High-Tide Flood Alert for Bangkok and Six Central Provinces

The Department of Disaster Prevention and Mitigation has placed six central provinces and Bangkok on alert for possible flooding from very high tides expected between Tuesday and Saturday this week, urging residents in low-lying riverside communities to prepare for potential river overflows.

High Tide Flood Alert Issued for Bangkok and Six Provinces

Bangkok, Thailand — The Department of Disaster Prevention and Mitigation (DDPM) warned on Tuesday that low-lying areas in six central provinces and Bangkok should prepare for possible flooding caused by very high tides forecast from Tuesday to Saturday this week, 25-29 August. The warning covers the evening hours between 5pm and 8pm over the five-day period, when tidal peaks are expected to coincide with the monsoon season's high river flows.

The alert follows a familiar pattern for communities along the Chao Phraya River, who have faced similar warnings several times already this year. The DDPM has issued comparable high-tide alerts for the same six central provinces and Bangkok in January (18-22), June (14-20) and July (13-19), drawing on water-level data from the Royal Thai Navy's Hydrographic Department. This week's warning carries added significance because the August full moon falls on Friday 28 August, inside the alert window, amplifying spring tide risks in the Chao Phraya estuary.

What the Warning Covers

The DDPM has placed specific districts on alert across the six provinces. In Pathum Thani province, Muang and Sam Khok districts are named. Nonthaburi province faces risks in Muang, Pakkret and Bang Kruai districts. Nakhon Pathom province has Bang Len, Nakhon Chaisi and Sam Phran districts on watch. Samut Prakan province includes Muang, Phra Samut Chedi, Phra Pradaeng and Bang Bo districts. All districts in Samut Sakhon and Samut Songkhram provinces are under alert, alongside the entire Bangkok metropolitan area.

Residents in low-lying communities or those living outside permanent floodwalls, including in Bangkok, could experience river overflows, the department said. The warning specifically targets areas along rivers and canals where permanent flood defences are absent or incomplete. The department urges people to monitor the situation closely through the "Thai Disaster Alert" app, which provides real-time information on flood risks and water levels, and to treat the warning as a precaution rather than a certainty.

Why High Tides Threaten the Chao Phraya Basin

The Chao Phraya River, which flows through the heart of Bangkok and into the Gulf of Thailand, is particularly vulnerable to tidal influences. When very high tides push seawater upstream, they can raise river levels significantly, especially when combined with heavy monsoon rainfall and upstream dam releases. The Royal Thai Navy's Hydrographic Department provides the water-level data that informs these warnings, allowing the DDPM to forecast when tidal peaks will occur.

This week's alert window coincides with the August full moon on Friday 28 August, when spring tides are naturally at their highest in the lunar cycle. The gravitational pull of the sun and moon aligns during full moons, creating higher-than-normal tidal ranges. In the Chao Phraya estuary, this effect is magnified by the river's relatively flat gradient and the region's low elevation. The DDPM's warning of very high tides between 5pm and 8pm reflects the daily tidal cycle, when evening peaks can coincide with local rainfall and drainage patterns, increasing flood risk in vulnerable communities.

A Recurring Risk for River Communities

For residents of Nonthaburi, Pathum Thani and Samut Prakan, this week's warning is a familiar ritual. The DDPM has issued similar alerts four times in 2026 alone, with the Central Disaster Prevention and Mitigation Command Center (CDPMCC) coordinating with provincial authorities to inform residents and riverside businesses when tides are expected to peak. Alerted businesses include contractors working on floodwalls and riverbank protection structures, floating restaurants and other operations situated on or beside rivers and canals.

The memory of November 2025 remains fresh for many river communities. In October-November of that year, the Chao Phraya Dam released water at rates of up to 2,200 cubic metres per second, and tidal surges through October — especially during 13-23 October — raised river levels by an estimated 0.60-0.70 metres. Bangkok prepared about 1.5 million sandbags, while Nonthaburi residents built sandbag walls along the river as northern runoff moved downstream. A Bangkok Post photograph from November 2025 shows Nonthaburi residents constructing a flood wall of sandbags as the Chao Phraya River rose, a scene that may repeat this week in communities outside permanent flood defences.

