Urban Flooding

  • Last Updated : 15-Sep-2022
  • Environment
  • 2520 views
Urban Flooding

When there is heavy and/or sustained rainfall, urban flooding is triggered, which overwhelms the drainage system's capacity.
It is significantly different from rural flooding as urbanisation leads to developed catchments which increases the flood peaks from 1.8 to 8 times and flood volumes by up to 6 times. Consequently, flooding occurs very quickly due to faster flow times, sometimes in a matter of minutes.
In recent years, there has been a growing pattern of urban flood disasters in India, with major cities such as Mumbai and Chennai seriously affected.
Global climate change leads to changed weather patterns and increased episodes of high-intensity rainfall events that occur in shorter periods of time, which has been the key reason behind this rising urban flooding frequency.
 
REASONS BEHIND FLOODING URBAN:
Ecological Factors:

  • Strong and frequent precipitation. E.g. Inundations of Srinagar.

  • Synchronization of runoff from separate watershed parts.

  • Glacial Lakes Bursting. Uh. E.g. The Glacier of Chorabari in Uttarakhand.

  • Small-scale storms

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Anthropogenic Factors:

  • Bad urban planning: the inability of states to implement zoning has led to a rise in floodplain invasions, often allowed and properly approved by planning authorities.

  • Encroachment of floodplains-e.g. Most of the exurban development of Mumbai has been in townships along the Ulhas River, with little respect for the river system 's integrity.

  • In 2015, Maharashtra deleted its River Regulation Zone policy-a move that residents are now protesting near the Ulhas River and agreed to construct a new airport on low-lying land in Navi Mumbai.

  • Inefficient management of religious events such as Nasik's Kumbh Mela. This results in unnecessary river concretization, which narrows their channels down.

  • Surface sealing (which increases run-off) due to urbanization.

 
Deforestation:

  • The Mumbai Metropolitan Region Development Authority (MMRDA) reported in a March 2015 study that forest cover in the MMR had dropped from about a third of the total area in 1987 to 21% in 2015.

  • Urban Heat Island Impact- As a result, rainfall has risen in and around urban areas.

  • Insufficient disposal of solid waste-and its root segregation. This results in drains being blocked.

  • Poor implementation of flood control schemes that took 56 years to complete, such as the Narmada River Project.

 
Measures to prevent Urban Flooding:
> Framework and Contact for Early Warning:
The distribution of flood alerts using a wide variety of the new technology must be carried out. This will assist in delivering information in real time where conventional systems struggle.
 
> Urban Drainage System Design and Maintenance: Careful drainage system maintenance is important to ensure that water is not collected in one location. Hydraulic roughness is exacerbated by solid waste, creating blockage and generally reducing flow capacity. To allow the free flow of water, these drains need to be cleaned on a regular basis.
 
> Rainwater harvesting: Groundwater recycling has declined due to urbanisation and the peak runoff from rainfall and consequent flooding has increased. The twin objectives of lowering the peak runoff and raising the ground water level will be fulfilled. In India, several municipal corporations have already made it compulsory to collect rainwater.
 
> Protection of water sources: In the management of urban flooding, urban water bodies such as reservoirs, tanks and ponds also play a very important role in limiting stormwater runoff by collecting it.

 
Yokohama Strategy:
> The Yokohama Strategy for a Safer World: Guidelines for Natural Disaster Prevention, Preparedness and Mitigation and its Plan of Action adopted in 1994 provides landmark guidance on reducing disaster risk and the impacts of disasters.
> The review of progress made in implementing the Yokohama Strategy identifies major challenges for the coming years in ensuring more systematic action to address disaster risks in the context of sustainable development and in building resilience through enhanced national and local capabilities to manage and reduce risk.

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