Legacy sediment’s impact on stream ecology

Raising awareness about the role legacy sediment plays in stream ecology is a primary goal for LandStudies. That is why we recently partnered with colleagues at Franklin and Marshall College, Dr. Bob Walter and Dorothy Merritts, to take Natural Resources Conservation Service (NRCS) staff on a tour on legacy sediment projects in Lancaster County. Our aim was to show which soils and landscapes existed pre-mill dam and how legacy sediment site restoration could apply to various NRCS programs.

The tour included the Roller Mill Dam on Chiques Creek, which is an intact but defunct mill dam that has trapped substantial amounts of legacy sediment and altered the natural flow of the stream. We used the site to show how dams and legacy sediment impact stream ecosystems. Participants then went to where the Krady Mill Dam used to be on Chiques Creek (American Rivers removed the dam in 2018) so they could see what happens with erosion of legacy sediment once a dam is gone. The final stop was our Big Spring Run restoration site, where we removed legacy sediment from 1,500 linear feet of the stream bottom. Now, instead of steeply eroding banks, a thriving wetland full of native plants exists.

Each of these tour sites is described in more detail in the NRCS Soil and Plant Science Division Weekly Update for June 3, 2022. Having this article in a nationally distributed publication is sure to help elevate the importance of legacy sediments and floodplain restoration work!