A Multi-Scale Hydrometeorological Analysis of Flash Flood Event in Masamba, South Sulawesi on 13th July 2020

Abstract:

During 12-13 July 2020, heavy rainfall has caused Masamba, Rongkang and Rada rivers to overflow, causing flash floods in the Masamba region. This extreme event resulted in many casualties, at least 38 people died and displaced thousands of people. This study presents a multi-scale analysis of the hydrometeorological settings that led to the development of the intense storms and flash flood over the region. Boreal Summer Intraseasonal Oscillation (BSISO) 1 was on phase 3 and 4 during 7 - 13 July, impacting the convective cloud growth over the Indonesian Maritime Continent (IMC). In addition, the sub-seasonal tropical disturbance of Kelvin Waves was active over the Sulawesi region on 7 - 13 July, increasing the chance of convective precipitation at the region. The positive anomalies of Sea Surface Temperature (SST) over the Bone Bay region at the south of Masamba supported the increased amount of water vapors. These water vapors were transported to the Masamba highlands by the strong easterly wind (Australian monsoon), feeding to the convective clouds formation. The satellite-derived precipitation products indicated the daily rainfall accumulation on July 12 and 13 were concentrated in the eastern part of Sulawesi reaching >150 mm/day, but in Masamba, reaching 50 mm/day.