Urban Flooding as a Result of Improper Urban Planning
By: Khushi Somani | Date: 7th December 2020
Worldwide there has been an increasing trend of Urban flooding, with resultant damage, due to climate change and urbanization. One might think that Urban flooding is the flooding that happens in the Urban areas but it is much more than that.
This isn’t what happens when a river overflows its banks or when a hurricane drives a storm surge across a coastal neighborhood. Urban flooding is the result of the excess surface runoff water in developed areas where water does not have any place to go.
When during intense heavy rainfall conditions, the existing drainage system fails to accommodate the rainwater, the excess water overflows and inundates the urban structures and regions resulting in Urban flooding.
Increasing Urbanization coupled with poor Urban planning is one of the major factors resulting in Urban Flooding. Impervious surfaces compact the soil and obstruct percolation of water and insufficient and inadequate stormwater drainage capacity increases surface water runoff leading to floods in Urban Areas.
UNEP recognizes that integrated planning is an ideal entry point to ensure environmentally sensitive urban development.
Urban flooding as a result of improper urban planning in Pune:
According to 2011, Census of India, Pune district is the fifth urbanised district in Maharashtra state with an urban population of 60.99 % and the eight most urbanised district in India. The growth of Pune city has been phenomenal in the last few decades.
This has considerably increased the impervious surfaces leaving very little room for green spaces or stormwater management facilities. The World Urbanisation Prospects predict that the whole Pune urban agglomeration will reach 8.1 million inhabitants by 2030.
This rise in Urbanisation has put pressure on land and water resources and also resulted in climatic changes. Rainfall has been increasing for the last five years except 2018, when there was a drought. In 2019, Pune received 1561 mm of rainfall, higher than the average of 721mm.
This year too, Pune has received intensive rainfall and along with it floods too. This increase in rainfall is due to climate change. There are less rainy days, but the intensity of rain on the rainy days are severe.
Due to incessant rain and failure of proper urban planning to contain these heavy rains in Pune, there has been urban flooding.Most dams in the outskirts are full and on top of this, the storm water drainage system in the district is still ineffective.
No thought has gone into planning the city’s drainage system and water logging and flooding are the consequences of it. The nullahs are very narrow and therefore at some places even a small amount of rainfall results in overflowing of these nullahs.
It is very important to have an integrated planning of the entire drainage system and increase the width of the nullahs, so that the water is drained and does not get accumulated.
The total number of closed drainage is 62-8, open drainage is 13- 5, and no drainage is 23-7. The total existing network coverage of storm water drainage in the city is 55% as against 100% requirement in service level benchmarking criteria specified by the Ministry of Urban Development.
The incidence of flooding areas is as high as 52% as against the zero percent requirements specified in the norms.However, some experts believe that even 100% proper drainage system in Pune will not stop the flooding.
Heavy rainfall resulting in flooding of city areas over the last few years has brought into light that impervious surfaces have fundamentally altered the way water moves through the landscape.
Earlier, roads with 12m width in Pune had soil on the sides enabling water to percolate underground. But now, we have end-to-end concreting.There is absolutely no space for water to seep in the ground which increases the surface water run-off, and further causes floods.
If we look at the Kothrud region in Pune, unpaved areas have now transformed into paved areas like footpath.The paved areas increase runoff by restricting water from seeping underground.
After witnessing how improper Urban planning has aggravated the situation of Urban flooding in Pune, the PMC as suggested by the UNEP should initiate an integrated Urban development scheme by including all the stakeholders and actors. There is a need to widen the nullahs and also reduce the concretization of all the pavements.
A systematic drainage system must be implemented and constructions along the nullahs should be prohibited as they result in the blockage of these nullahs.