Interpretation

Theoretical Background

According to Strahler (1983), the shape of land is the land surface configuration generated by natural processes. Further Whitton (1984) stated that the land forms a morphology and surface characteristics of land as a result of interaction between physical processes and crustal movements by coating the surface of the earth's geology. Under the second definition, it can be concluded that the shape of the land is part of the earth's surface that has a distinctive topographic forms, due to the strong influence of natural processes and geological structures in the rock material in a specific chronological time and space. Or it can also be said that the landform is formed on the surface of the earth as a result of changes in the form of the earth's surface by geomorphic processes operating in the earth's surface. Each landform is characterized by the differences in terms of structure and process geomorphology, relief/topography, and the constituent material (lithology).
Geomorphological structure provides information about the origin (genesis) of the land form. Geomorphological processes mirrored by the level erosion, while the relief is determined by the difference in the highest point with the lowest point and slope. Relief or topography gives the impression of information about the configuration of the surface shape is determined by the state land morphometric. Lithological information types and characteristics of rocks and their constituent minerals, which would affect the formation of landforms.
By looking at very complex the landscape that is in the earth's surface, it must first be classified into landform units. Thus, the classification of landform aims to simplify a complex landscape in the earth's surface into simple units (of land) that have a similarity in the nature.
Verstappen (1983) has classified based on landform genesis into ten main classes, namely:

1. Structural landform origin.
2. Volcanic landform origin.
3. Denudational landform origin.
4. Fluvial landform origin.
5. Marine landform origin.
6. Glacial landform origin.
7. Aeolian landform origin.
8. Solusional landform origin.
9. Organic landform origin.
10. Anthropogenic landform origin.

The earth’s surface composes three rocks types: igneous, sedimentary and metamorphic rocks. Each type of the rocks has a certain characteriristic that is reflected in the relief, topography, drainage pattern, drainage density, the landform and land cover/land use.
Constituent aspects of landform units, rock type and geological structure can be identified from photo or image characteristics such as: tone or color, mottling, texture, pattern, shape, size, shadow, site and geographical situation, which are then carried out field checks. Interpretation of aerial photos will provide an overview geomorphological processes such as erosion, sedimentation, weathering, and rock mass movement. The rocks types and the geological structures data or information can be used as basic data for the other thematic maps construction, such hydrogeomorphologic, morphoconservation and soil maps. Both rock types and geological structures are important factors for land evaluation, hazard assessment as input data for regional planning.

Aim of the exercise
1. to identify the rock types from landsat image
2. to identify geological structure from landsat image
3. to identify the landform unit from landsat image
4. to analyze spatial distribution of the rock type, geological structure and landform unit in relation to landuse or land cover.


CHAPTER II
METHOD

Material and equipments
1. Landsat TM 5 Composite Band 457 Kendal-Temanggung and Surrounding Area, Central Java
2. Topographical maps, Geological maps
3. Computer

Procedure
1. Delineation of the drainage pattern
2. Delineation of the relief or morphology
3. The analysis of the vegetation and land use
4. Analysis of the rocks type (lithology) and its structures
5. Deliniation of the lithological unit and draw the geological structure
6. Deliniation the landform unit
7. Identify geomorphic processes



Analysis of the lithological, geological structure, and landform unit based on Land Unit

River Delta
Locate of this area is in coastal area and flat relief area. This is an outlet of river. This area has dark red color, it shows that the area has high density vegetation, and it is possible that the vegetation is mangrove because locate in coastal area. Red color shows vegetation object in the satellite images with 457 composite bands. Fine texture shows that the type of rock in this area is alluvium, result of sedimentation from upper area. Because the process of this area be influenced by sedimentation that is transported by river, so the geomorphic process is fluvial landform.

Fluvial Marine Plain
This area is in flat relief area. In the past time, this area is a river delta, it is proven by pattern of this area like a fan. There is a accumulation place of sediment that is transported by river. So in the past, geomorphic process of this area is fluvial marine. But now the geomorphic process of this area is fluvial landform. Because it has many sediment of river transport that deposite on this area and the soil type is alluvium. In image is appeared with fine texture. The landuse of this area is rice field with red color and regular pattern, like rectangle. Vegetation is seen by red color in image. The drainage pattern in this area is meandering. It shows that the area has located in lower part of fluvial system.

