Evaluation of effect of dike merging measures on flood control and drainage in plain river network cities: A case study of Xinchengnanwei in Wuhu City

Abstract

[Objective] Plain river network cities in the middle and lower reaches of the Yangtze River are located in flat and open terrain with crisscrossed river networks. During flood seasons, higher water levels combined with lower urban elevation often lead to poor drainage, making these areas highly susceptible to flooding. Dike merging has proven to be an effective method for addressing flood issues within dike areas. [Methods] Taking Xinchengnanwei in Wuhu City as an example, the effect of dike merging measures on flood control and drainage was systematically evaluated. A refined flood-inundation coupled model was developed, incorporating engineering infrastructure, rainfall, and external river water levels. Seven scenarios were designed to simulate changes in flood risks before and after the implementation of dike merging measures. [Results] The result showed that, under different rainfall conditions and external river flood return periods, the inundation area in the study area decreased compared to before the implementation of dike merging measures. Specifically, when the return period was 10 years, the reduction in inundation area in high-risk zones was the most significant, reaching 18.40%. As the design storm and flood return periods increased, the effectiveness of these measures gradually diminished. After implementing the dike merging measures, the main drainage infrastructure in the dike area, such as the Jingfang Pump Station and Zhugang Pump Station, was able to meet the urban drainage needs. However, for rainfall events exceeding a 20-year return period, it was necessary to pre-lower the water level of the Jingshan River by activating pump stations in advance to ensure their proper operation. [Conclusion] Dike merging measures can effectively reduce the flood and inundation risks in plain river network cities. Combined with drainage engineering projects, pre-lowering internal river water levels enhances the city's flood control and drainage capacity. The refined flood-inundation coupled model can comprehensively simulate the interaction between floods and urban inundation. Technical support can be provided for flood control and drainage planning, as well as water engineering scheduling in plain river network cities, along with theoretical guidance for establishing refined flood-inundation coupled models in similar dike areas.

Keywords

dike merging / plain river network cities / flood control and drainage / numerical simulation / Wuhu City