Methodology for the construction of an urban flood hazard chart

ABSTRACT Flood events are one of the major causes of economic loss and the loss of life worldwide. Unfortunately, their occurrence has become increasingly more frequent and of greater magnitude. In order to minimize the population’s exposure to danger, it is necessary to invest in tools that aid in the decision-making process related to urban drainage management. The present work proposes a methodology for the construction of a Flood Hazard Chart for urban watersheds. The Storm Water Management Model (SWMM) was applied to the Cachoeirinha Watershed (Belo Horizonte, Brazil). The model was calibrated and validated using precipitation data and water levels recorded in monitoring stations located in the study area. The Nash-Sutcliffe Coefficients for the calibration and validation were 0.72 and 0.70, respectively. The performance of the model was satisfactory, although the model was not able to represent the more intense rain events that led to emergency and overflow warnings. Modeling results allowed the construction of the hazard chart, which defined hazard ranges or warning levels of hazard as a function of accumulated rainfall and duration. The constructed graph was assessed from real precipitation events and proved to be valid, since most events corresponded with the defined warning levels in the chart. The Flood Hazard Chart proposed in this research is a valuable tool for flood risk management as it has the potential to reduce exposure to flood disasters.

摘要：洪涝事件是全球范围内造成经济损失与人员伤亡的主要诱因之一。当前，其发生频率愈发攀升、影响强度持续增大。为降低民众面临的洪涝风险，亟需研发可辅助城市排水管理相关决策的工具。本研究提出一种面向城市流域的洪涝风险图（Flood Hazard Chart）构建方法：以巴西贝洛奥里藏特市的卡舒埃里尼亚流域为研究对象，应用雨水管理模型（Storm Water Management Model, SWMM）开展模拟；利用研究区域内监测站点获取的降水与水位观测数据，对该模型进行率定与验证，率定与验证阶段的纳什-舒特克利夫效率系数（Nash-Sutcliffe Coefficients）分别为0.72与0.70。尽管该模型无法精准复现触发应急预警与溢流警报的强降雨事件，但整体模拟表现仍令人满意。基于模拟结果构建的洪涝风险图以累积降雨量与降雨历时为变量，划定了不同的风险区间与灾害预警等级。通过真实降雨事件对该风险图进行验证后发现，绝大多数事件均与图中划定的预警等级匹配，证明其具备有效性。本研究提出的洪涝风险图可有效辅助洪涝风险管理，具备降低民众洪涝灾害暴露风险的应用潜力。