Alluvial Plain
This area is in flat area and associate with meandering drainage pattern. The meandering drainage pattern shows that the area has fine texture of soil. It is possible that the soil is alluvium. Differ with fluvial marine plain, this area has green color. It shows that the area has low density vegetation. Green color shows soil object in the satellite images with 457 composite bands. Low density vegetation shows landuse in this area is not rice field or rice field but not planted. This is a tight area with hilly area on the surrounding area.
Fluvial Volcanic Plain
This area is in sloping relief area. The drainage pattern in this area is meandering. The meandering drainage pattern shows that the area has fine texture of rock. It is possible that the rocktype is tuff, because this area still be influenced by volcanic geomorphic process. Color of this area is green, it shows that vegetation in this area is low density and maybe the landuse is dry field. In some place of this area, there are several object which have dark blue color. The object is the water surface and It is possible that the landuse is pond.

Foot Volcanic Plain
This area is rolling relief area. Drainage pattern in this area is dendritic. The dendritic drainage pattern shows that this area is in upper land. The texture in this area is medium texture, it shows the rocktype in this area is medium texture. It is possible that the rocktype is tuff, because this area still be influenced by volcanic geomorphic process. Color of this area is orange and green color. Orange and green color show that this area has various landuse, maybe forest, dryfield, or open land. But many places in this area have dark blue color. The object is the water surface and it is possible that the landuse is pond.

Lower Volcanic Slope
This area is in hilly relief area. Drainage pattern in this area is dendritic. The dendritic drainage pattern shows that this area is in upper land. The texture in this area is almost coarse texture, it shows the rock type in this area is coarse texture. It is possible that the rock type is breccia, because this area still be influenced by volcanic geomorphic process. Color of this area is orange color. It shows that the area is dominated with medium density vegetation. This area has straight pattern that likely valley. It shows that erosion process in this area is high.

Middle Volcanic Slope
This area is in hilly-steeply relief area. Drainage pattern in this area is parallel. The type of this drainage is consequen. It is drainage that has direction same with direction of slope. The texture in this area is almost coarse texture, it shows the rock type in this area is coarse texture. It is possible that the rock type is breccia, because this area still be influenced by volcanic geomorphic process. Color of this area is orange and young green color. Orange and green color shows that this area has various landuse, maybe forest or orchad with various density of vegetation. There are high density and medium density vegetation.

Upper Volcanic Slope
This area is in steeply relief area. Drainage pattern in this area is radial sentrifugal. Drainage forms radial pattern from a peak to lower part sentrifugally. The type of this drainage is consequen. It is drainage that has direction same with direction of slope. The texture in this area is almost coarse texture, it shows the rocktype in this area is coarse texture. It is possible that the rocktype is andesite, because this area is near with peak of volcanic mountain. Color of this area is young green color. Young green color shows that this area has low density vegetation. It is possible that landuse is ochard.

Volcanic Cone
This area is in mountainous relief area. Drainage pattern in this area is radial sentrifugal. Drainage forms radial pattern from a peak to lower part sentrifugally. This area has conical pattern, it shows that this area is a peak of volcanic mountainous. The type of this drainage is consequen. It is drainage that has direction same with direction of slope. The texture in this area is almost coarse texture, it shows the rocktype in this area is coarse texture. It is possible that the rocktype is andesite, because this area is a peak of volcanic mountain. Color of this area is young green color. Young green color shows that this area has low density vegetation. It is possible that landuse is open land.

High Eroded Denudational Hill
This area is in hilly relief area. The drainage pattern in this area is irregular pattern. The density of drainage pattern is high, it shows that this area has fine texture of rock type. It is possible that the rock type is breccia, because this area still be influenced by volcanic geomorphic process. The rock with fine texture and inresistant material made this area became to be eroded. The erosion happened with high scale. It can be seen with the irregular pattern of crest. This area has orange color, it shows that the landuse is forest with high density vegetation.

Medium Eroded Denudational Hill
Same with high eroded denudational hill, this area is in hilly relief area, but the drainage pattern in this area is dendritic pattern. The density of drainage pattern is almost high, it shows that this area has fine texture of rock type. It is possible that the rock type is breccia, because this area still be influenced by volcanic geomorphic process. The rock with fine texture and inresistant material made this area became to be eroded. The erosion happened with medium to high scale. It can be seen with the irregular pattern of crest. This area has orange color, it shows that the landuse is forest with high density vegetation.