Thailand's Sinking Capital: The Bigger Picture

The recurring high-tide warnings point to a deeper crisis facing Bangkok and the central plains. Bangkok is one of the world's most flood-vulnerable metropolises, with land subsidence in parts of the capital estimated at 1-2 centimetres per year. A study published in May 2026 put the city average at about 8.5 millimetres per year, a rate that compounds the effects of rising sea levels in the Gulf of Thailand, which are increasing by up to about 5 millimetres per year. Researchers point to decades of intensive groundwater pumping beneath the metropolitan region as a historic driver of this sinking, alongside the weight of dense urban development on soft delta soils.

Academics have warned that Bangkok faces a compounding flood crisis driven by land subsidence, rising sea levels and the loss of natural floodplains. A leading environmental academic, in a warning covered by Nation Thailand, has cautioned that most of the city could face submersion risk by 2030 without a fundamental rethink of flood management. The loss of natural floodplains upstream and the continued development of low-lying areas have reduced the landscape's ability to absorb and channel floodwaters, making tidal surges and river overflows more damaging when they occur.

What Residents Should Do

For those living outside permanent floodwalls or in areas without flood defences, the risk of river overflows is greatest during the evening tidal peaks between 5pm and 8pm. The department recommends staying informed through the "Thai Disaster Alert" app, which provides real-time updates on water levels and flood warnings, and preparing to move belongings to higher ground if water begins to rise.

For assistance, residents can contact the 1784 disaster hotline, available 24 hours a day, or use the LINE account @1784DDPM ("DDPM Incident Reporting 1784"). These channels allow residents to report flooding incidents and receive guidance from disaster response officials. The CDPMCC is coordinating with provincial authorities to ensure that information reaches riverside businesses and communities in a timely manner, particularly those operating floating restaurants and construction projects along the river and canals.

Regional Lessons for Southeast Asia

Thailand's experience with tidal flooding and land subsidence offers important lessons for Southeast Asian coastal cities facing similar pressures. Across the region, from Jakarta to Ho Chi Minh City, urban centres are grappling with the combined challenges of sinking land, rising seas and increasingly intense monsoon rainfall. The Chao Phraya Basin's struggles with high tides, upstream dam releases and inadequate flood defences mirror challenges faced by other river deltas in the region.

The recurring nature of these warnings — four times in 2026 alone — underscores the need for long-term investment in flood infrastructure and urban planning. Thailand's approach to coordinating disaster warnings through the DDPM, the Hydrographic Department and provincial authorities provides a model for regional cooperation on disaster risk reduction. As ASEAN member states strengthen their climate resilience frameworks, the lessons from Thailand's river communities — from sandbag walls in Nonthaburi to the Thai Disaster Alert app — offer practical examples of community-level adaptation.

What to Watch For

Over the coming days, residents and authorities will be watching the evening tidal peaks closely. The full moon on Friday 28 August is expected to bring the highest tides of the week, and the DDPM has warned that river overflows could occur in low-lying areas outside permanent floodwalls. Recent weeks have already seen flooding in northern provinces including Nan, where rivers overflowed and roads were cut, highlighting the broader monsoon season risks across the country. Satellite monitoring by Thailand's Geo-Informatics and Space Technology Development Agency (GISTDA) has flagged flood risks across thousands of square kilometres of the North in recent weeks, and the same seasonal pressures are now converging on the central plains.

Thailand is in its monsoon season, which typically runs from roughly May to October, with the heaviest rainfall usually falling in August and September. The combination of seasonal rains, upstream runoff and high tides creates a potent convergence of pressures for the Chao Phraya Basin. Residents in the affected districts should remain vigilant, monitor the Thai Disaster Alert app and be prepared to move belongings to higher ground if water levels rise. The DDPM and provincial authorities will continue to provide updates as the situation develops through the week.

This article was prepared with the assistance of AI and reviewed by our editorial team.

By Ann Srisawat, Staff Writer

This article was produced with AI-assisted research and editorial support. Reporting is based on sources cited in the article.