Proceeding Joint Scientific Program and One Day Seminar on EcoDRR 2012_Pages 10-21

Yogyakarta, Indonesia: 8 December 2012

ECOSYSTEM BASEDDISASTER RISK REDUCTION

JOINT SCIENTIFIC PROGRAMAND ONE DAY SEMINAR ON:

FACULTY OF GEOGRAPHY - UNIVERSITAS GADJAH MADA

MASTER ROGRAM ON PLANNING AND MANAGEMENT

OF COASTAL AREA AND WATERSHED (MPPDAS)

PROCEEDINGS

Editors : Junun Sartohadi, Jiba Raj Pokarel, Udo Michael Nehren,Guilherme Fernandez, Simone Sandholz

2013

IN COOPERATION WITH: CENTER FOR NATURAL RESOURCES AND DEVELOPMENT (CNRD)

ISBN: 978-602-14856-1-5

Ecosystem Based Disaster Risk Reduction 2013, Yogyakarta-INDONESIA

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STUDY OF LANDSLIDE DYNAMIC WITH SPATIAL-TEMPORALAPPROACH AND ITS RELATION TO THE EXISTING ECO-DRR

PROGRAM ON A PART OF DIENG AREA, INDONESIA

Fredi Satya Candra Rosaji1,Arief Darmawan1, Danang Sri Hadmoko1, Diana Paola Ordonez Coboz2, Johannes Husener2, Udo Michael Nehren2, Nirmal Raj Harma3, Ghanashyam

Sapkota3, Shreema Rana3, Ajay Chandra Lal3

1Master Program on Planning and Management of Coastal Area and Watershed, Faculty of Geography, Universitas Gadjah Mada, Yogyakarta, Indonesia.

Email: [email protected], [email protected], [email protected] University of Applied Sciences, Institute for Technology and ResourceManagement in the

Tropics and Subtropics, Germany3Master Program on Disaster Risk Management, Department of Civil Engineering, Tribhuvan University,

Kathmandu, Nepal

AbstractLandslide in Dieng complex is one of disaster that has caused damages and casualties in recent years. Comprehensive approach to see phenomena in wider perspective is needed for studying the landslides. Spatial-temporal approach combined with Eco-DRR perspective becomes abeneficial approach in analyzing the occurring landslide in a certain area. This research tried to answer the dynamic of landslide in Dieng Area from environment-human aspect, and also its relation to the existing Eco-DRR program. GIS, in this research, became a powerful tool during the application of spatial and temporal approach and Focus Group Discussion (FGD).Survey using questionnaire was conducted to get the figure of existing Eco-DRR program applied in the study area. The results give important information that landslide in Dieng area has been more intense in these years because it’s triggered by human factor. Furthermore, it can be highlighted that deforestation or land conversion is the most influencing factor that contributes to vulnerability of landslides. There is already an Eco-DRR Program in Dieng area but it still needs to be improved for wider coverage and affectivity.

Keywords: landslides, spatial-temporal approach, Eco-DRR program.

I. Introductions

Landslide is one of the most common natural disasters in hilly/mountainous regions. Itis a phenomenon of downward and outward movement of slope formed by materials composed of rocks, soils, artificial fills and also combination of all these materials along surfaces of separation by falling, sliding and flowing, either slowly or quickly, from one place to another (Highland and Bobrowsky 2008).

The major factors that cause landslides can be broadly classified into two types, natural factors and anthropogenic factors. The natural factors can be due to by gravity, geological factors, heavy and prolonged rainfall, earthquakes, forest fire, volcanoes and waves. Anthropogenic factors include inappropriate drainage system, cutting and deep excavations of slopes for constructing buildings, roads, canals and mining, and change in slope/land use pattern, deforestation and agricultural practices on steep slopes.

During the period of 1981-2007, landslide caused an estimated 2,095 casualties and 552 wounded people in Java. Nowadays, the increasing of population growth and urbanization

mailto:[email protected]




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at hazardous area causes such damage and casualties tend to increase (Hadmoko et al. 2009). In Dieng area, the worst landslide happened in 2010 and 2011 at Tieng Village, and as reported in 2010, 12 houses were damaged and 6 people died. At 2011, landslide followed by flash flood caused 13 damaged houses and 11 people died (Wiyoko 2011).

