Analysis of Methods to Determine the Sediment Retained by Check Dams and to Estimate Erosion Rates in Badlands.

Check dams are useful structures at a catchment scale to determine erosion rates using the sediment retained in their wedges. Several studies employ different complex, accurate methods to estimate them. We likewise evaluate which catchment variables affect these erosion rate values. Our study aims to compare five frequently used methods (two prismatic and three topographic) to evaluate how they estimate total sediment yield (TSY) at two locations in Central Spain. For this purpose, we determine the sediment trapped in each area by 25 check dams built during the twentieth century. We also evaluate the catchment variables influencing TSY rates. Results show differences between methods in TSY determinations at the 90 % confidence level, although there are no differences between locations or the location-method iteration. We found that the natural logarithm of the drainage area was the factor that best explained TSY, presenting a negative trend (partial correlation coefficient, 0.83). Vegetation cover factor had no influence in estimating TSY for the two locations. We conclude that the determination of TSY rates depends on the chosen method and four related variables: check dam length, check dam height, wedge length and check dam drainage area. Furthermore, it is important to analyse and select the best method to estimate erosion rates based on the sediment retained by check dams depending on the characteristics of the study area (channel and sediment wedge shape), method accuracy and field effort. A more accurate estimation of erosion rates will allow researchers to determine the role of check dams in controlling sediment in each specific restoration project.