The Marina Barrage is the apparent pride and joy of Mr Lee, senior. Justifiably so too, but one wonders if it is possible at all for you, as the minister in charge now, to take a good and careful look at this huge project to see if certain ‘small’ issues had been left out, ‘lost’ inadvertently, in the midst of the hundreds perhaps thousands of details that must surely have gone into its planning, study, design and eventual construction?
I ask because from the freely available literature on the Internet on the subject of hydraulic structures and their constructions, including barrages, there is this mention of ‘AFFLUX’ which is defined by one source as:
The rise in maximum flood level of the river upstream of the barrage as a result of its construction is defined as Afflux. Afflux, though confined in the beginning to a short length of the river above the barrage, extends gradually very far up till the final slope of the river upstream of the barrage is established.” – Design of Barrage – How to – Criteria for Design of barrage
Afflux, Flooding, Operation of Barrage Gates and Afflux Bunds
It really is all highly involved and technical stuff.
I can clearly recall during the early days of the Great Orchard Road flood several months back the PUB discounting what some netizens have blogged about the possibility of the Marina Barrage having a ‘hand’ in the flood. According to the PUB then, Stamford Canal/Orchard Road is too far (upstream) to be affected by the Barrage. Netizens pointed out the fact that the recent flooding started only AFTER the Barrage was commissioned. To any layman (like me, and others) the coincidence is simply hard to dismiss as, well, coincidental! The significance of Quote 1 is the possibility therefore that afflux caused by the Barrage structure can cause water levels to rise throughout the drainage/waterway system, including the Stamford Canal, draining into the reservoir formed by the construction of the Barrage. The impounded water could also have effectively raised the levels of the waterways (and the water table) and correspondingly reduced their abilities to hold more water in a heavy downpour.
In two of the above quotes, what caught my attention also was the mention of a need to build Afflux bunds to help cope with keeping water from overflowing the banks of the river in the event of a ‘design’ high flood level situation and above.
My question, was this taken into consideration by the PUB in the construction of the Barrage? In any case, would it had been possible to build the bunds (or their equivalent) for the Stamford Canal even if the PUB had wanted to, given the limiting factor that the entire length of the canal runs underground beneath the road surface – down Orchard Road to Stamford Road to Raffles Avenue, before turning south and emptying into Marina Bay? Seen in this light, the flooding of Orchard Road appears inevitable.
The minister is spot on when he admitted recently that the Stamford Canal has already reached its maximum capacity. Perhaps, he may want to consider looking into the possibility that the Barrage might just be responsible for ‘prematurely’ hastening this. Should he also prematurely rule out the possibility that modifying the operation of the Barrage might just have a role in the overall solution to the Orchard Road flooding?
P.S. Additional Comments.
Is it not possible for instance to verify this by opening all the gates at the Barrage to allow maximum unimpeded water flow to the sea (to the extent possible with the Barrage structure already in situ) so as to roughly simulate ‘pre-Barrage’ days conditions? The severity and any occurrences of flooding when it rains can be tracked and the results later compared with flood and deluge data gathered earlier. The tracking should be over a reasonable period during which some comparably heavy rainfall must have fallen to enable some realistic comparison to be made. Such indirect empirical data may be one way to obtain some indications of whether there is or isn’t an issue as far as the Barrage is concerned. Is the idea feasible? If it does help to remove some doubts, why not give it a go? As the Barrage is something we got to live with, one way or another, we should know, and we better know.
– inserted 4 Jan 12, 11.30 pm
Just my two pebbles’ worth.