II. ObjectivesThis paper aimed to: 1) find a relation of the worst landslide in 2010 and 2011 and

define its linkage to a series of data that has been recorded since years ago; and 2) figure outthe linkage between existing Eco-DRR program in Dieng Area, which is applied by the Government and community, and its result to reduce the disaster risk.

III. Methodology3.1. Data

Data were prepared to analyze spatial-temporal landslide as well as 2010 and 2011 landslide reconstruction, to make landslide susceptibility map and to investigate Eco-DRR program in that area. Data used in this research are as followed:1. Topographical map, used to build a DEM from its contour line, and other map properties

such as toponimi, road network, stream /drainage network, etc.2. DEM derived from contour lines, used to create slope steepness map, line profile and

Hillshade model to support the GIS analysis.3. Temporal imagery data, included B/W panchromatic aerial photograph in 1970and hi-res

satellite imagery SPOT© with 5m spatial resolution downloaded from GoogleEarth™, used to investigate landuse/landcover (LULC) changes.

4. Landslide Historical Data from Wonosobo governance agency and other historical data about landslide.

3.2. MethodsMethods used in this study, in order to gain broader perspective in understanding

landslide dynamic in Dieng Area, involved both physical and socio-economic aspects. This is due to the need to combine both aspects especially in sustainable development and planning. Methods used in this study are as followed:1. Focus group discussion

FGD was conducted to understand the human and environmental system composed by the abiotic (land and water), biotic (forest, vegetations, crops) and socio-culture around the area. It produced a description of agricultural factors as important components in this context and, also, socio-economic interest that may cause landslide. The agricultural activity in Dieng includes: cropping pattern, fertilizer, terrace farming etc. On the other hand, the physical condition of that area, for instance, slope, is vulnerable to landslide disaster.

2. Site visitIn order to find the root causes of the landslide, a general observation of the study area was done. It was conducted to see the direct impact of landslides in Tieng and Surengede that were happened in 2011 and 2010. Slope and topography condition after landslide disaster were investigated. Pictures and interview of victims were taken during site visit.


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3. Surveying using questionnaireTwo villages (Tieng and Surengede) in Sub-District of Kejajar had been visited and Local farmers were interviewed using the questionnaire regarding landslide in the past, their preparedness level, DRR program that has been conducted by government etc.

4. GIS analysesGIS analyses are used to see spatial and temporal landslide in the area, re-construct landslide 2010 and 2011 from spatial approach, and to view landuse change.

Landslide Susceptibility map is one of important things in understanding physical factors in the study area toward landslide. It was prepared by overlaying several factors that are possibly prone to landslide with a method of scoring and weighted for each individual maps according to their properties. Here are the parameters used in simple landslide susceptibility map.1. Landform unit

Landform unit gives information of where landslide possibly occurs. For instance, denudational landform is susceptible to landslide than inactive crater (maar). We usedbinary score for that data, 1 for landslide-prone unit and 0 (restricted) for the opposite i.e. no landslide possibly occurs. We used combination of DEM, hillshade model, and imagery for the landform interpretations with 3D Analyst on ArcGIS.

2. Landuse/Landcover (LULC)LULC was derived from SPOT© 5m imagery interpretation. We classified LULC into 6 classes: brush, cropland, lake, openland, settlement, and woodland/forest. For each class were scored toward their susceptibility for landslide.

3. Slope steepnessSlope steepness was divided into 7 classes: 0 – 2 %, 2 – 8%, 8 – 13%, 13 – 20%, 20 – 55 %, 55 – 140% and > 140 %. The higher slope steepness assumed more susceptible toward landslide, so the scoring will be higher for the high slope than flat/almost flat area.

4. Drainage density (Dd)The drainage density was derived from topographical map (river network). Kernel Density as one of density analysis method was used for the data to get drainage density. The drainage density is an important factor as rain water percolates in area with low drainage density. Low Dd is assumed to be more susceptible to landslide than high Dd.

