The Chao Phraya dam in Chainat province in the Central Plains has discharged less volume of the excess water from the last storms, at 2,545 cu m per second today, but is instructed to brace for new rain and water next week. Credit: National Water Command Center

Weather experts warn the public to brace for impacts of coming tropical storms

They agree that this year’s rainfall and flooding behaviour is different from the previous years although climate change is not directly pinpointed as having a role yet

Hydro-Informatics Institute Director Dr. Sutat Weesakul has shared this year’s rainfall pattern with the Foundation of National Disaster Warning Council today, revealing that rainfalls came early this year, starting from the dry month of April, when they had resulted in more rainwater than May, the start of the rainy season.

But when the country entered the rainy season, rainfalls became absent twice in late June and early August before they heavily poured down in the Lower North and the Central Plains with two major storms hitting the country in September.

Fortunately, the storms did not bring the same high volume of rainwater as that recorded in the year of great flooding in 2011, which was over 1,800 millimetres. This year’s rains, with a total volume of around 1,200 mm. so far, have caused overflows in certain water channels including the Chao Phraya River, not massive floodwater all over the country like in 2011, noted Dr. Sutat.

The water stored in major dams this year, meanwhile, is far less than that stored in 2011, so the dams can hold the water and do not have to discharge its excess liquid downstream and exacerbate the situation, he added.

However, the weather experts have cautioned about the coming storms, saying people should not be complacent to protect themselves from possible flooding.

Credit: TMD

Dr. Sutat said Lionrock and Kompasu that are forming in the Pacific are travelling towards Thailand. Lionrock has reportedly landed in Northern Vietnam this afternoon. It will lose strength and become the tropical depression that likely hits possible the Lower North and the Upper Northeast of Thailand. Kompasu, meanwhile, is expected to have landed on the same part of Vietnam in the next few days whereas its impact is less clear, noted Dr. Sutat.

Dr. Sutat said the storms could intensify the Southwestern Monsoon which is blowing through the Upper South, resulting in heavy rain in the area.

“The two storms would likely bring less rainwater than the previous ones, but they could influence the Monsoon, which can result in more rain in our areas than usual,” said Dr. Sutas.

Read: Authorities rush to discharge massive water volume from last rains to keep Bangkok safe from great flooding risk

The flooding in Angthong, as of yesterday. Credit: RID

The obstruction

Dr. Seree Supratid, Director of the Climate Change and Disaster Center at Rangsit University, said people should not be complacent about the two storms and another low-pressure cell forming in the sea.

According to Dr. Seree, 16 storms have formed in the Pacific Ocean so far. It is predicted that there could be around 25 tropical storms this year. Based on this prediction, Dr. Seree, who has posted on his Facebook Page, said there could be as many as nine more storms forming in the sea and 30% of them could hit the region and the country.

He pointed that at present only a few storms could cause great flooding as the ocean’s temperature is warmer due to climate change, thus more moisture strengthens the storms.

The country’s climate expert is also concerned about obstruction against the flow of the current excess water in the Central Plains.

Following his fresh inspection, the water levels of the overflows in several locations are now close to those of the 2011 floodwater, despite the fact that the volume is far less.

This has resulted from flood prevention infrastructure as well as untidy city planning that have lifted the water levels to a critical point, he pointed. In some areas in Angthong’s Chaiyo and Pa Moke districts as well as in Ayutthaya’s Bang Ban further downstream, the water pressure has broken down dykes and flooded them, he revealed.

The situation has become so intensified that some residents have stepped out to compete for safety from local flooding with guns, he said.

“They have warded off others to not build dykes and block the water in their areas,” Dr. Seree shared the fresh information to the foundation.

I The flooding situation in the Lower North and the Central Plains caused by the last two storms. Up to 1.4 million rai remains flooded, as recorded by GISDA on October 8. Credit: GISDA

The climate expert said the new storms could result in 150 to 200 mm in the country and cause the water levels in the Central Plains to rise by at least 50 cm. The greater risk could be with the Pasak Jolasid dam, which was overly filled up the last time and may need to discharge the excess water downstream again, thus exacerbating the situation in the Central Plains.

The expert agrees that the storms and the Monsoon could hit the Upper Northeast, the East, and the Upper South the hardest, with rainfall over 200 mm over the next week.

He is particularly concerned about several middle-sized and small dams that have been almost filled up from the last storms.

The climate expert said there is a gap in flood risk management and flood prediction and warning that need to be filled up so that people can better prepare themselves for possible flood disasters.

“You cannot warn people by letters. They cannot picture what will be going in their areas,” pointed Dr. Seree.

The National Water Command Center, meanwhile, has issued its 22nd warning, projecting possible flooding and landslides in several areas following the Monsoon and the coming storms next week.

The center has also instructed concerned officials to monitor areas with rainfall over 90 mm. in 24 hours as well as major and middle-sized dams with 80% of stored water. They must adjust the rule curves to ensure that the dams will not hold water beyond their capacity while ensuring that the excess water subject to discharging will not affect areas downstream.

In addition, they must also monitor possible flooding and overflows in low lying areas. Flood management plans to handle possible flooding and overflows must be put in place in advance along with flood management equipment and personnel and water retention areas. Last but not least, a warning for emergency evacuation must be issued immediately if there is a situation, the centre has instructed concerned officials.

As of today, the Disaster Prevention and Mitigation Department has reported that 33 provinces and over 300,000 residents have been affected by the two previous storms. 16 provinces have recovered from the flooding, while the rest of 17 are still coping with floods in their areas.

Vast fields in the Central Plains have been used to help hold up over 900 million cu m of the excess water from the two last storms. Credit: ONWR