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8/10/2019 Risk Assesment of Lahar Flow Hazard in Merapi Volcano
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MODULE D
RISK ASSESSMENT AND MANAGEMENT
GROUP ASSIGNMENT
(For Volcanic Hazard)
Lecturer
Prof. Sutikno
By:
Pradiptya Setyahadi 14/370647/PMU/8191
Iriansa 14/370694/PMU/8198Siti Dahlia 14/373799/PMU/8418
Purwita Eka Sari 14/370504/PMU/8143
MAGISTER GEO-INFORMATION FOR SPATIAL PLANNING
AND DISASTER RISK MANAGEMENT
GRADUATE SCHOOL
UNIVERSITY OF GADJAH MADA
YOGYAKARTA2014
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
P.Setyahadi, Iriansya, S.Dahlia & P.E. Sari
Magister Geo-Information for Spatial Planning and Disaster Risk Management, Gadjah
Mada University, D.I.Yogyakarta, Indonesia.
ABSTRACT
Merapi Volcano in Sleman, D.I.Yogyakarta. The height of Merapi Volcano around 2,968
meters above sea level and has experienced 84 times (event) until 2010 within eruption average
is 5 years. Due to the active crater of Merapi volcano is now open to the west - southwest. So
that during the growth of the lava still in dome and not go beyond the walls of the crater, the
eruption will be heading west - south-west. The method in lahar flow assessing to settlement
used qualitative methode include with aprroch is spatial approach, ecological approach and
disaster approach with the technique of spatial multi-criteria analysis. Result analysis from this
research namely (a) potential hazards, (b) vulnerability, (c) element at risk, (d) capacity, (e) risk
assesment. We also given recommendation for mitigation in that area.
Keyword :Risk Assesment, Lahar Flow in Ginibangunharjo.
A. Introduction
One output of the eruption from Merapi volcanoe is lava, which then generates
became lahar flow. Lahar flow formed when in a volcano crater there is a crater, the
water in the lake will be very hot when it erupted. The hot water carrying mud material
and rocks, while the lava occurs when rain fell with high intensity rainfall mixed with
loose volcanic material to form a stream. Although lava material composed of volcanic
ash and rock fragments, but the flood of lava can flow more rapidly and faster when
compared with normal water flow (Daryono, 2011).
A lahar is a general term for a rapidly flowing mixture of rock debris and water
(other than normal streamflow) from a volcano and refers to the moving flow. Located
in the populated area of Central Java, the stratovolcano Merapi (2965 m) is prone to
lahar generation, due to three main factors: millions of cubic meters of pyroclastic
deposits are the product of frequent pyroclastic flows, which have occurred on 2- to 4-
year intervals, rainfall intensity is high (often 40 mm in 2 h on average) during the rainy
season, and drainage pattern is very dense.
The Boyong and Kuning river are river through the Hargobinangun village, and
one of the lines of lahar flow from Merapi Volcano, it is have material can be sand,
rocks and gravel where the lava material has a volume of 10 million m3. While the
flow along the Kuning and Boyong river, there are many seattlement areas. So that this
region could potentially have affected the risk of lahar flow hazard in Merapi volcano.
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
B. Study Area
In this task, the area sampled for the identified impact on the settlement of the lava
flow is Hargobinangun village located in the northern District of Pakem. This region is
located in the northern district of Sleman, Yogyakarta. Distance sub-district to district
government center. Wide of Sleman is about 14 km. This area is located at the
coordinates 77.66708 'LS and 110.42011' BT and has an area of approximately
4384.04 ha, the total population of 32.561 people, with a population density reaches
1,551 / km2.
The geology of this region there are deposits surface of alluvium there are grovel,
sand, silt and clay along larger streams. Selected deposits of merapi volcano is
undifferented tuff, ash, breccia, agglomerate and lava flow. This region is located in the
highlands, precisely located at an altitude of 600 meters above sea level. Tropical
climate with cool weather as his trademark. The highest recorded temperature was 32C
with the lowest temperature of 18C. Expanse territory in the form of land area choppy,
hills and mountains. Based on the location, on the slopes of Mount Merapi. This region
is located in the highlands, precisely located at an altitude of 600 meters above sea level.
Tropical climate with cool weather as his trademark. The highest recorded temperature
was 32C with the lowest temperature of 18C. Expanse territory in the form of landarea choppy, hills and mountains. Based on the location,on the slopes of Merapi
volcano.
