Combining 137 Cs and topographic surveys for measuring soil erosion/deposition patterns in a rapidly accreting area1

Abstract

Narrow, stiff grass hedges are biological barriers designed to slow run off and capture soils carried in run off water. This study was designed to measure quantitatively the deposition of soil up slope of a narrow, stiff grass hedge using topographic and 137Cs surveys. Topographic surveys made in 1991, 1995, and 1998 measured 1 to 2 cm yr - 1 of recent sediment deposited up slope of the grass hedge. 137Cs analyses of soil samples were used to determine the medium-term (45 years) soil redistribution patterns. Erosion rates and patterns determined using 137Cs measured medium-term erosion near the hedge do not reflect the recent deposition patterns near the grass hedge measured by topographic surveys. Using the combination of topographic and 137Cs surveys allows a better understanding of the role of grass hedges as barriers for capturing eroding soils and suggest that the recent deposition is associated with the grass hedge but that there is still a net loss of soil near the hedge position over the past 45 years.