EVALUATION OF DISASTER MITIGATION SYSTEM AGAINST LAHAR FLOW OF PUTIH RIVER, MT. MERAPI AREA
Abstract: Merapi mount lies in
the border of Yogyakarta and Central Java province. It frequently produces lava
sediment deposit in the upper part of the mount, or is called as lava dome.
During the rain, the sediment can cause secondary disaster in form of lahar
flood, which is potential to produce casualties, especially to the miners
working along the river. Kali Putih, that is located in Magelang regency, is
the area that undergoes frequents lahar flood that is 125 times in the period
of 1931-1996. Meanwhile, there are 5,076 sand miners there. Therefore, it needs
an evaluation toward the existing mitigation system that is related to the
safety of sand miners.
The evaluation is done toward structural mitigation system (Sabo Dam) and
non-structural one (e.g. early warning, counseling, and evacuation system).
Structural mitigation system is evaluated by comparing the availability of
control volume of Sabo Dam to the sediment load during lahar flood, and
comparing the travel time of the lahar flood with and without Sabo Dam.
Non-structural mitigation system is evaluated by testing the accuracy of the
lahar flood estimation chart, and by identifying early warning equipment system
installed in field. Interview is also conducted with the miners to see their
perception and opinions toward the mitigation.
Result of the evaluation shows that the existing early warning system
does not produce sufficient time for the sand miners to save themselves. The
proposed solution is to divide sand mine area in Putih River into 3 zones, each
zone has different procedure of the early warning and evacuation. This is
arranged to avoid casualties to the sand miners.
Author: T. Maksal Saputra
Journal Code: jptsipilgg130023
