Urban Floods

Tide–Rainfall Flood Quotient


From UPSC perspective, the following things are important :

Prelims level : Tide–Rainfall Flood Quotient

Mains level : Flood management

To understand if a coastal city is more prone to floods caused by tidal events or extreme rainfall, a team from the IIT Bombay devised a new metric or measure called the Tide–Rainfall Flood Quotient.

Try this PYQ:

The 2004 Tsunami made people realize that mangroves can serve as a reliable safety hedge against coastal calamities. How do mangroves function as a safety hedge?

(a) The mangrove swamps separate the human settlements from the sea by a wide zone in which people neither live nor venture out

(b) The mangroves provide both food and medicines which people are in need of after any natural disaster

(c) The mangrove trees are tall with dense canopies and serve as art excellent shelter during a cyclone or tsunami

(d) The mangrove trees do not get uprooted by storms and tides because of their extensive roots

Tide–Rainfall Flood Quotient

  • Using the past rainfall data, tidal data, and topography of the region one can apply this framework to pinpoint the major factor at play.
  • This quotient helps understand the main driver of the flooding events for effective disaster management.
  • It considers three geographically diverse flood-prone coastal regions – Mithi Catchment in Mumbai, , Jagatsinghpur District in Odisha, and Greater Chennai to test their new metric.
  • The new method helped classify these regions into ‘storm-tide dominated’ or ‘pluvial (rainfall) dominated’ regions.
  • In Mithi, they found a devastating impact of storm-tide reaching even up to a distance of 7 km from the coastal boundary.
  • It concluded that Mithi catchment was ‘storm-tide dominated’, while Jagatsinghpur and Chennai were ‘pluvial dominated’

A tool for flood management

  • This metric can help disaster management experts in framing better flood risk management systems directed towards long term planning.
  • For storm-tide dominated regions, severe flood hazard can be alleviated by building coastal defence structures such as closure dams, tide breakers, and storm-surge barriers at appropriate locations.
  • The tide and surge forecasting systems in these regions should be equipped with state-of-the-art ocean circulation models.
  • On the other hand, for pluvial dominated regions, structural measures such as rainwater storage structures, lakes, and detention basins should be prioritized in the flood management plans.
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