Simulation study on urban waterlogging response characteristics under combined influence of wind fields and rainstorms

Abstract

[Objective] To investigate the characteristics of urban waterlogging response under the combined influence of wind fields and rainstorms in densely built mountainous cities. [Methods] Taking a drainage area in Yuelai New City of Chongqing as the study area, a rainfall-runoff process simulation method under the combined influence of wind and rainfall was proposed based on the Storm Water Management Model(SWMM) and the LISFLOOD-FP model. Rainfall design was carried out based on seven rainstorm patterns. Using historical observed wind fields, the most adverse wind direction leading to the maximum runoff yield and overflow in the study area was simulated. The urban waterlogging response characteristics under the combined influence of wind fields and rainstorms were systematically analyzed. [Results] The result showed that when the wind direction was 225°(with due north as 0°), the runoff yield and overflow volumes in the study area were significantly higher than those under other wind directions, and the influence of wind direction intensified with increasing rainfall intensity. Under the influence of three wind field types(with average wind speeds of 0~2 m/s for light wind, 2~4 m/s for moderate wind, and 4~6 m/s for strong wind), the waterlogged area increased by an average of 1.6%~6.5% compared with no wind field conditions, with local increases exceeding 9.0%. Compared with the waterlogged area, the changes in overflow onset time and overflow peak became more pronounced with increasing return periods. Under the influence of wind fields, the waterlogged area increased most significantly under rainfall Pattern Ⅲ when the return period was less than 50 years, while the increase was more pronounced under Pattern Ⅱ when the return period exceeded 50 years. Changes under uniform and bimodal rainstorm patterns were relatively minor. [Conclusion] In simulating urban waterlogging in densely built urban districts, neglecting the influence of wind fields may underestimate both runoff yield and waterlogging severity. The proposed method for rainfall-runoff simulation coupled with wind field influence demonstrates strong applicability in simulating waterlogging in mountainous cities.

Keywords

urban waterlogging / wind field / rainstorm pattern / LISFLOOD-FP / SWMM / rainfall / Chongqing City / runoff producing