Dam Management, Drainage Keys To Flood Prevention In Thailand

[webfact]

EXCLUSIVE INTERVIEW

Dam management, drainage keys to flood prevention

Chularat Saengpassa, Jeerapong Prasertpolkrang

The Nation

BANGKOK: -- Petipong Pungbun Na Ayudhya, a flood and water management expert, gives Local News Desk editor Chularat Saengpassa his ideas to cope with the next flood season by August.

In terms of the overall management plan, in areas which are sources of the water, the middle areas and lower areas, what needs to be understood when the seasonal peak tides come?

There are plans in place, which are subject to changes on a daily basis, starting from the sources of the water - how much dams can trap rainwater, and later how much catchment areas can hold water, and the lower areas, down from Ayutthaya, can cope with the leftover [water]. The main principle is how the water should be drained when it travels to the lower areas, and the other key is how to manage the dams' operations to retain much of the water.

Did the heavy flooding last year result from water in the upper or lower areas?

Both. Rainwater volume was excessive in areas north of the dams, while the volume in lower areas [the Central plains] during the seasonal peak tide was very high.

Around 10 billion cubic metres (units) can be trapped by the dams, while the rest in the plains must be managed to keep the water at two metres for around 20 days to over a month in the plains, totalling about 4.6 million rai, which will gradually accommodate the 10 billion units, in order to slow down the current so that it would cause the least damage.

Which area will be hit hardest?

The 4.6million rai plains, but the severity will not be as bad as last year, if rainwater volume decreases, because waterways in the lower areas have been dredged.

To slow down the floodwater, we have to make sure how many days Phichit and Uttaradit can be allowed to be flooded. In a special area designated as a slope, the water can stay up to 20 days, while other areas where the water does not go, we may negotiate with farmers to ask them to plant the first two crops, while they will decide whether to do a third crop.

What are plans for rainwater volume in areas downstream of dams?

In the Chao Phraya basin, there are irrigation networks in place in provinces southward from Nakhon Sawan, but they are fewer in Phichit, which are however still manageable. The key is to cut out the excess water in Ayutthaya, which is the final line of defence. A key problem resulting in heavy flooding last year was the water from the swelling Pa Sak River crossed the Chao Phraya River to flood the plains on its east. To solve this problem, improvement to waterways connecting to Rangsit Canal have been made to drain water southward to pumping stations as quick as possible, while more flood barriers are being built and more pumps provided.

The main strategy is to keep the water north of dams in the dams - slowing down the water in the plains and making use of it the most. And the efficiency of flood drainage in the lower areas is maximised through building floodways, flood barriers, doubling roads as flood barriers, and drilling holes in roads or railways that block currents.

We have to think what to do if these projects, numbering more than 100, cannot be done in time. How do we drain water out of eastern areas of Bangkok? How do we do it in the west of Bangkok? By relying on natural waterways and increasing drainage capacity with more pumps and getting rid of natural obstacles?

If everything is done, no floodwater will reach Bangkok?

A. Some may, if flood barriers are demolished by people, or collapse by themselves. The new barriers don't need to be concrete, but in short term they should be heightened, or roads which double as barriers be heightened. Building new barriers within three months is out of question. It's not possible. The key worry is about barriers being demolished by people. But what can we do about it?

Q. What scenario will be likely or presented to the public?

A. It's up to rainwater volume, both in areas north and south of dams. No one knows about it now, but we can do an estimate in per centtime volume, whether it will increase or decrease from last year. For example, if it's 5 or 10 per cent less than last year, what scenario and management methods would be likely or used. What do we do if it rains when it should not, or rains at different volumes, in areas north or south of dams?

Q. Then there are many scenarios.

A. No. What I say is designation in parameters, and working out scenarios is based on the use of many parameters, and also on three other factors, or dimensions, which are time, volume and locations. Working out scenarios is also based on these three factors.

Q. The management has been planned from the aspect of the central government, what about local administrations, like the BMA?

