Risk assessments of debris flow based on improved analytic hierarchy process and efficacy coefficient method

In order to evaluate the danger of debris flow properly , eight factors were selected as the risk assess- ment indexes of the debris flow , namely the vertical slope , valley relative difference , hillside slope , area of ba- sin , loose solid material reserves , the path length of sediment supply probability , silting and scouring derricking and vegetation coverage. The improved Analytic Hierarchy Process ( AHP ) method was used to obtain the weights of the factors ; and the efficacy coefficient method was adopted to evaluate the risks of six typical debris flow gullies. According to the research , the improved AHP method not only avoids the subjectivity in the indi- vidual factor valuation by comparing two factors of each layer , but also makes the subsequent consistency check