Streambank erosion adjacent to different riparian land-use practices and stream patterns along Bear Creek, in north central Iowa

摘要

Sediment load in streams is the major non-point source pollutant originating from agriculture landscapes. Bank erosion can contribute 45-60% of the sediment load in streams. Land-use practices such as row cropping and grazing, combined with channelization of meandering reaches of streams have accelerated bank erosion rates and increased the sediment load in streams. An 11 km reach of Bear Creek was selected to compare bank erosion and soil loss of riparian buffers, corn or soybean row-cropped fields and cow or horse pastures along meandering and channelized reaches. The pin method was used to measure bank erosion because it is very good for short time-scale studies with high resolution that capture small differences in bank erosion at relatively low cost. Thirty three erosion pin plots were randomly assigned to the land-use practice sites that contained approximately 1100 pins. The pins were measured approximately every month from June 1998 to May 1999. Bulk densities were estimated with the core method, while the length and average height of all the eroding sites were also measured. Bank erosion rates and soil losses were affected by land-use practices although bulk densities were not very different.;The highest bank erosion rates where on the outside bends of cattle grazed pastures and crop fields with losses of 33 and 34 cm yr−1. Buffered banks had the lowest erosion rates, with only 12 cm yr−1 lost. Cattle grazed pastures and crop fields lost 341 kg m−1and 288 kg m−1 while riparian buffers lost only 55 kg m−1. If the entire 11 km reach of Bear Creek had riparian multi-species buffers the bank soil loss would be reduced by 62 percent. Riparian buffers provide an alternative land-use practice that will reduce soil bank loss and sediment load in the streams while also being financially attractive to farmers because the Conservation Reserve Program subsidizes the agricultural land lost.