Cost-benefit analysis of vetiver system-based rehabilitation measures for landslide-damaged mountainous agricultural lands in the lower Northern Thailand

On May 23, 2006, the landslide-debris flow occurred in several places of the lower Northern Thailand. These destroyed about 4,000 houses resulting in about 10,000 people having to be permanently evacuated. They also damaged large areas of high potential agricultural growth in the highland and mountains in the region. The impact of the landslide was both in terms of disruption of agricultural production and lowering of land productivity. A cost-benefit analysis (CBA) was used to compare the net welfare gained from different land rehabilitation measures applied in landslide-damaged agricultural areas in the lower Northern Thailand. In this paper, ex ante CBA was conducted based on the interviews with knowledgeable stakeholders prior to land rehabilitation project and policy implementations. The alternative measures were as follows: Measure 1—planting of vetiver grass (Chrysopogon zizanioides (L.) Roberty) with waterway construction; Measure 2—planting vetiver grass with intercropping of durian seedling and sunn hemp (Crotalaria juncea L.) including waterway construction; Measure 3—planting vetiver grass with intercropping of durian seedling and banana (Musa sapientum L.) including waterway construction; and Measure 4—status quo (under natural ecological succession process). For a 20-year project period, the highest net present value (NPV) was obtained from Measure 2 followed by Measure 3. The NPV of Status Quo option was higher than Measure 1. This is because if the land were to be left to naturally regenerate as is the case under Status quo, farmers would benefit from the natural rehabilitation process by native pioneer plants. The appropriate measures as studied in this research can be competent representative model for rehabilitating the landslide-damaged areas in the lower Northern Thailand where rehabilitation systems have not yet been introduced.