Tuesday, July 20, 2010

How the Marina Barrage Crest Gate works....

"The Marina Barrage reservoir did help in preventing a bigger disaster during the recent flash floods, said Dr Amy Khor, who was present at yesterday's event in Bukit Gombak"

"The Senior Parliamentary Secretary, Ministry of Environment and Water Resources, said that six out of the seven gates at the barrage were left open to manage the amount of rainfall during the heavy thunderstorms last month."

- Today 12 Jul 2010[Link]


Here's a set of pictures (courtesy of Kojakbt) that appeared in the Straits Times explaining how the crest gate works to alleviate floods:


You won't need a Phd or a engineering degree to understand where I'm getting at. Just simple common sense will suffice.

You look at the middle diagram which shows the crest gate lowered to allow storm water to go into the ocean. The pumps in the barrage are not used in this situation. The gate which has been retaining water is lowered to allow fresh water to flow into the ocean. Can someone tell me how this alleviates floods? When the barrage did not exist, water flowed unhindered into the ocean. Now we have to wait for the crest gates to open...and when they are fully open the passage for the water is much smaller than before when the barrage did not exist. When the gates are closed there is a lot of back pressure under heavy rainfall causing water to accumulate in the drainage system behind the barrage. It was reported that the crest gates were lowered during the recent floods so we did not face the situation where the sea level was higher than the fresh water level i.e. the pumps were not used during the recent floods.

I can understand that the barrage can block water from the sea when tide rises but I really can't understand how the barrage 'alleviates flood' when rainfall is heavy and the fresh water level rises above sea level. Can someone explain to me how having the barrage helps (compared with not having it)?

44 comments:

flooded said...

Barrage is typically used to alleviate floods in countries that are low-lying (almost below sea level). In this case, Singapore has no need for the barrage in the first place!

Anonymous said...

Who says we don't need it in the first place? We need it to create the Singapore Bund.

Anonymous said...

It is supposedly the vision of Old Man, so die die it cannot be blamed.

Anonymous said...

Amy Khor secured her next promotion by saying the Barrage prevented a DISASTER. It is equivalent to saying MM Lee prevented a disaster because MM Lee was the one who thought of having a barrage.

furrybrowndog said...

There are a couple of conflicting reports in the media. Here's the latest by PUB:
http://www.straitstimes.com/BreakingNews/Singapore/Story/STIStory_555796.html

Apparently they're now saying that the barrage didn't cause or alleviate the Orchard Road floods since the area was well above sea level and was too far away.

Anonymous said...

The barrage helps to reduce those flood cause by a coincidence of high tide and heavy rain. In this instance the Crest Gate will be closed to prevent the higher sea water from flowing inwards while the pumps work to drain away the excess rain water. However this is only effective if the pumps are fast enough to prevent rain water from increasing the overall water level in the WHOLE drainage system connected to the Marina Barrage beyond a flood-safe level.
The papists and their propaganda machines are dam fuckup in simple communication skills.

Anonymous said...

Lucky,

Correct me if I'm wrong. Sometime back, ST publish an article on the Marina Barrage and how it convert the sea water behind the barrage to freshwater from the rain water collected.

How can you re-concile the above mentioned process and flood prevention? Both are mutally exclusive. Either ST fed us wrong info last time or the minister are all lying this time round.

Paranoid Singaporean said...

If the barrage really did its job as the papers put it, there shouldn't be flood at all, right? It's suppose to prevent LOW-LYING area from flooding.

Let's see. water rises. Hey, I learned something new. WATER RISES! If Orchard Road isn't low-lying and barrage is supposed to prevent that from happening... pray tell; PAP, Water's suppose to flood from Oxley Rise first and then down to low-lying areas??! Right. They lost me.

All they are telling me is: We are doing something, but it was the wrong move all along but we are too prideful to admit it. *Facepalm*

Anonymous said...

just took at the size of the reservoir and you can see the real problems. PUB think that they are god and can do anything under the sky.
as usual without hearing the outcome of the paliament, they did not give a damn, so what?i'm god, you know.

Huang HW said...

Lucky, in a low-tide situation, the water level in the reservoir may be higher than if there is no barrage. In a heavy-rain situation, the rain water will build up behind the barrage causing a problem if the crest gates are not opened. If they are opened, then the water level while higher than in a situation without the barrage, is not allowed to go high enough to cause a problem.

Typically, the water level behind the barrage is somewhere between the high tide and low tide level; so the situation is no worse than the high tide situation before the barrage is built.

