Cause of red sand flood in Binh Thuan

Heavy rainfall in a short period of time and urban infrastructure obstructing groundwater are the two main causes of red sand floods in Binh Thuan, according to experts.

In the early morning of May 21, after heavy rain , a flood of red sand fell on coastal road 706 connecting Ham Tien - Mui Ne (Phan Thiet City) where there are many houses and tourist areas. The sand flood did not cause any loss of life, but caused many motorbikes, cars, and houses to be buried.

Red sand flood buried utensils in the area near the restaurant in Phan Thiet City, Binh Thuan. (Photo: Viet Quoc).

Rainfall measurement results recorded during the night of the red sand flood reached nearly 200 mm in 3 hours. According to Dr. Nguyen Ngoc Huy, a climate change expert, such rainfall is very large, in a short period of time and of extreme nature. The rain does not seep into the ground in time, causing it to flow away, creating a flood of sand.

According to Mr. Huy, sand has the ability to absorb water faster than other types of soil. Usually on sand dunes there is an underground path leading to the sea. This flow path helps keep the structure of the sand stable.

However, the scene of red sand landslides shows that in coastal forests there are housing projects built on sand and tourist areas near the coast. The foundations of these structures can block underground water flows from the sand dunes to the sea. This causes the sand inside to seep enough to not flow into the sea, creating a sand flood.

Mr. Huy said that in addition to natural factors due to extreme rainfall , authorities also need to pay attention to construction development planning. The sand dunes always have underground water connecting the sand dunes with the sea. If the groundwater is blocked, it will create a flood of mud and sand from the hills or landslides on beaches where waves hit. Therefore, it is necessary to let the water circuits operate freely to prevent sand floods.

The location of the area was buried by the sand flood. (Graphic: Khanh Hoang).

Agreeing, master Nguyen Ngoc Thiep, Ho Chi Minh City Water and Environment Association explained, when heavy rain falls, sand changes from dry to mushy. Strong enough water pressure combined with the slope of the hill creates a flow that slides down, forming a sand flood.

Mr. Thiep also recognized that the infrastructure around the hill is considered a wall to block flowing water. Even though these systems have water holes, with heavy rains, the sand will absorb too much water and will not be able to flow in time. Therefore, in development plans, it is necessary to take into account the natural characteristics of each region, minimizing human intervention to minimize natural disasters.

The hill area had landslides, creating sand floods for many structures and roads. (Photo: Nguyen Tu).

According to Dr. Nguyen Ngoc Huy, it is difficult to forecast sand floods from afar for each specific location . Based on weather and geological factors, it can only be predicted approximately 3 - 4 hours before the occurrence.

Mr. Huy said that people need to be careful when living under sand dunes interrupted by infrastructure and traffic works . " Sand floods have the characteristic of occurring in a narrow area and at a slower speed than pipe floods and flash floods . However, people need to be vigilant and prioritize human evacuation when floods occur ," Dr. Huy said.

Master Nguyen Ngoc Thiep also proposed that sand hills need to be planted with trees so that their roots can hold the soil, limiting the sand from slipping and causing floods that spill over to people's houses . "This is not the main measure to prevent sand floods, but it will partially limit it ," he said.

According to local people, red sand spills often occur in Mui Ne beach and Phan Thiet city every time it rains heavily. The most recent time in early October 2023, floodwaters caused red sand on the hills to spill over into the residential area and coastal road of Tien Thanh commune, Phan Thiet city, causing a traffic jam lasting more than 500m.