[Prowler]

Originally Posted by IamNikhil

Another year of a flood-like situation in Chennai? Saw these videos and pics posted by locals in Chennai. Really sad.

I am not sure those images and Videos are from Chennai at this time. The last video I had seen that last year purportedly coming from Bombay.

Be that as it may, the current cyclone has caused unprecedented rains in Madras. In south Madras it was 30 cm rains till 10.00 today morning. Surprisingly the EB hasn't cut the power in my locality yet.

[SuperGirl_Dad]

With most of Chennai in more than knee deep water, wonder what happened to vehicles such this (What amphibious vehicle is this, based on a Tata Xenon?)?

They would definitely help people suffering in flooded homes. Seems nothing was learnt from 2015 .

[Thad E Ginathom]

That's interesting to know that one of those videos is "fake" (as in not of the current situation). Thanks.

Having been glued to Kea Weather Blog for the past few days, as well as seeing some pics that should be reliable, and having felt very genuine fear for some hours, I think it's safe to say that Chennai is a mess. Very badly affected.

My locality got less rain on day one of the three major storm days, but still logged 457mm including a massive 322mm (over 12 inches) on just one of the days. Figures from a Kea Blogger's PWS not far away.

Very serious.

[searacer932]

1. 2023 rains were much lesser than 2015 rains but the disaster management of 2023 was worse than 2015.

2. The Government knew that about the impending rains and did not take any action at all. The less said about the actions post the rain the better.

3. The government said that have built storm water drains for 4000 crores and I am pretty sure the money has been siphoned off.


The cyclone did not even hit Chennai. In fact the cyclone was 60 to 100kms away from Chennai and hit Andhra. In fact the rains were due to the outer bands of the cyclone and hence I don't want anyone to think the cyclone had hit Chennai when the reality was it did not.

[Thad E Ginathom]

Originally Posted by searacer932

The cyclone did not even hit Chennai.

I think that people make too much of the eye itself. True, the strongest winds may be close (but not in, despite what the Indian media thinks when it misuses the expression "eye of the storm") to it, but there's plenty of damage and danger elsewhere too.

I think maybe we should call the entire system "the cyclone."

...Just my "I think"s

[Gansan]

^^ Inside the eye itself things will be very calm. When a cyclone crosses a place, the high velocity winds will blow from one particular direction, then when the eye passes directly over, the winds will calm down. The eye can be many kilometres across and the passing can take a few hours. Then when the rear of the storm hits, the high velocity winds will return, but from the opposite direction. This is when people without awareness get caught.

[Thad E Ginathom]

Exactly, Gansan. It doesn't have to be a cyclone even: this is how a strong Low Pressure System (Depression) will work. Even if we don't see the well-defined eye which looks so good on satellite pics.

[SuperGirl_Dad]

Originally Posted by searacer932

The cyclone did not even hit Chennai. In fact the cyclone was 60 to 100kms away from Chennai and hit Andhra. In fact the rains were due to the outer bands of the cyclone and hence I don't want anyone to think the cyclone had hit Chennai when the reality was it did not.

There are lot of videos of EYE (center) of the cyclone/hurricane. One of the best video below explaining the effect of winds and rains near the Cyclone eye.

https://www.youtube.com/watch?v=tuP5ART3dXM

[narayans80]

Originally Posted by searacer932

1. 2023 rains were much lesser than 2015 rains but the disaster management of 2023 was worse than 2015.

Not every place gets the same quantum. Kattankulathur got 380 mm, Nungambakkam got 290 mm. A former colleague who lived near SRM had water level enter 1st floor and had to move to 2nd floor.

During 2015 the house I grew up got flooded in the aftermath when Cooum (decently referred as Adyar River) was released on 3rd December. There were no floods in all 17 days of big rain spells that fell that year. So how is this better management?

Some roads near my workplace (like Bhavin Patel Road and Kalikundram Road) at Taramani were surprisingly waterlogging free on Tuesday and there was rain water overflowing out of IIT backside into Kanagam Road, while there was waist deep water outside Taj Wellington.

The cyclone did not even hit Chennai. In fact the cyclone was 60 to 100kms away from Chennai and hit Andhra. In fact the rains were due to the outer bands of the cyclone and hence I don't want anyone to think the cyclone had hit Chennai when the reality was it did not.

