Debris-flow prevention method by controlling debris-flow magnitude and avoiding to block main river

A method for preventing and controlling debris flow, comprising:

• determining a peak discharge QTotal of debris flow in compliance with a design standard, according to the floodmark investigation of historical debris-flow hazards or hydrological calculation of small watershed;
• determining a peak discharge QDrainage of debris flow which can be drained to a main river via one or more drainage channels of debris flow according to the transport capacity of the main river;
• when QTotal≦QDrainage adopting the drainage works for the prevention and control of debris flow;
• when QTotal>QDrainage, adopting both the drainage works and the blocking works for the prevention and control of debris flow, and determining a peak discharge QBlock of debris flow which is reduced through stability and blocking according to the blocking works at the upper and lower reaches of the watershed;
• when QTotal≦QDrainage+QBlock, adopting both the drainage works and the blocking works for the prevention and control of debris flow;
• when QTotal>QDrainage+QBlock adopting the drainage works, blocking works and deposit stopping works for the prevention and control of debris flow, and determining a peak discharge QDeposit in deposit stopping works with the calculation formula of QDeposit=QTotal−QDrainage−QBlock.