A. The government has coordinated with local administrations, and given to them a Bt1billion budget for dredging waterways. I could feel their enthusiasm, for the first time, and I am following the progress of their works, which they will report back to the government within two weeks.

-- The Nation 2012-03-05

[hellodolly]

Sounds to me like all they are concerned about is Bangkok.

[lungmi]

Clean the congested waterways first before you dredge new ones! Millions of sandbags don't disappear by themselves.

[whybother]

Clean the congested waterways first before you dredge new ones! Millions of sandbags don't disappear by themselves.

You "dig" new canals. You "dredge" existing canals. "Dredging" IS cleaning the sand/silt out of an existing waterway.

(My English lesson for the day.)

[lungmi]

Clean the congested waterways first before you dredge new ones! Millions of sandbags don't disappear by themselves.

You "dig" new canals. You "dredge" existing canals. "Dredging" IS cleaning the sand/silt out of an existing waterway.

(My English lesson for the day.)

Thank you.

[zakk9]

Sounds to me like all they are concerned about is Bangkok.

You mean they should be concerned about farmers? In Thailand? But they only represent around 50% of the population and produce useless things like rice and vegetables. But in Bangkok, there are beautiful people with expensive, western style houses and fast cars. That's how real people live, real people who create real value, like... like.... oh yes, and Bangkok is the economic hub of Thailand, isn't it? I mean, all those factories upcountry won't be able to produce anything if people in Bangkok get their feet wet. That's obvious, isn't it?

[alexakap]

Talks. Just and only talks...

Now it is March already. Govt keeps talking.

But the raining season is already scheduled...

[billd766]

The main key to flood prevention is corruption prevention.

Manage that and the rest is easy.

[hellodolly]

Would also be a big help to have a reasonable plan in action for reforestation.

But that is a long term permanent solution with out enough tea money in it.

[miksguevara]

Would also be a big help to have a reasonable plan in action for reforestation.

But that is a long term permanent solution with out enough tea money in it.

this +1

[sparebox2]

Danm cannot prevent flood, it can only delay it.

Only Buddha can prevent flood.

[belg]

some people still in denial and blaming natural causes for what happend last year? how come they will not just say the during the peak of the monsoon, they released all the water out of the dams all toghether to be sure we would be flooded for months

[koto]

Aloha

Many wise, well thought out remarks and I agree. But one other thing that always seems to bother, The Pollution Solution Group, is that way to many people, Thai's and Farang's, either think Storm Drains are Sewers or they just don't care or know better, many use them as garbage disposals or Throw Their Trash on the Highways, Roads, Streets, If the trash isn't dumped directly into the Storm Drain, With Wind or Rain, all of these things, Plastic, Styrofoam, Toxic Cigarette Butts, Bottle-Caps, Cooking and Motor-Oil, Camera-Batteries, Old-Spoiled-Unsold-Food, Disposable-Lighters and what ever else one can imagine, Diapers, the list goes on, It all will end up in the Storm Drains, that should only carry our Life's Blood (Water) Into our Ocean, Lakes, Rivers, Streams, Creeks.

Two things happen here, due to the lack of the pumping out the Toxic Waste, much of it ends up in our waterways, be it Fresh or Salt, Drinking, Seafood , then when the big rains come, many of the Storm Drains, Plug-up and Back-up Spewing Toxic-Waste, Onto Our Streets, Into Our Homes, causing, Contamination, Bacteria, Infections.

We admit Flooding is Hell, but Toxic-Waste coming into ones Home is Living Hell, this can and should be Avoided.

Education, Education, Education, Stencil Storm Drains in heavy traffic areas, Thai, English Russian, with a Picture so All understand, Impose Fines. When we are not backing up and flooding our homes, this Toxic waste is Killing, Fish, Turtles, Crabs, Dolphins, Sea-Birds, all Sea-Creatures.

We "all" need to take an active part in making a difference, Appear, Call or Write your City Hall, News Papers, Radio, TV Stations, lets Nip it in the Butt, before we "Play It Again Sam" We are all in this neighborhood together.

