Factor affecting July 13th, 2020 flash flood in Masamba Area, North Luwu, South Sulawesi
Adi Maulana (a,b*), Iswandy Utama (a)

(a) Centre for Diasaster Study, Hasanuddin University
(b) Geology Department, Hasanuddin University

Abstract

The paper discussed the factor affecting flash flood that occurred on July 13th 2020 in Masamba Area, North Luwu, South Sulawesi. At least two major river catchment areas were severely hit by the flash flooding, namely Rongkong and Baliase catchment area. Based on a quick geological observation and a desk study on climatological data couple with a new satellite image interpretation, it is concluded that combination of geology, climatology and bad land use change, play an important role in triggering the flash flood in Rongkong and Baliase River catchment areas. Highly weathered granitic rocks, steep slope morphology and faults system developing in the upstream are some main geological factors that generating the widespread of numerous landslides in which contributing the accumulation of massive debris content in the river. Although rainfall average within three days prior to flooding suggest a moderate pattern (less than 100 mm/day) yet the duration and intensity of the rainfall had caused high volume of water discharge in some sub catchment areas, namely Radda and Masamba sub catchment areas (Baliase) and Binuang sub catchment areas (Rongkong). Spotted and uncontrolled land use change eventually provoke the massive flash flood especially in Rongkong River. Considering the geology and climatology factors affecting the flash flood will not be very easy to overcome in the near future, a comprehensive river upstream management should be implemented immediately to avoid any fatality. It is therefore highly recommended that structural and non-structural mitigation should be applied to mitigate the future disaster.

Keywords: Geology- Climatology- Flash flood- Masamba- North Luwu- South Sulawesi

Topic: Sustainable Development