Free WATERWAYS

Free WATERWAYS
In the fourth of the series on drains, The Times of India looks at some solutions to prevent flooding along storm water drains, lakes and valleys

Good network of cross drainage system vital
The efficiency of any drainage system in the city is dependent on the network of surface and storm water drains and collecting basins such as tanks and lakes. The salient parameters of the drains are the cross-section, the bed level and the bed slopes.
Any restrictions at the cross-section, due to encroachments, silt build-up, debris or non-maintenance affects the bed level, results in overflow and flooding.
Debris from construction sites is a major menace today and a good maintenance regime of drains is a must. But this is lacking in our city. We only see ad-hoc attempts to solve the problem. What we really need is a master scheme which needs to be implemented in one go and one which will comprise mainly removal of encroachments and obstructions. Regular maintenance of the bed slope and bed levels, ensuring that cross drainage works such as culverts or constrictions above the drains do not restrict the flow, are the other measures.
Whenever roads are surfaced or resurfaced, the geometry of the road profile should be given due attention, which is not the case now. Further, when new layouts are formed, instead of concentrating on maximising the number of sites, efforts should be to maximise the drainage areas.
In a nutshell, the solution lies in a good network, open storm water drains and not closed ones, appropriately designed cross drainage systems, a good maintenance regime and special attention on the good condition of tanks and lakes.
Dr C S Viswanatha | CHIEF EXECUTIVE, TORSTEEL RESEARCH FOUNDATION IN INDIA
Interconnectivity of lakes will stop flooding
Blame it on intense urbanisation, lack of vision, exploitation of natural resources. Flooding in Bangalore is a perennial problem today and there is only one solution — making right decisions to remove wrongs. There are no short term measures.
We need to understand that flash floods occur because there is no place for the water to drain out. Earlier, water used to seep into the earth or join the storm water drain and there on flow into the lake, which are nothing but natural rain water harvesting systems or natural reservoir. Removal of lakes and open spaces are the prime reasons for the present day water problems, whether it is floods or shortage. Flash floods happen due to paved surfaces (urbanisation) and lack of sinks for water (waterbodies and open spaces).
Bangalore city currently has 34 live tanks as against 262 in the mid 80’s. Many of these tanks are either being encroached on or being converted for public utility. The government needs to intervene with appropriate legislation to prevent further encroachment of open spaces and alteration of the topography.
The conversion of waterbodies to residential and commercial areas highlight the poor planning by our present day rulers. When the waterbodies are removed, the interconnectivity is lost among lakes. Take for example, Ulsoor lake: Today it is nothing but an urban bowl. Water enters the lake and that is the end of it. Excess water leads to breaching. Earlier, excess water used to flow out, reach Challaghatta Lake and move on to Bellandur lake. What happened to Challaghatta lake - it is now KGA golf course! This is just one of the cases.
The National Games Village is on Koramangala Lake, Millers Town is on Millers Tank, Subhashnagar Bus Stand (Majestic) on Dharmabudhi Kere...the list is endless.
SOME WORKABLE SOLUTIONS
Ban developmental activities in the catchment areas of Hesargatta lake, T G Halli, etc. to avert water scarcity in the city; Bring in legislation to prevent encroachment of open spaces (waterbodies, parks); make regulatory authorities accountable for lapses; create natural water harvesting systems depending on the space available. This would be the best way of rainwater harvesting as this would help improve the groundwater situation in the region; identify missing interconnectivity among lakes and re-establish them so that water can transfer smoothly from one basin to another basin; remove encroachments on lakebeds and storm water drains with immediate effect.
DR T V Ramachandra | FACULTY, CENTER FOR ECOLOGICAL SCIENCES, IISC
SOLUTIONS FROM PUBLIC AUTHORITY
Expedite work on stormwater remodelling along four valleys to complete before December 2007. Outsourcing precast structures of bridges and culverts needing remodelling to avoid construction and to speed up works. (BBMP has remodelled 35 bridges and culverts out of 110.) Tackle 197 vulnerable spots prone to flooding before May 30. Treat SWDs as public assets rather than dumpyards. Stop dumping waste, building debris and encroachment. Segregation of sewage and stormwater drain network to prevent flow of sullage water in open drains across the city.
STEPS MOOTED BY BWSSB
Remove all obstructions in manholes, underbridges and culverts along stormwater drains. Stop flushing water harvested on rooftops and surfaces into manholes. Clear encroachments along open drains and valleys to maintain their width and carrying capacity. Give impetus to rainwater harvesting, groundwater recharging. Desilt lakes to improve percolation and clear water ways along valleys till the rivers to prevent reverse flow during rains.