Impact-Based Flood Risk Assessment for Actionable Resilience Strategies for Kochi, an Indian Coastal City.

Floods are attracting global attention; 23% (1.81 billion) of the world’s population live in areas directly exposed to floods. Floods are the most frequent and one of the costliest disasters worldwide, with 1.3 trillion USD loss in the past 30 years. Coastal urban areas require greater attention due to their increased vulnerability to Sea Level Rise (SLR), cyclones, storm surges and other related challenges. In Asia, India is one of the severely affected countries by floods. With a coastline of 7500km, Indian coastal urban areas such as Surat, Mumbai, Kolkata, Chennai, Kochi and Vishakapatanam face urban flood issues annually. Several criteria influence urban flood Risk, each contributing its share to the overall flood risk. A comprehensive output of the analysis of all these criteria/layers provides a platform to assess flood risk mitigation potential. Flood resilience strategies formulated at a broader administrative level are often implemented on a smaller scale, such as wards or blocks.

A uniform approach may not be advantageous for all the wards due to the diverse challenges across all the wards. Even with a similar overall risk index, the action needed will differ based on the severity of the individual risk criteria contributing to the risk. An Impact-based risk assessment analyses individual criteria layers, which can provide specific insights into the challenges and needs of the local context. The scientific approach in analysis is advantageous for impact-based assessment. The categorization of wards into different zones for the individual risk criteria makes it beneficial in developing custom-made actionable strategies.

For current study, Kochi Municipal Corporation (Kochi City), the commercial capital of Kerala, is selected as the Area of Interest (AOI). The city adjoins seacoast on the west-side, with backwaters entering the land mass, giving a distinctive landscape. Kochi is divided into 74 administrative wards, ranging from 17.38sqkm (Ward-03) to 595.67sqkm (Ward-29). The distinctive physical and social characteristics across the wards in the AOI call for a more specific approach to flood management strategies.

For Kochi City, eleven significant criteria under Hazard, Exposure, and Vulnerability components contributing to the urban flood risk are identified and analyzed spatially for the AOI. The wards are divided into five different zones based on the risk level. The zoning considers the individual criteria indices, hazard index, exposure index, vulnerability index and overall risk index. The individual criteria indices help identify more specific challenges and needs at the local level based on the socio-economic and environmental situation. The existing flood mitigation measures and management strategies are considered in the preparation of actionable solutions. Depending on the need and urgency, actionable solutions for different priority levels are formulated for each risk zone.

The approach is multifaceted, considering the overall risk and analyzing the specific issues associated with the individual or a group of wards with similar contexts. The prioritization of the actions offers an opportunity to better allocate the resources to risk zones that need immediate actions. Understanding the impacts specific to the wards helps develop targeted strategies to reduce the specific challenges, thereby enhancing overall resilience.