Here's why Delhi faces repeated waterlogging every monsoon

Here's why Delhi faces repeated waterlogging every monsoon

Despite consistent efforts by the civic body and the Public Works Department, waterlogging still continues in several areas in Delhi following rains in the capital region.

PWD officials and experts concur that even a perfectly clean drainage system can't prevent waterlogging in the city. But why is this the case?

OUTDATED DRAINAGE DESIGN

The primary issue lies in Delhi's antiquated drain design. The current infrastructure was designed to handle only 50 mm of rainwater. Any rainfall exceeding this threshold overwhelms the system, leading to waterlogging.

Additionally, the 'Drainage Master Plan,' which could potentially address these shortcomings, remains unapproved and pending for decades.

NO NEW DRAINAGE PLAN SINCE 1976

According to an anonymous PWD official, the existing drainage master plan dates back to 1976, designed to accommodate the city's population at that time and handle 50 mm of rain within 24 hours. However, during a recent downpour of 228 mm, Delhi was submerged, resulting in 11 fatalities. The PWD manages approximately 2,064.08 km of drains, accounting for 55 per cent of the city's total drainage network, yet fails to mitigate the annual urban waterlogging crisis during monsoons.

INADEQUATE IMPLEMENTATION

Court orders have designated PWD as the nodal agency for a new drainage plan, but so far, only one consultant has been appointed.

This consultant is responsible for drafting the drainage master plan for all three basins with a new design considering Delhi's increased population.

According to S Velmurugan, Senior Principal Scientist, the government has not learnt from past flooding events and continues implementing temporary fixes like silt removal and water pumps.

SEPARATE LAYOUT NEEDED FOR STORM WATER

Kunwar Chandresh, former CPWD executive engineer, emphasised that international standards maintain separate systems for sewage and stormwater to avoid overflow. However, these systems are often combined in Delhi, exacerbating the problem.

A 2018 IIT report recommended prioritising the separation of seasonal stormwater from year-round sewage flow. Although this report was later rejected in 2021 due to data flaws, the necessity for separate layouts remains urgent.

Delhi encompasses 201 natural drains across three basins: Najafgarh, Barapula, and Trans Yamuna.

The IIT report of 2016 identified slope issues in some areas, further complicating efficient drainage.

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