Settle in the Past, Engage in the Present, so if tomorrow happens, we will have covered our back-side.

[jombom]

An interesting interview indeed, both for what was said, implied, and left unsaid.

The 10 billion cbm stored by the dams, equates to 1 month full flow of the Chao Praya river (at 4000 cbm per second).

The 4.6 million rai at 2 meter depth average is 14 billion, or about another month of Chao Praya. In others words a glaring admission, that the dams are not nearly big enough.

[Thai at Heart]

Indeed, dam_n management is the solution.

Are there enough capable dam_n managers to get the job done in the country??

[ResX]

Danm cannot prevent flood, it can only delay it.

Only Buddha can prevent flood.

More accurate is dam cannot prevent flood. It can only trim it to make it smaller, as long as the sluice gates can be kept closed. Otherwise dam is going to make flood even worse.

Base on time left, the only one thing Thailand can rely on but can still produce a good result to develop a clear strategy to prevent opening of sluice gates during the peak flood flow. If they are required to be opened then do it before the flood reaches its peak or after it hits the peak.

This is like playing chess. Sluice gates are the King. Once they are opened most likely it is going to be a "Checkmate".

[ResX]

An interesting interview indeed, both for what was said, implied, and left unsaid.

The 10 billion cbm stored by the dams, equates to 1 month full flow of the Chao Praya river (at 4000 cbm per second).

The 4.6 million rai at 2 meter depth average is 14 billion, or about another month of Chao Praya. In others words a glaring admission, that the dams are not nearly big enough.

Here is the calculation. Bhumibol & Sirkit are good for up 7billion cubic meter without compromising their roles to genarate power and to provide waters to farmers. Chao Phara dam another one billion cubic meters. Thailand needs another 7 billion to deal with one-in -fifthy years flood. There are many other dams besides these three since all dams in Thaland have storage capacity 75billion cubic meter.

I don't see any problem for 75billion cubic meter dams to deal with 17billion, 7-14 days flood flow. Unless that 75billion cubic meter dams do not belong to the CP river.The more realistic problem, as far as the information that I have is, most of the dams are in series. Your water management experts don't seem to have any clue about what does this mean. In reality such dams arrangement requires very complex coordination to execute water releases when it comes to flood. Very..very complex. Simplification is allowed if there is no problem to get BKK 2m below the flood level again.

[rubl]

The most amazing idea in this list of ideas from Petipong Pungbun Na Ayudhya, a flood and water management expert, is

"we have to make sure how many days Phichit and Uttaradit can be allowed to be flooded"

Anyone with an idea how people in Phichit and Uttaradit will respond? Please, no bad language though

[folium]

Danm cannot prevent flood, it can only delay it.

Only Buddha can prevent flood.

Sounds like Thai government policy re flooding.

Shut your eyes, extend your hand and pray.

[jombom]

An interesting interview indeed, both for what was said, implied, and left unsaid.

The 10 billion cbm stored by the dams, equates to 1 month full flow of the Chao Praya river (at 4000 cbm per second).

The 4.6 million rai at 2 meter depth average is 14 billion, or about another month of Chao Praya. In others words a glaring admission, that the dams are not nearly big enough.

Here is the calculation. Bhumibol & Sirkit are good for up 7billion cubic meter without compromising their roles to genarate power and to provide waters to farmers. Chao Phara dam another one billion cubic meters. Thailand needs another 7 billion to deal with one-in -fifthy years flood. There are many other dams besides these three since all dams in Thaland have storage capacity 75billion cubic meter.

I don't see any problem for 75billion cubic meter dams to deal with 17billion, 7-14 days flood flow. Unless that 75billion cubic meter dams do not belong to the CP river.The more realistic problem, as far as the information that I have is, most of the dams are in series. Your water management experts don't seem to have any clue about what does this mean. In reality such dams arrangement requires very complex coordination to execute water releases when it comes to flood. Very..very complex. Simplification is allowed if there is no problem to get BKK 2m below the flood level again.

Thank you for your detailed response, most of which I can accept as reasonable.