Low Eroded Denudational Hill
This area is in hilly-steeply relief area with drainage pattern in this area is irregular pattern. The density of drainage pattern is medium, it shows that this area has almost fine texture of rock type. It is possible that the rock type is breccia, because this area still be influenced by volcanic geomorphic process. The rock with fine texture and inresistant material made this area became to be eroded. But differ with the other denudational hill, the erosion happened with low scale. It can be seen with the regular pattern of crest but almost to irregular pattern. This area has orange color, it shows that the landuse is forest with high density vegetation.


Natural resources in landform unit

Fluvial landform has soil type that contains organic matter. It make the soil became to fertile. It seen with the landuse in fluvial landform area is dominated by agricultural land. And in structural and denudational landform is dominated by forestry land. Agricultural and forestry aspect in this area can became to be resourced to increase regional economics.


Natural hazzard potency in landform unit

This area is dominated by hilly relief formation. With the texture of coarse rock which was dominated by sand, so it is possible to be an area prone to landslides. Especially in areas with the formation of denudational landforms. For that, we need the existence of a spatial planning that takes into account vulnerability to disasters, such as not make a planning to build settlement in high vulnerable areas of landslides disaster. In addition, the potential for lowland flooding. That's because the many rivers that flow and leads to the alluvial plains. Those rivers carry water from higher land. For that, we need the a plan regarding drainage to prevent flooding disasters that may occur.


REFERENCE


Ramadhani, Adi. 2008. Laporan Praktikum Penginderaan Jauh untuk Litosfer. Yogyakarta: Faculty of Geography, GMU
Ramadhani, Adi. 2008. Laporan Praktikum Analisis Medan. Yogyakarta: Faculty of Geography, GMU
Van Zuidam, R. A. and Van Zuidam-Cancelado. 1979. Terrain analysis and classification using aerial photographs. ITC Textbook of photo-interpretation, VII-6.

Atmosfer

PENGERTIAN ATMOSFER

Adalah lapisan udara yang menyelubungi bumi sampai ketinggian 300 km, terdiri dari campuran berbagai gas yaitu Niterogen, Oksigen, Argon, dan sejumlah gas kecil lainnya.

LAPISAN ATMOSFER TERDIRI ATAS :

TROPOSFER (ketinggian rata-rata 11 km)

STRATOSFER (ketinggian mencapai 50 km)

MESOSFER (ketinggian antara 50-85 km)

TERMOSFER (ketinggian antara 85-500 km)

EKSOSFER (ketinggian diatas 500 km)

Troposfer

Troposfer merupakan lapisan terbawah dari atmosfer. Ketebalan rata-ratanya 12 km, ketinggian dikhatulistiwa antara 0 - 16 km sedangkan di wilayah kutub berkisar antara 0 -8 km dan 4/5 dari massa udara terdapat pada lapisan troposfer. Semakin tinggi lapisan udara, suhunya semakin turun hingga mencapai -60°C. Setengah dari ketinggiannya terdapat awan dan di lapisan ini seluruh gejala-gejala cuaca terjadi. Pada troposfer setiap naik di atmosfer 100 meter maka temperatur akan turun 0,5°C (khusus Indonesia 0,6°C), terdapat lapisan peralihan antara troposfer dengan stratosfer yang disebut tropopause yang berketebalan ± 2 km

Stratosfer (lapisan yang berlapis)

Stratosfer terletak pada ketinggian antara 18 sampai 49 km dari permukaan bumi. Didalamnya terdapat molekul gas yang tidak terpakai di troposfer.Lapisan bawahnya sampai ketinggian 35 km mengandung nitrogen yang bila turun ke troposfer dan terkena petir akan mengalami oksidasi nitrat dan dapat membantu pembentukan hujan. Lapisan atasnya mengandung ozon yang berguna untuk menyerap sinar ultraviolet sehingga memungkinkan kehidupan di bumi. Temperatur di lapisan bawah stratosfer dapat naik sampai 55°C. Lapisan bawah ini sering disebut sebagai lapisan Isotermis.