Thus, given that is is a low tide situation, the barrage did not make the situation better but should not have made it so much worse that it because a problem. (However, it is wrong in this case to say the barrage alleviate the problem, just that it probably did not make it worse)

However, all bets are off if the PUB had kept the water level near or above the high tide level because they are "kiasu" and wanted to collect as much water as possible! In this case, it is not the barrage's problem per see, but the way it is operated.

Anonymous said...

The main purpose of the barrage is to serve as a reservoir . A reservoir is a containment of water . Before the barrage, water flowed both ways, in and out of our land. With the gates, we trapped the water we need for conversion and drained out excess water from the rain. So theoretically, high tide and low tide have to effect within the barrage unless in extreme cases. Previously, our inland water level rises and falls according to the tide. But given the current situation, I suspect those low lying areas will flood - with or without the barrage. Hence, the problem is not with the barrage but instead, my suspicion, at the canal and that's the reason why they are addressing the problem at the canal.

Anonymous said...

Lucky Tan,
you have nailed it. Our gov is well-known for engineering stupid design and implementation, and yet they think that they are superior of the world.

Anyone can remember how the MRT station used to have metallic bench who sit is slided at a angle where your button will slip off the slippery metal surface ?

Anonymous said...

Amy Khor is either incompetent or trying to deceive us with those remarks.

As parliament secretary for MEA she shows no understandibng of how the barrage works.

Anonymous said...

If the flood causes the loss of votes, garmen will act (especially so close to GE). garmen will have to find a scapegoat, most likely a lower level (not too low thou) civil servant.

Ministars cannot be faulted because they are paid millions. Otherwise, the myth is busted.

Maybe we should call in the myth busters.

Anonymous said...

hmm.. 17 July and 16 June.. both dates are high tides.
how come that Amy Khor say the gates are open?
based on the picture, those gates can't be lowered due to high tides..

Amy wrong or the picture wrong?

or they open wrongly and let in more water instead?

Anonymous said...

The contractor undersize the pumps? The inlet flowrate is faster than the outlet flow rate?

Anonymous said...

After looking at the diagram and explanations, I am almost convinced that the floods are caused by the barrage. This is because the water flowing outward has slowed while the rains are abnormally heavily in the last few times that we had floods. It is really no rocket science ! The gates and pumps do help to expedite the flow out; precisely we need them because the barrage retards water flowing out to the sea ! The barrage does have its advantage of creating a new reservoir and perhaps creating a new toursit destination. There is a price to pay for a new reservoir and can be explained well to the public. We can then solve the problem by relooking at the capacity of our existing infrastructure now. I am very concerned that we seem to have a more serious problem than flooding : Our leaders have to be always right and they cannot make any mistakes; they are equivalant to god ! This is the start of a downfall for any city states in history.

Anonymous said...

I believe there are several contributing factors to the floods we are experiencing.

These may include extreme weather conditions dumping more rain than expected, too rapid building development resulting in more water run-off instead of being absorbed by the grounds previously, and the effect of the marina barrage.

Even before completing a thorough analysis of the possible causes, why is the govt quickly dismisses the possible effect of the marina barrage ? Why are they ruling this out as a contributing factor ? Is it because it was MM's pet project ?

It was mentioned that the marina barrage will always maintained a minimum level to sustain its role as a reservoir. How is minimum level derived ? How is this level compared to previous low/high tide level before the MB is built ? What is the effect of maintaining this minimum level has on the network of canals/drains that empties into MB ?

Unless and until a thorough analysis is completed with supporting data published, all these rhetoric by the establishments will sound hollow, and citizens will not be convinced.

In fact, the more they defend the MB now, the more suspicious we will be become.

Anonymous said...

My questions to her are:

1. Why wasn't ALL the 7 gates opened during a flood? That almost 15% of wasted discharge capacity.

2. Why wasn't the pumps activated at the same time as lowering the gates during an emergency when an "intense storm" is underway and flood reports starts coming in?

Whatever she was smoking lately, I want some of that

Anonymous said...

In their haste to have our own S'pore Bund, the authorities did not calibrate properly the water levels in the Marina Reservoir. What we have seen is the miscalcutions of rainfall, drainage and back flow. Those engineers shd just admit to their mistakes and go back to the drawing blocks. In spite of the recent fiascos, I do admit that the barrage is very needed to ween us off M'sia water ans also for a nice water front city.

Anonymous said...

