Landslide costs on the national road network of Laos

Compared to most other countries in south and southeast Asia, Laos has a low road network density and low traffic volumes. Much of the road network is located in mountainous terrain where landslides cause regular engineering damage and blockage to traffic. The wet season of 2018 was particularly severe, and triggered many landslides that blocked roads for hours, and days in some cases. The cost of clearing these landslides amounted to an average of almost US$ 5,000 per km. Because of the relatively low traffic volumes that use the mountain road network, traffic costs due to road blockage delays were generally significantly lower per kilometre than engineering costs. Nevertheless, economic analysis demonstrates that investments in landslide stabilisation measures amounting to an average of US$ 50,000 for landslides above the road and US$ 120,000 for those below the road are economically justified if, without these measures, long and frequent delays would ensue. In certain cases, investments much higher than these can be justified. A priority list for landslide stabilisation is developed and outline cost estimates are prepared. Recommendations are made for enhanced landslide management and roadside slope improvement, and a comparison is made between the situation in Laos with that in Vietnam, Bhutan, Nepal and the Philippines. It is concluded that the imperative for investment is even greater in these countries, and especially in Nepal and the Philippines on account of the higher incidence of landslide hazards and greater volumes of road traffic.