A Catalogue of Best Practices for Building Flood Resilience

Urbanization in India has led to 31% of its total population residing in cities and urban areas contributing to 63% of the national GDP1 in 2011. The current projection indicates that the population in cities will increase to 40% of the total population, in parallel the percentage GDP contribution is also expected to increase to 75% of the national GDP. In this context, resilience of cities depends on effective functioning of complex infrastructure networks such as water, energy, sanitation, transport along with physical infrastructure such as housing, hospitals and educational institutions. The intensity of water related shocks and stresses faced by cities in India are beginning to pan out with increasing frequencies. Such events disrupt the socio-economic activities in a city and cause damages to critical infrastructure in addition to impacting the lives and livelihood of citizens. Every year, around 75 lakhs hectares of land is impacted by floods resulting in the loss of more than 1,600 lives and damages to houses and public utilities exceeding over Rs.1,800 crores. Many factors contribute to flooding in cities. Weather related events like prolonged rainfall, cloud burst, sea level rise and storm surges can expose cities to floods. Such events that cause flooding in cities are increasing due to climate change. The Sixth Assessment Report (AR6) by the Intergovernmental Panel on Climate Change (IPCC) highlights an increase in the frequency and magnitude of floods in India. The report also projects varying monsoons with erratic rainfall patterns that can cause floods. Additionally, sea level rise due to global warming is another reason compounding the flood risks, particularly for coastal cities. While the exposure to flooding in cities is projected to increase significantly, other factors like urban development and management play a crucial role in determining the vulnerability of cities to flooding. Urbanization related development like construction in low lying areas, natural drainage and flood plains along with inefficient storm water network are key for flooding and water logging. Further, with urban development, the area of impervious surfaces that deter ground water absorption are increasing, green cover that can absorb and divert flood water is decreasing and water bodies that have the potential to store flood water are disappearing. The outcome from such unplanned development patterns have resulted in severe flooding across many cities in the country. Moreover, water related management in cities like storm water management and maintenance of water bodies like rivers, lakes and canals are important. Efficient management can reduce the risk of flooding but an ineffective management can increase the vulnerability of cities to flooding. Many cities experience the dual challenge of flooding and water scarcity in a cyclic manner through the year. In order to overcome the these challenges, there are numerous development measures that cities can adopt to build flood and water resilience. Some of the measures which have been successfully implemented by Indian and Global cities towards mitigating floods and building water resilience are showcased in this document. The intent is to create a basket of solutions that Indian cities can choose based on their need and priority. Emphasis on replicability and scalability of interventions in the context of Indian cities has been considered while selecting the interventions. Additionally, the cost of implementation, scale of intervention and types of stakeholders involved in implementing flood measures are provided to help city officials plan for similar actions. Please read the section on ‘guide to read the document’ for further details. Overall, the interventions are categorized into the four themes namely Nature Based Solutions, Planning, Technological and Infrastructural Interventions