Urban Flooding: Causes, Impact & Mitigation Strategies in India
Description
Description: Explore the reasons behind urban floods in India and the measures taken to tackle this issue, including rainwater harvesting and conservation initiatives.
Urban Flooding: Causes, Impact & Mitigation Strategies in India
What are Urban Floods?
According to NDMA, Urban flooding is significantly different from rural flooding as urbanization leads to developed catchments, which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times.
Floods are basically result of both meteorological and hydrological factors.
• Meteorological factors: rainfall frequency and intensity, storms, temperature etc. and hydrological factors are associated with groundwater levels, extent of impervious surface etc.
• Anthropogenic factors: land-use changes, exploitation of floodplains by construction and similar activities, poor solid waste management, and destruction of drainage complicate the system.
Major reasons are:
• Destruction of wetlands: Lakes and wetlands are an important part of urban ecosystem. They perform significant environmental, social and economic functions, ranging from being a source of drinking water, recharging groundwater to acting as sponges, supporting biodiversity and providing livelihoods. Destruction of wetlands leads to decreased absorbing capacity leading to floods. Ex: Hyderabad has lost 3,245 ha of its wetlands. The vast network of lakes in the city had allowed the excess water from one lake to follow into another and eventually into the Musi river. With the destruction of this network any amount of heavy rains leads to flooding of the city as seen in 2016. Bengaluru, which had 262 lakes in the 1960s, has only 10 lakes that can be called healthy.
• Concretization: Management of Urban Flooding report, published by the National Disaster Management Authority in 2010, says that concretisation is a major problem in many cities and towns. concrete jungles obstruct and encroach upon the natural flow of water bodies and create pockets that trap water, which increases the flood intensity.
• Destruction of river basin area of rivers flowing in the cities: Natural streams and watercourses, formed over thousands of years due to the forces of flowing water in the respective watersheds, have been altered/reduced because of urbanization. There have been large scale encroachments on the natural drains and the river flood plains. Consequently, the capacity of natural drains has decreased, resulting in flooding during heavy rains. Ex three rivers in the Chennai city—Cooum, Adyar and Kosathalaiyar—are highly encroached upon and that has reduced the amount of water runoff into the Bay of Bengal. Kashmir floods of 2014 is the result of unplanned urbanization and encroachment of Jhelum flood plains decreasing its carrying capacity
• Migration: Explosive increase in the urban population without corresponding expansion of civic facilities such as adequate infrastructure for the disposal of waste. The sewerage generated by the people gets mixed with the water and clogs the natural channels and storm water drains leading to flooding when it receives excessive water. Guwahati’s Deepor beel lake is used by the municipal corporation to dump solid waste since 2006.
• Construction of dams on the river beds: Increased water that is released from these dams floods the low lying areas.
• Unmindful sand mining from the catchment areas and river beds also reduce the river absorbing capacity of excess water leading to floods during heavy rains. Vembanad Lake on the outskirts of Kochi has water level halved its intial level after the mining activity.
Steps taken to tackle urban flooding
• Master Plan for Artificial Recharge to Groundwater – 2020: It has been prepared by the Central Ground Water Board (CGWB) in collaboration with States/UTs. The plan aims to construct about 1.42 crore rain water harvesting and artificial recharge structures in the country to harness 185 Billion Cubic Meter (BCM) of water.
• The Government of India is implementing Jal Shakti Abhiyan (JSA) in the country in which special emphasis is being given for rainwater harvesting/groundwater recharge.
• The Amrit Sarovar Mission has been launched with an aim of developing and rejuvenating 75 water bodies in each district of the country.
• Under the Atal Mission for Rejuvenation and Urban Transformation (AMRUT) 2.0 Scheme, provisions have been made for harvesting the rainwater through storm water drains into the water body (which is not receiving sewage/effluent) & creation/ strengthening of storm water drains around the water body.
• Model Building Bye Laws (MBBL), 2016: It has been formulated by the Ministry of Housing & Urban Affairs (MoHUA) for the States/UTs.As per MBBL, all buildings having a plot size of 100 sq.m. or, more shall mandatorily include the complete proposal of rainwater harvesting. 35 States/ UTs have adopted the features of the Bye Laws.
• National Water Policy (2012) advocates that the conservation of rivers, river corridors, water bodies and infrastructure should be undertaken in a scientifically planned manner through community participation.
