Thailand’s Disaster Prevention and Mitigation Department (DDPM) reported flooding has affected 58,977 households across 27 provinces. Some of the affected areas had already seen flooding earlier this month after a period of heavy rain from 16 September brought by the Southwest Monsoon.

According to images and data from Thailand’s Geo-Informatics and Space Technology Development Agency (GISTDA), the worst of the flooding is in northern and central regions.

In the north, Sukhothai province is the worst hit area with 7,392 households affected, mostly in Sri Samrong, Khirimas and Muang districts, according to DDPM. Prime Minister Prayut Chan-o-cha visited flood-hit communities of Sukhothai’s Sri Samrong district.

In the central region, severe flooding struck in Lopburi Province where 37,451 households have been affected. Over the last 2 days flooding has also been particularly severe in the neighbouring Chaiyaphum Province, where as many as 10,000 homes have been flooded, mostly in Muang, Bamnet Narong and Chaturat districts, after overflows from the Chi river and the Lam Khan Chu reservoir dam.

Map of flooded areas (shown in blue) in Thailand as of 27 September 2021. Image: Geo-Informatics and Space Technology Development Agency

Rainfall, Rivers and Dams

The recent bout of heavy rainfall began around 23 September, influenced by Tropical Storm Dianmu. In a 24 hour period to 24 September, the city of Ubon Ratchathani recorded 146.6 mm of rain, according to the Thai Meteorological Department (TMD). The following day Tak Fa in Nakhon Sawan Province recorded 202 mm of rain and Phliu in Chanthaburi Province saw 182 mm.

According to figures from Thai Water, rivers are above flood level in 39 locations in the Bang Pakong, Tha Chin, Pa Sak, Sakae Krang, Chao Phraya, Nan, Yom, Ping, Mun and Chi rivers, as of 27 September 2021.

Levels of reservoirs and dams are critically high in 11 locations, Thai Water said, in particular in the Mae Mok dam in Lampong Province, the Chulabhorn dam in Chaiyaphum Province and Nong Pla Lai dam in Rayong Province.

The Meteorological Department’s latest forecast said the entire country, including Bangkok, will see further heavy rainfall. Authorities in Bangkok have been making preparations, installing flood barriers and pumps.