Sonca Storm in Thailand

August 3, 2017
Sutiwat Prutthiprasert

InterRisk Thai Flood Report 2017: Sonca Storm in Thailand


In the past week, the overall country was affected by the Sonca storm, especially in the northeast and north regions. There were floods in several provinces such as Sakolnakorn, Kalasin, Chaiyaphum, Phrae, and Phayao and the rain seems to be continued until next week.

The water level of the major dams has increased but still much less than the full capacity. The water level of the Yom river is high in Phrae, Pichit and Lampang. While for the Chao Phraya river, the water level is high in Ayutthaya and Angthong.

RID News:

RID revealed that the influence of “Sonca” storm caused heavy rain in several areas especially in the northeast region. The water level in Chee and Mool river has been increasing. For the situation in Sakolnakorn, there is still flood water in several areas. RID has supported 10 water pumping machines and 26 water propulsions to push flood water back to the river. While in Kalasin, the JMC committee of Lampao dam had decided to increase the drainage rate since 30th July from 15 to 20 million m3 which might cause flood in 5 districts, the governor had ordered for preparation.

Moreover, the RID also had flood prevention and relief plan in Bang Saphan Noi which is the flood affected area by dredging up Bang Saphan canal for 4.5km and planning to build water draining gate in Bang Saphan canal which will be finished in the next 2 years.


From 3rd-6th August, the overall country will have increasing rainfall and will be heavy in the Eastern region and west side of the South due to the southwest monsoon. There will be 2-3 meters waves in Andaman sea and the upper Thai Gulf sea.

Flood events

Flood incidents in the past week:

24th July: Continuous rainfall caused flash flood to overflow the river inundating the villages in Chiang Rai.
25th July: Continuous rainfall caused flash flood in Denchai District, Phrae Province.
26th July: Heavy rainfall in Phayao caused the water level in “Kwan Phayao” to reach its full capacity.
26th July: Several hours of raining caused flood in the Muang District of Kalasin, small cars are struggle to pass.
27th July: Flash flood destroyed roads in Khon Kaen. Landslide blocked the train tunnel in Chaiyaphum
27th July: High amount of rainfall in overall areas of Pitsanulok caused flood in many residential areas.
27th July: Broken flood wall caused the flood water to flow out into Sukhothai.
28th July: Heavy continuous rainfall caused flash flood to 8 provinces in Ranong.
28th July: Flooding in 8 Districts of Nakhon Rachasrima, 3 are severe.
28th July: The overflowed water from Huay Siton flowed into 10 residential areas, most severe in past 40 years.
29th July: Sakolnakorn in crisis. Flash flood hit the city, the runway had to be shut down.
29th July: The overflowed from Lam Kun Chu dam flowed into Bamnej Narong District caused flood.
30th July: The overflow of Chao Phraya river caused flooding in 6 Districts of Ayutthaya.
30th July: Yom river near Nakhon Sawan overflowed to the low level land.
31st July: Huay Sai Khamin reservoir in Sakolnakorn was broken by the flood water.

Flood in the north and north east of Thailand by tropical storm Sonca during 21-25 July 2017

Chiang Rai

100 houses flooded

480,000sq.m. of damaged crop fields

Sri Saket

32,000,000sq.m. of damaged crop fields


420 houses flooded

11,200,000sq.m. of damaged crop fields

Nakhon Panom

3,200,000sq.m. of damaged crop fields

Storage Level Sirikit Dam

Storage Level Bhumibol Dam

Amount of water stored is increased in both Major dam, especially Sirikit dam where the water increased by 10% however, the amount of water stored is still much lower than 2011 and from the dam capacity.

Storage Level Pasak Dam

Storage Level Kwae Noi Dam

Amount of water in has increased since last 2 weeks especially at Kwaenoi dam where the amount of water is much more than 2011 but still much below the dam capacity. Still, the amount of water in this dam alone would not determine the possibility of flood. However, the situation shall be monitored.

The Upper Chao Phraya River Flow

The amount of water from Upper Chaophraya has increased to almost double from last 2 weeks. Increased amout of water in the river in many region in the upper Chao Phraya River especially Wang, Yom and Nan river. At Phichit the amount of water is high but not yet flooded.

The Lower Chao Phraya River Flow

Amount of water in Chaopraya River increased especially in Ayutthaya and Angthong area due to increase amount of water release from Pasak dam. Amount of water from Upper Chao Phraya River has also increased. However, Irrigation department has diverted water to canal, therefore the amount of water at Chao Phraya Dam has slightly decreased due to the management.



Sutiwat Prutthiprasert