Bangkok flooding passes critical point: PM

Thai Prime Minister Yingluck Shinawatra on Tuesday reassured the Bangkok public that flooding in the capital has already passed its critical point and that floodwater in eastern part of the city should be totally drained into the sea before the year end.

The premier said the level of floodwater in Bangkok has continuously declined and, regarding the overall situation, the crisis has already peaked.

Ms Yingluck reasoned that drainage in east works efficiently and that she expects the situation to return to normal by the end of the year. But for western Bangkok, it still depends on repair work of the damaged temporary dykes along the Chao Phraya River, expected to be completed in the next few days. 

She conceded that some areas will remain under water but that she has instructed concerned agencies to speed up dredging canals so that they can drain as much water as possible during low tide.

Regarding the gap in the giant sandbag barrier, the ‘Big Bag Barrier’, which was widened and adjusted to a 10-metre spillway on Tuesday, the prime minister said its opening will minimize the impact on local residents and facilitate travel by boat. 

However, the amount of inflowing water must be limited to a volume that can be handled and drained out.

Echoing the prime minister, FROC spokesman Tongthong Chantarangsu said that the spillway will not cause a large amount of water inflow deeper into Bangkok but higher floodwater will be seen only in some areas such as Lak Si.

FROC will closely monitor the situation and speed up draining water.

‘Big Bags’, oversize sandbags, were used to build a barrier to slow the northern run-off into Bangkok to allow the authorities to drain the water out and to save Bangkok's inner areas, but some residents living outside the barrier-protected area angrily dismantled six meters of the embankment. 

It was later adjusted and described as a spillway on Tuesday.

Big Bag, draining 'key' to dry Bangkok

Today's flood news analysis on NBT, Dr Anond Snidvongs is joined by Dr Noppong Nopket, urban planning expert, who also works at Froc.

The key to save Bangkok is the efficiency of Royal Irrigation Department (RID) and Bangkok Metropolitan Administration's drainage system, noted Dr Anond.


How long to drain off floodwater in Bangkok?

Before answering this question from the anchor man, Dr Anond noted that before Big Bag about 15-20 million cubic metres a day leaking into inner Bangkok from Rangsit, flooding Vibhavadi, Phahonyothin down to Chatuchak and Lat Phrao. This is so because BMA's estimated drainage capacity is about 5 million cubic metres a day.

The floodwater also comes from the eastern front which in the past were low-lying areas for floodway such as Minburi, Nong Chok, and Lat Krabang. But there are now communities and industrial estates in these areas.

It will take 2-3 days to see how much impact Big Bag is but right now the floodwater level is lower about 30 cm below Big Bag.

Whether floodwater will overflow Bang Sue canal and creep downwards depends on BMA's drainage capacity. If the Bang Sue canal drainage capacity is less than the water replenishment then the invading water will overwhelm Khlong Bang Sue to Victory Monument and will be met by Khlong Sam Sen.

Asked directly whether it will reach there, Dr Anond and Dr Noppong think so but the level will be very shallow and small cars can navigate.

The estimated 14 days to drain off water from Don Mueang and Lak Si depends on the success of Big Bag that the northern front leak can be contained and the BMA's drainage capacity.

Froc's 71 pumps given to BMA will help a lot because the west of Bangkok has a lot of water to be drained off. With more pumps, the flooding days on the western front can be reduced.

Dr Anond recommends that the best way to solve the flood in Bangkok is to increase drainage capacity especially the natural pathway such as rivers and canals which Bangkok and Thailand have plenty but poorly maintained. This necessitates the intervention of big water pumps.

At a technical level, Dr Anond said he never experienced any difficulty from the first day working at Froc in coordinating with other organisations such as RID and BMA.

Dr Noppong Nopket noted that having toured various canals, RID and BMA accepted that canals were poorly maintained and could not function as natural pathway as efficiently as it should be. It is impossible to dredge all the canals in a few days to expedite waterflow. They should be done in an annual basis, comprehensively.

Dr Noppong also appealed to the TV audience that Big Bang at a great expense can help slow down waterflow. Bangkok is too important to let the whole city submerge.

Dr Anond chipped in that if Bangkok is inundated totally it may take 3-4 months to drain the city completely dry as the city is densely developed.