IV. Results and Discussion4.1. Study Area

This study took place on a part of the Dieng complex, as shown in Figure 1. Dieng complex is located administratively in Central Java Province and covers 6 Regencies, Wonosobo, Banjarnegara, Temanggung, Kendal, Pekalongan and Batang. This area is situated on about 2093

Figure 1. Map of study area


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meters (above msl) with receives the high annual rainfall that can reach for about 2400-4000 mm/year (Setiawan et al. 2012). Almost all of local people are farmers. The more benefit from fertile volcanic environment have been triggering local people to deforest this area as an intensive dry farming land.

4.2. Landslide Historical DataLandslide was not a new phenomenon in Dieng Area. It has been happening since

years ago, which is aligned with Zuidam (1978), as shown in aerial photogra ph interpretation (Figure 2-left). This means that disaster happening intensively in the Dieng Complex since 1970. Case of landslides in Java Island, as summarized by Hadmoko (2007), tended to increase year-by-year. In addition, according to National Unity and Community Protection Office in Wonosobo District (Kesbanglinmas), landslides in sub-districts around Dieng Area during 2004-2008 tended to increase (Figure 2-right)

Figure 2. Aerial photo landform interpretation (Van Zuidam 1978)-red box marks landslide events (left); Number of landslides occurring in Wonosobo in 2000-2008 (Kesbanglinmas Wonosobo, 2008) (right)

Based on information and map shown in Figure 3, in fact, landslides occur more frequently in the latest decade. Locations of the landslide were quite similar year by year. It is indicating that landslide potentially happens in Dieng Area.

4.3. Landslide Susceptibility MapLandform unit in the area is dominated by volcanic, denudation and fluvial process.

That is why many of lava flow (block lava), fluvio-volcanic flow, crater and denudation features can be found in the area. Landforms that especially formed from lava flow and denudational process are not stable. They are fragile and can easily drop because of the slope factor. Flat area is shown by green color on the map shown in Figure 4. Hilly area is shown inyellow to light brown. This map, then, inform the degree of dissected land unit in the area.

Based on information shown in the slope map (Figure 5), slope condition of the area is dominated by class 20 – 55 % to > 140 %. It is shown by color light brown to dark brown on


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Figure 3.Distribution map of landslide per sub district of Wonosobo Regency

the map. The area is in the range of steep to very steep condition. Naturally, with very steep condition, the area becomes prone to landslide. If it is combined with landform situation as explained above, vulnerability to landslide gets higher.

Moreover, drainage density (Figure 6) also has important role in term of relation to landslide vulnerability. Drainage density and pattern are naturally arranged by landform andgeological condition. At the flat area, the density is dense in contrast with the hilly area. Withdense drainage density, theoretically it tends to have good drainage. When rain falls to the area with good drainage, water will flow and not accumulate in the soil mass. And then soil mass will not be burdened, so although the slope is steep, it will not be easily triggered to fall as landslide.

Landuse/landcover (Figure 7) has contributed directly to the size of the surface runoff. Bare land/ open land is tend to have bigger surface runoff if compared with forest land. Leaves of the tree can reduce amount of water to fall directly to the soil and flow away as surface runoff, so in the forested/wood land susceptibility theoretically can be low. Unfortunately, the area is covered mainly with cropland where more susceptible to the landslide than other land cover.


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Figure 4. Landform unit interpretation of study area

Figure 5. Slope-steepness map of study area

Figure 6. Drainage density map of study area (km/km2)

Figure 7. Landuse/landcover in 2010 in the study area, based on interpretation.


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Landslide susceptibility map in the study area, as seen in Figure 8, showed that more than 60% of the area is prone to landslide (moderate to high susceptibility). They consist of several factors where theland can be failure, such as block of lava flow landform unit with high degree of slope, cropland and low drainage density. Based on the Eco-DRR perspective about the environment aspect, beside Van Zuidam interpretation of aerial photograph and landslide distribution/historical data, the result of landslide susceptibility map gave other evidence that the area is physically prone to landslide.

