NASA Captures Monsoon Rains Bringing Flooding to India

NASA provided estimates monsoon rainfall that affected India from Aug. 13 to 20.

The above average monsoon rains resulted in severe flooding in parts of India. Hardest hit was the state of Kerala located in the southwest corner near the bottom of the peninsula where at least 350 fatalities have been reported and many as 800,000 people displaced as a result of the extreme flooding and ensuing mudslides.

Rainfall accumulations from Aug. 13 to 20, 2018 showed two bands of heavy rain across India. The first band appeared much broader and extends across the northern part of the peninsula with weekly rainfall totals ranging from over 120 mm (~5 inches, in yellow) towards the western half of the peninsula to as much as 350 mm (~14 inches, in dark red) over parts of the eastern half towards the Bay of Bengal. The second band was more concentrated, intense and closely aligned with the southwest coast of India and the Western Ghats. Rainfall totals in this band are generally over 250 mm (~10 inches, in red) with embedded areas exceeding 400 mm (~16 inches, in purple). The maximum estimated value from IMERG in this band was 469 mm (~18.5 inches). Credits: NASA/JAXA/SSAI/Hal Pierce

The summer monsoon is a regular feature this time of year in India, and it can bring heavy rains to the region. However, periodically areas of low pressure can form within the general monsoon trough and bring even more rain.

Although the extreme Himalayan topography located to the north is much more well-known, another contributing factor to the heavy rains along the southwest coast of India is the Western Ghats. Though much smaller than the Himalayas, this mountain range runs parallel to the West Coast of India with many peaks over 2,000 meters (~6,500 feet). As a result, the Western Ghats are well positioned to enhance rainfall along the West Coast of India as they intercept the moisture laden air being drawn in off the warm waters of the northern Indian Ocean and Arabian Sea as part of the southwest monsoon circulation.

The Integrated Multi-satellitE Retrievals for GPM or IMERG is used to estimate precipitation from a combination of passive microwave sensors, including GPM’s GMI microwave sensor and geostationary IR (infrared) data. GPM is the Global Precipitation Measurement mission core satellite. GPM is a joint mission between NASA and the Japan Aerospace Agency, JAXA.

Accumulated IMERG rainfall estimates for the 1-week period from Aug. 13 to 20, 2018 showed two bands of heavy rain across India. The first band appeared much broader and extends across the northern part of the peninsula with weekly rainfall totals ranging from over 120 mm (~5 inches) towards the western half of the peninsula to as much as 350 mm (~14 inches) over parts of the eastern half towards the Bay of Bengal. This first band is associated with the general monsoon circulation.

The second band appeared more concentrated and intense and is closely aligned with the southwest coast of India and the Western Ghats where onshore flow was enhanced by an area of low pressure embedded within the general monsoon. Weekly rainfall totals in this band are generally over 250 mm (~10 inches) with embedded areas exceeding 400 mm (~16 inches). The maximum estimated value from IMERG in this band was 469 mm (~18.5 inches).

Source: NASA

Flood Summary

Last updated: August 30, 2018
Event
Kerala, India, July to August 2018
Date
July 9 to August 30, 2018
Type
Urban flood, Flash flood, Landslide, River flood
Cause
Reservoir release, Extreme rainfall, Long-term rainfall

Locations

A - Kollam
B - Kasaragod
C - Alappuzha
D - Thrissur
E - Kozhikode
F - Palakad
G - Malappuram
H - Pathanamthitta
I - Ernakulam
J - Kottyam
K - Idukki
L - Thiruvanthapuram
M - Wayanad

Magnitude

Rainfall level
64.2 mm in 24 hours
Idukki - July 16 to July 17, 2018
IMD figures
Rainfall level
56.9 mm in 24 hours
Ernakulam - July 16 to July 17, 2018
IMD figures
Rainfall level
78.7 mm in 24 hours
Cohin - July 17 to July 18, 2018
WMO figures
Rainfall level
112 mm in 24 hours
Kozhikode - July 17 to July 18, 2018
WMO figures
Dam level
731.18 metres
Idukki Reservoir - August 15 to August 15, 2018
Figures from Kerala Disaster Management (KSDMA) Idukki Reservoir level (given in feet) was 2,398.90 feet (731.18 m), where FRL is 2,403 feet (732.43 metres).
Dam level
169.20 metres
Idamalayar dam - August 15 to August 15, 2018
Full reservoir level (FRL) is 169 metres
River level
Overflowing
River Valapatnam at Perumannu in Kannur District - August 15 to August 15, 2018
India’s Central Water Commission Flood Forecast unit said that the River Valapatnam at Perumannu in Kannur District is flowing in “Extreme Flood Situation.”
Rainfall level
79.1 mm in 24 hours
Idukki - August 13 to August 14, 2018
India Meteorological Department (IMD) figures
Rainfall level
75.2 mm in 24 hours
Kasargod - August 13 to August 14, 2018
Rainfall level
83.4 mm in 24 hours
Kozikod - August 13 to August 14, 2018
Rainfall level
75.5 mm in 24 hours
Malappuram - August 13 to August 14, 2018
Rainfall level
73.3 mm in 24 hours
Wayanad - August 13 to August 14, 2018
Rainfall level
214 mm in 24 hours
Palakkad - August 8 to August 9, 2018
Local meteorological observers Chennai Rains said via Social Media that Palakkad recorded 214 mm of rainfall in 24 hours to early 09 August, adding “that’s just about 20 mm short of highest recorded 24 hour rainfall in the city, 236 mm way back in May 1957.”
Rainfall level
167.2 mm in 24 hours
Idukki - August 8 to August 9, 2018
India Meteorological Department (IMD) figures
Rainfall level
83.2 mm in 24 hours
Malappuram - August 8 to August 9, 2018
Rainfall level
170.9 mm in 24 hours
Wayanad - August 8 to August 9, 2018
River level
712 metres
River Kabini at Muthankera, Wynadu District - August 9 to August 9, 2018
India’s Central Water Commission Flood Forecast unit figures - this is a record high

Damages

Fatalities
480 people
Kerala - July 9 to August 28, 2018
Figures from India's National Emergency Response Centre (NERC) (pdf) report as of 28 August, 2018
Evacuated
1,452,425
Kerala - July 9 to August 28, 2018
According to NERC figures over 1 million people have been displaced by floods and accommodated in 5,645 relief camps. As of 28 August there remained 696 camps.
Buildings destroyed
1822 buildings
Kerala - July 9 to August 28, 2018
21,695 suffered partial damage
Rescued
535 people
August 9 to August 21, 2018
According to NERC, India's From 9 August, 2018 to 21 August, 2018, National Disaster Response Force had rescued 535 people and evacuated 25,225. Medical assistance was provided to 5562.