This study investigates the determination of compound risk under the co-existence of heavy rainfall and water level rise at Alappuzha, a coastal district in Southern Kerala, India using Copulas. In the case of Alappuzha, when the combined action of rainfall and water level rise occurs, the chances of compound flooding is more in and around Vembanad Lake and lower Kuttanad regions. So, the water level and rainfall of three different locations viz. Punnmada, Cherthala, Arookutty are considered for compound flood risk analysis. A joint probability model based on Copula is used to determine the combined risk of flooding. First the marginal distributions of daily rainfall and water level data are developed for each locations and the best fit distribution is used for finding the joint probability. The three most common Archimedean copulas Gumbel–Hougaard (GH), Clayton and Frank are used to find the joint probability of rainfall and water level and the best copula for each location is also identified. Subsequently, the joint and conditional return periods of rainfall and water level are also obtained in an exercise of risk modeling. By using the digital elevation model (DEM) in a Geographic Information System (GIS) platform, the flood prone areas are calculated and represented them graphically, for specific cases of joint return period-water level combinations. This helps as an aid for administrators or policy makers to effectively perform the disaster management at Alappuzha.

本研究使用 Copulas 调查了印度喀拉拉邦南部沿海地区 Alappuzha 在强降雨和水位上升并存的情况下确定复合风险的方法。在 Alappuzha 的情况下，当降雨和水位上升的共同作用发生时，Vembanad 湖及其周边地区和 Kuttanad 下游地区发生复合洪水的可能性更大。因此，三个不同位置的水位和降雨量即。Punnmada、Cherthala、Arookutty 被考虑用于复合洪水风险分析。基于 Copula 的联合概率模型用于确定洪水的综合风险。首先，为每个位置开发每日降雨量和水位数据的边际分布，并使用最佳拟合分布来寻找联合概率。三个最常见的阿基米德 copula Gumbel–Hougaard (GH)、Clayton 和 Frank 用于查找降雨和水位的联合概率，并且还确定了每个位置的最佳 copula。随后，在风险建模练习中也获得了降雨和水位的联合和条件重现期。通过使用地理信息系统 (GIS) 平台中的数字高程模型 (DEM)，针对联合重现期-水位组合的特定情况，计算洪水易发区并以图形方式表示。这有助于管理员或决策者有效地执行 Alappuzha 的灾害管理。降雨和水位的联合和条件重现期也在风险建模中获得。通过使用地理信息系统 (GIS) 平台中的数字高程模型 (DEM)，针对联合重现期-水位组合的特定情况，计算洪水易发区并以图形方式表示。这有助于管理员或决策者有效地执行 Alappuzha 的灾害管理。降雨和水位的联合和条件重现期也在风险建模中获得。通过使用地理信息系统 (GIS) 平台中的数字高程模型 (DEM)，针对联合重现期-水位组合的特定情况，计算洪水易发区并以图形方式表示。这有助于管理员或决策者有效地执行 Alappuzha 的灾害管理。