4.4. Understanding the 2010 Landslideand 2011 Flash Flood in Tieng Villages

The previous discussion led to a conclusion that physical condition as the influencing factors in landslides is true. Landslide repeatedly occurs from years to years, but the one occurring in 2010 and

2011 caused the greatest damage and casualties. By using spatial-temporal approach, it is true that population growth is one of the main influencing factors from human aspect. The increasing of population has positive correlation with land needed for settlement and also for agricultural. Agricultural sector is still a main livelihood for people in the village. In fact, population increase tends to speed up the land cover change in the area (Figure 9).

Unfortunately, land cover change is not aligned with regulation (spatial plan), and at the same time, enforcement from the Government related to this problem is relatively low. Conversion of land that supposed to be protected area is very intensive. It has been significantly reducing the extent of protected area. Comparison between land cover map in 1970 and land cover map 2010 results in an evidence of two types of land conversion (Figure

Figure 8. Landslide Susceptibility map of the study area

Figure 9. Graph of population growth in middle of Java province during 1964 – 2010 (Central Bureau Statistics of Central Java Province 2011)


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Tieng is one of the villages that grew up in the wrong direction. The new settlement is located in the footslope of Mt. Pakuwadja with high degree of slope-steepness and has high landslide susceptibility on that slope. It is one of the evidence of low enforcement in spatial planning from our government. From the screenshot shown in Figure 11a, the 2010 landslide and 2011 flash flood occurred in Tieng Village, overlaid on landslide susceptibility map. So, it is acceptable that landslides happening in this area may lead to significant damages and casualties (Figure 11b).

High precipitation and duration will be the triggering factor for the slope above Tieng to be failure. The secondary of triggering factor is collector road that overlaying on the high

Figure 10. Land use changes in 1970-2010 Figure 11. (a) Screenshot of the location of landslide in Tieng Village, overlaid on landslide susceptibility map (b) Photo documentation of landslide 2010 in Tieng villages (Afif 2010)

(a)

(b)


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slope above Tieng Village. Heavy vehicles such as truck and bus shake the ground and may trigger landslide.

Spatial reconstruction of flash flood in 2011 was built in 3D Analysis using 3D modeled DEM (Figure 12). Flash flood began from landslide that occurred in the upper part of Mt. Pakuwadja (a). The materials closed a river channels (b) like a temporary dam. Due to the long durations of heavy rain, lot of waters from surface run-off cannot pass over the dam. Suddenly, the temporary dam was broken and the big amount of water mixed up with materials moved downward very fast (Figure 13).

Figure 12. 3D realistic view of flash flood 2011 reconstruction (left); 3D profile of river channel (right)

The 3D profile of channel shows that Tieng is located in Mt. Pakuwadja foot slope with changing of slope gradient, so the big water and materials was spread out and hit several buildings and houses. Considering the physical factors, it is highly probably that flash flood happens repeatedly. Relocating people becomes the best solutions to prevent more casualties.

Figure 13. Photo documentation of after flash flood 2011 in Tieng villages (Wiyoko 2011)


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4.5. Eco-DRR Program in Dieng ComplexRelated to the second objective of this research, FGD was conducted in order to

figure out the linkage between Eco-DRR program that has been applied in Dieng Area by the Government and community. Some important information was derived from local authorities and local people perspectives toward landslides, as summarized in Figure 14.

Figure 14. Risk management cycle diagram, red dashed box is the weaknesses of DRR in the study area (Kienholz et al. 2004)

Almost all of farmers in Tieng village are not land-owners but labors. They were shifted the crop from tobacco to potato as it is the more benefit activity. Livelihood of people in the study area depends on the agriculture. There was lack of coordination between the local people and the governmental institutions. Similarly, there is lack of coordination among people at the upper and lower stream. There is no women participation in disaster related topics. Almost all of the farmers are ignorant about the disasters and their mitigation measures. The role of local government is found to be not efficient for pre- and during disaster.

Based on the FGD results listed above and its linkage to Common Procedure of Risk Management Cycle, as shown in Figure 15, there are lack of condition on risk assessment and risk prevention. DRR program applied by Government does not completely reach the target. It is indicated by less knowledge of mitigation and risk preparedness owned by almost of all people interviewed during FGD.