Mesosfer (campuran)

Mesosfer terletak pada ketinggian 49 - 82 km. Pada mesosfer semakin naik maka suhu akan turun mencolok hingga - 73°C, diketinggian 80 km disebut lapisan hangat (dilapisan inilah terbakarnya meteor yang tidak habis terbakar di eksosfer saat bergesekan dengan atmosfer bumi)

Termosfer (disebut juga lapisan ionosfer)

Termosfer terdapat pada ketinggian antara 82 - 800 km. Pada lapisan ini semakin tinggi maka suhu akan naik hingga mencapai 1232°C pada ketinggian 480 km. Perbedaan suhu antara siang dengan sore bisa mencapai ratusan derajat celcius, terdapat juga aurora dan awan pijar malam hari kadang berkilauan pada waktu pagi dan sore dari korona Matahari yang kemudian teralirkan ke kedua kutub bumi. Pada lapisan ini terdapat lapisan ionosfer di ketinggian 80 sampai dengan 360 km yang merupakan lapisan terjadinya ionisasi. Partikel ion yang terbentuk berfungsi sebagai pemantul gelombang suara dan cahaya dari bumi, yang disebut juga Appleton (lapisan F) dalam bentuk gelombang radio,

Gelombang panjang

ketinggian 30.000 - 1.000 meter di lapisan Kennely Heavyside

Gelombang menengah

ketinggian 1.000 - 200 meter

Gelombang pendek

ketinggian 200 - 10 meter di lapisan Appleton

Eksosfer (disebut juga Desifasister)

Eksosfer yang sering disebut sebagai ruang antar planet dan geostationer terdapat pada ketinggian 800 - 1.000 km. Dilapisan ini terjadi gerakan atom - atom secara bebas (tidak beraturan). Lapisan ini merupakan lapisan paling panas dan molekul udara dapat meninggalkan atmosfer sampai ketinggian 3150 km dari muka bumi. Lapisan ini merupakan lapisan yang sangat berbahaya karena lapisan ini terjadi kehancuran meteor dari ruang angkasa.

Susunan Udara

Lapisan udara tersusun oleh masing - masing kelompok zat. Masing - masing zat penyusun, kadarnya dapat berubah - ubah tergantung dari jenis dan intensitas aktifitas hidup manusia dan keadaan cuaca / iklim di bumi. Kelompok zat berupa gas dan rata - rata jumlahnya,
No. Nama Gas Jumlah

Zat Lemas (Nitrogen = N2) 78%

Zat Pembakar (Oksigen = O2)21%

Argon (Ar)0,9%%

Asam Arang (Carbon Dioksida = CO2)0,03%

Neon (Ne)0,0015%

Helium (He)0,00015%

Krypton (Kr)0,0001%

Xenon 0,000005%

Nitron Oksida 0,00005%

Methan 0,00002%

Kelompok zat lainnya adalah:

*

Debu dari jalan dan industri.

Setiap 1 m3 udara mengandung 250.000 butir debu kosmos dari angkasa luar

*

Uap air.

Jumlahnya tergantung kepada suhu, apabila suhu rendah maka uap air akan banyak. Di daerah tropis rata - rata uap air 3% dan untuk daerah kutub biasanya 0%.

Pengertian cuaca dan iklim

ž Cuaca

adalah keadaan udara pada suatu saat dan pada cakupan daerah yang sempit.

contoh : cuaca surabaya cerah, tidak berawan temperatur 20˚-30˚C

ž Iklim

adalah keadaan cuaca rata-rata pada daerah yang luas dan dalam kurun waktu yang lama (30 tahun)

Temperatur udara

ž Temperatur udara atau suhu udara salah satunya dipengaruhi oleh penyinaran matahari, alat yang digunakan untuk mengukur suhu udara adalah TERMOMETER. Termometer yang dapat mencatat sendiri disebut termograf.

ž Suhu tertinggi disebut suhu maksimum dan suhu terendah disebut suhu minimum. Suhu maksimum terjadi setelah matahari berada diatas kepala yaitu pada pukul 13.00.

Tekanan udara

ž Udara yang menyelubungi bumi adalah benda gas dan mempunyai massa, jadi di muka bumi terdapat tumpukan massa udara. Udara di bagian atas menindih (menekan) udara dibawahnya, tekanan ini yang dinamakan tekanan udara. Alat untuk mengukur tekanan udara adalah barometer, barometer yang dapat mencatat sendiri disebut barograf.

