Project Number: 6408-13000-018-24
Project Type: Reimbursable

Start Date: Oct 01, 2006
End Date: Mar 31, 2008

Objective:
The overall objective of this study is to provide EPA Region VIII and the States of Montana, North Dakota, and South Dakota with scientifically-defensible methodologies by which to develop TMDLs for sediment. The research aspects of the project will focus on determining "reference" conditions for suspended-sediment transport and bed-material characteristics for those states by defining those stream conditions for two of the six principle Level III ecoregions of the states, containing 154 sites: Ecoregion 43: Northwestern Great Plains; Ecoregion 48: Lake Agassiz Plain. An attempt will also be made to establish "reference" conditions for Level IV Ecoregions if sufficient data are available from a renewed set of data downloads from USGA web sites. In addition, links between sediment-transport characteristics and aquatic ecology will be investigated through a partnership with the University of Tennessee. Technology transfer aspects of the project will include workshops and training on a tiered approach of increasing detail and complexity to address sediment impacts and means to evaluate potential mitigation measures.

Approach:
Historical flow and sediment-transport data from sites across EPA region VIII will be used to develop sediment-transport rating relations and substrate-composition parameters at each site. Annual suspended-sediment loads will be calculated for all sites and sorted by Level III ecoregion to determine regional trends for stable and unstable sites. Trends of bed-material composition will similarly be identified. Rapid geomorphic assessments will be conducted to determine the relative stability of the stream and used to sort sites into stable and unstable groupings. The relative stability of streambeds and the likelihood that rates of bed erosion or deposition exceed background rates will be estimated at gauged sites using an excess shear-stress approach. Potential links between sediment-transport rates, bed-material conditions, and aquatic indices in Ecoregion 43 will be investigated using a range of sediment-transport metrics that can be functionally linked to biologic data. These will be developed based on published literature and discussions with aquatic ecologists. Dr. John Schwartz (University of Tennessee) will be the principle project scientist providing expertise on aquatic life-history attributes that could potentially be related to various sediment-transport metrics. It is hoped that a family of transport-duration ¿reference¿ conditions can be identified and ultimately linked to biologic conditions in the streams. Similarly, the average number of consecutive days that a given concentration is exceeded (duration) will be calculated for all sites, irregardless of the existence of biologic data.