This paper aims to demonstrate the research-to-application and operational use of numerical hydrologic and hydraulic modeling to (a) quantify potential flash flood risks in small urban communities with high spatial resolution; (b) assess the effectiveness of possible flood mitigation measures appropriate for such communities; and (c) construct an effective operational urban flash flood warning system. The analysis is exemplified through case studies pertaining to a small community with dense housing and steep terrain in Tegucigalpa, Honduras, through numerical simulations with a customized self-contained hydrologic and hydraulic modeling software. Issues associated with limited data and the corresponding modeling are discussed. In order to simulate the extreme scenarios, 24-h design storms with return periods from 1 to 100 years with distinctive temporal and spatial distributions were constructed using both daily and hourly precipitation for each month of the rainy season (May–October). Four flood mitigation plans were examined based on natural channel revegetation and the installation of gabion dams with detention basins. Due to limitations arising from the housing layout and budgets, a feasible plan to implement both measures in selected regions, instead of all regions, is recommended as one of the top candidates from a cost-to-performance ratio perspective. Numerical modeling, customized for the conditions of the case study, is proven to be an effective and robust tool to evaluate urban flood risks and to assess the performance of mitigation measures. The transition from hydrologic and hydraulic modeling to an effective urban flash warning operational system is demonstrated by the regional Urban Flash Flood Warning System (UFFWS) implemented in Istanbul, Turkey. With quality-controlled remotely sensed precipitation observations and forecast data, the system generates forcing in the hydrologic and hydraulic modeling network to generate both historical and forecast flow to assist forecasters in evaluating urban flash flood risks.

中文翻译：

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城市地区山洪灾害风险缓解和运行预警的数值模拟

本文旨在展示数值水文和水力模型的研究应用和业务使用，以 (a) 以高空间分辨率量化小型城市社区的潜在山洪风险；(b) 评估适合此类社区的可能的防洪措施的有效性；(c) 构建有效的可操作的城市山洪预警系统。通过使用定制的独立水文和水力建模软件进行数值模拟，该分析通过与洪都拉斯特古西加尔巴的一个拥有密集住房和陡峭地形的小社区有关的案例研究来举例说明。讨论了与有限数据和相应建模相关的问题。为了模拟极端场景，使用雨季（5 月至 10 月）每个月的每日和每小时降水量构建了 24 小时设计风暴，其重现期为 1 至 100 年，具有独特的时空分布。根据自然河道重新植被和安装带滞留池的石笼水坝，审查了四个防洪计划。由于住房布局和预算的限制，从成本绩效比的角度来看，建议将在选定区域而不是所有区域实施这两项措施的可行计划作为最佳候选方案之一。为案例研究条件定制的数值模型被证明是评估城市洪水风险和评估缓解措施绩效的有效且稳健的工具。在土耳其伊斯坦布尔实施的区域城市山洪预警系统 (UFFWS) 证明了从水文和水力建模到有效的城市山洪预警操作系统的过渡。通过质量控制的遥感降水观测和预报数据，该系统在水文和水力建模网络中产生强迫，以生成历史流量和预报流量，以帮助预报员评估城市山洪风险。