Abstract:

Debris flow,which commonly contains high kinetic energy,has terrible damage capacity to cause heavy disaster by its strong impact force and transporting huge volume materials.If the kinetic energy of debris flow could be completely or partly dissipated before its initiation or deposition,the disaster caused by debris flow may be avoided or be mitigated to minimization.Steppool systems have the maximum flow resistance and stability condition,which potentially could be used for mountain streams training and ecological restoration.In this paper,17 artificial steppool systems were built on Lanshan Gully,a tributary of Xihanshui River in Gansu Province in Northwest of China.The experimental study of steppool systems started from June 2009.Based on observation during two flood seasons of 20092010,the artificial steppool systems raised the base level by deposition.And the riverbed and bank was protected from erosion.Thus,the bed and bank slope were stabilized.Moreover,the kinetic energy of debris flow was dissipated by hydraulic drop and hydraulic jump of the steppool systems,and sediment deposited on the upstream of steps.Finally,there was little debris flow occurred in Lanshan Gully from 2009 to 2010.The results show that energy dissipation structures are the key to stabilize high gradient mountain streams.The resistance structures,such as steppool systems, whether developed by nature or by manmade could dissipate the flow energy and keep the kinetic energy of the flow below a critical energy for initiation of debris flows