C. Methodology
The purposed method in lahar flow assessing to settlement in the Hargobinangun,
Pakem Distrik of Sleman Yogyakarta by used qualitative methode include with aprroch
is spatial approach, ecological approach and disaster approach with the technique of
spatial multi-criteria analysis. Spatial approach and ecological approach is intended to
identify the characteristics of the physical environment and the characteristics of the
study area includes the settlements, topography, slope, rainfall, river flow, settlement
patterns, the distribution of settlements, building the model and direction to the direction
of flow. Disaster approach is intended to identify the characteristics of lava flow scoring
the study area, volume, period, distance, and direction of flowIn the review process
generally includes four processes namely, study literature, data collection, data analysisand reporting, as shown in the diagram below:
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Figure 1: Framework process for the study
1. Study of Literature
This process is the first step in this study are intended to seek and understand a
variety of approaches, methods and data analysis in risk analysis lahar flow. It is
from book, journal and internet.
2. Data Colection
After understanding the concept and scope of the study area, is the determination
of variables and collecting data required for the analysis of both primary data and
secondary data.
3. Data Analysis
This process is divided into three phases: phase analysis petensial lava flow hazard,
vulnerability level analysis phase of the residential building of the lava flow, and
risk assessment.
a. Analysis Potential Lava Flow Hazard
This process include several stage: at this stage include; Identification of the
characteristics of lahar flow, clasification of danger level and the danger level
of committing lahar flow zone.
Table 1 : Potential of Lahar Flow Hazard Zone
Zone
Distance from the vents
of Mount Merapi Carateristic o f the region Hazard
Zone 1 Radius 5 kmlocatedin the basin area, located in a radius
of 100 meters from the river high
Zone 2 Radius 10 km
locatedin the basin area and slope area,
located in a radius of 100 meters from the
river medium
Zone 3Outside a radius of 10
km
located in a radius of 100 meters from the
river low
Study Literature
Data Colection
Data Analysis
Report
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
b. Vulnerability level analysis phase of the residential building of the lava flow
This stage covers, identification and classification of building types based
materials, building of age, the building to the flow direction, the distance from
the road. As for the classification can be seen in Table 2.
Table 2: Potential of Vulnerability
NO
CHARACTERISTIC OF BUILDING
Vulnerability
Material
Age of
Building Direction to strem
1 Woodvery high
2 Stone > 40
50 - 90
(Perpendicular)
3 Stone >40 < 50 (Diretion)
High
4 Stone 20 - 40
50 - 90
((Perpendiculars)
5 Stone 20 - 40 < 50 (Diretion) Medium
6 Stone < 20
50 - 90
((Perpendicular) Low
7 Stone < 20 < 50 (Diretionh) Very Low
c. Risk Assesment data analysis
In this process, the results of the potential hazard zone that be overlay with
lava flow for the results of the vulnerability residential buildings
classification to the lava flow. The overlay results, will be analyzed by using
the formula of risk assessment and risk assessment matrix.
Risk = Hazard x Vulnerability
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Table 3: Risk Assesment Matrix of Value
Table 4: Risk Assesment Matrix of Data Analysis
Hazard
zone 1
(A)A1 A2 A3 A4 A5
zone 2
(B)B1 B2 B3 B4 B5
zone 3
(C)C1 C2 C3 C4 C5
very low
(1)low (2)
medium
(3)
high
(4)
very high
(5)
Vulnerabilty
Very Low
Low
Medium
High
Very High
0
1
2
3
4
5
HighMedium
Low
Risk Assessment Value
Hazard
HighLow Risk
Medium
Risk
High
risk
Very
high risk
Very high
risk
MediumVery low
risk
Low
Risk
Medium
Risk High risk
Very high
risk
LowVery low
risk
Very
low risk Low risk
Medium
Risk High risk
very low low medium high very high
Vulnerabilty
Where, Hazard = probability of occurrence of a given area being
affected by cause damage, loss, and death of people
in residential areas within a given period of time.
Vulnerabilty = proportion of settlement threatened likely to be in a
given hazardous event; degree of damage resulting
from the hazard.
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Figure 2: Framework Risk Assesment of Lahar Flow
D.
Result and Analysis
1. Potential Hazard
Hazard is a potentially damaging physical event, phenomenon or human
activity thay may cause the loss of life or injury, property damage, social and
economic disruption or environmental dagradation (C.J.Van Western. 2011.
Multi-hazard risk assessment. ITC).
Potential hazard that used in this task is lahar flow in Hargobinangun village,
because in Hargobinangun village through by Boyong and Kuning river, and it is
one of the lines of lahar flow from Merapi Volcano, taht have material can be sand,
rocks and gravel where the lava material has a volume of 10 million m3. And
there are many settlemen areas, So that this region could potentially have affected
the risk of lahar flow hazard. The following below map to the potential hazard
of lahar flow by Merapi volcano:
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Figure 3: Potential of Lahar Flow Hazard
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
2. Vulnerability
Vulnerability is a human condition or process resulting from physical, social,
economic, and environmental factors which determine the likelihood and scale of
damage from the impact of a given hazard(UNDP, 2004) .