Could you please give info on where your figure of 75 billion total storage originates. Also you mention dams in series. Do you have a breakdown for primary dams and secondary (downstream) dams. My information (from internet) is that Thailand stores 40 billion cbm annually in the primary dams. IMHO this is not nearly enough. 80 billion would be much safer.

Your statement that management of dams in series is very complex is correct. However, in this day and age these problems have been overcome in many countries. The time constants between dams are known, and software is available too deal with the maths.

Finally your figure for Bangkok being 2 m below flood level is interesting. My understanding is that Bangkok is presently 1.2 m above sea level. I don't wish to have a major discussion about decimal points of 1 m, as this is all very close to the edge. --- so close in fact, that my toes are feeling wet.

[ResX]

An interesting interview indeed, both for what was said, implied, and left unsaid.

The 10 billion cbm stored by the dams, equates to 1 month full flow of the Chao Praya river (at 4000 cbm per second).

The 4.6 million rai at 2 meter depth average is 14 billion, or about another month of Chao Praya. In others words a glaring admission, that the dams are not nearly big enough.

Here is the calculation. Bhumibol & Sirkit are good for up 7billion cubic meter without compromising their roles to genarate power and to provide waters to farmers. Chao Phara dam another one billion cubic meters. Thailand needs another 7 billion to deal with one-in -fifthy years flood. There are many other dams besides these three since all dams in Thaland have storage capacity 75billion cubic meter.

I don't see any problem for 75billion cubic meter dams to deal with 17billion, 7-14 days flood flow. Unless that 75billion cubic meter dams do not belong to the CP river.The more realistic problem, as far as the information that I have is, most of the dams are in series. Your water management experts don't seem to have any clue about what does this mean. In reality such dams arrangement requires very complex coordination to execute water releases when it comes to flood. Very..very complex. Simplification is allowed if there is no problem to get BKK 2m below the flood level again.

Thank you for your detailed response, most of which I can accept as reasonable.

Could you please give info on where your figure of 75 billion total storage originates. Also you mention dams in series. Do you have a breakdown for primary dams and secondary (downstream) dams. My information (from internet) is that Thailand stores 40 billion cbm annually in the primary dams. IMHO this is not nearly enough. 80 billion would be much safer.

Your statement that management of dams in series is very complex is correct. However, in this day and age these problems have been overcome in many countries. The time constants between dams are known, and software is available too deal with the maths.

Finally your figure for Bangkok being 2 m below flood level is interesting. My understanding is that Bangkok is presently 1.2 m above sea level. I don't wish to have a major discussion about decimal points of 1 m, as this is all very close to the edge. --- so close in fact, that my toes are feeling wet.

It mentioned here 85 billion cubic meter, if my maths was correct. As I mentioned I didn't know what percentage belongs to the CP. Most likely not as high as I thought.

http://www.fao.org/nr/water/espim/country/thailand/index.stm

If I painted the river system for the CP correctly, Bhumibol and Sirkit are in parallel. But they are discharging to the mainstream of CP. That ultimately makes them in series too. Most of the downstream reservoirs such as Pasak Jalasid will end up discharging to the main stream of the CP too. Chao Pharaya dam is another one to be included. Therefore, series configuration is more accurate to describe their arrangement. These four reservoirs alone have the total live storage capacity of 20 billion ++ cubic meter.

Finally, can BKK tp be submerged 2m below flood water level? I think it is possible if the level of flood water mismanagement is around 17-20 billion cubic meter. Last year it was just around 10 billion cubic meter.

[jombom]

Thank you for the link. It will take me some time to digest it, as my spare time is in short supply, at the moment.

[jombom]

Reading the link and trying to understand the units, did not help a great deal. However, it was very useful.

It appears the Chao Phraya system drains 35% of the land area of Thailand.

From the wikipedia it appears the Bhumidol and Sirikit dams control 22% of the runoff. This is not a great situation, in an emergency.

Quote '' The Bhumibol and Sirkit Dams control 22% of the Chao Phraya's annual runoff combined.[3.

End Quote.

