**3. Rainfall and Landslide Data**

The daily rainfall data were collected from the three rain gauges from Malbase, Gedu, and Chukha. These three rain gauges are maintained by the National Center for Hydrology and Meteorology, Royal Government of Bhutan. The presence of a properly distributed rain gauge network is essential for determining rainfall thresholds. Figure 3 depicts the cumulative rainfall distribution for the study period (2004–2014). The rainfall data collected for 2004–2014 shows that about 78% of the annual rainfall falls during the monsoon (June–September) with pre-monsoon (March–May) and post-monsoon (October–December) contributing 18% and 4%, respectively.

**Figure 3.** Variation of cumulative daily rainfall with time (2004–2014).

The landslide data were provided by project Dantak of Border Road Organization (BRO), of the Govt. of India. The landslide locations are confined along the Phuentsholing–Thimphu highway, most prominent trade route, which connects the capital city Thimphu with neighbouring countries by road. The total number of landslides during the study period was 248, out of which 63, 81, and 105 landslides occurred in Malbase, Gedu, and Chukha regions respectively. The landslides in the region are mostly shallow with depths ranging from few decimetres to metres [25]. The catalogue of landslides included coordinates and date of failures. Figure 4 depicts the year-wise landslide occurrences.

**Figure 4.** Year-wise landslide occurrences in Chukha Dzongkhag (2004–2014).
