Explained: As Delhi gets battered by heavy rains, decoding why trees fall down in cities

Delhi and the adjoining National Capital Region (NCR) woke up on Tuesday morning to streets strewn with uprooted trees and a night without power after a severe thunderstorm and heavy rains hit the city on Monday.

News agency PTI reported that several parts of North Delhi, including Narela, Bawana, Burari, Rohini, and Civil Lines, faced power disruptions primarily due to felling of trees and branches on overhead electricity lines and poles.

An official from Tata Power Delhi Distribution Limited (TPDDL) was quoted as saying on Monday, “Gusty winds, thunderstorm and heavy rain enveloped Delhi this evening, the power supply was affected in several parts of North Delhi. The storm inflicted damages to the electrical network, causing power disruption due to tripping, and falling of trees and branches on the overhead electricity lines and poles.”

Besides power outages, the uprooted trees also caused obstruction of traffic — the trees had uprooted at several spots, including Bhai Vir Singh Marg on Gole Market near the Nepal Embassy and Parliament Street police station as well as Kasturba Gandhi Marg.

Fire Services Director Atul Garg said the fire department was making all efforts to clear the road in central Delhi where the maximum trees fell besides attending normal calls.

A Times of India report said that more than 100 trees had uprooted in the storm that ravaged Delhi-NCR region. Further, it said that in Noida, nearly 50 trees were uprooted and the branches of 60-70 others were broken.

“Our teams are on the field to remove the trees and clear the roads as fast as possible,” Indu Prakash, an officer on special duty at the Noida Authority was quoted as telling Times of India.

The trees keeling over during the squall also led to a death of a man in North Delhi’s Angoori Bagh; a 65-year-old homeless man, who was resting near a tree on a footpath, died after the tree fell on him.

As Delhi-NCR picks up the pieces after the storm and normalcy returns, we take a closer look at why such incidents happen every time there’s heavy rain and what can be done to stop this phenomenon.

Reasons for trees falling over during rains

Serious injuries, fatalities and major property damage can occur when trees come crashing down during high-wind and heavy-rain events.

The most common contributors to trees falling are soggy soil, a compromised root system and asphyxiated trees.

Most trees in major urban cities such as Delhi, Mumbai, Bengaluru have been asphyxiated with concrete — land around their trunk is covered by cement. Trees intake air and water from open ground around them. If this area is covered with bitumen or concrete, capillary water supply is cut causing slow death of trees.

CR Babu, professor emeritus at the Centre for Environmental Management of Degraded Ecosystem in Delhi University, had explained in a report published by The Hindu, “If the roots are not given breathing space, they will decay and easily get infested.”

In fact, there are regulations and laws that have been made to stop the concretisation around trees. The Urban Greening Guidelines, which came into place in 2000, required one to leave six inches of areas un-cemented around the trunk of trees. This was increased by the National Green Tribunal (NGT) in 2013, when it ordered that the space around trees must be concrete-free by one metre.

However, despite the laws and guidelines, areas around trees continue to be cemented, causing them to die a slow death, many of them getting uprooted during storms and gusty winds.

Another reason for the asphyxiation of trees is the lack of proper urban tree management. Dr AN Yellappa Reddy, environmentalist and former IFS officer, blamed it on the way roads and pavements are concreted and asphalted. “Trees are a living entity. They need 400-500 litres of water every day. With no urban tree management, not even a drop of water can get into the tree’s root system.This is why trees with weak roots are getting uprooted with slightest winds,” he was quoted as telling Economic Times.

Soggy soil or poor soil quality is another reason why trees fall down during bad windy weather. Experts note that in strong winds, tree roots are more likely to break free from wet soil than drier soil.

They state that when the soil is completely saturated and the wind is blowing, the movement of the tree causes the wet soil to take on a gravy-like consistency. Once this begins to happen, the tree’s roots are no longer held by the soil, but are rather slipping and sliding through it. At this point, if the wind is strong enough, the whole tree might topple.

In other instances, when soil is excavated for activities like laying cables, pipelines or constructing new roads, the soil is not replaced — making the roots of the trees weak. In some case, contractors actually fill up the land with cement or gravel, which harms the trees.

Large trees growing on heavily compacted soils are also good candidates for toppling in wet, windy weather. Tree roots can only grow in soils that have space for oxygen. The more compacted a soil is, the less pore space for oxygen and the shallower the root system.

Similarly, trees growing in tight spaces are also primed for toppling.

Poor planting techniques and the planting of the wrong type of trees is another reason cities in India witness multiple accidents. For instance, in Mumbai, officials were planting gulmohar trees, which is not suited to the city’s topography.

Hence, growing the right kind of tree rather than the number of trees is more important.

Environmentalists and activists are also of the opinion that many contractors hired by the civic bodies of the cities use wrong methods to prune trees, making them unstable.

Marselin Almeida, a botanist, in a Hindustan Times report said, “Improper trimming forces trees to become slanted. This alters their original form and balance, which leads to tree fall during bad Weather Conditions .”

Save the trees

It is a must that cities do more to save their green lungs as it provides for better air.

Experts state that there are some steps that city officials and planners must follow to save the trees and also stop them from falling over and causing additional damage.

Besides not choking trees by concretising the bases and also maintaining soil quality, officials can replant the uprooted trees wherever possible.

According to an expert, if an uprooted tree had some roots intact, still going deep into the ground, it could be replanted at the same spot, and the tree would survive.

Trees are definitely needed in Indian cities to mitigate some of the negative impacts and social consequences of urbanisation, and thus make cities more resilient to these changes.

For instance, a mature tree can absorb up to 150 kg of carbon dioxide per year. As a result, trees play an important role in climate change mitigation. Especially in cities with high levels of pollution, trees can improve air quality, making cities healthier places to live in.

Also, large trees are excellent filters for urban pollutants and fine particulates.

Research also shows that living in close proximity of urban green spaces and having access to them, can improve physical and mental health, for example by decreasing high blood pressure and stress. This, in turn, contributes to the well-being of urban communities.

It’s time we wake up and realise the importance of trees in cities and do more to protect them from falling over.

With inputs from agencies

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