Obviously there has been a serious mismatch for many years.

Therefore, the doubling of storage on the Chao Phraya, as mentioned by the OP, is a large step, in the right direction ---- but not a final solution --- more a temporary solution.

[ResX]

Reading the link and trying to understand the units, did not help a great deal. However, it was very useful.

It appears the Chao Phraya system drains 35% of the land area of Thailand.

From the wikipedia it appears the Bhumidol and Sirikit dams control 22% of the runoff. This is not a great situation, in an emergency.

Quote '' The Bhumibol and Sirkit Dams control 22% of the Chao Phraya's annual runoff combined.[3.

End Quote.

Obviously there has been a serious mismatch for many years.

Therefore, the doubling of storage on the Chao Phraya, as mentioned by the OP, is a large step, in the right direction ---- but not a final solution --- more a temporary solution.

Going through the link you wil find a figure that states 85km3. This is actually equal to 85 billion cubic meter or 85 X 1000 X 1000 X 1000 m3

Based on taverage annual inflow of 75 billion cubic meter for the CP river, it is more than sufficient to keep flood risk around 2% if the dams in the north can hold at least 7 billion cubic meter for at least two weeks. The dams (in the north) shall able to hold the flood water and they shall not be allowed to be under "force to release scenario", i.e. they have to open their sluice gates. It is reasonably acceptable if the dams have to discharge through their natural overflow spillways, if they have ones. Care shall be taken to prevent opening of sluice gates. there must be a clear strategy from the start to prevent opening the sluices gates unless for the very extreme flood flow (return frequency lower than 1-in-50).

Once the downstream is "starved" by 7 billion cubic meter of water by the dams in the north during 1-in-50 year flood return, it is unlikely the entire flood waters within the CP catchment can cause much damage. The total active flood volume has reduced to 10 billion cubic meter. The entire CP river alone can store natural flood, based on my estimate, is 1-1.5 billion cubic meter. There are many smaller dams along the CP river. They have to be used effectively to deal with the remaining 8-9 billion cubic meter.

There are two critical success fartors to deal with floods in Thailand: 1) How effective dams in the north to serve as pilot dams to control the entire flow dowstream 2) If the dams in the north are going to fail to keep flood waters, sluice gates opening has to be well coordinated -Right time and right sequence relative to the down stream dams

[AleG]

Aloha

Many wise, well thought out remarks and I agree. But one other thing that always seems to bother, The Pollution Solution Group, is that way to many people, Thai's and Farang's, either think Storm Drains are Sewers or they just don't care or know better, many use them as garbage disposals or Throw Their Trash on the Highways, Roads, Streets, If the trash isn't dumped directly into the Storm Drain, With Wind or Rain, all of these things, Plastic, Styrofoam, Toxic Cigarette Butts, Bottle-Caps, Cooking and Motor-Oil, Camera-Batteries, Old-Spoiled-Unsold-Food, Disposable-Lighters and what ever else one can imagine, Diapers, the list goes on, It all will end up in the Storm Drains, that should only carry our Life's Blood (Water) Into our Ocean, Lakes, Rivers, Streams, Creeks.

Two things happen here, due to the lack of the pumping out the Toxic Waste, much of it ends up in our waterways, be it Fresh or Salt, Drinking, Seafood , then when the big rains come, many of the Storm Drains, Plug-up and Back-up Spewing Toxic-Waste, Onto Our Streets, Into Our Homes, causing, Contamination, Bacteria, Infections.

We admit Flooding is Hell, but Toxic-Waste coming into ones Home is Living Hell, this can and should be Avoided.

Education, Education, Education, Stencil Storm Drains in heavy traffic areas, Thai, English Russian, with a Picture so All understand, Impose Fines. When we are not backing up and flooding our homes, this Toxic waste is Killing, Fish, Turtles, Crabs, Dolphins, Sea-Birds, all Sea-Creatures.

We "all" need to take an active part in making a difference, Appear, Call or Write your City Hall, News Papers, Radio, TV Stations, lets Nip it in the Butt, before we "Play It Again Sam" We are all in this neighborhood together.

