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The Great Singapore Flood – a case of ponding

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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.

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23 Comments

  1. bookjunkie says:

    wow…excellent investigation! i gained quite a bit of insight from your post.

  2. thetwophilo says:

    IMO there should have been consideration to level up such areas before they are built upon, be it a road or a condo. As I have mentioned in the caption of the first picture, it cannot be perceived on the ground, i.e., one wouldn’t know his condo is sitting in a depression. Perhaps, the land dept people should be obliged to inform developers of this and require them to either level up or raise the floor of their structures or to include measures to prevent water flowing into the basement. This may cost more, but surely no one wants his home flooded or cars submerged.

    As things now stand, properties, esp. a new development in such sites would find few takers. In fact, those in the market to buy should be well advised to check it out using Google Earth before commiting!

  3. Darkness 2010 says:

    Mmmmh….do you see what I see in ALL these sat photos? A pattern is emerging. No doubt abt it. That simply means, they can spend 100 years digging up the whole of Singapore and yet still not nail this sucker. They’re dealing with a moving target. And you know what is really ironical, the answer is in all these photos – it’s right here in this blog believe it or not. But it has nothing to do with datum. Even less to do with level sensors. Forget the cameras as well.

    I tell you there is $ to be made here. And where there is $ it never ever pays to volunteer information for free – only psychopaths who need attention do that – besides that can only be an admirable sentiment in this age.

    Let them chase their own tails a few more times; when they try everything and it fails – they will know what to do. They have too.

    Tip: Where does Orcam’s Razor runneth the straightest?

    Thank you so much, good work.

    Darkness 2010 – The Brotherhood

  4. kitana says:

    OMG! Hello Doe eyed Bambi Bad Darkness. Where does Orkams razor run the straightest? Dats a trick question isinit? The straightest line is the shortest distance between two points. So it is anywhere in a circle. Am I right?

  5. […] Flood of Singapore – TOC: Floods and politicking – which hits worse? – Thetwophilo’s Blog: The Great Singapore Flood – a case of ponding [Thanks […]

  6. Kerry says:

    It is hard to believe that the elevation on that stretch of Orchard Road varies from 51 m to 27 m. Must drive through that straight road again with a iPod 4 to verify the roller coaster run. The Google map must be pretty old, the patch of grass next to the Orchard MRT station is now all concrete, that same place where Filipino maids liked to hang out and picnic on Sundays.

    • thetwophilo says:

      I agree that the Google sat. map is not the most up-to-date. But the point is really not so much about the precision of the measurements – that would require an on the spot surveying with clinometer, theodolite etc. The sat. maps’ value is that they established the existence of basins or depressions in the flooded places which led to ponding when rain water run-off collected at the lowest point in the vicinity. In the case of Orchard Road-Scotts Road-Paterson junction the lowest point is right in the middle of the junction itself – the concrete jungle and sealed road surfaces effectively trapped the ponding water and caused it to accumulate.

      Incidentally, I did a couple more of reported floods – at Gentle Road and Marymount Road/Marymount Lane Junction -and found the same characteristic basin feature. (In physical geography, a BASIN is defined as a hollow or depression in the earth’s surface, wholly or partly surrounded by higher land.)

      I would be interested if you can provide an update of the elevation of that road. But please keep within the law while you are at it and ensure that your instrument is properly calibrated!

