Sediment has been recognized as an important water contaminant and there has been substantial research into the sources and sinks of sediment on the landscape. However, ravines are an understudied erosive landform. The flashy, intermittent flows in ravines make them difficult environments to study and manage. The goals of this study were to collect data on the hydrology, sediment, and vegetation in ravines and to use that data to model sediment loads in a steep ravine in the Seven Mile Creek watershed in south-central Minnesota. There are many ravines throughout the Seven Mile Creek watershed and the Minnesota River Basin (MRB), of which it is a small part. The MRB carries the largest sediment loads entering the Mississippi River in the state of Minnesota and these sediments are creating problems downstream including rapid infilling of Lake Pepin. In the present study the Bank Stability and Toe Erosion Model (BSTEM) was used along with substantial field data on hydrology, sediment, and vegetation to model sediment loads generated in ravines in the Seven Mile Creek watershed. The results of the study show that substantial sediment loads can be generated in ravines. Sediment loads varied from a few metric tons/reach/year to tens of thousands of metric tons/reach/year with the strongest control exerted by hydrology followed by sediment, slope, and added cohesion from vegetation. The depth to water table and depth and duration of flow exerted strong control on sediment loads. Changing the water table and depth and duration of water flow caused a relative change in sediment load of at least 193% for the whole ravine results. It is hoped that the field data and modeling results from this study can aid researchers in understanding the magnitudes of sediment loads that can be expected in ravines and that it can guide managers in placing best management practices on the landscape in order to decrease erosion and sediment delivery from ravines to larger streams and rivers.
Hammer-Lester, Rebecca F.
Using BSTEM to Estimate Sediment Erosion in Seven Mile Creek Watershed.
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