黄土丘陵沟壑区退耕还林工程前后淤地坝的拦沙特征

In order to analyze the change of sediment trapped in check dams pre and post the Program of Conversion of Cropland to Forest in hilly-gully Loess Plateau, we estimated the amount of sediment trapped behind the check dams in Majiagou watershed, Ansai County, northern Shaanxi province with GPS,remote sensing and GIS technologies, combined with previous published results of sediment amount in check dams. The result showed that the amount of sediment trapped in check dams was large and there were no significant differences among the stages before conversion of cropland to forest. The watersheds controlled by check dams were mainly domained by fierce soil erosion, while they were domained by slight soil erosion after conversion of cropland to forest with a significant reduction of trapped sediment. Thus, based on current efforts of conversion of cropland to forest, contradiction of human activities and ecological restoration should be coordinated, which could reduce erosion and sediment yield in watersheds. Also, construction of check dams in regions implemented the Program of Conversion of Cropland to Forest successfully should be slowed down.