Vulnerability is the degree of the loss to a given element or set of elements
at risk resulting from the occurrence of a natural phenomenon of a given magnitude
and expressed on a scale from 0 (no damage) to 1 (total loss). In lay terms, it means
the degree to which individual, family, community, class or region is at risk from
suffering a sudden and serious misfortune following an extreme natural event. To
determinate value of vulnerability based on building characteristic of settlement.
The following in table 2.
Table 2: Potential of Vulnerability
No
Characteristic Of Building
Vulnerability
Material
Age of
Building Direction to strem
1 Woodvery high
2 Stone > 40
50 - 90
(Perpendicular)
3 Stone >40 < 50 (Diretion)
High
4 Stone 20 - 40
50 - 90
((Perpendiculars)
5 Stone 20 - 40 < 50 (Diretion) Medium
6 Stone < 20
50 - 90
((Perpendicular) Low
7 Stone < 20 < 50 (Diretionh) Very Low
Based on the above data, characteristic of a settlemen building with very high
vulnerability criteria, namely the building of wood, this was due to the wooden
buildings are more vulnerability to the of lahar flow hazard from the shape of the
building stone, so of wood with very high vulnerability premises given a score of
1 and for a stone with a low vulnerability values given a score of 0.2. Other than
building materials, other factors that determine vulnerability, namely: the age of
the building, the shape of the building to the flow direction and distance to the
river.
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Figure 4: Seattlement Vulnerability of Lahar Flow Map
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
3. Element at Risk
Population, properties, economic activities including public service or any
other defined value exposed to hazard in a given area. Also referenced to as
assets. The amount of element at risk can be quantified either in numbers (of
buildings, people, etc), in monetary value (replacement costs, market costs, etc),
area or preseption (importance of element at risk). (Western, etc. 2011. Multi-
hazard risk assessment. ITC)
Element at risk which used on this task is settelmen in Hargobinangun Village.
it is chosen as the location of this settlement has the potential hazard of the lava
flow. The following below table of number and distribusi of seattlement in
Hargobinangun Village.
Table 5: Number of Seattlement in Hargobinangun Village
4. Capacity
Capacity is the positive managerial capabilities of individuals, households, and
comunnities to confront, the threat of disasters (eg through awaerenes raising, early
warning and preparedness planning). (Western, etc. 2011. Multi-hazard risk
assessment. ITC)
0
500
1000
1500
Upper ZoneMiddle ZoneLower Zone
Total Seattlement
Zona Total Seattlement
Upper Zone 487
Middle Zone 327
Lower Zone 1186
Total 2000
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Indonesia is a country that is prone to geological disasters earthquakes,
landslides, volcanic eruptions, and tsunamis. As a consequence of the state's
obligation to protect its people, the government is expected to take appropriate
measures to reduce the risks and have contingency plans to minimize the impact of
disasters.
Currently available legislation on national disaster management UU No. 24 of
2007. The Act serves as the basic guidelines governing authority, rights, obligations
and sanctions for all providers and stakeholders in the field of disaster management.
According to UU No. 24 of 2007, the implementation of disaster management in
the event of a disaster potential conditions include: (a) preparedness (b) early
warning and (c) disaster mitigation.
Organizations that are in this region is the area of disaster management agency
(BPBDs) and BPPTK. Implemented through coordination BNPB. The organization
runs in accordance with the work program, one of which is the dissemination of
information, forums of Merapi and mandatory practice. That is a sustainable
program that is expected to form a culture of preparedness in communities
5. Risk Assessment
Risk assessment is a methodology to determine the nature and extent of risk
by analyzing potential hazard and evaluating existing conditions of vulnerability
that could pose a potential threat or harm to people, livelihoods and the
environment on which they depend.
The process of characterizing hazard within risk area, analyzing them for
their potential mishap consequences and probabilities of occurrence and
combining the two estimate to reach a risk ranking.
