rill gully soil erosion溯源侵蚀
gully head erosion沟头侵蚀
protection of gully head erosion沟头防护
hillslope-gully slope erosion system坡沟系统
hill slope-gully side erosion system坡面
harm of gully erosion侵蚀危害
gully and valley erosion沟谷侵蚀
gully erosion development process沟蚀演变
collapse gully erosion崩岗侵蚀