GEOMORPHIC ANALYSIS OF THE DRY RUN CREEK WATERSHED, BLACK HAWK COUNTY (IOWA)

The Dry Run Creek (DRC) watershed is located in northwestern Black Hawk County. It is fed predominantly by agricultural runoff in its upper reaches, and becomes heavily urbanized as it travels through the city of Cedar Falls, before draining into the Cedar River. The stream is perennial, however some segments have been tiled and new segments have developed either naturally and/or artificially. A previous, 2005, DRC study contributed to the creek being placed on Iowa’s 303(d) impaired streams list for lack of aquatic diversity (2002) and high bacteria levels (2008). A 2016-17 watershed evaluation of DRC identified further changes to its urban and rural reaches. These watershed analyses were conducted by University of Northern Iowa, Environmental Science (2005) and Geomorphology (2016), students using handheld GPS devices and standardized data sheets (e.g. RASCAL). As the watershed’s urbanization continues identifying changes in land use and bank stability were of significant importance. Current findings indicate that bank stability within the watershed has decreased since 2005. In 2005, 42.57 % of the DRC Watershed lied within Cedar Fall’s city limits as compared to 43.98% of stream segments in 2017.

2017 Geographic data includes: Right and left bank land use, right 44% row crop and left 40% row crop; row crop being the dominate land use. 58% of the stream has less than 10% canopy cover with 62% of the banks dominantly silt. 41% of the steam has none or less than 30% in-stream habitat. Bank stability ranging from 13% moderately stable to 19% moderately unstable. On-going laboratory investigations seek to further characterize DRC’s, physical (particle-size analyses) and chemical properties (aqueous Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). In addition, to a second DRC Clean-up session (UNI Earth Day, April 2018); The plan (May 2018) is to plant native vegetation (shade tolerant – prairie grass plugs) near the UNI water monitoring wellsite, creating a natural buffer that may decrease runoff and reduce bank erosion, increasing bank stability. The end goal is to continue working with the DRC Watershed Advisory Board, University of Northern Iowa, and the entire community of Cedar Falls on efforts that will improve the stream’s ‘health’, ideally removing it from Iowa’s Impaired Streams list!