Water Resources Research Act Program

Details for Project ID 2012OK248B

Identifying Nutrient Pathways to Streams: Sediment and Phosphorus Loads from Streambank Erosion and Failure in the Illinois River Watershed

Institute: Oklahoma
Year Established: 2012 Start Date: 2012-03-01 End Date: 2013-02-28
Total Federal Funds: $25,000 Total Non-Federal Funds: $50,000

Principal Investigators: Garey Fox, Chad Penn, Daniel Storm

Abstract: Streambank erosion is known to contribute a majority of the total sediment load to streams and rivers in some watersheds. In fact, sediment loads and streambank stability have been major concerns for decades and billions of dollars have been spent on streambank stabilization. In many cases, sediment loads introduced into streams may contain sorbed phosphorus. Various state and federal agencies, including the Oklahoma Conservation Commission (OCC), have invested heavily in riparian protection in the Illinois River watershed for both sediment and phosphorus mitigation. Riparian protection can significantly decrease streambank erosion in some locations, but estimates of actual load reductions in both sediment and sediment-bound phosphorus (P) due to implementation of riparian protection are limited. The objective of this research is to monitor and numerically model streambanks with and without implemented riparian management practices to derive sediment and P load reduction estimates from streambank protection. This project will use the Bank Stability and Toe Erosion Model (BSTEM), one of the most commonly used and most advanced streambank stability models. Sites will be selected in collaboration with the Oklahoma Conservation Commission and will include sites with (1) no riparian protection and (2) recent implementation of riparian protection. Three sites in each category above (six total study sites) will be selected on tributaries of the Illinois River. At each study reach, bank height, bank stratigraphy (layering), bank slope (overall and slopes of different layers), and bankfull height/depth will be measured. Sites will be instrumented with erosion pins and monitored for streambank erosion over the project period. Water level loggers will be installed at each site to measure water pressure (i.e., stream stage). Sites will be characterized for P distribution in streambank sediment by collecting soil cores from the streambanks. Mehlich III soil test phosphorus (STP) will be measured vertically and laterally within each streambank. Jet tests, borehole shear tests, and root cohesion tests will be conducted to estimate streambank properties related to fluvial erosion and bank failure resistance. Aerial photography, when feasible, will be used to estimate lateral bank retreat over a seven year period (2003-2010). Parameters in BSTEM will be calibrated using lateral bank retreat from monitoring data using bank erosion pins and aerial photography. BSTEM will then be used to estimate sediment loading through streambank erosion and failure using a long-term flow record derived for each site over a range of hydraulic conditions. These simulations will be used to derive sediment and P loading rates, and correspondingly load reductions, from sites with no protection and sites with riparian protection in order to derive load reductions across a range of hydraulic stresses and geotechnical conditions. There are numerous research benefits that will be obtained through completion of this research project. Streambank erosion and failure may be one pathway for sediment and P loading to streams but insufficient data exists on actual loading from this source. The calibrated and validated BSTEM will help target future bank stabilization projects and the best methods utilized for stabilization. This information can be incorporated into future watershed plans to determine the most appropriate methodologies for reducing sediment and P loading from streambank reaches. Also, a total maximum daily load (TMDL) is being developed for the Illinois River watershed without documented estimates of potential loadings from streambanks. Results from this study will verify whether TMDL model estimates were in line with reality.