Floods in South Central Vietnam are the worst in over 50 years.

The phenomenon of simultaneous record-breaking floods across 3-5 river basins is "extremely rare, almost unprecedented in over 50 years of observation," according to the Department of Meteorology and Hydrology.

The phenomenon of simultaneous record-breaking floods across 3-5 river basins is "extremely rare, almost unprecedented in over 50 years of observation," according to the Department of Meteorology and Hydrology.

On the afternoon of November 23rd, the Department of Meteorology and Hydrology ( Ministry of Agriculture and Environment ) reported on the heavy rain and flooding in the South Central region. The total rainfall from 7 PM on November 15th to 7 PM on November 21st in eastern Dak Lak was generally 500-1,200 mm, with Song Hinh recording 1,861 mm, Hoa My Tay 1,575 mm, and Son Long 1,363 mm. In the western part of the province, rainfall ranged from 150-400 mm, with some areas receiving even higher amounts such as M'Drak (805 mm) and Hoa Phong (434 mm).

Gia Lai experienced widespread rainfall of 300-600 mm, with some areas receiving even more, such as Canh Lien (1,000 mm), An Quang (988 mm), and Van Canh (927 mm); the western part of the province received 100-300 mm, with Nghia An (498 mm) and Ho An Khe (438 mm). Khanh Hoa also experienced exceptionally heavy rainfall, averaging 500-700 mm in the north, with some areas such as Dai Lanh (1,071 mm), Khanh Hiep (1,002 mm), and Son Thai (877 mm).

Hoa Thinh commune area.

The Department of Meteorology and Hydrology assessed that rainfall in Son Hoa (Dak Lak) at 601 mm and in Quy Nhon (Gia Lai) at 380 mm exceeded historical records. Citing the classification of the World Meteorological Organization (WMO), the Department stated that "these are rare events, almost impossible to accurately predict quantitatively."

Combined with the fact that rainfall in South Central Vietnam from October to mid-November 2025 was 120-200% higher than the multi-year average, the soil is saturated, so when the main rainy season arrives, just an additional 300-500 mm of rain will cause major flooding.

A series of rivers in South Central Vietnam surpassed their historical flood peaks between January 15th and 21st. The Ky Lo River (Dak Lak) exceeded the 2009 record; the Ba River exceeded the 1993 record, and the Dinh Ninh Hoa River (Khanh Hoa) exceeded the 1986 record. The flood peak on the Ba River at the Phu Lam station has an estimated recurrence cycle of 50 years (a rare occurrence).

The Department of Meteorology and Hydrology assesses that simultaneous record-breaking floods across 3-5 river basins are extremely rare, not within the scope of conventional flood calculations, and that accurate forecasting alone is insufficient to prevent historically unprecedented natural disasters.

River	Station	A historic flood year	Comparison of 2025 flood peak with historical flood levels (cm)
Three	Cung Son	1993	LLS 109
Three	Phu Lam	1993	LLS 19
Kon	Thanh Hoa	2013
Ninh Hoa Palace	Ninh Hoa	1986	LLS 19
Nha Trang	Dong Trang	2009
Krong Ana	Giang Son	1998	< LLS 266cm
Srepok	Bản Đôn	1993	< LLS 106cm

Statistics from the past 30 years show that major floods in the South Central region usually occur before November 15th, but this particular flood occurred later. This indicates that the traditional flood pattern is changing, and weather trends are becoming increasingly extreme and unpredictable, according to the Department of Meteorology and Hydrology.

Extreme weather combination causes heavy rain and flooding.

The meteorological agency attributed the heavy rainfall to a combination of extreme weather patterns. At high altitudes, disturbances in the easterly wind zone at 1,500-5,000 meters were active, combined with very strong cold air, creating a convergence zone of moisture from the lower to the upper atmosphere.

Moisture from the East Sea is continuously transported inland to Central Vietnam and the Central Highlands, while the Truong Son mountain range acts as a windbreak, stimulating strong convection and maintaining prolonged rainfall. Rainfall amounts commonly range from 800-1,700 mm in many areas, far exceeding the natural drainage capacity.

Besides weather factors, the topographical and hydrological characteristics of Central Vietnam also increase the risk of major floods. Short river basins with steep slopes cause rainwater to concentrate quickly downstream, leading to flash floods, landslides, and rapidly rising floodwaters within hours. Water levels inland rise, while large waves (3-5 meters) appear in the East Sea, slowing down drainage.

Flood map of the downstream area of ​​the Ba River - the "flood epicenter" of Hoa Thinh and Dong Hoa. Flood depth data provided by VegaCosmos & VSGA processed from 3m resolution STRIX (Synspective) satellite imagery to extract flooded areas. Graphics: Quang Tue

In addition, climate change is making extreme rainfall patterns more intense and difficult to predict, increasing the frequency of major floods in the last 10-15 years, with many stations recording rainfall exceeding historical levels of 1,000-1,700 mm per event.

The forecasting and warning methods need to be changed.

Professor Tran Thuc, President of the Vietnam Meteorological and Hydrological Association, believes that in the context of climate change and increasingly extreme weather, forecasting and warning methods need to be changed. With this flood, while the rainfall area was predicted, the total rainfall at some localized points still had errors, with some areas experiencing higher-than-expected rainfall. This is a common limitation in tropical monsoon regions with highly fragmented terrain, making it very difficult to predict localized heavy rainfall within a narrow area.

Furthermore, landslide warnings remain mostly at the "high risk in communes and wards" level, failing to pinpoint specific landslide locations (hillsides, small roads). The network of automated monitoring stations in upstream and remote mountainous areas (where flash floods originate) in the South Central region is still quite sparse, leading to a lack of real-time data for warning of rapidly rising flood levels.

Professor Thuc proposed three groups of solutions. Regarding technology and infrastructure, it is necessary to increase the density of the monitoring network by installing additional automatic rain gauge stations and specialized hydrological stations in upstream areas and mobile phone signal "dead zones" in the South Central region; and to strengthen the weather radar system in urban areas and mountainous regions to scan clouds and rain in detail, serving for very short-term warnings.

A young child bursts into tears as she is rescued from a flooded area on October 23rd Street, Tay Nha Trang Ward, on November 20th.

Forecasting agencies need to develop AI machine learning models based on local historical flood data to provide real-time warnings of urban flooding (such as Nha Trang and Phan Rang) and landslides; and finalize large-scale (1:2000 or 1:5000) disaster risk zoning maps for key populated areas.

Regarding weather forecasting, Professor Thuc suggested a shift to "impact-based forecasting." For example, instead of simply announcing 200 mm of rain, the bulletin should specifically describe the consequences of such rainfall, such as how deep the flooding on road A will be, the risk of landslides at pass B, and the risk of water overflowing dike C. This would help authorities and the public easily visualize the level of danger.

Furthermore, experts emphasized the need to tighten the operation procedures of interconnected reservoirs in river basins in the South Central region (short and steep rivers). Flood releases need to be optimally calculated using rainfall forecast data to avoid "consecutive floods" downstream. Warning information also needs to be transmitted directly to the public through multiple platforms, even in the event of power outages or local network congestion.

vnexpress.net

Source: https://baolaocai.vn/lu-nam-trung-bo-lon-nhat-trong-hon-50-nam-qua-post887429.html