Is Nagalagam Street flooding now?

As of Tue, 27 Oct, 4:28 am (Sri Lanka time), the Kelani Ganga at Nagalagam Street was 4.5 ft, above the 4.0 ft alert level, and rising slowly.

Will the Kelani Ganga at Nagalagam Street rise in the next hour?

In the next hour the Kelani Ganga at Nagalagam Street could fall to about 4.3 ft (4.1–4.5 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.

What is the flood level at Nagalagam Street?

The official marks for this gauge are alert 4.0 ft, minor flood 5.0 ft, major flood 7.0 ft. Alert means the river has reached the alert mark: move valuables up and charge your phone. Minor flood means water is spilling over low ground, and major flood means move to safety.

Where does this come from and how often does it update?

River readings come from the Department of Irrigation's gauges, roughly once an hour, and this page checks for new ones every minute. This site is independent and not an official warning service: follow the Disaster Management Centre and call 117 in an emergency.

Nagalagam Street Kelani Ganga water level today (live)

Official warning:

An amber warning says minor flooding may affect low-lying areas of the Kelani River Valley in Ruwanwella, Seethawaka, Dompe, Dehiowita, Eheliyagoda, Yatiyantota and Bulathkohupitiya within 24 hours; residents and motorists should exercise extreme caution, and flooding may extend downstream of Hanwella if heavy rain continues.

Irrigation Department

Reading at 4:28 am · 19 min ago

Alert

4.5 ft

Next hour

Falling

Next 24 hours

No estimate yet

Move valuables up, charge your phone

The level is above the alert level and is expected to stay there for the next 24 hours.

Call 117 Colombo DMC office

Details

Above alert level now and expected to stay there for the next 24 hours.

Elevated river-flow outlook this week.

In	Level	80% range	At
1h	4.3 ft	4.1 to 4.5	5:28 am
3h	3.6 ft	3.1 to 4.3	7:28 am
6h	3.1 ft	2.7 to 4.3	10:28 am
12h	3.7 ft	3.2 to 4.2	4:28 pm
24h	4.3 ft	3.5 to 5.2	4:28 am

Minor flood (5.0 ft): unlikely, about 1 in 10
Major flood (7.0 ft): unlikely, about 1 in 10

Local trend

+0.04 ft/h

Upstream avg

-0.2 ft/h

Rain that fell: This gauge has no rain sensor.Nearest rain gauge upstream, Holombuwa: 0.0 mm in 3 hours, 127 mm in 24 hours.
Rain forecast: 13 mm in the next 24 hours over the catchment (moderate rain). Forecast model estimate.

Satellite estimate of rain over the catchment: 3.9 mm in the last 6 hours, 84.7 mm in the last 24 hours (to 4:30 am). It can differ from the gauges. GSMaP data by Japan Aerospace Exploration Agency (JAXA)

Deraniyagala 2.2mm · Glencourse 1.1mm

· Outlook: the GloFAS global flood model has river flow at 751 m3/s in its highest member within 7 days, above the 1-in-20 level (338 m3/s). This is a heads-up only; it does not change the levels above.
· Part of the range is above the highest level this model has seen (3.2 ft); treat it as a rough guide.

How this is worked out
· Latest level at Nagalagam Street and recent change, plus upstream gauges: Hanwella, Glencourse.
· Forecast model estimate of catchment rain (Open-Meteo, area average over 9 grid cells above Nagalagam Street): 62 mm modelled for the last 24 hours, 13 mm forecast for the next 24 hours, with ECMWF ensemble spread.
· The 1, 3, 6, 12, 24 hour steps use this gauge's own recent changes and the other gauges on the river (fitted to about 11 months of hourly readings, including the November 2025 Ditwah floods); where this was tested against 'level stays the same' it missed by less.
· The 12, 24 hour steps read the rain the satellite measured over Nagalagam Street's catchment (JAXA GSMaP, corrected for how it reads here), with rain beside the gauge and rain on the channels upstream timed separately (about 6 h from beside the gauge, about 6 h from upstream). Tested storm by storm it was closer than the version that reads the weather model's rain.
· Heavy rain upstream is part of the 1, 3, 6, 12, 24 hour steps: rain that has fallen or is forecast over the catchment above Nagalagam Street raises the level, and the top of the range allows for the heavier forecast rain. Tested storm by storm (leaving each storm out, Ditwah included) it was closer than the river's own trend alone.

Is this right?

Each answer helps us improve the forecast for your area.

Water level

When does Nagalagam Street flood?

Flood warnings come mostly in May, with a smaller peak between October and November.

It’s October: the smaller flood season here. Floods are possible after heavy rain.

Recent floods

27 Dec 2025Minor flood
28 Nov – 3 Dec 2025Major flood
27 Nov 2024Minor flood · estimated

Every day since 2022, year by year

Other stations

Along the Kelani Ganga

Arrows show the change over the last 3 hours.

Reservoirs upstream

In the newsNews reports, not official.

RiverSource: Daily Mirror26 Oct, 7:31 pm (9 h ago)
Flood warnings issued for Kelani, Attanagalu Oya basins(opens the news site in a new tab)
The Irrigation Department has issued a minor flood warning for low-lying areas of the Kelani River Valley, covering the Divisional…
RiverSource: Newswire26 Oct, 7:10 pm (10 h ago)
Amber flood warning issued for low-lying areas of Kelani and Attanagalu river basins(opens the news site in a new tab)
The Department of Irrigation has issued Amber flood warnings for low-lying areas in the Kelani River and Attanagalu Oya basins…

Towns that depend on this gauge

Common questions

Is Nagalagam Street flooding now?: As of Tue, 27 Oct, 4:28 am (Sri Lanka time), the Kelani Ganga at Nagalagam Street was 4.5 ft, above the 4.0 ft alert level, and rising slowly.
Will the Kelani Ganga at Nagalagam Street rise in the next hour?: In the next hour the Kelani Ganga at Nagalagam Street could fall to about 4.3 ft (4.1–4.5 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.
What is the flood level at Nagalagam Street?: The official marks for this gauge are alert 4.0 ft, minor flood 5.0 ft, major flood 7.0 ft. Alert means the river has reached the alert mark: move valuables up and charge your phone. Minor flood means water is spilling over low ground, and major flood means move to safety.
Where does this come from and how often does it update?: River readings come from the Department of Irrigation's gauges, roughly once an hour, and this page checks for new ones every minute. This site is independent and not an official warning service: follow the Disaster Management Centre and call 117 in an emergency.