Best practices for flood resilient cities

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.

Many cities experience the dual challenge of flooding and water scarcity in a cyclic manner through the year. In order to overcome these challenges, there are numerous development measures that cities can adopt to build flood and water resilience.

A recent report ‘Catalogue of best practices for building flood resilience’ showcases some of the measures which have been successfully implemented by Indian and global cities towards mitigating floods and building water resilience. 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.

Overall, the interventions are categorized into the four themes namely Nature Based Solutions, Planning, Technological and Infrastructural Interventions.

Nature based solutions

Nature based solutions can help in reducing the impact of floods by diverting and retaining flood water besides slowing down the flow of water. The interventions covered in this document include: wetland restoration, river/lake restoration, restoring natural drainage, terrain riparian, vegetation restoration, mangrove restoration and reviving ecological areas. Restoration includes a variety of ecological, physical, spatial and management interventions aimed at restoring the natural state and functioning of the ecosystem.

It is a cost-effective approach for mitigating floods and the interventions have multiple other benefits such as improving the water and soil quality, reducing heat island effect, improving urban spaces that can be used for recreation and enhancing urban biodiversity. Cities can develop an appropriate blend of various nature based solutions to maximize benefits while minimizing costs.

Planning interventions

Mainstreaming actions for building flood resilience requires appropriate policy regulations at national, state and city level. Along with regulations, strategic planning is crucial to ensure multi-sectoral and multi-stakeholder coordination for successful implementation of flood resilience measures. Studies indicate that poor planning and urban management are expected to cost Indian cities somewhere between USD 2.6 and USD 13 Billion annually.

With increasing risks to floods, a coordinated approach informed by risk assessment, and socio-economic and spatial vulnerabilities can shape land use and steer long term development for building flood resilience. Planning can help cities achieve short and long-term impacts in the physical environment by systematically incorporating nature based solutions, increasing green cover and demarcating flood zones etc.

For instance, the National Water Policy (2002) adopted by the National Water Resources Council (NWRC) stresses the need for developing master plans to control floods. The Standard Operating Procedure (SOP) for flood management by the Ministry of Housing and Urban Affairs (MoHUA) provides a framework for cities to better manage floods. Such plans, guidelines and frameworks are important for cities to develop a roadmap for strengthening flood resilience.

The planning interventions covered in the document are – urban river management plan, river basin management plan, flood resilience strategy, plan for interlinking rivers and canals, and community based flood management plan.

Technology interventions

With increasing risk of flooding, data driven decision-making for flood risk management is proving to be significant. With the advancement in technology, improvements in computational flood models and flood forecasting have emerged in the last two decades. This has enabled cities to develop appropriate policy regulations, planning measures and prioritize investment options. Further, integrating the models with Geographical Information System (GIS) can help identify spatial vulnerabilities and inform emergency flood management.

Technology can also be leveraged to streamline coordination across various government departments, communities and businesses to take timely action in events of a flood. Many cities have demonstrated the use of technology interventions in successfully monitoring, forecasting, assessing risk, communicating warnings and informing preparedness activities for floods.

The technology interventions covered in the document are – hydrodynamic modelling, end to end early warning system, cloudburst management, community based early warning system, data driven flood management, and flood control centre.

Infrastructure interventions

In the context of flooding, infrastructure interventions are structural and engineered solutions that act as flood barriers, convey storm water and also store the water. Some of the commonly used structural flood measures include reservoirs, embankments and levees. These measures not only support in detaining run off water from vulnerable places but also consume less land space. Hence, they are a viable option in areas with high concentration of population and assets to reduce the impact of floods. In addition to building flood resilience, such interventions can be designed as multipurpose structures or buildings that provide recreational and public spaces.

Some of the infrastructure interventions are high on cost and need to be planned and designed to have high impact on mitigating floods. Some of the infrastructural interventions may also require regular maintenance for efficient functioning. Overall, the selection of structural measures needs to be made carefully as they change the pattern of environment and can disturb the natural ecosystem if not implemented properly. The infrastructural interventions covered in this document include: reservoirs, swales, retention area, underground storage structures, water squares, comprehensive drainage structure sand flood mitigation structures.

The cases included in the document are:

• Nature-Based Solutions: Traditional Rainwater Harvesting (Alwar), River Restoration (Chennai), Mangrove Management (Mumbai), Yanweizhou Park (Jinhua), Chulalongkorn Centenary Park (Bangkok), Water Garden (New Orleans), Wetland Management (Kolkata).
• Planning Interventions: Lake Conservation (Udaipur), Room for the River (Netherlands), Sponge City Concept (China), Flood Resilient Communities (Dakar), Water Resilience (Cape Town), Flood Mitigation Plan (Kochi), River Centric Master Plan (Kanpur).  
• Technological Interventions: Flood Control Centre (Bangkok), Bioremediation of Lakes (Delhi), Cloudburst Management (Copenhagen), Data Informed Flood Preparedness (Da Nang), Community Based Early Warning System (Semarang), Hydrodynamic Modelling (Jakarta), Flood Forecasting and Early Warning System (Kolkata), Flood Early Warning System (Guwahati).
• Infrastructural Interventions: The Nile River Basin Management; Water Management Strategy (Singapore); Flood Management Programme (Japan), Cheonggyecheon Restoration Project (Seoul), Underground Flood Defence System (Tokyo), Kibera Public Space Project (Nairobi), Waterproof city (Rotterdam), Storm Water Drainage (Delhi).

The document has an elaborate guide with the seven resilience qualities of the intervention indicated in it. Approximate cost of intervention is highlighted across three ranges of less than INR 10 million, INR 10 million to 1 billion and above INR 1 billion. Further, with an intention to highlight the replicability of intervention in other cities, a range of 1 to 5 is used to indicate the potential for scaling up.

The full report can be accessed here