Managing urban flooding with nature inspired design.
Relentless rains have made the recent monsoon season a nightmare for urban dwellers of major Indian cities. India’s tech capital Bangalore and India’s financial capital Mumbai had come to a complete standstill this monsoon season during heavy downpours. Chennai, Hyderabad, Ahmedabad, Pune and Chandigarh have battled similar civic crisis. The chaotic scenes of urban flooding seem straight from a horrific dystopian movie. But such images of our cities are maddeningly familiar every monsoon. According to ecological experts, the original sin that have made urban floods all too common in most Indian cities is because we have often built extensively over wet lands and natural water bodies. These wetlands were where the water would naturally drain, get stored and spill over during high rain events. Today, these are some of the most water-logged neighborhoods in our cities. ST Bed Layout in Bangalore’s hip start-up district which was flooded extensively in the recent rains was once a water body.
Secondly, decaying and garbage clogged storm water drain networks add to the crisis as there is no way for the water to drain out. Poor desilting of the city’s clogged water networks like creeks, rivers and lakes heighten the crisis. Mumbai’s Mithi River can’t function as the city’s drainage sink when it’s jammed with silt and garbage. Lastly and most importantly, the rise in intensity of urban flooding is because of our fondness for concrete over green spaces. The overwhelming rise of impervious surfaces in our cities from buildings, roads, sidewalks, parking lots has intensified flooding. Our cities are rapidly losing spaces that act like a sponge and absorb water. Natural ground cover has only 10 % water run-off and absorbs/evaporates over 80 % of water from a rain event while impervious concretized cities have over 55% run off. Consequently, floods get escalated in urban areas.
The technical solutions to address this range from barring construction on wetlands, fixing the storm water drainage networks, de-clogging water bodies and bringing nature into urban areas to act as a natural sponge. The reason Indian cities continue to fail is not for the lack of technical solutions. We fail due to lack of political drive and complete failure of governance. All of us have to devise innovative ways to implement these solutions and establish accountable and responsive governance structures that deliver. Because even as we start to combat these increasingly common rain led disruptions; Climate scientists are already warning us to anticipate 30% heavier rains in the future along with more extreme climate events. So we don’t just have to prepare our cities to address current challenges but will have to develop plans & policies to address a future with extreme weather events.
Cities around the world are coming up with innovative ideas to future-proof their city from extreme climate events. The Danish capital of Copenhagen is at the forefront of such innovations. In 2011, a 3-hour rain event caused the city over 1 billion USD worth of damage. “Climate change is real and upon us. We have dealt with major cloud burst events. Copenhagen needed to transform to deal with this new reality.” Says Mayor of Environment Morten Kabell. The city designed “green,” nature-based structures to manage rain water. No major city had tried using nature systems i.e. plants and water to battle extreme weather events. “We could have used more engineering solutions and built more sewers or levee dikes. Instead we opted for nature based engineering. This solution also costs only 1/3rd of the conventional approaches” He explains. While this may not fully protect cities like Mumbai from sea water rise; it is an approach that can alleviate flooding in most cities.
It is a revolutionary change from traditional approaches to dealing with excess water through bigger sewers. This plan imagines the neighbourhood becoming into a temporary Venice or a water park during a heavy storm event. The city has developed a comprehensive mater plan for rain water management. The plan consists of green streets, green urban squares, and cloudburst streets that divert rainwater away from the city when extreme rainfall events occur. The integrated system of rain gardens on streets act as streams during rains. The pocket parks and squares can transform into retention areas and water basins. The plan also features “cloudburst boulevards” which ordinarily function as streets with raised sidewalks that will transform into canals moving rainwater away from the city into the harbour during heavy rains. The city’s first pilot was implemented at the St. Kjeld neighbourhood where paved squares were replaced with green. The sidewalks were slightly raised in the center to allow water to run off to the sides and leave walkable paths. Last year, the St. Kjeld Climate Quarter passed the test when a storm struck and basements remained dry even as the square became a mini water park. The Copenhagen model serves as an inspiration to many cities that are attempting to tackle climate change.
