Heavy rainfall in a short period, combined with urban infrastructure obstructing groundwater flow, are the two main causes of the red sand floods in Bình Thuận, according to experts.
In the early hours of May 21, after a heavy rain, red sand floods hit the coastal route 706 connecting Hàm Tiến – Mũi Né (Phan Thiết City), an area with many residential homes and tourist resorts. The floods did not cause any casualties but buried many motorbikes, cars, and houses.
Red sand floods bury belongings near a restaurant in Phan Thiết City, Bình Thuận. (Photo: Việt Quốc).
The recorded rainfall during the night of the red sand floods reached nearly 200 mm within 3 hours. According to Dr. Nguyễn Ngọc Huy, a climate change expert, such rainfall is significant, occurring in a short time and exhibiting extreme characteristics. The rainwater soaked into the ground too quickly, causing runoff that resulted in red sand floods.
According to Mr. Huy, the nature of sand allows it to absorb water more quickly than other types of soil. Typically, there are underground streams on sandy hills that flow into the sea. This stream helps maintain the structural integrity of the sand.
However, the scene of the red sand floods showed that there were residential constructions built on sandy foundations in coastal forest areas and tourist resorts near the sea. The foundations of these buildings may obstruct the underground water flows from the sandy hills to the sea. This leads to the sand absorbing enough water that cannot flow to the sea, resulting in sand floods.
Mr. Huy believes that in addition to the natural factor of extreme rainfall, authorities must also pay attention to construction development planning. The base of sandy areas always has an underground water flow connecting the sandy hills to the sea. Blocking this groundwater flow will create mud and sand floods from the hills or cause coastal erosion where waves crash. Therefore, it is essential to allow these water flows to operate freely to prevent sand floods.
Location of the area affected by the red sand flood. (Graphic: Khánh Hoàng).
Agreeing, Master Nguyễn Ngọc Thiệp from the Hồ Chí Minh City Water and Environment Association explained, when heavy rains fall, sand transitions from a dry state to a slurry state. The water pressure, combined with the slope of the hill, creates a flow that slides down, resulting in sand floods.
Mr. Thiệp also recognized that surrounding infrastructure constructions are considered as barriers to the water flow. Although these systems may create drainage holes, with heavy rainfall, sand absorbing a lot of water will not drain fast enough. Therefore, in development planning, it is necessary to consider the natural characteristics of each area and minimize human intervention to reduce natural disasters.
The hilly area where landslides occurred, creating sand floods with many constructions and roads. (Photo: Nguyên Tư).
According to Dr. Nguyễn Ngọc Huy, it is very challenging to predict sand floods in advance for specific locations. Based on weather and geological factors, predictions can only be made approximately 3 to 4 hours before they occur.
Mr. Huy believes that residents need to be cautious when living under sandy hills that are crossed by infrastructure and transportation projects. “Sand floods occur over a limited area and at a slower speed compared to flash floods and landslides. However, residents should remain vigilant and prioritize evacuating people when floods occur,” said Dr. Huy.
Master Nguyễn Ngọc Thiệp also suggested that sandy hills should be planted with trees to anchor the soil with their roots, reducing the risk of sand sliding and flooding into residential homes. “This is not the main measure to prevent sand floods, but it will help to some extent,” he stated.
According to local residents, red sand overflow incidents commonly occur in Mũi Né beach and Phan Thiết City whenever heavy rains fall. The most recent incident was in early October 2023, when floodwaters caused red sand from the hills to overflow into residential areas and along the coastal road in Tiến Thành commune, Phan Thiết City, causing traffic congestion over 500 meters long.
