Why does Silkboard always flood?

BANGALORE: When it rains heavily, the abysmal manner in which the city has been planned stands pitifully exposed. Storm water drains overflow, roads turn into rivers, people are stuck for hours and life comes to a standstill. Particularly affected are the southern parts of the city which fall under the Koramangala-Challaghatta valley, also called the Bellandur catchment area. Extending up to about 280 sq. km., the catchment area is one of the largest wetlands in the city. It comprises Puttenhalli, Varthur and Hulimavu chains of lakes and includes 22 tanks. What this also means is that any unplanned development activity in this ecologically sensitive area can affect adversely several parts of the city, which fall under the catchment area. As many as 41 wards are part of the catchment area including Gandhinagar, J.P. Nagar, Jayanagar, Lakkasandra, BTM layout, Madivala, Koramangala, Airport, Shanthi Nagar, Richmond town, Sampangiramnagar, Shivajinagar, Ulsoor and Devarajeevanahalli. But the city’s unplanned growth, significantly concentrated in the catchment area, has meant that every time it rains heavily, the much-neglected lakes in this area such as Arakere, Begur, Puttenahalli, Madivala and Agara overflow, causing flood-like situation in surrounding areas. Tracing the implications of the haphazard development, a report prepared recently by the Centre for Ecological Sciences at the Indian Institute of Science says that land use changes have resulted in the alteration and even loss of natural drainage networks. “There are no mechanisms for the excessive storm water to drain and thus the water stagnates flooding the surroundings itself,” the report says. Titled “Environment Impact of Development Activities in the Bellandur Catchment Areas,” the report says that the alteration of landscape topography has resulted in “the storm water runoff to take a new course that might get into the existing residential areas.” Remote sensing data for the catchment area in 1972 showed that the network of tanks in the catchment area were well connected to each other as well as the vegetation along the drainage linking these tanks. In contrast, data from 2000 shows that the entire catchment area had succumbed to urban sprawl with water bodies, vegetation and drainage disappearing. “The city has over the past twenty years received more than 110 mm of rainfall on a single day on at least four instances. This kind of rainfall is enough to fill up all the tanks in the city, even if they are totally dry. Earlier, excess water flowed from one lake into the nearby lake. Water has followed this course for hundreds of years and the development activities in the recent decade will not make it alter its course,” says H.S. Sudhira, land use researcher from IISc. He further adds: “If we want to prevent flooding, we must ensure that some low lying areas are evacuated and drain management taken seriously.” Until then, rain woes will continue to plague the hapless citizens of the IT city. Source: The Hindu

Why are the authorities not taking pre-emptive steps against water stagnation in Bangalore? Swati Shivanand wades through ... At Puttenahalli, a man accompanies his brother, wading through stagnant water of three days with a bucket of fresh water so that his sibling can wash his feet at a dry place and go to work without smelling. Areas are flooded in J.P. Nagar and the instant solution is to dig up a road to convert it to a drain, and never mind that the residents have to go without power for three whole days. An important link road at Bhadrappa Layout is closed and pedestrians are forced to negotiate over the treacherous parapet of a bridge, where one wrong step could land them right into the drain. After the deluge in 2005, it probably would not have been too much to expect that flooding such as last weekend’s do not recur, at least as often. So why does Bangalore take a beating every time it pours? Have the administrators started to look at long-term solutions or are they merely adapting? Public Eye explores possible solutions to mitigate rain misery. Pretty pavements With an increase in impervious surfaces such as roads and pavements, rain water finds no way to seep into the ground. “A gradual fall in vegetation and natural surfaces has meant there are no sinks to absorb the rain. Chances of flash floods increase,” says T.V. Ramachandra from Centre for Ecological Sciences at the Indian Institute of Science. Granite slabs on pavements are being replaced with interlocking tiles, as part of beautifying the city. “These surfaces are feasible in countries abroad because they do not receive as much rain as we do. We need pavements that allow for water to seep in and not interlocking tiles that rainwater merely runs over,” says Meera Baindur, an environment researcher. Drains Overflowing drains have always been held up as the main culprit for flooding in the city. Tertiary drains carry runoff water from residential areas to secondary ones. These are then linked to primary storm water drains that carry the runoff to lakes. “In many areas, we found that the tertiary drainage system was completely absent,” says Raja Rao, who led the expert committee constituted by the Karnataka High Court to look into the state of roads in Bangalore. Only if we evolve an effective system to carry run off water from localities can we control flooding to a large extent, he says. Critical about the way drains are laid, Capt. Rao said the current method is to lay a uniform-sized drain along the road. “But the drain size must be augmented as it goes along because the amount of water that flows into it increases.” For clogged drains, the committee had recommended that mechanical screens be installed to permit free flow of water. Preserving lake ecology With lakes being the final destination for storm water drains, preserving water bodies assumes more significance. Even so, there continue to be more instances of lake beds being encroached than of restoration of lakes. There are even fewer attempts to restore the now degraded links between the lakes. “We simply must link our lakes again. Otherwise, the ones remaining will turn into water bowls that dry up when there is no rainfall. Eventually they will lose their water-holding capacity completely and rain water will have to find its way to low-lying areas,” says Prof. Ramachandra. Consider this: J.P. Nagar and areas around are flooded constantly because the large amount of weeds covering Puttenahalli Lake has diminished its water-holding capacity. Majestic and surrounding areas are under water because the Kempegowda bus stand has been built on Dharmanbudhi Tank. Madivala, Arakere, Hulimavu, Begur, Puttenahalli, Sarakki and Lalbagh lakes overflow into surrounding residential layouts because the links between them have been broken. With the city at a crucial juncture of its development, the huge investments in its infrastructure could come to naught if severe action is not taken against authorities who have been blatantly allowing encroachments and ecological parameters are ignored while chalking out long-term solutions. ---------- more on this tomorrow ...