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Fishpot Creek, St. Louis County, Missouri
The Challenge
Fishpot Creek in western St. Louis county is an Ozarkian drainage network that has relatively steep slopes and channels in which the underlying carbonate rock-chert strata are exposed. Coarse sediment dominates geomorphic processes. The watershed is heavily developed and channel instability and flooding problems are common.
Clients/Cooperators
The St. Louis County Soil and Water Conservation District (SWCD), the Missouri Department of Natural Resources and the Metropolitan St. Louis Sewer District.
Working with Intuition & Logic, the St. Louis County SWCD, and the Metropolitan St. Louis Sewer District, Little River Research & Design owner & principal Steve Gough played a key role in conceiving this project and writing the EPA 319 proposal that funded it. Total project budget was over $400,000. Innovative goals included demonstrating the use of fluvial geomorphology and watershed-scale analysis in urban stormwater design in order to change the civil engineering paradigm in the St. Louis region. The project included geomorphic reconnaissance of over 19 miles of channel in urban and suburban areas, analysis of development history, development of process-response models for channels, and conceptual design recommendations for stability and flooding problems in the watershed. LRRD conducted most of the field work and geomorphological analysis. Steve also guided engineering design for projects to be built based on his analysis. For this project, Steve designed and implemented innovative Global Positioning System-based data collection methods that mesh with ArcView Geographic Information System technology to efficiently organize, display, and analyze geomorphological data.
Better understanding of channel morphology and sediment transport processes has enabled improved bridge design.
Steve looked at coarse sediment dynamics at undersized bridge openings throughout the Fishpot Creek Watershed. His work showed that deposition and erosion processes were complex and probably aggravated flooding problems. Prior to Steve’s work, these processes had gone unrecognized despite extensive hydrologic modeling work.
Using ArcView GIS technology and location by GPS, geomorphic attributes of the Fishpot Creek watershed were mapped and symbolized. This enabled watershed-scale analysis of key geomorphic features. Shown here are bar graphs giving bed material particle size distributions.
At several sites in the watershed, bed particles were marked. After flooding, these sites were revisited. These data confirmed sediment transport and revealed important processes, particularly at bridge sites.
Downstream hydrualic geometry for Fishpot Creek, from field measurements. Despite severe alteration of channels and the watershed, channel morphology is strongly related to drainage area. Dunne and Leopold’s (1978) data for the Eastern United States is also plotted. Note that both width and depth for Fishpot Creek are much larger than expected for Dunne and Leopold’s data, which are for rural watersheds.
Many bridges in the watershed are not designed to accommodate sediment transport. Coarse sediment has been deposited in these culverts at Ries Road on a tributary of Fishpot Creek.
This schematic shows sediment transport dynamics at a typical bridge culvert.
