Urban Flooding : Management Challenges

By - M Shashidhar Reddy
*Member, National Disaster Management Authority/Convener of NDMA Steering Committee on Urban Flooding./Member, National Disaster Management Authority.

Urban flood disasters are now affecting a large number of people living in urban areas in India. Major cities in India have witnessed loss of life and property, disruptions to transport and power and incidences of epidemics during the monsoons, most notable amongst them being Mumbai in 2005, Surat in 2006 and Kolkata in 2007. The annual disasters from urban flooding are now much greater than the annual economic losses due to other disasters.

Background
In 2001, there were 285 million people residing in 35 metro cities (having a population of 1 million plus). This is estimated to exceed 600 million by 2021 in over a 100 metro cities. There is a marked impact of globalization on city growth and most growth is increasingly concentrated in and around dynamic urban areas, large and small. Rapid urban development and the pressures of population have resulted in constructions in flood-prone areas and the urban population is now more vulnerable to flooding.
A special feature in India is that, heavy rainfall occurs mainly during the monsoon, hence unique solutions and approaches are needed for Indian cities. In addition, the urban heat island effect has resulted in an increase in rainfall over urban areas. Global climate change is resulting in changed weather patterns and increased intensities of rainfall in lesser number of rainfall events during the monsoons. Thus, many of our cities located on the coast, on river banks, on downstream of major dams and even otherwise need to have special provision for mitigation of urban flood disasters. To survive in a global economy, our urban centers should quickly recover from flooding incidences through adequate flood disaster mitigation measures.

Urban Flooding is Different
Urban flooding is significantly different from rural flooding, as urbanization increases flood risk by up to 3 times, peak flows result in flooding very quickly due to faster flow times ( in a matter of minutes), large number of people are affected in dense population clusters and severe economic and infrastructure loss to industry and commerce.
Urban flooding can be reduced with measures like maintaining existing drainage channels, providing alternative drainage paths (may be underground), on site storage of rainwater, control of solid waste entering the drainage systems, providing porous pavements to allow infiltration of rainwater, reserve low-lying areas for playgrounds and parks, using state-of-the-art technologies to address current problems, etc.

Running Urban Centres 24x7
To keep the urban centers running 24x7, flood damages need to be minimized through proper planning and enforcement. Four main objectives have to be achieved, which include a) warming the people of an impending flooding, b) protecting the existing infrastructure, c) maintaining the transport and communication through the worst possible event- with special emphasis on air transport and communications , and d) minimizing urban flooding in future cities/suburbs through improved master drainage plans.

National Guidelines from NDMA
Recognizing the fact that urban flooding is now a major disaster which affects a large number of people, National Disaster Management Authority (NDMA) is now dealing with this as a separate subject, de-linking it from rural flooding. NDMA has initiated the process for evolving National Guidelines for Management of Urban Flooding with the involvement of all stakeholders. NDMA will review present status of Urban Flood management, identify gaps and challenges.
Guidelines will focus on S&T Tools for more effective early warning and monitoring, with state- of- the- art equipment, impact assessment framework, climate change impact. It will also look at optimal design of storm water drainage (SWD) systems, adaptation strategies, management of water bodies, regulation and enforcement, guidelines for new developments, awareness and preparedness, medical preparedness and epidemic control, inert-agency coordinated rescue, response and relief and improved community preparedness and response, besides several other things.