At this point, when they approved all the new developments, could they have known that there is a remote possibility of flooding in these areas but took their chances anyway and now realized that they had miscalculated? Have they passed all the new constructions without providing adequate drainages?
The recorded total rainfall in a given area may not take into account of the dynamics between a straight fall and a wind assisted rainfall. For instance, in a straight fall on the ground without surrounding construction and a wind assisted fall with plenty of high rise buildings around, what would be the impact on drainages? I suspect accelerated drainage can develop under the latter scenario and could exacerbate bottleneck flooding if the central drainage system failed to factor the torrential output.
Could the problem then be a design oversight?

That said, the MB is likely to be a highly sophisticated precision controlled catchment with a generous barrier so is the least suspect.

We Want Truth said...

Great! The newspapers just reinforced my belief that MB contributed to the Great Singapore Flood.

So much for LKY's foretelling abilities...

Anonymous said...

To Anon 21/7/10 07:26

"hmm.. 17 July and 16 June.. both dates are high tides.
how come that Amy Khor say the gates are open?
based on the picture, those gates can't be lowered due to high tides.."

Everyday there are 2 high and 2 low tides, and you seemed ignorant of this fact.

That being said, can anyone explain why districts not connected to the Marina Barrage also had floods? My take on this is, that there are too many recent building developments and the 20-30 year old drainage system cannot cope when there is a torrential rainstorm. The amount of rainfall within 2 hours or more overwhelmed the canals. What is odd is that Opera Estate can be flooded despite the huge canal leading directly to the sea.

Anonymous said...

If the problem is at the barrage, it is easier to solve than a strained canal. The latter is a big headache for the authorities to solve. They have miscalculated and should take the wrap? Pay for damages to properties?

Anonymous said...

LKY couldn't care 2 hoots for the flooding or damage to properties or people's livelihoods. He's more concerned with creating 100% catchment area in Singapore, just like he said to hundreds of foreigners and in front of TV camera.

Otherwise by now, LKY would have banged table and throw a LCD monitor to have immediate task force to trace the actual problems and initiate rectifications. Will also have employed international experts on project basis by now. Just fly them in business class and put up in Raffles Hotel, pay them $200K each for the job can already. No need to spend like the ministers' multi-million dollar salaries -- which by the way the ministers are still going to collect, plus at least 40% increase in bonuses and pay increments too.

Anonymous said...

Someone has likened the Marina Bay entering into the sea like a woman's reproductive organ being blocked (by barrage) at the entrance.

Look at the map of Marina bay and barrage in www.map.gov.sg.

Any fengshui experts can enlighten?

Anonymous said...

The pumps (at one olympic size pool per 50 sec) and lowering of the gates can never make up for the lost of speed of the flow of water cause by the dam.

If all 'arteries' are connected, bleeding at one side doesn't affect the other far side? Maybe not visible yet until certain threshold is reached.

Could also be all the massive diggings around the island.

Kojakbt said...

"Someone has likened the Marina Bay entering into the sea like a woman's reproductive organ being blocked (by barrage) at the entrance."

Yes, there is a big (& hilarious) discussion about this on 3in1kopitiam forum:
http://forums.delphiforums.com/3in1kopitiam/messages?msg=36417.1

(warning: discussion thread is R-rated)

Kojakbt said...
This comment has been removed by the author.
Kojakbt said...

This info may be of interest to all here. Posted on 3in1kopitiam:

Some good folks in Stomp did us a favor by compiling the flood areas. We can see from the map other than Bedok, all flooded areas are in close vicinity of stamford, rochor, alexandra, geylang and kallang river, the canals/rivers flow towards kallang basin and then to the marine barrage, the MIWs are turning a blind eye to all tell-tale signs.

Example:marine parade is flooded and the nearest river in marine parade is geylang river which goes right into kallang basin and then towards the marine barrage or u guys call it the CHEE BYE.


Map of Flood Areas

Marina Reservoir and Canal Map

Anonymous said...

OMG our own netizens are doing much better investigative work than the 154th so-called "journalists", SHOCKING!

btw, i oso find it extremely distasteful that the 154th is trying to massage impression by reporting floods in China killing 7xx people. hey, you ass***** there, how about comparing the two countries' land mass and ministerial pay???

The Pariah said...

Huang HW's explanation (21 Jul, 01:19 hours) makes sense for low-tide days.

But other postings pointed out that those two flood days were high-tide days.

So how?

The Pariah, www.singaporeenbloc.blogspot.com

Anonymous said...

The floods happen during low tide lah. That's why there is no need to use those pumps and the flood gates were lowered. Anyone who say double whammy of high tide and rain is only finding a convenient excuse for the flooding.

Anonymous said...

