The same rain fell throughout the island but only in some places there is flooding. Why? I did some ‘exploring’ with Google Earth and uncovered one common denominator in all the cases of flooding I inspected, namely, the Orchard Rd-Scotts Rd-Paterson Rd Junction, The Tessarina Condo at Bukit Timah and Upper Thomson Road where a Roti Prata shop among other business suffered damages and losses from flood water invading their business premises.
In all these cases, ONE factor has unfailingly stood out – the flooding was likely the result of PONDING, i.e., collection of rain water, in depressions or basins. (In physical geography, a BASIN is defined as a hollow or depression in the earth’s surface, wholly or partly surrounded by higher land.) This is in fact the case in all the three flooded places investigated using Google Earth.
Since a picture equals a thousand words, I will let the following graphics prepared with the help of Google Earth ‘speak’ for themselves. It should be pointed out that the basins by themselves do not cause flooding IF rain water is able to flow away/out from them via the drainage system. Flooding occurs when either the drainage system in the locality is blocked or failed to clear the precipitation fast enough, i.e., more water falling that the drainage network is able to carry it away.
In the present flood, many has raised the issue of the Marina Barrage being implicated. Although the NEA has defended the Barrage, the minister, Dr Yaacob, failed to provide what I consider to be vital data to convince Singaporeans. Sweeping vague statements cannot hope to convince. Vital information which has so far not been made known to the public include: How has the barrage increased the everyday ordinary DRY weather height/level of water in the rivers, streams, canals, monsoon drains etc which form the network feeding the Marina reservoir? The concern here is, in order to impound/accumulate water, which is the raison detre for the construction of the barrage, the water level in all the feeder waterways would definitely have gone up due to the blocking effect of the barrage. By how much? Then there is also the question of whether the capacity of these feeder rivers, streams, canals and drains have been enlarged/modified to cater for a daily higher water level AS WELL AS an even higher level in the event of a downpour? Has any thought been given to this point by the NEA? Was there a miscalculation? When you have more water in the system on a ‘dry’ day, wouldn’t this logically mean that the carrying capacity in the network for rain/storm water has been correspondingly REDUCED for ‘wet’ days if no modification or improvement has been made to expand the network’s carrying capacity in order to accommodate the impounding role of the barrage? One begins to wonder in the light of the flooding. Rocket science this isn’t. But a lack of care is suggested in the overall study, planning, development and execution of the Marina Barrage project. Actually, it would appear that there is already an indirect admission that this was overlooked in the original planning and development when Yaacob replied in parliament that future modification to enlarge the extant capacity of waterways esp. Stamford canal etc will be looked into. Hindsight. Afterthought. Like locking the gates after the horses have bolted.
One more point. Although there are ‘sensors’ distributed within the system (according to the minister) to detect water level, the question is how are they primed? Commonsense suggests that waterways furthest away from the barrage might have to be set at a lower trigger or tolerance point since it would take time for ‘far’ water to flow through the network to reach the barrage point. The further away, the longer it would take? The sort of sensors used is of interest too. IMO, it would be far better to monitor specific points using remote cameras pointed at specific water level markers planted throughout the network or even stretches of waterways then some electrical/electronic devices. Nothing like being able to actually eyeball a situation. If the LTA can mount cameras throughout its extensive network of roads, there is no reason why this cannot be similarly done for the waterway network.
On the pics:
The elevation profile at the bottom corresponds to the thick red line in the satellite map. The vertical scaling (by Google Earth) makes the presence of the basin obvious. On the ground, the basin’s presence is not obvious esp in a built-up area. Double click the mouse left button to enlarge the picture.