This IS precisely the problem. If the landfall happened close to Madras, it would have ended up like Mandous or even lesser. Rain quantum was much lesser (~ 100 mm), but there were more wind related destruction.

In the lead up to the massive rains, the consensus was that we will get a huge quantum if the storm is 100 km or lesser and moderate rains if its further away.

The closest comparison to Michaung is the storm from late November of 1976 (per wiki it is Tropical Storm 13). Nungambakkam's record 452 mm happened on 25th November 1976. The outer bands fell on late Saturday and early Sunday. The dense inner bands started falling on Sunday evening and Monday morning when bulk of the quantum was recorded.

Since IMDs cutoff happens at 0830 IST, the official quantum would be distributed between Sunday and Monday records. Between Sunday evening and Monday evening, the 24 hour was rain was well over 400 mm (I remember seeing 329 mm around 3 pm on Monday in KWS).

[Thad E Ginathom]

Originally Posted by narayans80

During 2015 the house I grew up got flooded in the aftermath when Cooum (decently referred as Adyar River) was released on 3rd December.

Some confusion. Cooum and Adyar are different rivers in different parts of the city.

Neither "got released," What did get released was water from from overfull reservoirs, particularly Chembarambakkam. This is what was not managed in 2015, whereas, this time, the release began some days ago and was slowly increased.

Chembarambakkam is released into Adyar River. From there it floods directly and via Buckingham Canal, both North and South.

This IS precisely the problem. If the landfall happened close to Madras, it would have ended up like Mandous or even lesser. Rain quantum was much lesser (~ 100 mm), but there were more wind related destruction.

This is, more or less, my way of thinking too, but it does depend on the cyclone and on its speed.

Vardah passed (pretty-much IIRC) straight over us. The winds and the rain were intense. There was a great deal of damage, but rain was less in total as the system moved fast. It was a matter of hours only.

Originally Posted by SuperGirl_Dad

There are lot of videos of EYE (center) of the cyclone/hurricane.

I have some experience. Not a lot --- and I do not want more!

[Gansan]

Cooum and Adyar rivers are different. The former gets the reputation of a sewer only after it enters Chennai because of the effluents let into it here. For the initial 45 odd Km till it enters Chennai, it still has potable water and irrigates fields.

In fact T.Muthuswamy Iyer, the first Indian lawyer to be appointed as judge of Madras High court in 1877 under the British raj, has written in his memoirs about going to the cooum river in Chennai every morning, bathing in it and offering his morning prayers before returning home and proceeding to the court! It was such a clean river those days!

[pypkmsrikanth]

Originally Posted by searacer932

1. 2023 rains were much lesser than 2015 rains but the disaster management of 2023 was worse than 2015.

2. The Government knew that about the impending rains and did not take any action at all. The less said about the actions post the rain the better.

3. The government said that have built storm water drains for 4000 crores and I am pretty sure the money has been siphoned off.


The cyclone did not even hit Chennai. In fact the cyclone was 60 to 100kms away from Chennai and hit Andhra. In fact the rains were due to the outer bands of the cyclone and hence I don't want anyone to think the cyclone had hit Chennai when the reality was it did not.

Had to quote the full tweet to give context to the answer.

Chennai got rains from primary bands between late night of Sunday and evening of Monday. Many places recorded 9 cms in a 3 hour spell during the wee hours of Monday.

One of the biggest reasons for the water stagnation during Cyclone Michaung was the slow movement around Chennai coast, it spent pretty much a day close to Chennai latitude triggering a storm surge around the coast. This storm surge did not allow the rivers to drain the water as they could do under normal conditions. With river flow higher than SWD levels in many places the SWD could not move the water into the rivers / canals resulting in flooding around the streets. Southern suburbs of Chennai need a large scale correction and SWD is not going to work there because they are inherently marshland and used to be the water sink of Chennai before releasing them gradually.

One of the reasons why places like Ashok Nagar / Jafferkhanpet etc did not get flooded on the scale of 2015 was because Chembarambakkam discharge was managed this year using a Real Time Flood Forecasting Model. IIT Madras monitored discharges from the Aadhanur catchment into Adyar river this year peaked at 40000 cusecs apparently. What we may have to do is also get a large scale Flood Forecasting Set up for Chennai basin covering the KTCC districts including urban flooding forecast. This could give us a better platform to proactively manage rather than react.