Settle in the Past, Engage in the Present, so if tomorrow happens, we will have covered our back-side.

I recently visited Japan, on the village of Shirakawa-Go I saw trouts swimming in the drains on the side of the streets. Blew my mind right off.

I reckon half that level of care for the environment would take generations, if ever to reach Thailand.

[jombom]

Reading the link and trying to understand the units, did not help a great deal. However, it was very useful.

It appears the Chao Phraya system drains 35% of the land area of Thailand.

From the wikipedia it appears the Bhumidol and Sirikit dams control 22% of the runoff. This is not a great situation, in an emergency.

Quote '' The Bhumibol and Sirkit Dams control 22% of the Chao Phraya's annual runoff combined.[3.

End Quote.

Obviously there has been a serious mismatch for many years.

Therefore, the doubling of storage on the Chao Phraya, as mentioned by the OP, is a large step, in the right direction ---- but not a final solution --- more a temporary solution.

Going through the link you will find a figure that states 85km3. This is actually equal to 85 billion cubic meter or 85 X 1000 X 1000 X 1000 m3

Based on taverage annual inflow of 75 billion cubic meter for the CP river, it is more than sufficient to keep flood risk around 2% if the dams in the north can hold at least 7 billion cubic meter for at least two weeks. The dams (in the north) shall able to hold the flood water and they shall not be allowed to be under "force to release scenario", i.e. they have to open their sluice gates. It is reasonably acceptable if the dams have to discharge through their natural overflow spillways, if they have ones. Care shall be taken to prevent opening of sluice gates. there must be a clear strategy from the start to prevent opening the sluices gates unless for the very extreme flood flow (return frequency lower than 1-in-50).

Once the downstream is "starved" by 7 billion cubic meter of water by the dams in the north during 1-in-50 year flood return, it is unlikely the entire flood waters within the CP catchment can cause much damage. The total active flood volume has reduced to 10 billion cubic meter. The entire CP river alone can store natural flood, based on my estimate, is 1-1.5 billion cubic meter. There are many smaller dams along the CP river. They have to be used effectively to deal with the remaining 8-9 billion cubic meter.

There are two critical success fartors to deal with floods in Thailand: 1) How effective dams in the north to serve as pilot dams to control the entire flow dowstream 2) If the dams in the north are going to fail to keep flood waters, sluice gates opening has to be well coordinated -Right time and right sequence relative to the down stream dams

Yes I am familiar with the units. You continue to mention the 1 in 50 year flood, but we know BKK has serious flooding every 15 years or so. The link below from the World Bank, gives predictions for 1 in 10 years, 1 in 30 etc. See page 48.

http://siteresources.worldbank.org/EASTASIAPACIFICEXT/Resources/226300-1287600424406/coastal_megacities_fullreport.pdf

My view, is that long term, some effort needs to be made to get the excess water, out of the Chao Phraya basin. A slightly strange idea, is to build a water paipeline from the Chiang Mai area, to say the mountains south of Korat. The south eastern seaboard area, has problems with water supply sometimes, and is earmarked for development. Chiang Mai has an elevation above sealevel of 300 metres, so gravity will do a lot of the work. Link below is for a pipeline under construction at the moment in the USA, with a delivery of 1 billion cbm per year (if my calculations are correct).

http://www.lcrws.org/pdf/EngineeringReport/chapter3.pdf.

Likewise something similar could move a lot of water from the mountains north of Phetchabun to the highlands near Mukdahan. So 2 pipelines and 2 billion cbm moved. People in Isaan could have a decent water supply ---- maybe.

In conclusion;

1) -- When the water reaches BKK it is far too late.

2) -- Water is an extremely precious resource. The idea of sending it into the sea asap, is a waste of money.

3) -- The OP has already accepted, that relief of the Chao Phraya basin is required. The solution has to be short-term, while a better system, is developed.

[jombom]

The search fuction on this website is atrocious. It seems to recognise nothing, but absolutely precise descriptions.