Mount Merapi eruption in 2010 caused primary and secondary hazards.
Primary hazard consist of lava and pyroclastic flow, locally known as wedhus
gembel. The secondary hazard, which was also very dangerous, included volcanic
ash and lahar flood. Four rivers drained off the volcanic materials of Mount Merapi
and overflowed as lahar flood to 13 villages in Kabupaten Magelang. Kali Putih had
the most victims and losses among the other rivers. Lahar flood of Kali Putih caused
damages in Desa Gulon, Seloboro, Sirahan, and Blongkeng. It was not only harmed
people and their houses, but also ruined agricultural land and critical infrastructures.
It also forced a mount of people to evacuate in a long period of time. Titik Kumpul
Evakuasi (TKE) as evacuation place for lahar flood�s evacuees is one facility that
must have been prepared in disaster management according to the Law 24 in 2007 on
Disaster Management. REKOMPAK together with the local goverment and the
community had planned the TKE in case of lahar flood ever come back in the future
as Mount Merapi eruption�s cycle. They had planned the TKE based on assumptions
and local agreements. The TKE had not been evaluated whether it could
accommodate lahar flood�s evacuees entirely or not. This research was done to find
new buildings for TKE, evaluate the TKE, and define the catchment area of each
TKE for accommodating the evacuees.
Analysis was done to the TKE planned by REKOMPAK and the village
goverment threatened by Kali Putih�s lahar flood and the TKE from field survey. The
number of inhabitants was distributed to regular hexagonal tessellation calculated in
spatial database. The capacity of each TKE for accommodating the evacuees was
calculated by formulas based on building areas and building uses. The catchment
area of each TKE was analysed in three scenarios using two Catchment Area
Analysis methods in Flowmap software. The scenarios were active scenario (day
time), passive scenario (night time), and final (combined) scenario. The methods
were Second Best Catchment Area Analysis for time evacuation priority and
Catchment Area Analysis with Linear Optimization for TKE capacity priority.
The result of this research shows that the current proposed TKE are not
capable to accommodate all of the Kali Putih lahar flood�s evacuees in active
scenario, passive scenario, and final scenario. Second Best Catchment Distance
method resulted the catchment area for almost all of the evacuees but it accumulated
a huge number of evacuees in some TKEs. Catchment Area Analysis with Linear
Optimization method could distributed the evacuees appropriately to fulfill the
capacity of each TKE depend on its evacuation capacity, but its catchment area was
only accommodating under half of all the evacuees