Evolution characteristics and variability analyzation of rainfall and runoff based on time scale

With the rapid development of economy, the hardening area of city is increasing, which leads to the change of the runoff production law in the city. In order to understand the change of urban rainfall and runoff in the changing environment, the control basin of the Dahongmen hydrological station of Liangshui river in Beijing was selected as the research object. Mann - Kendall nonparametric rank correlation test, Non-parametric Pettitt test and qualitative and quantitative models of the Variable fuzzy set were used to study the evolution characteristics and variability of rainfall and runoff based on the measured data from 1980 to 2015. The results show that the flood peak and flood amount in the 1990s were smaller than those in 1980s, and the flood peak and flood amount were significantly greater than those in the 1980s and 1990s after 2000. The actual maximum flood peak and flood amount had significantly rising trend. For variability analysis, the mutation point of annual rainfall and runoff occurred in 1996 and 1993 respectively. They did not change qualitatively on the time scale, but only showed the quantitative variation. This study results can provide a basis for rational decision of flood prevention departments.