Colombo’s municipal authorities convened an emergency meeting on Saturday morning to agree urgent measures after Friday evening’s flooding, as the Department of Meteorology forecast a further 100mm of rain and issued a severe lightning advisory covering 22 of the country’s 25 districts.
The drainage system was built for a quarter of what fell
Mayor of Colombo Vraie Cally Balthazaar said the city’s drainage system is designed to handle rainfall of roughly 30 millimetres, but that Colombo received nearly four times that amount, NewsFirst reported. She described the result as an exceptional situation and acknowledged the significant disruption caused to residents.
That ratio is broadly consistent with the Met Department’s own measurement of 129mm at its Colombo station on Friday evening, which is about 4.3 times the 30mm design capacity the Mayor cited.
Representatives of the police, the Tri-Forces, Divisional Secretariats, the Governor’s Office, the Sri Lanka Land Development Corporation and the Urban Development Authority were expected to attend. The Mayor said the Colombo Municipal Council intends to work with those bodies on immediate solutions, with the discussion focused on improving drainage and addressing the city’s canal network and road infrastructure.
More rain on the way
Meril Mendis, Director of the Met Department’s Forecasting Division, said showers or thundershowers could be expected in several areas from about 1.00 p.m. on Saturday, with heavy falls above 100mm in several parts of the island, NewsFirst reported.
He said the cloud formations are expected to develop over the next two to three days, with heavy rainfall likely particularly towards the fourth or fifth day — placing the heaviest conditions around the middle of next week rather than this weekend.
Hiru News reported the Met Department naming the specific areas at risk of falls above 100mm on Saturday: the Western, Sabaragamuwa, Central and North-Western provinces and the Galle and Matara districts. Hiru added that misty conditions could prevail in the early morning in parts of the Western, Sabaragamuwa, Central and Uva provinces, and that the department asked the public to take precautions against temporary strong winds and lightning.
Lightning advisory covers 22 districts
The Met Department issued an amber advisory for severe lightning across 22 districts: Anuradhapura, Ampara, Kalutara, Kegalle, Kilinochchi, Kurunegala, Colombo, Gampaha, Galle, Nuwara Eliya, Puttalam, Polonnaruwa, Badulla, Batticaloa, Mannar, Kandy, Matara, Mullaitivu, Monaragala, Ratnapura, Vavuniya and Hambantota.
Mendis urged the public to follow forecasts and advisories closely in the coming days.
No casualties or evacuations had been reported by any of the newsrooms covering the flooding at the time of filing.
Update — the overnight figures: 146.6mm at Thimbirigasyaya
The heaviest rainfall in the 12 hours to 6.00 a.m. on Saturday was recorded at Thimbirigasyaya in Colombo, at 146.6mm, Hiru News reported, citing the Disaster Management Centre.
Two other stations were close behind:
| Station | Rainfall, 12 hours to 6.00 a.m. Saturday |
|---|---|
| Thimbirigasyaya | 146.6 mm |
| Mattakkuliya | 125.5 mm |
| Bopagama | 117.6 mm |
These are a different measurement from the 129mm figure cited above, and should not be read as a revision of it. The 129mm is the Met Department’s Colombo reading for Friday evening’s downpour; these are Disaster Management Centre station totals for the overnight period that followed. Taken together they show the rain continued well past the evening peak that flooded the city — and that the 12-hour overnight total at Thimbirigasyaya alone was close to five times the 30mm the drainage system is designed for.
The Mayor’s meeting went ahead
The Daily Mirror confirmed the emergency discussion was convened, reporting that Mayor Balthazaar held it with representatives of key government institutions to identify immediate solutions, focused on the city’s drainage systems, canal network and road infrastructure.
The Daily Mirror independently repeats the Mayor’s central comparison — a system designed for about 30mm against 129mm received within a few hours on Friday — corroborating the NewsFirst account above from a second newsroom.
Update — why it flooded: the Met Department names blocked drains and El Niño
The Department of Meteorology’s Director General, Ajith Wijemanne, set out the mechanism behind Friday’s flooding in a briefing carried by NewsFirst on Saturday at 12.16 p.m.
More than 100mm fell over Colombo in less than an hour on Friday evening, he said, and it was the intensity of that fall within a very short period — not the daily total alone — that produced flash flooding. He put the day’s Colombo total at close to 123mm, and noted the city has previously recorded rates approaching 140mm per hour.
Wijemanne also pointed to blocked or obstructed drainage systems as a contributing factor. That is a notable addition: it places part of the cause outside rainfall intensity, and it is the same mechanism the UNP and the Opposition Leader allege — though the Met Department apportions no blame and names no responsible body.
Why more of this is likely
Sri Lanka is in its Second Inter-Monsoon season, when convective rainfall is common: cloud builds after sunny mornings and delivers heavy showers within 30 minutes to an hour, typically after 1 p.m. — which matches the Forecasting Division’s 1 p.m. timing for Saturday noted above.
Two larger systems are reinforcing it. El Niño conditions are prevailing, and the Intertropical Convergence Zone is in the vicinity of the island; shifting wind direction and instability in the lower atmosphere are further favouring sudden, intense falls. Wijemanne warned these conditions could continue for weeks across the Western, Sabaragamuwa, North Western, Central and Southern provinces including Galle and Matara, with some areas again exceeding 100mm in a very short period.
A third rainfall figure — read these carefully
Wijemanne’s ~123mm is a third measurement now in circulation for this event, alongside the 129mm and 146.6mm above. None is a correction of another:
| Figure | What it measures |
|---|---|
| ~123 mm | Met Department, Colombo, Friday (DG Wijemanne) |
| 129 mm | Met Department, Colombo, Friday evening downpour |
| 146.6 mm | Disaster Management Centre, Thimbirigasyaya, 12 hours to 6 a.m. Saturday |
The ~123mm and 129mm readings differ modestly and are not reconciled by any filing; the 146.6mm figure covers a different station and a different window. The Met Department’s own “>100mm in under an hour” is the figure that explains the flooding, since Colombo’s drainage is built for about 30mm.
Note also that this briefing comes from the Department’s Director General, while the forecast detail above is attributed to Meril Mendis of its Forecasting Division — two officials of the same department, not conflicting sources.