  7. Lee Chee Huang says:

    Where does Arkam’s Razor runneth the straightest? A circle says Kitana. Arkam’s rule states when you eliminate the most complicated explanation. You are left with the most likely explanation to account for the phenomenon. The circle line. Before Smrt built it. There was no problem with these areas. 🙂 Nice site

  8. […] This post was mentioned on Twitter by Daphne Maia, 河蟹 09. 河蟹 09 said: shares http://tinyurl.com/255lhr5 (The Great Singapore Flood – a case of ponding) http://plurk.com/p/6mafx3 […]

  9. […] Orchard Road flooded (again) (& again) / Tree fall down x 3 The Great Singapore Flood – a case of ponding | Thetwophilo's Blog The Great Singapore Flood – a case of ponding Posted on July 22, 2010 by thetwophilo The […]

  10. David Tay says:

    The concept and reasoning is not complicated but the poster has made it very clear and proven it with the diagrams. Thanks for posting, those million dollar salaried guys up there need to wake up to reality. The problem is not just with the rainfall…

  11. […] insurers: report – TOC: Floods and politicking – which hits worse? – Thetwophilo’s Blog: The Great Singapore Flood – a case of ponding [Thanks George] [Recommended] – The Kent Ridge Common: Flooding woes – the critical cause of poor […]

  12. George Washington Apples says:

    Darkness of the Brotherhood actually comes here? Coool. Great site! Will book mark it.

  13. […] alarms insurers: report – TOC: Floods and politicking – which hits worse? – Thetwophilo’s Blog: The Great Singapore Flood – a case of ponding [Thanks George] [Recommended] – The Kent Ridge Common: Flooding woes – the critical cause of poor […]

  14. […] Blog uses Google Earth to prove that the flooding was likely the result of ponding, or a “collection of rain water in depressions or basins.” The government has published its […]

  15. michael says:

    I entered the SLA challenge with a team of classmates, also investigating why Bt Timah floods, at one of your highlight spots. But sadly, I only found your website after we submitted our paper and presentation.

    Thanks for doing this analysis. It is indeed insightful. My project involved predicting the inundation based on hypothetical rainfall scenarios and pre-determined flow rate (Q) and drain capacity.

    Many hydrologists informally blame the recent floods on the Barrage. I personally think its a software issue, and experts may have operated in silos (not sharing hard hydro data), and not considering the big picture (no central planner/regulatory agent), or just simply lack of inter-agency co-ordination (very typical of certain departments).

    • thetwophilo says:

      Hi Michael,
      The concern about the Barrage is a valid one since its purpose is to impound water which effectively raised the water level within the drainage area blocked by the barrage. You can visit the barrage and observe the difference in the water level inside the impoundment and the sea level, separated by the gates.

      A consistently higher water level in the impoundment also raises the general water level throughout the drainage system feeding the reservoir (Marina reservoir). This means that the water table throughout has also been raised. The extent to which the water level is raised may be different depending on factors such as gradient and elevation above sea level. But basically what happens is that a raised water table would effectively reduce the water absorption ability of the ground involved i.e. in a given area the ground would be able to absorb less run off when it rains due to the additional water already in the raised water table.

      IMO, there is also the question of inertia. Even if the flood gates at the barrage is opened in a heavy thunderstorm, it will still take time for the impounded water to flow out into the sea through the open gates. Looking at the size of the Marina reservoir impoundment plus the drainage system, one can imagined that it would take quite a while for the ‘excess’ water to flow out into the sea through the gates. When the rate of precipitation is markedly higher than usual, as was apparently the case according to the NEA, you can imagine why flooding has occurred in places which were not previously flood prone. In fact, one location in Macpherson which was reported to be flooded most recently was just several metres from a canal indicating that the flood was caused by either water overflowing the banks of the canal or the canal was so full that it had failed to drained away the precipitation in that area.

      When unusual flooding occurs it is usually multi-factorial in causes and manifesting itself when a tipping point is reach. Yes indeed. All relevant depts must come together to find a solution. Before that they must first of all understand the causes before they could even begin to consider implementing remedies.

  16. anon says:

    Hi,
    Can you share a bit on what is the SLA challenge about?
    Thanks.

    • michael says:

      Its a pre-U and tertiary level competition where students use GIS (geog information systems) to analyse or solve a problem of their choice. (www.sla.gov.sg)

  17. […] showing the elevations around Orchard Road vicinity and it was turning into a sort of a pond. (see link and map […]

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