There is urgent need for comprehensive disaster management and infrastructure reforms to protect lives and property from future monsoon fury

In the warming world Sea surface temperature is rising followed by excessive evaporation and deposition of moisture leaden vapours in the form of clouds. When conditions are favourable, incessant rainfall occurs. Many times, half the annual rainfall occurs in 24 to 48 hours. Urban infrastructures are unable to take the challenge; flooding on roads, public places, ground floors and the basement of buildings is quite common leading to disruption of rail, road and air traffic as well as businesses. Rural areas face the brunt of the mayhem; loss of crops, landslides, and landslips in hilly terrain can claim lives and livelihoods and can throw the economy out of gear.

It can put additional stress on the budget as the public fund (taxpayers’ money) has to be diverted for the reconstruction of damaged infrastructures and also for compensating the losses for the private properties. The disaster that hit Wayanad on 30th July claimed more than 400 human lives and injured an equal number has been one of the worst of its kind in living memory.

Big boulders and stones from an 8.26 ha (82600 sq meter) area on the top of the hill located at 1550 meters above the mean Sea level have rolled for 7 km on a downward slope and smashed buildings, damaged roads and bridges etc in three-four villages at 650 meters above the mean Sea level. One ton boulder has attained the energy of 9 mega Joule, which is enough to destabilize and knock down an RCC building in a rural area.  Monsoon mayhem has caused damage in many other places in Western Ghats as well as in the Himalayas. Landslides and damage to roads and bridges have posed a challenge to people and tourists in Himachal Pradesh and Uttarakhand.

In this column let me confine to the issues faced by metropolitan cities and make some suggestions to deal with it. The death of three civil service aspirants in the basement flooding of Rau’s coaching centre in Rajendranagar Delhi last month and also another aspirant dying of electrocution are chilling reminders of the apathy of the civic body. We must know the precautions that must be undertaken by the agencies and the building occupants to make sure that such incidents are not repeated. Civic Body of Mumbai had earlier designed stormwater drains and related infrastructure to take care of 25 mm of rain in an hour.

Severe flooding repeatedly occurring during the past several years has forced them to remodel their drainage system to take care of more intense rains up to 50 mm per hour. However, in places like Mumbai, Ratnagiri, Satara, Mahabaleshwar and many other locations 80 to 100 mm of rain per hour has been recorded. Similarly, places in some other regions of the country are also experiencing frequent cloud bursts resulting in 80 to 100 mm of rainfall per hour for three to four hours. Wayanad tragedy was the result of 570 mm of rain in 48 hours.

All Civic authorities in cities like Mumbai, Chennai, Hyderabad, Bengaluru, Delhi, Gurugram etc should remodel the drainage system to take care of at least 100 mm of rain per hour. The encroachments on storm water drains as well as on lake beds should be removed.

Further, the drains should be regularly de-silted and cleaned up so that plastics, polythene bags silts etc are removed and disposed of at far-off places. The lakes in the cities are balancing reservoirs where the water level should be regulated by opening the sluice gates. De-weeding and de-siltation of lakes are also required to be done periodically to ensure that the water reservoirs are kept clean up to maximum flood level. All the inlets of the lakes are monitored to ensure that none carry untreated sewage into them.

There is the possibility that lake water may enter people’s houses at the time of flash floods; it must be ensured that sewage water does not enter houses. Stormwater drains in metropolitan cities are often found partly encroached and occupied for living by erecting small huts. Such occupants must be rehabilitated elsewhere and drains must be fully opened for flow of water. Let us not forget that the existing stormwater drain is insufficient to take the load of more than 25 mm of rainfall per hour.

Beds of many urban lakes have also been encroached. Lake beds up to high flood levels are meant for storage of water. The reduction in volume for storage indicates that the water flows in the basement and ground floor of the buildings, causing undue hardship for the people. Incessant rains in November 2015 (approximately 483 mm in 24 hours) led to one of the biggest catastrophes in Chennai. 500 people were killed and nearly 10 lakh houses were submerged resulting in the displacement of 1.8 million people. Two reasons were attributed to the disaster.

One was the encroachments on lake beds in Chennai and the other was the delay in regulating the water level in the Chembaram Bakkam reservoir. The situation came under control only when 1.5 lakh cusecs water from this reservoir was released into the Adiyar river.

Many wetlands in Chennai have been occupied by communities. Pallikarnai wetland used to have an extent of over 5000 ha has shrunk to 10% and only 500 ha is remaining as wetland at present. Unless the encroachments are cleared, we are likely to face a similar tragedy in future.Civic bodies while working on drainage systems for stormwater as well as sewer lines must take enough precautions and keep the drains and man-hole covered, so that no person accidentally falls into them and perishes.

When the road is flooded and becomes a flowing river, uncovered drains and sewer lines cannot be identified by people wading through.People in Mumbai, Delhi, Gurugram and many other metropolitan cities find flood water trapped in the basements of their houses. Often they resort to pumping it out, which requires time and energy. It is advisable to construct a sump underneath so that the rainwater can be effectively harvested and later used for various purposes.

If the basement is kept clean, then flood water collected would be of drinkable quality. Several Civic Bodies mandate water harvesting structures along with new constructions while approving Plans. At the implementation stage, however, such structures generally take care of harvesting water from the rooftop and ignore basements, prone to flooding during cloud bursts.

Water harvesting for basements should be made compulsory and must be seriously implemented. Building by-laws if necessary be amended by respective civic agencies to make sure that the basement of the buildings is used for parking vehicles, storing unserviceable items and water harvesting/ storage only. In no circumstances should people be permitted to use it for housing, hotels and businesses.

(The writer is retired principal chief conservator of forests, Head of forest force, Karnataka; views are personal)