Water Resources Research Act Program

Details for Project ID 2015TN112B

Characterizing Stream Sediment Source Potentials in Small Urbanizing Watershed

Institute: Tennessee
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-28
Total Federal Funds: $17,195 Total Non-Federal Funds: $34,744

Principal Investigators: John Schwartz

Project Summary: Urbanization causes widespread changes to watershed hydrology and channel geomorphic processes, where increased impervious surfaces cause hydromodification mostly observed as greater peak stormflows and longer durations. Hydromodification leads to channel bed and bank erosion increasing fine sediment loads to stream. These increases in fine sediment loads result in degradation of aquatic habitat and impairment of biotic integrity. Impacted streams are identified on federal/state 303(d) list requiring a total daily maximum loads (TMDLs) for suspended sediment to be produced, in addition to an implementation plan to achieve loading targets. In urban watersheds, the potential generation of fine sediment loads from geomorphic incision cannot be separated from uplands stormwater management practices. Although stormwater control measures improve water quality from local sites, a key question remains on what levels of treated stormwater discharges are acceptable to maintain in-stream geomorphic stability, termed channel protection flows. However, the linkages between urbanization, stormwater management policy, and stream channel response are still poorly understood over the range of watershed settings. Therefore, a critical need exists for state and local agencies charged with the water quality protection of streams to have geomorphic field assessment tools that can prioritize streams reaches most vulnerable to in-channel bank/bed erosion. This research proposes to clarify interrelationships between hydromodification from urbanization, fluvial geomorphological processes, and stormwater management and policy. It is proposed that classification of urban stream reaches by trajectory of response to hydromodification allows an approximation of impacts of land-use modifications, development of effective regulation to avoid or minimize externalities, and prioritization of mitigation efforts between stormwater control measures and stream rehabilitation. The classification scheme will be based on in improved geomorphic field assessment protocol for urban streams. Ultimately, this research is expected to support stream system rehabilitation in Ecoregion 67 through adaptation of mitigation practices relative to channel hydraulic resistance properties and adapted for use in channel protection efforts throughout the nation.