The rainfall numbers are always debatable whether this event was bigger or the earlier event was bigger. As a weather enthusiast in my view there are areas where we have seen a positive change but there is a lot of learning from 2023 that needs to be introspected. A responsible govt would introspect and I hope the current govt does also.

[narayans80]

Originally Posted by Thad E Ginathom

Some confusion. Cooum and Adyar are different rivers in different parts of the city.

Originally Posted by Gansan

Cooum and Adyar rivers are different. The former gets the reputation of a sewer only after it enters Chennai because of the effluents let into it here.

Thank you. I don't remember the exact events by memory. But we (areas like Kotturpuram, T. Nagar) got flood water about 4 feet tall the day after the rains.

This is, more or less, my way of thinking too, but it does depend on the cyclone and on its speed.

Mainly the dense rain bands. The slow speed ensured we got heavier rains for a longer duration.

In fact T.Muthuswamy Iyer, the first Indian lawyer to be appointed as judge of Madras High court in 1877

Thank you for the history. Was he the namesake for the zero point bridge?

[Thad E Ginathom]

Originally Posted by pypkmsrikanth

Chennai got rains from primary bands between late night of Sunday and evening of Monday. Many places recorded 9 cms in a 3 hour spell during the wee hours of Monday.

The big question was whether or not those rain bands would curve around bringing their rain to Chennai from the north. Models differed. They did

One of the biggest reasons for the water stagnation during Cyclone Michaung was the slow movement around Chennai coast, it spent pretty much a day close to Chennai latitude triggering a storm surge around the coast. This storm surge did not allow the rivers to drain the water as they could do under normal conditions.

Oh, thank you! I had heard on the grapevine that water could not be released from Buckingham Canal into the sea because it was too rough. I was doubtful as to the accuracy of this, but storm surge did not occur to me. I'm no weather expert, but it should have!

I don't recall it being mentioned on the Kea blog, which dominated my internet during those days. It probably was and I must have missed it.

One of the reasons why places like Ashok Nagar / Jafferkhanpet etc did not get flooded on the scale of 2015 was because Chembarambakkam discharge was managed this year using a Real Time Flood Forecasting Model.

Yesterday, The Hindu had a whole page on 2015 v 2023. I haven't read it all yet, but there are charts of the Chembarambakkam release.

The rainfall numbers are always debatable whether this event was bigger or the earlier event was bigger. As a weather enthusiast in my view there are areas where we have seen a positive change but there is a lot of learning from 2023 that needs to be introspected. A responsible govt would introspect and I hope the current govt does also.

Yes, and people will cherry/random pick areas and weather stations. My area only got 30-something mm on day one of this storm.

Originally Posted by narayans80

Thank you. I don't remember the exact events by memory. But we (areas like Kotturpuram, T. Nagar) got flood water about 4 feet tall the day after the rains.

Kotturpuram was directly flooded by Adyar R.
Areas south were also flooded by Buckingham canal.
Whole of OMR area was badly affected. This included me.

People in posh Defence Colony, on Adyar side were forced to the terraces of 2-story houses. One of my wife's friends, living in a poorer village on the river side had their small ground floor home full. They had water inside too.

A wealthy area, Venus Colony, was very badly flooded this time, with several feet of water.

We could go on listing experiences from both events for ever

[srvm]

In the last year, I have made a few trips from Bangalore to Medavakkam via Sunguvarchatram, Vandalur, Tambaram.
Why are the roads around Perungalathur so bad on GST road? Such an arterial road, with so much dust kicking up as buses and trucks gallop at speeds while smaller vehicles take potholes slowly and carefully.

Also, two wheeler riders in Chennai seem to be more suicidal than the ones I encounter in Bangalore simply because the average speeds are higher in Chennai arterial roads. I saw numerous close shaves in just 2 days.

Auto drivers are a big menace. The trailing distance they maintain at good speeds made me very nervous. Any sudden deceleration by the leading vehicle was a sure shot rear-ending

Losing hope that conditions will ever improve on our roads.