Risk assessment in the analysis in this task is the level of risk of damage
settlements caused by lava flow from Mount Merapi. With the purpose of risk
assessment outcome data, can be used as a form of preparedness so as to reduce
the impact of hazards. Based on Table 1 and Table 2, it can be determined the
value of a risk assessment based on the characteristic of the potential hazards and
vulnerabilities value. Below are the results of the calculation of the combined
value of the potential hazards and vulnerability:
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Table 6: Qualitative matrix of consequences
HAZARD
Zone 1
(A)
radius 5 km by
road, located in thebasin area, located
in a radius of 100
meters by the river,
material stone with
< 20 age of
building, and < 500direction to stream
radius 5 km by
road, located in thebasin area, located
in a radius of 100
meters by the river,
material stone with
< 20 age of
building, and 50 -900 (perpendicular)
direction to stream
radius 5 km by
road, locatedin the basin
area, located
in a radius of
100 meters by
the river,
material stonewith 20 - 40
age of
building, and
< 500direction
to strem
radius 5 km by
road, located in thebasin area, located
in a radius of 100
meters by the river,
material stone with
20 - 40 age of
building with 50 -900 (perpendicular)
direction to strem,
and material stone
with > 40 age of
building with < 500direction to strem
radius 5 km by
road, located in thebasin area, located
in a radius of 100
meters by the river,
material stone with
> 40 age of building
with 50 - 900(perpendicular)
direction to strem,
material wood
Zone 2
(B)
radius 10 km by
road, located in the
basin area and slope
area, located in a
radius of 100
meters by the river,material stone with
< 20 age of
building, and < 500
direction to stream
radius 10 kmby
road, located in the
basin area and slope
area, located in a
radius of 100
meters by the river,material stone with
< 20 age of
building, and 50 -
900 (perpendicular)
direction to stream
radius 10 km
by road,
located in the
basin area and
slope area,
located in aradius of 100
meters by the
river, material
stone with 20 -
40 age ofbuilding, and
< 500direction
to strem
radius 10 km by
road, located in the
basin area and slope
area, located in a
radius of 100
meters by the river,material stone with
20 - 40 age of
building with 50 -
900(perpendicular)
direction to strem,and material stone
with > 40 age of
building with < 500
direction to strem
radius 10 km by
road, located in the
basin area and slope
area, located in a
radius of 100
meters by the river,material stone with
> 40 age of building
with 50 - 900
(perpendicular)
direction to strem,material wood
Zone 3
(C)
outside a radius of
10 km by road,
located in a radiusof 100 meters by
the river, material
stone with < 20 age
of building, and 40 age of
building with < 500
direction to strem
outside a radius of
10 km by road,
located in a radiusof 100 meters by
the river, material
stone with > 40 age
of building with 50
- 900
(perpendicular)
direction to strem,
material wood
Very low (1) Low (2) Medium (3) High (4) Very High (5)
VULNERABILITY
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
Figure 5: Risk Assessment of Lahar Flow Map
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
E. Conclusion
One result of the eruption of Merapi volcanoe is lava, which then generates lahar
flow. The Boyong and Kuning river are river through the Hargobinangun village, and one
of the lines of lahar flow from Merapi Volcno, it is have material can be sand, rocks and
gravel While the flow along the Kuning and Boyong river, there are many settlemen
areas. So that this region could potentially have affected the risk of lahar flow hazard.
Representation of risk assessment that caused by lahar flow, it can determinate using
vulnerability value and potential hazard using formula by UN-ISDR. Value of
vulnerability base on element at risk ie settelmen, so data analysis used characteristic
building and spatial analysis using GIS. And than, of potential hazard which selected is
lahar flow, so that the required data is lava volume and intensity of rainfall.
Based on calculations of UN-ISDR, for the risk assessment of settelmen by lava flow
hazard in HargobinangunVillage, then there are three zones, namely the risk of high,
medium and low. Where Hargobinangun village in general are at high and medium zones.
But the biggest risk in the medium zone. This is due to the location of the village is located
in Zone II based maps Disaster Prone Areas. so as to risk vulnerability to hazards lava
flow that is middel.
Based on the risk assessment of the lava flow in Hargobinangun Village, so we theauthors provide recommendations to the community to:
1. Building a house in the location on the radius of> 100 m from the river, with a view
to avoiding vulnerable areas impacted. because lava flow generally follows the
direction of the river.
2. The shape of the house building should extends to the north - south, to avoid the
lava flow direction of flow. Thereby reducing the damage to the house when in
passing lava flow.
3. The Material houses of building suggested of bricks, because bricks material
stronger to withstand lava flow compared with wood material where higher levels
of vulnerability.
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Risk Assesment of Lahar Flow Hazard in Merapi Volcano
F. Refference
Andreastuti1, S, etc. 2006.Menelusuri kebenaran letusan Gunung Merapi 1006.Jurnal
Geologi Indonesia, Vol. 1 No. 4 Desember 2006: 201-207.
BNPB dan BAPPENAS. 2011.Rencana Aksi Rehabilitasi dan Rekonstruksi:Pascabencana Erupsi Gunung Merapi Provinsi D.I.Yogyakarta dan Provinsi Jawa
Tengah Tahun 20112013.
Daryono. 2011. Ancaman Banjir Lahar Merapi. (on www.bmkg.go.id (Badan
Meteorologi Klimatologi dan Geofisika) access on 13November 2014 (Risk
Modelling of Lahar Hazard in Kali Putih, Magelang).
UNISDR. 2004. Terminology: Basic terms of disaster risk reduction. Available at :
http://www.unisdr.org/files/7817_7819isdrterminology11.pdf. Access on 13
November 2014.
Western, etc. 2011.Multi-hazard risk assessment. ITC