IMPACT OF EXTERNAL WATER INFLOW ON FLOODING RISK IN URBAN AREAS AND OPTIMIZATION SCHEMES

To evaluate the impact of the external water inflow on the urban drainage pressure in a city in Shandong Province, a one-dimensional and two-dimensional combined model was established on InfoWorks ICM to analyze the drainage capacity and flooding distribution in the urban under different rainfall conditions. Then the optimization schemes were proposed. The results showed that the inflow of external water was the main reason for the drainage pipe network overloading, nodes overflowing, and flooding in the main urban area of the city. More than half of the pipes were overloaded under the design rainfall recurrence of 2 a and 3 a with a duration of 2 h, and the overflow nodes accounted for 1.38% and 3.1%, respectively. The proportion of flooded areas was 35.9% and 38.7% under the design rainfall recurrence of 20 a and 30 a with a duration of 24 h, respectively, among which 9.60% and 9.94% of the area were posted at high risk. Considering both economy and effectiveness, the construction of surface culverts and flood discharge ditches was adopted to intercept surface runoff and alleviate the drainage pressure of urban pipeline networks. The optimized plan can effectively reduce the flooded areas in urban under external water inflow, especially for high-risk areas. The high-risk area was reduced by 75% and 71% under the design rainfall recurrence of 20 a and 30 a with a duration of 24 h, respectively, and the maximum flooding depth decreased to 1 meter below.