Water

Future shock: The leaning towers of Najafgarh Jheel

Why construction activity around the southwest Delhi water body is a recipe for disaster  

 
By Ritu Rao
Published: Wednesday 07 October 2020

The Najafgarh Jheel, the second-largest water body in the National Capital Region (NCR) after the Yamuna, is in danger of disappearing due to encroachment.

At one time, the jheel (lake), which lies in Delhi and Haryana’s Gurugram district, was spread over 220 square kilometres. It was fed by the Sahibi river and flood waters from Gurugram, Rewari, Jhajjar districts and northwest Delhi.

From the 1860s onwards, the jheel has been systematically drained either to secure more arable lands or to mitigate floods. There is pressure from the real estate sector to reclaim the jheel land for construction. The jheel today measures a mere seven square kilometres. 

Almost 85 per cent of the world’s wetlands have disappeared owing to anthropogenic pressures. Without immediate intervention, the Najafgarh jheel too will join this ignominious list.

Two narratives

As one moves around the jheel, two narratives are evident. The Delhi side, separated by an embankment for the most part, has been earmarked in the Delhi Master Plan. No largescale construction activity is permitted in this zone.

However, on the Haryana side of the jheel, an altogether different story emerges. Globally, no construction activity is permitted within the High Flood Level (HFL) line attained in a water body in the last 100 years.

While similar views have been enunciated in the guidelines of the state environment impact assessment authority of Haryana, it omits to mention the HFL value of 212.5 metres above mean sea level (mamsl) for the jheel, as recorded by the department of irrigation and flood control of Delhi. This omission enables project proponents to affirm compliance to this clause in letter, without adhering to it in spirit.

According to Manu Bhatnagar, principal director, Indian National Trust for Art and Cultural Heritage or INTACH, this line should have been taken into account to create a ‘no construction zone’ within the HFL.

If the HFL line is overlaid on the 2031 Master Plan of Gurgaon, it cuts across sectors 101,102, 103, 104, 105, 106, 107, 108, 109, 110, 112, 113, 114, 115. Barring four sectors (sectors 101, 107, 114 and 115), the remaining are either already built upon or construction is underway.

100-year High Flood Level at 212.5 mamsl overlaid on Gurgaon Master Plan 2031

Source: INTACH

I inquired at one of the residential societies located near the jheel only to find that their basements were fitted with de-watering pumps to eject flood waters. This implies that developers are situating their projects within the HFL of the jheel despite being aware of the risk of flooding.

After the recent spell of rains in August 2020, a spate of complaints of seepage and flooding of basements in the residential projects in Gurugram near the Najafgarh jheel were received. Acting on these complaints, the Department of Town and Country Planning of Gurugram district has decided not to give any fresh approvals to builders for projects near the Najafgarh jheel.

Shaking ground

In June 2020, an earthquake of 4.7 magnitude struck Gurugram. This was one of a series of minor and moderate temblors to have hit parts of northern India since April this year.

According to some geologists, these tremors in the Delhi-NCR may be a precursor to larger earthquake(s). Both Delhi and Gurugram fall in the seismic zone IV (high damage-risk zone). The NCR is a Central planning region centered around Delhi and encompasses several districts of Haryana, Uttar Pradesh and Rajasthan.

The highest magnitude earthquake, experienced in the NCR in a century, was measured at 5.6 on the Richter’s Scale in 1960. Records reveal that this quake damaged some buildings in the New Delhi area. At that time, Gurugram was a village and escaped almost unscathed.

According to a study by National Institute of Technology (NIT) Kurukshetra, it has been predicted that in the coming 50 years, the region maybe hit by a severe earthquake of over 6.0 magnitude on the Richter’s Scale with an 80 per cent probability of the seismograph recording a 7.0 magnitude.

While earthquakes do not kill people, buildings do. In such an eventuality, both Delhi and Gurugram are bound to suffer huge losses. This is attributable to the usage of poor construction material and non-compliance to building safety codes. High rises are particularly vulnerable to collapse.

Seismic Zones of India

 

Source: Criteria for Earthquake Resistant Design Structures, BIS 2016

Ground as liquid

This threat of earthquake is further compounded in the vicinity of rivers or lakes. The vigorous shaking of the ground evidenced during earthquakes, when coupled with the saturated, loose, or sandy soil endemic to areas around water bodies, results in that ground turning into a slurry.

The ground starts behaving like a liquid owing to a process known as liquefaction. In the NCR, apart from the Yamuna river belt, the areas adjoining Najafgarh jheel are particularly vulnerable to this process. If this unfortunate combination of events come to pass, it may result in the tilting or total collapse of buildings in the area.

The aforementioned NIT Kurukshetra study was initiated in 2014 for screening of liquefiable areas in Haryana. It took into account lithology, geomorphology, depth of ground water table and seismic history for assessing liquefaction potential in Haryana.

This study concluded that the district of Gurugram has been observed to be moderately susceptible to liquefaction during earthquakes. This moderate susceptibility was primarily attributed to the deep-water table in Gurugram.

However, a Central Ground Water Board report of 2012 indicates that the areas adjoining Najafgarh jheel have a shallow water table that is less than 10 metres below ground level (mbgl). 

The above study had posited that liquefaction is most likely to occur in areas where the ground water table lies within 10 metres of the ground surface.

An interaction with villagers from Khekri Majra on the Haryana side of the jheel, revealed that depth to ground water table was just 1 mbgl in the immediate aftermath of the monsoons. Thus, it may be surmised that the areas adjoining Najafgarh jheel are more susceptible to liquefaction.

This is further corroborated by the Seismic Hazard Microzonation of NCT Delhi, 2016, which reveals that a very small part of southwest Delhi where the Najafgarh jheel lies, falls in the high hazard zone marked in red on the map. Therefore, leaning towers of Najafgarh jheel, in the event of an earthquake, is not beyond the realm of imagination.

Liquefaction Hazard Index Map

 

Source: Seismic Hazard Microzonation of NCT Delhi, National Center for Seismology, et al,2016

An impending disaster

Given the susceptibility of the Najafgarh jheel area to liquefaction, as elaborated in the aforesaid scenario, construction in the jheel area is a big no-no. Regrettably, this threat is going unheeded.

This incredible shortsightedness may yet wreak unimaginable havoc on the buildings in the area and cause incalculable damage to life and property. Even if we were to discount the probability of an earthquake, the threat of floods, subsidence, soil instability, etc cannot be ignored.

Water bodies and their adjoining wetlands are excellent at purifying wastewater, recharging aquifers and harbouring biodiversity. They also act as catchment areas preventing floods. But they are almost always terrible places to build or construct.

Ritu Rao is a PhD scholar at Teri School of Advanced Studies and works on urban water bodies

Subscribe to Weekly Newsletter :

Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.