Stream Bank Erosion Rates in Two Watersheds of the Central Claypan Region.

Sedimentation of surface waters in the United States is a significant environmental concern. Investigating land use impacts on stream bank erosion rates is intended to lead to the development of improved management practices and provide the basis for targeting the placement of management practices to mitigate this problem. The overall objective of this research was to determine the effect of stream order, adjacent land use, and season on stream bank erosion rates. Study sites were established in 2007 and 2008 within Crooked and Otter Creek watersheds, two claypan watersheds located in northeast Missouri. Detailed site information was recorded, including eroded stream bank length, soil descriptions, gullies, debris dams, cattle access areas, and point bars. A factorial experimental design was implemented with four land uses (cropped, forest, pasture, and riparian forest) and three stream orders (1^st, 2^nd, 3^rd). Each treatment was replicated three times for each stream order. Erosion pins were installed based on bank height and length at each site to measure bank erosion/deposition rates. The effect of different seasons was assessed by measuring the length of the exposed pins three times per year (March, July, and November). Statistical analyses were performed to determine the effect of stream order, land use, and season on erosion rates. Additionally, using data from the National Hydrography Data, measured erosion rates will be applied at a watershed scale to calculate the sediment contribution of stream banks from specific stream orders as well as from the entire watershed. The results showed that the seasonal effect was highly significant, with much greater erosion rates in the winter compared to the other seasons. Land use was significant when low magnitude deposition was observed and was not significant in any of the seasons in which erosion occurred.

Key Words: bank erosion, stream order, land use, claypan watersheds, erosion pins.