The frequent urban flooding due to flawed and non-existent storm water management in our cities during the monsoon highlights our perpetual inability to recognize the rainwater as a precious resource. It’s a great irony that on one hand our cities are complaining of a rapidly depleting water table and on the other, we are letting the rainwater gets washed away into drains and sewers. In turn, also adding increased pressure over the drainage/sewerage network.
Historically the cities have always had natural storm water outlets culminating into either local watersheds, rivulets, or rivers. Water tends to find its way naturally towards the lower points of the topography. Not too back in history the Baolis and stepped wells were common features of cities designed to redirect storm water into the Groundwater.
However callous human intervention has taken it all away. The traditional system has taken a backseat due to unplanned development. Lakes and ponds no more exist in cities. At the beginning of 1960, Bengaluru had 262 lakes. Now, only 10 of them hold water. In 2001, when the collector of Ahmedabad listed the waterbodies in the city following a high court order, he found that 65 of the 137 listed lakes encroached.
Cities are also replacing the permeable land with impervious surfaces. The problem gets aggravated by the fact that drains do not have sufficient slope to draw water from surface water and channelize it.
By the 1860s, Bengaluru had evolved an intricate system of harvesting rainwater. Laid out in 1866 by then commissioner of the city, Lewing Bentham Bowring, these drains carried rainwater to outlying tanks. But modern Bengaluru discounted this security and is now grappling with severe water shortage. So is Chennai, which has traditionally depended on temple tanks, or kulams lams, for harvesting rain. There are 39 kulams in Chennai, each spanning 0.4-2.8 hectares (ha). The kulams also act as flood-control devices.
Lately, the natural course of storm-water drains, leading to these kulams, has been changed due to unplanned settlements near the catchment areas. The drains now flow directly to the sea without filling the tanks. Storm-water channels also formed an integral part of the forts and palaces of desert cities of Rajasthan. Jaigarh fort in Jaipur is a classic example of this. The fort has three underground sumps, which stored runoff rainwater drained from the Aravallis through well-designed channels. The fort still uses the stored rainwater during peak water scarcity periods in summer.
Urban flooding is absolutely preventable. All that we need to do is to let Storm water find its right of way. Storm water management has two aspectsa-Qualitative and Quantitative. The learned Engineers in our municipal corporations are already taking care of the quantitative aspect.
Importance Of Storm water Management As opposed to allowing for flooding in cities,
Smart storm water management opens up several opportunities including:
1. Channelling it to irrigation systems, where it is needed the most.2. Controlling erosion and making our natural river systems cleaner.
3. Removal of pollutants, since storm water carries a large amount of urban trash along.
4. Flood control and restoring city life to normalcy.
5. Restoring the natural topography of our river systems.
Apart from this, the storm water system also:
1. Makes our homes and land stronger and less prone to water damage2. Lowers property maintenance costs
3. Reduces our water dependence, thus lower water bills
4. Increases the value of our land.
Thank You !!!