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