Mumbai, India's Commercial Hub, Disrupted by Monsoon
On 26 th July 2005 within a span of less than 24 hours Mumbai, received unpredicted heavy rainfall.
Santa Cruz- 94.4 cm
Vihar Lake 104.5 cm of rainfall for the day
Mumbai suffered a loss of more than 10000 crores
If this disaster had been forecasted then the property and life loss could have been minimized.
During the period of 26July, the monsoon over major parts of the country, particularly over the west coast and peninsular India, was in its active phase.
A low-pressure area formed over north Bay of Bengal off Gangetic West Bengal and Orissa coast on 24 July.
There was strong cross-equatorial flow. As the system moved westward, the low-level jet gained strength and strong westerly winds lashed the north Konkan and Goa coasts. This resulted in widespread heavy rainfall over these regions.
It was "a cloudburst," a phenomenon in which there is very heavy rainfall, though for a brief period. But this was "an unusual cloudburst lasting close to 24 hours" which has bewildered weathermen.
The type of storm we saw on July 26 had very small dimension of 25-30 km. And that could be termed under the category of what we call cloudburst. It could be termed as cloudburst because particularly after 14:30 IST, received very intense showers accompanied with thunderstorm. This clearly shows this was some kind of very violent.
But it was a very unusual kind of cloudburst. Cloudbursts generally do not have that prolonged longevity. They are very short-lived. Whereas in this case, the phenomenon was noticed for 12-18 hours… the intense rainfall. Therefore it was a unique type of cloudburst.
All the ingredients that we see in a cloudburst were available there on that day. It was very highly localized.
Main Causes of Floods Siltation of drains/ nallas Siltation of drains/ nallas Obstructions of utilities Obstructions of utilities No access for desilting Dilapidated drains Slums along outfalls Increase in runoff coefficient Garbage dumping in SWDs/ Nallas mainly in slums Loss of holding ponds Encroachment along nallas Level of outfalls Low ground levels Low ground levels Suburbs City
Above picture is courtesy Mid-day. Text goes "Lying in wait: More than, 1,000 outstation commuters slept at the Chhatrapati Shivaji Terminus last night, as several trains on the Konkan route were delayed due to the rainfall. Many local train commuters who missed the last train also spent the night at the station."
Impacts of Heavy Rain:
Public transport came to a grinding halt
People stranded in trains/buses/ offices
Educational Institutions closed for two days
Students stayed in schools/colleges overnight
Staff stranded in offices overnight
Mobile phone networks collapsed
Over 2 million. landline phones were affected
Electricity supply was cut off in most parts of Mumbai
To prevent damage to pumps at the sewage pumping stations, pumps switched off,
– Led to sewage backflow and floodwaters being contaminated with sewage
Most arterial roads and highways in the suburbs severely affected due to water logging and traffic jams resulting from vehicle breakdown in deep waters
Suburban trains, the lifelines of the city, could not operate from around 4:30 pm for close to 36 hours, stranding an estimated 150,000 people as well as long-distance trains leaving Mumbai
Over 750 flights in and out of Mumbai were suspended/diverted
Approximately 1307 buffaloes , 5000 sheep and goats had to be disposed.
Mithi River overflowed and consequently led to water logging of Western Express Highway
Six landslides on 26th, 3 on 27th, one each on 28th, 30thand 1stAugust respectively –at least 65 killed, others injured
Measures to prevent further floods
All major nallahs in suburban Mumbai, which carry storm water to the sea, are being scraped clean right to the sediment floor.
Automatic rain gauges are being installed in 26 locations across the city.
The state government has directed the irrigation department to avoid filling up dams to their maximum water storage levels during the initial phase of the monsoon.
Six fire brigade control rooms/ rescue command centres to be equipped