gullyn.小峡谷；排水沟v.在…上开沟；形成冲沟=gulley.gully control dam谷坊gully development冲沟分布gully head forward沟头前伸gully head erosion沟头侵蚀,沟头冲蚀gully erosion form沟蚀形态gully bank extension沟岸扩展gully head protectio沟头防护gully bed downcutting沟床下切gully head protection沟头防护gully and hill region丘陵沟壑区