Project Number: 6408-13000-018-27
Project Type: Reimbursable

Start Date: Apr 20, 2007
End Date: Jun 30, 2009

Objective:
The overall objective of this study is to provide the state of Minnesota 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 three Level III ecoregions of the states, containing 80 sites: Northern Lakes and Forests, North Central Hardwoods, and Northern Wetlands ecoregions. A sub-objective aims to determine potential course of future work by the states to determine future monitoring needs as well as the potential for a pilot study of sediment loadings and the magnitude of load reductions that can be anticipated using a variety of mitigation strategies.

Approach:
Historical flow and sediment-transport data from sites across the three ecoregions 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. The frequency and duration of specific sediment concentrations will be determined from the historical database for stable and unstable streams from each ecoregion to provide sediment metrics that can ultimately be linked to aquatic ecology.