Method for calculating rainstorm overflow risk of urban catchment area

The invention relates to a method for calculating the rainstorm overflow risk of an urban catchment area, and the method comprises the following steps: 1, calculating a rainstorm intensity threshold value when overflow occurs in the catchment area according to a rainstorm intensity formula designed by a rainwater pipeline; 2, dividing rainfall events according to years of self-recording rainfall records; 3, obtaining an overflow process in the rainfall event according to the rainstorm intensity threshold value; 4, calculating the overflow duration, the average overflow strength and the overflow depth of the overflow event; 5, sampling the overflow depth by using an annual maximum value method; 6, calculating an overflow depth extreme value and an empirical frequency thereof; and 7, calculating the overflow risk according to the product of each overflow depth extreme value and the empirical frequency thereof, and determining the maximum value of the overflow risk. According to the method, the return period sta