Bangkok has been battered by intense rain, flooding roads, pushing canals towards critical levels and forcing schools to close. Thailand has certainly not conquered urban flooding, but the machinery it puts into action before, during and after heavy rain leaves Sri Lanka with an uncomfortable question. How many times can the same roads flood before a predictable event becomes a failure of planning?
Bangkok is under water again. Heavy rainfall over the past several days has overwhelmed parts of the Thai capital, flooding dozens of roads, pushing water levels in several canals towards critical levels and forcing municipal schools to close while authorities attempt to drain accumulated water from the city.
The scale of the problem should not be understated. Bangkok authorities reported flooding across 93 roads, with five major canals reaching critical levels and pumping and drainage systems operating at maximum capacity. Officials warned that even after the rain stopped, some areas could require two or three rain-free days before accumulated water was removed.
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There is, however, an important part of the Bangkok story that begins before the flooding. Thailand’s meteorological authorities had warned of heavy to very heavy rainfall between September 23 and 27, and Bangkok Governor Chadchart Sittipunt publicly outlined preparations being made by the Bangkok Metropolitan Administration. Drainage systems were prepared, canal levels monitored and pumping capacity placed on alert.
It did not prevent Bangkok from flooding, nor should anybody pretend otherwise. Tropical cities cannot realistically construct drainage systems capable of absorbing every conceivable rainfall event, particularly as changing weather patterns produce increasingly intense downpours over relatively short periods. The more useful measurement is therefore not whether water appears on a road, but how prepared the authorities were when it arrived and how quickly they can remove it afterwards.
That is where the comparison with Sri Lanka becomes uncomfortable. Colombo is hardly unfamiliar with heavy rain, and neither are the authorities responsible for its drainage, canals, roads and wetlands. There are locations around the commercial capital where flooding is so predictable that motorists can identify the vulnerable roads almost as easily as the engineers responsible for maintaining them.
Sri Lanka has also spent serious money attempting to solve the problem. The Metro Colombo Urban Development Project improved drainage infrastructure, rehabilitated canals and pumping facilities and protected wetlands that provide natural storage for stormwater. The World Bank estimates that approximately 2.5 million people benefited from improved flood protection associated with the programme.
The existence of that investment makes the questions following subsequent flooding more important, not less important. Infrastructure does not maintain itself once the project consultants have departed, and a canal cleared with international financing eventually fills again unless somebody continues clearing it. Pumps require maintenance, drains require cleaning and wetlands protected under one programme remain vulnerable if subsequent development gradually reduces their capacity to absorb water.
Colombo’s wetlands are particularly important because they are sometimes treated in public discussion as undeveloped land rather than functioning urban infrastructure. A wetland capable of holding millions of litres of stormwater is performing a service every time heavy rain falls. Filling it may create commercially valuable land, but the water that would have occupied it does not disappear simply because somebody has obtained permission to build there.
There is also a responsibility that falls upon the public. Plastic, household rubbish and construction waste thrown into drains and canals reduce the ability of the system to carry water precisely when that capacity is most needed. Businesses and households cannot treat waterways as convenient rubbish dumps during dry weather and then place the entire responsibility upon government when those waterways fail during a storm.
Government nevertheless carries the greater responsibility because managing collective behaviour is precisely why regulation exists. Illegal filling must be prevented, drainage reservations protected, building approvals subjected to serious stormwater requirements and waste collection made sufficiently reliable that dumping into waterways is neither necessary nor tolerated. Enforcement that begins only after somebody’s living room is underwater is not flood management.
Bangkok provides an interesting comparison because it has invested heavily in a permanent flood-control system. The city uses pumping stations, canals, retention areas and enormous underground drainage tunnels designed to move stormwater towards the Chao Phraya River. During the present flooding, authorities have been monitoring individual canals, operating pumps continuously and publicly explaining how long different areas may take to drain.
Yet Bangkok still flooded. That should prevent Sri Lanka from drawing the simplistic conclusion that more concrete and more pumps will eliminate the problem. The lesson is instead that flood resilience requires infrastructure, maintenance, planning and operational readiness to function together, year after year, including during the years when there is no dramatic flood to remind anybody why the money is being spent.
Sri Lanka’s difficulty has too often been continuity. Governments enjoy inaugurating infrastructure because openings produce photographs and speeches, while cleaning drains, servicing pumps and preventing politically connected encroachments produce considerably less ceremony. Flood management, unfortunately, depends far more upon the second category than the first.
There is another habit that deserves examination. Following major flooding, Sri Lankan authorities frequently point to exceptional rainfall, and sometimes that explanation is entirely justified. No drainage network has unlimited capacity, and extraordinary rainfall can overwhelm even a well-managed system, as Bangkok is demonstrating this week.
The explanation becomes less convincing when the same location floods repeatedly. Once authorities know where water collects, what capacity the existing drainage possesses and what level of rainfall overwhelms it, the next flood is no longer entirely unexpected. It becomes a known vulnerability against which government can either act or decide not to act.
Climate change makes that distinction increasingly important. Infrastructure designed according to rainfall patterns of several decades ago may no longer be adequate for the storms cities are experiencing today. What engineers once regarded as exceptional rainfall cannot remain an excuse if exceptional events become sufficiently frequent to form part of the new climate reality.
Bangkok’s present experience should therefore interest Sri Lanka for reasons extending well beyond Thailand. It demonstrates that even a city with extensive flood infrastructure can be overwhelmed, while simultaneously demonstrating the importance of maintaining permanent systems for forecasting, monitoring, pumping, drainage and recovery.
Colombo already possesses parts of that system and has benefited from substantial investment in flood resilience. The question is whether we protect that investment with the same seriousness with which we announced it, and whether urban development decisions made today are quietly recreating vulnerabilities that yesterday’s projects were designed to remove.
Be that as it may, government cannot reasonably be blamed because rain falls. It can, however, be questioned about whether drains work, whether pumps are maintained, whether wetlands survive and whether lessons from the last flood were still being acted upon when the next one arrived.
Bangkok is presently discovering the limits of its flood defences under enormous pressure. Sri Lanka should watch closely, because the useful comparison is not which capital gets more water. It is which city learns more from the water after it has gone.