The barrages of 'excuses' and impact mitigating words of the Parliamentarians had caused many to have the impression that they are not seriously looking into the problems as a result of the floods.

Me thinks that it is definitely alright for parliamentarians to ask for time to look seriously into the unexpected event(s) and sincerely come up with politically correct explanations and whatever measures that need to be done.

No, they just simply haphazardly said something to wriggle out of the problem. Be sincere to the people, if it cannot be helped, no citizen will force You to do the impossible, neither do they have the power to command the commanders of the State.

Anonymous said...

My apology;

the Comment at 22/7/10 at 0100 Hrs is by me patriot.

Anonymous said...

Majority of Singaporeans are a funny lot.

They question government's decisions after the consequences.

Before that, no one cares enough to even give a hoot.

I suspect these floods get more attention because it is not the poor HDB dwellers who are suffering. Those living in landed properties are getting the negative consequences of reduced home values and business losses.

Actually floods are okay to me. When it floods, companies declare off day and singaporeans can enjoy more family time together.

New flood related businesses can emerge giving our retail scene a much needed diversification.

Kojakbt said...

"New flood related businesses can emerge giving our retail scene a much needed diversification."

Canoeing tour along Orchard Rd?

Moe Gan Thai said...

Looks like the barrage becomes a white elephant.I remember MM Lee said before the barrage is more for preventing sea water from entering the low lying area in the city such as China town during high tide.Remember during high tide, China Town always flooded years back before the barrage was built.

Anonymous said...

Rex comments as follows,
to moe gan thai.

You said chinatown always flooded before the barrage build.
Really? i do not recall at all. The barrage was build fairly recently. maybe less than 4 years. i have never heard of anyplace get flooded as serious as orchard road, in chinatown or anywhere else in singapore after 1 hour rain, prior to the barrage works.

That, alone, proves that building the barrage to "prevent seawater coming in" and floods, is nonsense. As we are told by PUB, Orchard rd is 4 to 6 m above sea level, quite far from sea. Therefore as far as flood control of Orchard area is concerned, it is ABSOLUTELY unnecessary to build the barrage. History has shown that the discharge of ORchard road rain water to sea downstream via stamford canal was quite efficient, due to high gradient, and hence no floods for 1 or 2 hours heavy rain.
I think as good scientists, we should demolish the barrage and see what happens.

rex

Anonymous said...

Me thinks there is no need to demolish the Barrage if it is indeed contributing to cause floods. Probably another manmade waterway acting as a tributary to the existing river and draining into the sea will help. This will mean a second barrage will have to be built.

Alternatively, additional stronger and reliable pumps could probably be installed in addition to the existing ones.

If the Authority and relevant departments are willing to seriously and sincerely look into it, me believes they will surely be able to alleviate the problem.

Me likes to say that me am a layman using commonsense for the ideas suggested above. Do pardon if they are too far-fetched.

patriot

Anonymous said...

Rex comments as follows on patriot's post,

You are quite right, one possible solution is to open another tributary out to sea.
But then this is a one step forward two steps back solution. Without the barrage the discharge is good, no floods. With one barrage you obstruct the opening, therefore build another openign and another barrage. What a joke.
I hid my head in embarassment as Malaysians or Inodnesians laugh at us for succumbing to one hour of rainfall and blaming it on god and saying no amount of engineering can solve the problems. It is so unreal, i don't know if i am dreaming or it is reality that Singapore leaders had degenerated to such a sorry state.

rex

Anonymous said...

The excuses and reasons offered by the ministers lately are real cause for worries. All the leaders have shown themselves to be complacent, not serious in dealing with unfortunate and damaging floods, falling trees resulting in loss and injuries of live. Thoughtless answers were haphazardly offered when interviewed.

One even said that god had caused the natural events brushing aside the expectations of the people asking for measures to minimize the impacts, damages and inconveniences. Such attitudes and behaviors are indeed highly irresponsible.

Kevin said...

Orchard and many other places flooded yet again. I really believe the Marina Barrage is the cause of all these events. Reasons being these.
1. PUB stored more water than necessary thus raising the water level in the city.
2. Without the dam, the water level used to be self equalisation. Now, the barrage operator have to anticipate a heavy storm and release water in advance even before the water level starts to rise.
3. After Orchard road from Wisma till Centrepoint is raised up, the excess water will definately affect nearby areas thats not been raised. Simple common sense!

Kojakbt said...

PAP won't admit that it's the inadequate design of the Barrage that is causing the flood. Admission means damage payments of hundreds of millions of dollars to those affected Orchard Rd shops...