Flooding kills two in Thailand as more than 13,000 households are affected

Torrential rain has caused severe flooding across northern Thailand, killing two people in Nan province and affecting more than 13,000 households, while authorities warn that further rainfall could trigger flash floods, landslides and renewed river flooding in the coming days.

The flooding began after heavy rain hit Nan on Wednesday, with rainfall totals reaching 380 millimetres in some areas. Run-off from the upstream district of Pua flowed southwards, inundating communities along the Nan River and affecting several downstream districts.

Two people killed as Nan River overflows

Deputy Interior Minister Jaseth Thaiseth said two people had died in the flooding, one in Pua district and another in Tha Wang Pha district.

The Department of Disaster Prevention and Mitigation (DDPM) later reported that flooding remained active in four districts of Nan — Pua, Tha Wang Pha, Phu Phiang and Santi Suk — affecting 24 subdistricts and 99 villages. A total of 13,132 households, or 30,313 people, were affected.

Floodwater from Pua moved south towards Tha Wang Pha, Muang, Phu Phiang and Wiang Sa districts before continuing towards Sirikit Dam in neighbouring Uttaradit province.

The DDPM urged residents living near the Nan River to move household belongings, vehicles and other valuable property to higher ground. Authorities also instructed families to relocate vulnerable people, including bedridden patients, to safer areas.

Water levels rise in Nan municipality

The Nan River began overflowing in Phu Phiang district at 4.51pm on Wednesday and in Muang district at 6.58pm, according to the DDPM.

Officials forecast that the river would reach a peak of 9.10 metres at about 2am on Thursday, slightly below last year's peak of 9.49 metres.

Residents in several subdistricts of Muang and Phu Phiang were instructed to evacuate vulnerable relatives and move belongings to higher ground.

In Phu Phiang district, 17 evacuation shelters were established, mainly at Buddhist temples, schools and local auditoriums.

Floodwaters in Pua and Tha Wang Pha had begun receding by Wednesday evening. Pua recorded about 340mm of accumulated rainfall during the flooding.

Thousands lose power after electricity poles fall

The flooding and severe weather also disrupted transport and electricity supplies.

Fifteen high-voltage electricity poles were toppled and another 23 were left leaning along Highway 1256 in Doi Phu Kha National Park in Pua district, making the road impassable.

The damage caused a power outage affecting about 27,000 people. Electricity officials began restoring supplies, prioritising hospitals and evacuation centres.

Officials said the run-off had affected 72 villages in Pua district, although water levels were shallow enough for people to leave evacuation centres on Wednesday evening.

In Muang district, Nan governor Chainarong Wongyai said sandbags had been placed to protect Nan Hospital.

Four hospital buildings were equipped with concrete embankments, while generators could provide electricity for up to three days. The hospital also established a field hospital at the provincial public health office to receive accident and emergency patients.

Flooding spreads beyond Nan

Flood risks were also reported in other parts of northern and northeastern Thailand.

In Sukhothai province, flooding affected three districts, 16 subdistricts and 89 villages, according to provincial authorities. Preliminary information indicated that 1,732 households were affected, although the district-level figures provided by the province totalled 1,731.

No deaths or injuries had been reported in Sukhothai in the preliminary assessment.

The affected districts were Si Satchanalai, Si Nakhon and Sawankhalok. Si Satchanalai reported around 769 affected households, Si Nakhon 104 and Sawankhalok 858.

Agricultural damage in Si Satchanalai was estimated at about 112 hectares, equivalent to 700 rai.

Authorities evacuated residents, moved household belongings to higher ground and deployed vehicles, boats, machinery and rescue equipment. Food, drinking water and other essential supplies were also distributed.

A temporary shelter was opened at Wat Mon Kaeo in Ban Tuek subdistrict, Si Satchanalai district. One person was staying at the shelter at the time of the report.

Health authorities also deployed first-aid teams at Wat Ban Plai Na and Wat Mon Kaeo Subdistrict Health Promoting Hospital.

Satellite data shows wider flood-risk areas

Satellite-based assessments on Thursday showed an expansion of areas classified as facing very high flood risk across parts of northern and northeastern Thailand.

The Check Nam application, using satellite imagery from the Geo-Informatics and Space Technology Development Agency (GISTDA), showed extensive dark-red areas at 3.33pm on Thursday.

In Sukhothai, high-risk areas extended from Si Satchanalai and Sawankhalok in the north through Mueang Sukhothai and towards Kong Krailat district.

