Midwest Fish & Wildlife Conference 2016

AUTHORS: Todd Wills*, Michigan Department of Natural Resources; Troy Zorn, Michigan Department of Natural Resources

ABSTRACT: Excessive sand bedload is recognized as a major pollutant in streams and rivers across the Midwestern United States because of both the quantity released and the miles of stream affected. The devastating effects of sediment on stream channel morphology and trout populations has been well-documented and lead to the widespread use of sediment traps to restore channel habitats in Michigan since the 1980s. However, little information exists to evaluate the effectiveness of these sediment trapping efforts in restoring desirable river substrates and channel habitats, which is especially problematic considering the diverse array of river habitats in Michigan. In order to determine the effect of sediment trapping efforts on stream channel morphology, we quantified the rate and spatial extent of change in bed elevation and substrate conditions of seven streams during an 11-year period. The data from our study streams show that excavation of sediment traps generally had only small effects on mean channel depth and substrate, with changes occurring both upstream and downstream of the trap. The lateral position of the channels examined remained constant, indicating little side cutting had occurred. Changes in channel area remain variable and appear as likely to occur at transects proximal to the sediment traps as at transects located further upstream or downstream. These results suggest that current sediment trapping practices have not achieved the desired goals of increased downcutting and exposure of coarse substrates downstream of the sediment traps studied.