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Marina Barrage - Fighting With Nature

Introduction
There was recent spate of flooding in Singapore. The famous Orchard Road was under 300 mm of water. Some blamed the Marina Barrage that was completed 3 years ago. This article will examine how the barrage works and if it can alleviate flooding in low-lying areas.

The Marina Barrage
The Marina Barrage (Chinese:滨海堤坝) is a 350 metres low level dam in Singapore built across the mouth of the bay, between Marina East and Marina South. It was officially opened on 1 November 2008.

The barrage serves 3 purposes:-
a) Provide Water Supply
b) Perform Flood Control
c) Lifestyle Attraction

The video about the barrage can be found here

How the Barrage Works?


During heavy rain, the series of 9 crest gates at the dam will be opened to release flood water into the open sea when the tide is low. The 7 Nos of 40 m3/s (about 2.5 MW @ 3.5 m head) pumps, capable of pumping an Olympics-size swimming pool per minute will work when the tide is high. This mechanism is supposed to alleviate flooding in the low-lying areas in the city such as Chinatown, Boat Quay, Jalan Besar and Geylang.

The video of the crest gate and the pumps can be found here and here.


The Marina Basin



The Marina Basin has a surface area of about 240 ha (240,000 m2). It is linked to a 100-km2 rain catchment area shown green in the attached model. During raining days, the drains and canals will channel the flood water into the Marina Basin.


The flood
A series of flood occurring after the Barrage was completed



Can the Marina Barrage Cope?
The Barrage and the basin will not eliminate flooding totally if there is a very heavy downpour and the tide is high. This is because the rain fall from the water catchment, if more than those on 17 July, may raise the water level Marina Basin by more than 4.0 metres (discounting the retained water on the surface of the catchment and the buffer in drains/canals/river) during a heavy downpour as shown in table 1.


2o August 2010
What Can We Do?
a) Reduce the Water Catchment Area
If we were to reduce the catchment area by 40%, this will reduce the water level rise in the basin by about the same proportion to 4.5 metres per hour without pumps and 4.0 metres per hour with pumps in full operation. The alternative is to regulate the flood water flow from higher areas.

b) Allow More Buffer Capacity In Basin
With the present barrage, there is a limit on how much a buffer can be created in the basin because the gates are not totally water tight. There will be seawater leeching into the basin if there is large difference in the level of water in the basin and the open sea; also, the pumping electricity cost would be high if we keep the water level in the basin low.

Reducing the water catchment area appears to be a better of the 2 solutions for the present setup at the Marina Barrage.

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