*2.1. Study Area and Period*

The study was conducted in Isan, in the northeastern region of Thailand (Figure 1). This region is part of the Mekong-river basin, with an average discharge of 475 km3/year. The Mekong river basin covers a total drainage area of 795.000 km<sup>2</sup> and it is characteristically divided into the upper and lower basins. The Lower Mekong river in Thailand is located in the Lower Mekong basin, covering 23% of the total drainage area (184.000 km2) and representing 36% of the country (Figure 1).

**Figure 1.** Digital elevation of the Lower Mekong Basin in Thailand. Red rectangle corresponds to the study area in the Isan region. Red dots represent the hourly rain gauge stations from www.thaiwater.net. Blue line represents the Lower Mekong river network.

Heavy rainfall often occurs in the Lower Mekong river basin during the Asian monsoon period between June to October. In this period, the covariability of the Indian summer monsoon and East Asian summer monsoon impacts the Lower Mekong basin, causing high convective storm events that are the main trigger for flash floods and landslides [44,45]. We focused on the wet months for the years 2014 to 2017, as these disasters are mostly occurring during the wet season.
