Preliminary survey and assessment of landslides in Lam Dong and Dak Nong
The objective of the survey team is to initially assess the causes and mechanisms of the formation of landslides and cracks occurring in July and August, 2023 in Lam Dong and Dak Nong provinces and propose further research and implementation plans to prevent and mitigate damage.
The survey team collected information on topographic features, geology, measurement and drawing of sliding blocks, fissure parameters, and mantle. These data serve the construction of geological and geomorphological cross-sections of the area of interest. For some sliding blocks or key areas, the survey team conducts geophysical measurements to evaluate in detail the geological structure and sliding block characteristics, combined with analysis of remote sensing image data before, during and after the survey period to see the whole picture of this phenomenon.
Conduct geophysical measurements in some key areas
From August 15-17, 2023, in Dak Nong, the delegation conducted a direct survey in 6 landslide areas: Dak N'ting irrigation lake; residential areas of Bon Bu Krac and Bon Bu Prang 1A (Quang Truc commune, Tuy Duc district, Dak Nong province); land cracking area at the junction of Pham Van Dong, Thanh Giong, Vo Van Kiet, Gia Nghia city; landslide on Provincial Highway 1A, Quang Tam commune; landslides on Nguyen Tat Thanh street/ National Highway 14/ Quarry slope, Gia Nghia city; and landslide at Tran Hung Dao Street, Nghia Tan Ward, Gia Nghia City.
In Bon Bu Krac and Bon Bu Prang 1 areas, the delegation conducted geophysical measurements along a 470m long line, the maximum survey depth reached more than 50m. In the area of Dak N'Ting irrigation lake, the delegation conducted geophysical measurements along a 300m long line, the maximum survey depth reached more than 40m.
In general, these areas are complicated, with many wide, deep cracks, potentially posing a risk of large landslides. The delegation realized that it is necessary to pay special attention to the development of the following areas: landslides at Dak N'ting irrigation lake; landslide at Provincial Highway 1A, Quang Tam commune; and residential areas of Bon Bu Krac and Bon Bu Prang 1A.
Topography of Dak N'ting reservoir area
There are many cracks and damage points around the Dak N'ting reservoir area
Long and deep cracks formed in the area of Dak Buk So commune
Image of subsidence and large-scale slide block in Quang Tam commune
At the end of the survey trip in Dak Nong (17/8), the delegation made some comments and recommendations for the current disasters occurring in Dak Nong, in order to help the Command Board of Natural Disaster Prevention and Search and Rescue of Dak Nong province and provincial authorities have a response orientation, prevent incidents, minimize adverse impacts on infrastructure works and people's lives.
The subsidence monitoring point of the Institute of Geology, Vietnam Academy of Science and Technology (scientific research results of TN18/T13, under the Central Highlands Program 2016- 2020) located at Tran Hung Dao street measured a displacement of ~168mm at a depth of 39.5m (16/8/2023) compared to the time of starting measurement (07/1/2020).
Survey of newly formed cracks at Pham Van Dong street, Gia Nghia city
From Dak Nong, the delegation continues the survey and research trip at the site in Lam Dong province on August 18-22, 2023. According to the plan, the survey team will continue to study the current status and developments of landslide cracking, thereby making a general assessment of hillslide accidents in Lam Dong and Dak Nong provinces, and will soon have an assessment report on the causes, mechanisms and trends of accidents in the survey areas, and propose plans to prevent and minimize immediate and long-term damage.
Translated by Phuong Ha
Link to Vietnamese version