Abstract: Since 1990,a gradually rising trend of flood damage has been apparent and the situation of flood defense is greatly severe.Besides hydrometeorological factors,human activity is an important factor causing much more flood damages.Human activities throughout watersheds directly or indirectly change some natural elements,such as land cover,available storage,land slope and river morphology,which influence flood-producing process and flood characteristics.By reviewing the existing literatures,this paper discusse...