-acre tract of farmland to a grassy meadow in hopes that their efforts will reduce sediment and improve water quality.

Academy scientists are assessing the impact of the new meadow by installing traps up and down the slope of the field that will measure the amount of fine sediment running off during storms. If successful, the meadow vegetation will hold onto the soil, slowing water flow and increasing infiltration into the ground.

This article first appeared in Drexel University’s 2015 research magazine Exel.

To read some other stories in this series,visit Invasion of Knotweed, Index for the Delaware, Funds for the Delaware,Tales of a Watershed Scientist, and Fish Ecology in Pictures.

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