Abstract: The invention discloses a debris-flow prevention method by controlling debris-flow magnitude and avoiding to block main river. This method first adopts the drainage works for delivering debris flow in corporation with the transport of the main river; if the drained sediment cannot be transported by the main river, the blocking works are adopted; and if the sediment still exceeds the delivering capacity, the deposit stopping works are adopted. Compared with the prior art, this invention makes full use of the main river's transport capacity, gives priority to dredging and also reasonably distributes the sediment and deploys the engineering system, so as to realize the safe discharge of debris flow, and avoid the secondary disaster of “barrier lake” caused by the blocking of main river due to excessive discharge of debris flow and fully guarantee the safety of mountain towns, major projects and infrastructure located at the mouth of debris flow gully.

Abstract: A system of debris-flow drainage canal with cascaded sills is provided, which allows a high-efficient and low-cost realization of debris flow drainage and scour prevention. The canal contains two converging walls and a series of scour prevention sills, which are laid between the two converging walls. The sills are embedded to a certain depth and are evenly spaced and symmetrical to the centre line of the canal to form a cascaded structure for scour prevention. The drainage canal's width is 2 times wider than the sill's horizontal length along the cross-section. Compared with the prior art, this system can drain off a wide variety of flows from debris flow to flood and prevent debris-flow siltation even on a gentle slope. This system has a much higher stability and longer life of service. Moreover, this system can maintain the aquatic habitat in gullies and contribute to ecological restoration.