chances it gets flooded. For example, in 2012, Jaipur received 170 mm of rainfall in just two hours; similarly, Chennai was severely affected due to heavy rainfall in December 2015, and in 2016, Gurugram( Gurgaon), Bengaluru and Hyderabad have witnessed severe disruptions. So, in my opinion, in today ' s times, all cities are equally vulnerable to flooding- be it coastal cities, inland cities, hilly cities, cities on the banks of major rivers or near dams / reservoirs.
Q. Talking about infrastructural improvement for mitigating the risk, what are the major infrastructural improvements that should be brought about in urban planning at various levels?
A. To avoid urban flooding, several infrastructural improvements are required. Firstly, the existing drainage path should be well demarcated. There should be no encroachments on the natural drainage channels of the city. Secondly, a large number of bridges, flyovers and metro projects are being constructed with their supporting columns located in the existing drainage channels. This can be avoided using proper engineering designs, such as cantilever construction. Storage of rainwater in tanks at the rooftop, intermediate, ground or underground levels can reduce the overflows and help in reducing urban flood volumes.
Storage or holding ponds should also be provided at judiciously selected locations to store water during heavy rainfall so that it does not cause downstream flooding. Once the rain subsides, the water can be released gradually.
It has also been observed that roads are surfaced and resurfaced several times, thus increasing their level above the plinth-level. The Indian Roads Congress has recommended that whenever a road is resurfaced, the existing layer be scraped first and then the new layer be laid. This shall ensure that the plinth level and the road level remain where they were prior to the resurfacing. Also, various cities, across the world, have constructed porous pavements. These allow the water to gradually infiltrate into the underlying soil thereby maintaining the pre-development sub-soil water conditions.
Q. Will the instances of urban flooding increase in the future if the current trends continue?
A. If we take appropriate measures, we can ensure that the flood incidences remain within tolerable limits. The Intergovernmental Panel on Climate Change( IPCC) has indicated that in future, there could be increase in instances of heavy rainfall in shorter spans of time. This means that our existing drainage systems have to be redesigned to accommodate the increased flow-levels. This can be done either by resizing the drains or by judiciously integrating the best management practices into the drainage infrastructure.
Q. What is that first basic issue that needs to be addressed at the individual, community and authoritative levels?
A. Each one of us should realize that disasters like floods and earthquakes can happen anytime. Just like we take life insurance and motor vehicle insurance, we should also insure our belongings against natural disasters and be prepared for such an eventuality. Obviously, if we know the flood risk map of our city, then we can avoid living in the low-lying areas. Alternatively, future constructions in low-lying areas should be on stilts.
At the community level, people should spread awareness and be ready to respond to a flood as a community. Schools have a greater role to play- as children need to be sensitized not only about floods but other disasters as well.
November 2016 21 www. smartgovernance. in