Habitat Changes in Agricultural Streams After Implementing Channel and Riparian Management

Elaine Langone Center, Terrace Room

Sediment from stream bank erosion and runoff from agricultural fields can transform rocky-bottom stream channels with varying depths to silt-clogged waterways with homogeneous habitat. Physical modifications to stream banks can be used to increase water velocity and direct stream flow toward the center of the channel, which can mobilize and transport sediments and increase depth heterogeneity in streams. State agencies (PA-FBC, PA-DEP) have partnered with local organizations (NPC, county conservation districts, watershed groups) and landowners to implement stream restoration practices along a number of agricultural streams in central Pennsylvania through the Northcentral Stream Restoration Partnership. In May and June 2017, bank stabilization and flow control structures were installed along a 0.5-mile reach of Conley Run, a tributary of Rapid Run in Union County impaired by agriculture. We conducted surveys of water quality, in-stream habitat, algal biomass, benthic macroinvertebrates, and fish in a 350-m section of the restoration reach prior to restoration. We sampled Conley Run in October 2017 to quantify changes in water quality, and surveyed again in May 2018 to quantify water quality as well as stream velocity, depth, substrate characteristics, and channel shape as a result of the structural modifications to the stream. Based on data from a nearby site in Turtle Creek, we expected Conley Run to have faster velocity, more variable depth, less silt and more coarse substrates, and decreased width compared to pre-restoration conditions. We found an increase in velocity, decreased silt which is related to increased course substrate, and a decreased width, as we predicted. However, depth variability did not increase as we predicted. These changes should improve in-stream habitat conditions for biota and lead to higher diversity of invertebrates and fish. Once it becomes established, riparian vegetation along the creek should also improve shade and cover, and the new riparian buffer should help to improve water quality by reducing inputs of sediment and nutrients from nearby agricultural fields and pastures.