Water Resources Research Act Program

Details for Project ID 2016TN118B

Urban Stream Restoration Planning: Towards Cost-Effective Mitigation of the Effects of Hydromodification

Institute: Tennessee
Year Established: 2016 Start Date: 2016-03-01 End Date: 2017-02-28
Total Federal Funds: $5,000 Total Non-Federal Funds: $2,550

Principal Investigators: Robert Woockman, John Schwartz

Abstract: In-stream channel degradation as a result of alterations to flow and/or sediment caused by urbanization can have detrimental ecological and socioeconomic impacts. Although steps have been taken to minimize these impacts through stormwater regulatory efforts, regulation typically takes the form of uniform volume control measures designed around a pre-disturbance condition. These uniform style regulations are often favored because the simplicity of implementation in a wide variety of municipal settings. Although implementation of such uniform regulations offers many conveniences for agencies, their effectiveness is not universal as a result of not integrating efforts with local stream system morphological attributes. Creating a scenario where additional costs may be imposed on the private sector, there is little or no improvement to externalities, and therefore social costs actually increase. This research proposes to integrate fluvial geomorphology concepts with engineering design and evaluate mitigation efforts through an economic framework. Hydrological modeling and field surveys are used to explore surrogate measures of eroding and resisting force with the intent to capture potential imbalances and define attributes that determine stability within the Ridge and Valley Province of Tennessee. Detailed in-situ flow monitoring was completed at three small stream systems to calibrate and validate coupled continuous simulation models of hillslope and in-channel processes. Models are utilized to explore response trajectory and efficacy of various mitigating suites with the intent to answer the following question: are cost effective mitigation strategies (intended to mitigate channel degradation in small stream systems) improved through consideration of stream channel erosive resistance elements? This research is expected to improve the body of knowledge available to municipalities as they move towards mitigating the impacts of urban hydromodification. Planning measures, which include an integrated systems approach, have the potential to improve channel protection flow design standards and guidance for in-lieu fee programs. This research is anticipated to result in three publications related to the topic discussed in the abstract. The central research questions that will be the focus of each article are listed below: What are the thresholds of destabilization, among 2nd and 3rd order stream reaches of the Ridge and Valley of Tennessee, and do these vary based on channel erosive resistance elements? Can the model platforms of SWMM & CONCEPTS be integrated successfully to represent Effective Work Regimes and the influence that channel erosive resistance elements and in- channel restoration practices have on regimes? Does the cost-effective BMP suite, for the purposes of mitigating channel instability due to urbanization, vary with consideration of channel erosive resistance elements and effective work performed on the channel? These questions are intended to improve our understanding of the linkages between urbanization, stormwater management policy, stream channel morphology, and degradational response over a range of watershed conditions and stream restoration practices. Although current research has made promising steps towards providing policy makers with adequate information and tools to cost effectively mitigate hydromodification effects, there remains a dearth of adequate information at regional levels. Therefore, it is the objective of this research to advance the available information necessary for cost effective mitigation strategies in the Ridge and Valley province of Tennessee. Through studying the interaction between increased eroding forces (due to hydrologic alteration) and resisting forces at the reach scale in 2nd and 3rd order streams.