Development and application of a fuzzy membership model for identifying erosive rainfall events

Soil erosion caused by rains is a continuous process of changes.Such a soil erosion character is used in the development of a fuzzy membership model for identifying erosive rainfall events.The precipitation amount (P)and the maximum 30 min rainfall intensity (I₃₀)of a rainfall event are used as two physical parameters in the model.The model involves three parts.The first part calculates the membership values of P and I₃₀,and constructs the fuzzy membership functions.Secondly,the membership values of P and I₃₀ are combined to form a new membership value of individual rainfall event.And finally,an erosive rainfall event is identified using the new membership values.The identified events can be validated through the mistaking degrees and the missing degree.The model is applied over three small-sized watersheds in the Three Gorges Reservoir region of southwest China,including Chenjiagou (8.32 km²),Daijiagou (0.67 km²),and Qiaojia (0.02 km²).The mistaking degrees on the three watersheds are less than 20%.The model has a simple structure,and its parameters have clear physical meaning and can be derived directly from the hydro-meteorological observations.