Urban Risk Assessment of Lahar Flows in Merapi Volcano (Study Case: Muntilan Urban Area, Central Java)

Abstract

The objective of the research was to analyse probability of lahar flows occurrence in Muntilan urban area,
Central Java. By using integrated methods, which involve the numerical simulation program, Geographic Information
System (GIS), Remote Sensing (RS) and field verification to produce lahar flows Hazard Map and Risk Map. Muntilan
urban area located at western flank of Merapi volcano, and in down stream of Lamat river. The river is Lahar River that
is endangering from Merapi volcano, which flowing down to cuts a cross of that area. Therefore, Muntilan urban area
is vulnerable area from lahar flows disaster. Lahar flows, generally occur during intense rainfall on saturated volcanic
deposit in upper stream of river or wall of volcano. Lahar flows are extremely dangerous especially to those living in
valley areas near a volcano, which can undercut banks and cause houses destruction situated on the banks, and can
bury and destroy resident, structures, infrastructure facilities including roads and bridges. Meanwhile, development of
Muntilan urban area that caused many illegal settlements appears surrounding that area. Occasionally, un-benefit people
constructing house in disaster prone area, such as down stream of river side that have lahar flows risk. The research was
concluded that lahar flow occurrence in 100 years return period will be buried the Muntilan urban area. With the methods
integrating of GIS, RS, field verification can be done analysing of lahar flows hazard map, and risks map to produce
risk assessment in Muntilan urban area.