Much of neighbouring Phitsanulok was also shown as facing very high risk, particularly around Phrom Phiram district.

Red and yellow risk zones were also appearing across southern Uttaradit and northern Phichit.

In the upper Northeast, five provinces were identified as having particularly extensive high-risk areas.

Sakon Nakhon had the broadest red zones, including areas around the Nong Han basin and central parts of the province. High-risk areas were also visible along the Mekong River and inland catchments in Nong Khai and Bueng Kan.

In Nakhon Phanom, red zones extended along tributary basins in northern and central areas. Eastern Udon Thani also had concentrated risk zones close to Nong Khai and Sakon Nakhon.

Scattered red zones and yellow warning symbols were reported in parts of Kalasin, Mukdahan and Yasothon.

The satellite-based risk assessment indicated areas requiring close monitoring rather than confirming that all locations shown had been flooded.

Authorities issue warnings in Phetchabun and Ubon Ratchathani

The DDPM also issued urgent warnings on Thursday for parts of Phetchabun and Ubon Ratchathani.

In Phetchabun, heavy rainfall over two to three days created risks of flash floods, rapid run-off, mudslides, overflowing waterways and waterlogging.

The warning covered Sila, Tat Kloi, Na Sam and Hin Hao subdistricts in Lom Kao district, as well as nearby communities.

Residents were told to move belongings and vehicles to higher ground, secure valuables and important documents, avoid electrical hazards and assist vulnerable people.

Cell Broadcast warnings were sent directly to mobile phones in the affected subdistricts through the DDPM and mobile operators AIS, True and NT.

In Ubon Ratchathani, the Mekong River was continuing to rise and could overflow into low-lying riverside communities between August 20 and 25.

The warning covered parts of Khemarat, Si Mueang Mai, Pho Sai, Khong Chiam and Na Tan districts.

Residents in low-lying areas along the Mekong were advised to move belongings and vehicles to higher ground, monitor vulnerable family members and follow information from local authorities.

Further rain forecast for Nan

Although water levels in Nan were stabilising and gradually receding on Thursday, flooding remained severe in parts of Wiang Sa district.

Seree Supratid, director of the Climate Change and Disaster Centre at Rangsit University, said conditions were expected to improve over the following two days, with water levels likely to fall significantly on Friday and Saturday. The Nan River was expected to fall below its banks on Friday.

However, forecasters were monitoring a low-pressure system over northern Vietnam that could bring another period of rain to northern Thailand on Sunday.

Seree said another spell of rain was forecast for August 23, although the situation would need to be updated daily.

He warned that the soil in Nan and parts of the lower North was already saturated after days of heavy rain, leaving limited capacity to absorb additional rainfall.

This could increase the risk of landslides and flash floods, particularly in upper areas.

Forest loss highlighted after repeated flooding

Environmental academic Sonthi Kotchawat said recurring flooding in Nan was also associated with long-term environmental degradation, including deforestation and encroachment into protected forest areas.

He said large areas of natural forest had been converted to monoculture agriculture, particularly maize cultivation on steep mountain slopes.

Sonthi, a member of the Thai Environmental Academics Club, cited data showing that nearly 800,000 rai in Nan was devoted to maize cultivation. He also said about 1.8 million rai, or 24% of the province's 7.6 million rai of forest land, had been converted into areas described as “bald mountains” through agricultural expansion.

He said the combination of steep terrain, heavy monsoon rainfall and reduced forest cover had accelerated run-off into rivers and low-lying communities.

Reforestation and sustainable farming programmes have expanded in recent years, but large areas of degraded land remain vulnerable to erosion and rapid run-off during heavy storms, according to Sonthi.

Authorities strengthen disaster response

The DDPM has ordered provincial agencies to accelerate the deployment of personnel, machinery and disaster-response equipment to affected communities.

Officials were instructed to move vehicles and high-value property out of areas at risk before flooding occurs and to prioritise the evacuation of vulnerable residents.

Provincial agencies were also told to coordinate with irrigation authorities and district chiefs to monitor flood trends and estimate how long water would take to reach downstream areas.

That information is to be passed to the National Disaster Warning Centre so that Cell Broadcast alerts can be issued in advance to communities expected to be affected.

The authorities' response comes as several parts of northern and northeastern Thailand continue to face elevated flood risks following widespread heavy rainfall.