Bangkok 'can handle' deluge if there is no more downpour

"The situation should be manageable if no rain's coming," Sanya Sheenimit said yesterday in his capacity as the head of the Bangkok Metropolitan Administration (BMA) Drainage and Sewerage Department.

The runoff water is expected to reach Bangkok on either the coming Monday or Tuesday. Yet the huge volume of arriving water is unlikely to send floods to the capital given that the average height of embankment along the most vulnerable stretch of the Chao Phraya River in Bangkok is now at 2.5 metres. That height is enough to cope with the flow of 3,500 cubic metres of water per second.

As of press time, about 3,183 cubic metres of water flew past Ayutthaya's Bang Ban district per second. Ayutthaya is just about onehour drive from the capital.

Although up to 3,700 cubic metres of water was expected to travel past the Chao Phraya Dam in Chai Nat on Monday and Tuesday, not all will head directly to Bangkok. The overflowing river will definitely send runoff water to Nakhon Sawan, Sing Buri, Lop Buri, Angthong, Ayutthaya and Chai Nat before affecting the capital.

Emptied paddy fields, ponds and waterretention areas in these six provinces can be expected to cushion the overflowing impacts, if any, on Bangkok.

Open fields in Ayutthaya, for example, will be able to accommodate up to 450 million cubic metres of water. Nakhon Sawan's fields and a big pond can take in up to two billion cubic metres of water, while Sing Buri's open fields are able to receive 400 million cubic metres of water.

In an exclusive interview with The Nation, Sanya said Bangkok was equipped with many floodprevention tools too.

"The embankment along the Chao Phraya River here has already stretched as far as 75.8 metres. Moreover, we have formed sandbags as embankment for another stretch of about 1.2 kilometres," he pointed out.

The Chao Phraya River's portion in Bangkok stretches over an 86km distance. Embankment construction for the remaining stretch is going on.

Sanya reckoned that the runoff water from the North could lead Rapipat and Maha Sawas canals to overflow in Bangkok but again proper measures were already in place.

Water in the Rapipat Canal, which stretches from the Chao Phraya River, can flow quickly to drainage lines prepared by the Royal Irrigation Department.

"The drainage lines will push water out to the sea," Sanya pointed out.

The water flow related to the Rapipat Canal can affect Bangkok's eastern areas like Nong Chok, Min Buri and Lat Krabang districts.

Sanya said when the runoff water from the North arrives, the water level in Maha Sawas Canal could climb up. This waterway, after all, is connected to the Tha Chin and Nakhon Chaisi rivers.

"But embankment along the Maha Sawas canal is in place," he added, explaining why he was optimistic about Bangkok's prospect even in the wake of floods that now rage across 29 provinces.

He said Bangkok presently had 158 pump stations, 21 waterretention areas, and more than 200 water gates to manage the situation.

He said the waterretention areas in Bangkok can hold up to 12 trillion cubic metres of water. With this improved system, the BMA can also reduce the water levels in the capital's canals much faster and more efficiently than before.

 "In the past, we could at most push the water level in the San Saeb Canal to 20 centimetres below sea level. But now, we can keep it at 70 centimetres below sea level," Sanya explained as to why Bangkok's canals became more prepared to deal with the runoff water from the North.

The lowering of the water level in canals needs the help not just of water gates but also of pumping stations.

According to Sanya, the Phra Khanong Pump Station, for example, could push out up to four million cubic metres of water per day.

Sanya urged Bangkok residents to stay on alert but not become too worried.

"We have a proper floodprevention system in place," he said. He added that in the event of floods, drainage tunnels in Bangkok would ensure the floodwater subsided quickly.

He said if the floodwater was about 20 to 30 centimetres deep in the past, relevant authorities would need about three to four hours to drain the floodwater.

"But now, we will be able to do it within oneandahalf hour. Also, if floods hit, the depth of floodwater should be much less than before," he said.

On the repeatedly flooded areas in Bangkok, Sanya said those areas were directly in the floods ways and thus residents there would have to know how to deal with the rising water sometimes.

"Water level in those communities will naturally go up and down. But we can provide assistance such as forming raised walkways for them during flooding," he said.