Kelembaban udara

ž Udara yang jenuh uap air disebut memiliki kelembaban maksimum. Udara yang mengandung sejumlah uap air tertentu pada udara terbuka dinamakan memiliki kelembaban absolut. Perbandingan antara kelembaban absolut dan kelembaban maksimum yang dinyatakan dalam persen (%) disebut kelembaban relatif.

ž Alat untuk mengukur kelembaban udara adalah higrometer. Higrometer yang dapat mencatat sendiri disebut higrograf. Alat lain yang dapat digunakan di sebut Psychrometer

Awan

ž Udara yang telah jenuh ketika mendapat tambahan uap air atau mengalami pendinginan akan mengalami proses kondensasi dan terbentuklah titik-titik air. Titik-titik air yang melayang-layang diudara disebut awan.

ž Awan memiliki banyak nama atau jenis yang dibedakan berdasarkan morfologi, ketinggian dan material pembentuknya.

Curah hujan

ž Adalah banyaknya air hujan atau kristal es yang jatuh hingga permukaan bumi. Alat yang digunakan untuk mengukur curah hujan disebut AMBROMETER.

ž Berdasarkan proses terjadinya hujan dibedakan sebagai berikut :

v Hujan orografis

v Hujan konveksi atau hujan zenithal

v Hujan front

Masa udara

ž Merupakan kumpulan udara pada daerah yang luas dan memiliki ciri-ciri sama yaitu temperatur sama dan kelembaban seragam (homogen). Masa udara dibedakan berdasarkan lokasi dan temperaturnya.

v Lokasi

a) Massa udara polar (kutub)

b) Massa udara tropik

c) Massa udara kontinental

d) Massa udara maritim

v Temperatur

a) Massa udara panas

b) Massa udara dingin

Angin

ž Merupakan udara yang bergerak dari daerah bertekanan tinggi menuju daerah yang bertekanan rendah.

ž Angin di permukaan bumi dibedakan menjadi dua yaitu : angin tetap dan angin lokal.

v Angin tetap

angin yang bergerak terus-menerus sepanjang tahun dengan arah yang tetap.

contoh : angin pasat, angin barat

v Angin lokal

angin yang hanya bertiup atau terjadi di daerah tertentu.

contoh : angin darat dan angin laut

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RISK MAPPING FOR LANDSLIDE POTENTIAL HAZARDS KULONPROGO REGENCY

Risk Mapping for Landslide Potential Hazards

A. Scope Area
The study area location at a little part of Purworejo Regency in part of Kaligesing district; Kulon Progo
Regency covering Girimulyo, Pengasih, Nanggulan district, part of Kokap, Samigaluh, Kalibawang,Sentolo Wates, Panjatan, Galur, and Lendah district; Sleman Regency covering part of Moyudan and Minggir district, and Bantul Regency covering part of Sedayu district.

B. Material
1) Elevation Countour
Source: Digital Topographical Indonesia Map, Scale of 1:25,000 Bakosurtanal
Coordinate system: (UTM WGS 84 zone 49S)
2) Streams
Source: Digital Topographical Indonesia Map, Scale of 1:25,000 Bakosurtanal
Coordinate system: (UTM WGS 84 zone 49S)
3) Geological Map
Source : Geological Map of Yogyakarta Sheet, Scale of 1:100,000
Coordinate system: (UTM WGS 84 zone 49S)



4) Administration Boundary
Source: Digital Topographical Indonesia Map, Scale of 1:25,000 Bakosurtanal
Coordinate system: (UTM WGS 84 zone 49S)
5) Landuse Map
Source: Digital Topographical Indonesia Map, Scale of 1:25,000 Bakosurtanal
Coordinate system: (UTM WGS 84 zone 49S)
6) Soil Map
Source: Spatial Planning Laboratory, Faculty of Geography, GMU
Coordinate system: (UTM WGS 84 zone 49S)
7) Average Annual Rainfall Station Data
Source : PUSPICS, Faculty of Geography, GMU
Coordinate system: (UTM WGS 84 zone 49S)

