To stall gushing waters

CHENNAI: For the past few years, the city has suffered, not just because of the pandemic but the flooding that was caused by heavy downpour during the monsoon season.

Seasonal flooding aside, it’s the trauma of having to see their homes, personal belongings and establishments destroyed that has plagued the denizens of Chennai.

This year, they can rest easy, it seems, as the Water Resources Department (WRD) has commenced flood mitigation work at Porur lake, Kolathur lake, Adyar river and Kosasthalaiyar river.

Additionally, as part of the pre-monsoon work, the department is awaiting a GO to desilt channels across the city.

Usually, as pre-monsoon work, the river channels will be maintained to prevent low-lying areas from inundation.

However, with intense rainfall and reservoirs catchment reaching almost full capacity, it forced the department released more cusecs of water.

This led to flooding in many parts of Chennai. To avoid such a situation this year, the government has allocated Rs 434 crore for permanent flood mitigation works.

Porur lake

One of the most impacted areas during the monsoons in 2021 was around Porur lake — Iyyappanthangal, Srinivasapuram, Baraniputhur, Pattur and Kolunthuvancheery. Because the patta land was encroached and turned into residential places, the river flow was blocked and the hydrology flowed through Ramapuram and Manapakkam to Adyar River.

“Later, the encroachments were identified, notices issued, and eviction was completed. The flood mitigation work costs Rs 100 crore. We’ll construct box culverts in a push-through system, where the channel will be laid between Thanthikal channel and surplus channel. And another one will be built between the lake and Ramapuram stream,” said a senior WRD official.

Usually, the Porur tank gets filled during the monsoon and in summertime, it will be drought.

Few years ago, after Metro Water department released water in the tank, at least 75% of water remained in the water body.

But for the past 3 years, due to the heavy spell, the Porur lake has been full. There’s no space to accommodate excess water in the catchment. It’s one of the reasons for flooding in the locality,” explained the official.

The tank has a weir that’d be converted into a gate. So, whenever water level increases, the gate will be opened for discharge.

The work is expected to be completed by September 30.

There won’t be inundation during this monsoon season especially at these impacted areas.

Unlike previous years, north Chennai was severely impacted during the northeast monsoon last year. So, the department commenced work to enhance Kosasthalaiyar River recently.

“Several works such as bund strengthening are going on between Velivayal (Ponneri) and Manali, which will be increased up to 3-4 metres. The obstruction that blocks water flow will also be removed. We’ve also started flood mitigation work to ensure there’s no inundation this year,” said another WRD official.

The department has been carrying out the work even at Kolathur and Pallikaranai, which were inundated so badly that people were unable to step out of the house for over a week. As the water did not drain, officials did not return to visit the spot.

Now, they decided to improvise the drains which are not proper due to encroachments. Though illegal buildings were removed recently, another part will be evicted soon.

The official explained, “In Pallikaranai Marshland, ideally, the water should reach Madurampakkam and Ottiyampakkam. But these are not connected by any channel. That’s why, we’re constructing an artificial channel at a total cost of Rs 164 crore. The goal is to have zero flooding during this monsoon season.”

However, it seems that residents around the Buckingham Canal are likely to suffer even this year, as the WRD is yet to get CRZ clearance certificate, despite submitting a drawing of the restoration project, along with survey of the encroachments by a consultant. They claimed that it’d take over 6 months to get the certificate and begin work.

A senior official said, “The water body has sufficient capacity to hold water even during the rainy season. The flooding was due to the unmaintained stormwater drains (SWD), which were filed with deposits and not cleared, and blocked the water flow. Only if the Greater Chennai Corporation takes steps to make SWD dirt-free, there won’t be an inundation situation this year.”

Apart from this, the government has directed to desilt channels in the city for extra water to flow into the sea.

WRD is awaiting a GO, which is expected by next month. They’ve planned to complete the work before the seasonal rain begins.