As the evidence, from questionnaire also shown that people were not had any good preparation regarding to the disaster, for example they have no allocation of money to disaster preparedness, no plan for evacuation routes, etc. It seems like Risk Prevention step as shown in Common Procedure of Risk Management Cycle were low. People need to pay much more attention on the disaster and what-to-prepare.

It is also found that the program for DRR still doesn’t reach women in the community. Although women mostly are housewives, they have significant role in the community so that an understanding of disaster and how to reduce it is possibly introduced. At the last, it is also found that the program does not reach the landowner. Landowner is a group of people who have ownership and legal authority of the piece of land.


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It seems to be a good opportunity to include DRR program into primary of secondary school. The subject can be a part of local content or as extra information for the students. Hopefully this can increase disaster awareness from early ages. In the future, new generation will understand and aware more about their environment condition and environmental problems around them.

V. ConclusionSpatial-temporal approach is powerful to help understanding landslide dynamics

crossing time and space. Of course it is with the support of GIS as spatial analysis tool. With series of data and information that can be combined and analyzed during the study, it is understood that landslide disaster in Dieng Area is not a new phenomenon. It occurs repeatedly.

Landslide in Dieng area was more intense during recent years because was triggered by human factor. People in the area tempted to deforest in order to have wider farming area and economic profit. From this study, it can be highlighted that deforestation or land conversion contributes to vulnerability of landslide. Eco-DRR Program in part of Dieng Area exists in the area of study. But, it still needs to be improved for better coverage and reach, especially to include woman/housewife and landowner to the Eco-DRR Program. Moreover, including DRR program into primary or secondary schools is also a good opportunity in increasing disaster awareness from early ages.

VI. AcknowledgementWe would like to express our gratitude to all those who gave us the possibility to

complete this paper. Firstly, we are deeply indebted to CNRD (Center for Natural Resources and Development) for supporting Join Student Project in Dieng area December 2 – 7, 2012. Secondly, we also would like to thank Mr. Aris Fathoni as our local facilitator during the research.

VII. ReferencesAfif. W (2010) Mengingat Bencana Di Awal Tahun 2010. September 2010 19:19 WIB,

www.diengplateau.comCentral Bureau Statistics of Central Java Province (2011) Perhitungan TFR dari Sensus

Penduduk [PowerPoint presentation]. RAKERDA Pembangunan Kependudukan dan Keluarga Berencana, 7 Februari 2011, Semarang.

Hadmoko DS (2007) Toward GIS-based integrated landslide hazard assessment: a criticaloverview. Indones J Geogr (in press)

Hadmoko DS, J. Sartohadi, G. Samodra, N. Christanto, F. Lavigne (2009) GIS application for comprehensive spatial landslides analysis in Kayangan Catchment, Menoreh Mountain, Java, Indonesia

Highland LM and Bobrowsky P (2008)The Landslide Handbook.US Geological Survey, Virginia, US

Kienholz H, Krummenacher B, Kifper A, and Perret S (2004). Aspects of Integral Risk Management in Practice - Considerations with Respect to Mountain Hazards in Switzerland.ÖsterreichischeWasser- und Abfallwirtschaft, 56. Jg.(3-4), 43-50.

Kesbanglinmas Wonosobo (2008) Landslide Historical Data in Wonosobo 2004 – 2008. Setiawan A et al. (2012) Practical Guide Joint Student Project on Ecosystem-Based Disaster

Risk Reduction. UGM, Yogyakarta.


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Van Zuidam (1978) ITC Textbook of Photo-Interpretation, Volume II for use of aerial detection in geomorphology and geophysical landscape analysis. Enschede, The Netherlands

Wiyoko H (2011) Kerusakan Lingkungan Penyebab Longsor Gunung Pakuwojo, TribunJateng - Rabu, 21 Desember 2011 08:38 WIB, www.tribunjateng.com

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Proceeding Joint Scientific Program and One Day Seminar on EcoDRR 2012_Pages 10-21