Sri Lanka Flood Monitoring Bulletin

A developing tropical cyclone has brought torrential rains over southern parts of the Bay of Bengal.

Satellite image for 15th May 2016Wunderground.com

IWMI-FLD-SL-2016.V1

Flooding downpours threaten Sri Lanka, India as widespread first rain of season soaks region

The first significant rainfall of the summer season will target SriLanka and southern India this week leading to travel delays andflooding.

The low pressure area is moving away from the island, hencerainy conditions over the island will be reduced to some extent,but strong wind conditions will continue for some more days.

Heavy to very heavy rainfall (100-150 mm) are likely at severalplaces, particularly in the North, North Central, North Westernprovinces. Showers or thunder showers will occur at time inWestern, Central, Sabaragamuwa, Uva provinces and Galle andMatara districts.

15/05/201508/05/2015

Heavy rains also forced for two spill gates of the Rajanganaya Reservoir to be opened.

MODIS TERRA Satellite imagery dated 15th May 2016 . Island is completely covered with clouds unusually intense tropical cyclones compared to the image dated 8th May 2016

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13th May 14th May

Rainfall accumulation for the past 36 hrs.

• Districts with rainfall more than 150mm (Ampara -161mm, Moneragala - 188mm, Badulla -160mm, Nuwara Eliya - 120mm, Kandy - 104mm, Colombo -107mm)

• Through Wednesday, widespread rainfall of 100-200 mm (4-8 inches) of rain will fall across the region.

15th May 2.30pm

Accumulated Daily Rainfall Estimates using Global Precipitation Measurements (GPM)

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0

0.5

1

1.5

2

2.5

3

3.5

4

3/16 3/26 4/5 4/15 4/25 5/5 5/15

2016 2015

Mahaweli-Ganga (Flood Signal monitored using AMSR2)

Flooding downpours threaten Sri Lanka, India as widespread first rain of season soaks region

The flood magnitude is a measure of the size of the flood. Since lower signals generally accounts for increased water coverage, extreme events, or major floods, should represent anomalies in the time series of a given site. The reference value for normal flow is calculated as the average signal for the site since June 2002. Flood magnitude is defined as the number of standard deviations (sd) from the mean (avg).

• Exceptional flooding along the Mahaweli-Ganga river with major population exposed to risk including Peradeniya and Nawalapitiya

• Water levels of the Mahaweli River have gradually risen with the opening of the spill gates of the Parakrama Samudraya.

• Local news confirms the rise of water levels in the Malwathu Oya on either side of its banks and several houses will be inundated.

• Heavy rains also forced for two spill gates of the Rajanganaya Reservoir to be opened.

• At least eight districts also issued landslide warnings.