Urban growth is one of the major causes of flooding in urban areas. This affects the runoff coefficients, which is among the most important factors that affect the design of storm water drainage systems. Changing the runoff coefficient will affect the design parameters of the drainage network, including outfall discharge, velocity, lag time and cost of construction. This study aims to assess the effect of changing the runoff coefficient due to urban growth on the design of a storm water drainage system. The hydrological models Hyfran, StormCAD and GIS are used to analyze different runoff coefficients. This study examines three zones in Dammam in the Kingdom of Saudi Arabia (KSA). The data developed from the models for the current case studies are used to develop an empirical equation to predict the max discharge for other catchments. The discharge is a function of the return period, runoff coefficient, drainage density, longest path, rainfall intensity and catchment area. To validate the developed equation, we use it to estimate the discharge in a real case study in South Korea. A comparison between the measured discharge and estimated discharge shows that the empirical equation is capable of predicting the maximum discharge for different catchments with high accuracy. Then, the validation of the models is carried out to determine the effect of the runoff coefficient on the design of a storm water drainage system in a case study in KSA. The results show that an increasing runoff coefficient due to urban growth increases the outfall discharge and velocity of storm water drainage systems, as well as affecting the cost of construction and decreasing the lag time. The cost increases by two to three times with increasing urbanization. This study provides a new perspective on the hydrologic impact of urban growth on the design of storm water drainage systems, which are essential for flood management. Moreover, the relationship between urban growth and the cost of storm drainage networks is explored, which could help decision makers to make appropriate judgements.

中文翻译：

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评估城市发展对雨水排水系统设计的影响

城市发展是城市地区洪水泛滥的主要原因之一。这会影响径流系数，这是影响雨水排放系统设计的最重要因素之一。改变径流系数会影响排水管网的设计参数，包括排污口流量、流速、滞后时间和建设成本。本研究旨在评估因城市发展而改变径流系数对雨水排放系统设计的影响。水文模型 Hyfran、StormCAD 和 GIS 用于分析不同的径流系数。本研究考察了沙特阿拉伯王国 (KSA) 达曼的三个区域。从当前案例研究的模型开发的数据用于开发经验方程，以预测其他集水区的最大流量。流量是重现期、径流系数、排水密度、最长路径、降雨强度和集水区的函数。为了验证开发的方程，我们使用它来估计韩国真实案例研究中的排放量。实测流量和估算流量之间的比较表明，经验方程能够高精度地预测不同流域的最大流量。然后，在沙特阿拉伯的一个案例研究中，对模型进行了验证，以确定径流系数对雨水排水系统设计的影响。结果表明，城市增长导致的径流系数增加会增加雨水排放系统的排污口流量和流速，同时影响建设成本并减少滞后时间。随着城市化进程的加快，成本增加了两到三倍。这项研究为城市发展对雨水排放系统设计的水文影响提供了新的视角，这对于洪水管理至关重要。此外，还探讨了城市增长与雨水排放网络成本之间的关系，这有助于决策者做出适当的判断。