Flooding in urban basins is a major natural catastrophe that leads to many causalities of life and property. The semi-urbanized Koraiyar River basin in Tamil Nadu has important cities like Tiruchirappalli and many towns located in it. The basin unfailingly experiences a flood event in almost every decade. It is anticipated that the basin will undergo rapid unplanned urbanization in the years to come. Such fast and erratic urban developments will only increase the risk of urban floods ultimately resulting in loss of human lives and extensive damages to property and infrastructure. The effects of urbanization can be quantified in the form of land use land cover (LULC) changes. The LULC change and its impacts on urban runoff are studied for the continuous 30-year present time period of (1986–2016) to reliably predict the anticipated impact in the future time period of (2026–2036). The analysis of land cover patterns over the years shows that urbanization is more prevalent in the northern part of the basin of the chosen study area when compared with the other regions. The extreme rainfall events that occurred in the past, and the probable future LULC changes, as well as their influence on urban runoff, are studied together in the current study. In order to minimize flood damages due to these changing land use conditions, certain preventive and protective measures have to be adopted at the earliest. There are some inevitable limitations while applying traditional measures in flood modeling studies. This investigative work considers a case study on the ungauged Koraiyar floodplains. The spatial scale risk assessment is assessed by coupling geographic information systems, remote sensing, hydrologic, and hydraulic modeling, to estimate the flood hazard probabilities in the Koraiyar basin. The maximum flood flow is generated from the Hydrologic Engineering Centre-Hydrologic Modeling System (HEC-HMS), the hydrologic model adopted in the present study. The maximum flood flow is given as input to the Hydrologic Engineering Centre-River Analysis System (HEC-RAS), an effective hydraulic model that generates water depth and flood spread area in the basin. The flood depth and hazard maps are derived for 2, 5, 10, 50, and 100-year return periods. From the analysis, it is observed that the minimum flood depth is less than 1.2 m to a maximum of 4.7 m for the 100-year return period of past to predicted future years. The simulated results show that the maximum flood depth of 4.7 m with flood hazard area of 4.32% is identified as high hazard zones from the years 1986–2036, located in the center of the basin in Tiruchirappalli city. The very high hazard flood-affected zone in the Koraiyar basin during this period is about 198.85 km². It is noticed that the very low hazard zone occupies more area in the basin for the present and future simulations of flood hazard maps. The results show that the increase in peak runoff and runoff volume is marginally varied.

城市流域的洪水是主要的自然灾害，导致许多生命和财产因果关系。泰米尔纳德邦的半城市化的科赖亚尔河流域拥有重要的城市，如蒂鲁吉拉伯帕利和许多城镇。流域几乎每十年都会经历一次洪水事件。预计该流域在未来几年将经历快速的计划外城市化。如此迅速而不稳定的城市发展只会增加城市洪灾的风险，最终导致人员伤亡以及财产和基础设施的广泛破坏。城市化的影响可以用土地利用土地覆盖（LULC）变化的形式来量化。在连续30年的当前时间段（1986–2016）中研究了LULC变化及其对城市径流的影响，从而可靠地预测了未来时间段（2026–2036）的预期影响。多年来对土地覆盖格局的分析表明，与其他地区相比，所选研究区流域北部的城市化更为普遍。在本研究中，一起研究了过去发生的极端降雨事件以及将来可能发生的LULC变化及其对城市径流的影响。为了最大程度地减少由于这些不断变化的土地使用条件而造成的洪灾损害，必须尽早采取某些预防和保护措施。在洪水模型研究中应用传统措施时，存在一些不可避免的局限性。这项调查工作考虑了一个关于未开封的科赖亚尔洪泛区的案例研究。通过结合地理信息系统，遥感，水文和水力模型来评估空间尺度的风险评估，以评估科赖亚尔河流域的洪灾危险概率。最大洪水流量来自本研究采用的水文工程中心-水文工程中心水文模拟系统（HEC-HMS）。最大洪水流量作为水文工程中心-河流分析系统（HEC-RAS）的输入，这是一种有效的水力模型，可在盆地中产生水深和洪水扩散面积。得出了2年，5年，10年，50年和100年回归期的洪水深度和灾害图。从分析中可以看出，最小洪水深度小于1.2 m，最大为4。从过去的100年返回期到预测的未来年为7 m。模拟结果表明，从1986年至2036年，最大的洪水深度为4.7 m，洪水危险区为4.32％，被确定为高危险区，位于蒂鲁吉拉伯利市盆地的中心。在此期间，科赖亚尔盆地的高危洪灾区约为198.85 km²。注意到对于当前和将来的洪水灾害图模拟，非常低的危险区在流域中占据了更大的面积。结果表明，峰值径流量和径流量的增加略有变化。