C. Methods

a. Landslide Hazard Determination

Determination of landslide hazard considers several parameters that have influence to
landslide hazard occurence. There are 6 landslide hazard determination parameters:
1. Slope
Slope is the level steepness represented in morphology. In general, the greater level of slopes, the further increase the likelihood of landslides in an area. It is also associated with the force of gravity pulling masses of rock from top to bottom. Higher level of slope will be more easily attracted to the bottom resulting in the occurrence of landslides. The steeper of slope in the area, the more potential of landslides occurence. Slope is the most influential factor to the occurrence of landslides, so it is given a weight value of 30%.
2. Type of Soil
Land is the result of rock weathering, with large sand or clay content, have weak
resistance which has low value of cohesion (c) and inside angle of shear (����. In the rainy season, the soil resistance decrease with increasing water content in the soil. The decrease is due to the soil volume expansion due to water content. Qualitatively, the resilience of the soil can be analyzed through the variable soil texture. Qualitative value of the land as a factor contributing to the landslide occurence that is measured based on the texture.
3. Landuse
Landuse can increase the burden that is borned by the lithology. If the burden borned is greater than the strength of lithology, there will occur landslide. Vegetation also affects the level of slope stability. Some vegetation can increase the stability of the slope because the roots can bind the rock mass making it more compact. But some kind of vegetations that have weak roots can actually reduce the level of slope stability which may impact on the landslides occurrence. Too tightly crops planting can result in heavy on the slopes so increasing the driving force of land on the slopes.
4. Rainfall Intensity
Rainfall is one of the determinants of the level of potential landslide hazard in the study area. If value of rainfall is high, it can be ascertained that the region is a region which has the highest potential for landslides. Basically, to find out the potential danger of landslides used daily rainfall data, but data is hard to find then it is used the average annual rainfall calculated based on its intensity. Because the average annual rainfall effect is not too significant to the occurrence of landslides, it is given a value of 10%.
5. Geology
Geology related to type of rock. The weather rock material is not massive and not stable, so with little influence of the movement will cause shift in position or landslides occurence.The more massive the rock without any cracks or fractures, the more resistant to weathering processes. It means that the rate of weathering of rocks getting smaller so the landslide susceptibility levels also getting smaller. Thus, the physical condition of rocks (the massive and the cracks or fractures presence) is one of the factors causing the occurrence of landslides.
6. Geological Structure (Fault)
Geological structure is a weak zone on a rock or lithology, especially fault zone. Fault that is occurred reduce holding capacity of rocks, thereby reducing the level of resistance of rock. In addition, fault form also became the place of entry of water so weathering and erosion run with more intensive. Rocks that have sufficiently intense structures have greater potential for the occurrence of landslides. The more getting close to the fault zone, the greater of this influence.
Landslide Hazard Map Acquisition àWeighted Overlay Operation Weighted Overlay is a technique for applying a common measurement scale of values to diverse and dissimilar inputs to create an integrated analysis. Geographic problems often
require the analysis of many different factors. In this case, determining the landslide hazard areas means assessing such things as slope, soil type, landuse, rainfall, and geological condition. Additionally, the factors in analysis may not be equally important. It may be that the slope is more important in choosing a site than geological structure. How much more important to decide. Weighted Overlay only accepts integer rasters as input, such as a raster of land use or soil types. Continuous (floating point) rasters must be reclassified as integer before they can be used. Generally, the values of continuous rasters are grouped into ranges, such as for slope, or Euclidean distance outputs. Each range must be assigned a single value before it can be used in the Weighted Overlay tool. The Reclassify tool allows for such rasters to be reclassified. You can either leave the value assigned to each range (but note the range of values to which the new value corresponds) and assign weights to the cell values in the Weighted Overlay dialog box later, or you can assign weights at the time of reclassifying. With the correct evaluation scale chosen, simply add the raster to the Weighted Overlay dialog box.The cells in the raster will already be set according to suitability or preference, risk, or some similarly unifying scale. The output rasters can be weighted by importance and added to produce an output raster. The steps for running weighted overlay are select an evaluation scale, add rasters, set scale values, assign weights to input rasters, assign restricted rule(optional), and run the Weighted Overlay tool. If the tool was used for suitability modeling (to locate suitable areas), higher values generally indicate that a location is more suitable. If the tool was used to generate a cost surface (to find out how much it will cost to travel through the landscape for instance), high values will generally indicate higher travel costs. You must understand the scale values you apply to input rasters so you know what the values in the output raster mean. In the illustration, the two input rasters have been reclassified to a common measurement scale of 1 to 3. Each raster is assigned a percentage influence. The cell values are multiplied by their percentage influence, and the results are added together to create the output raster. For example, consider the top left cell. The values for the two inputs become (2 * 0.75) = 1.5 and (3 * 0.25) = 0.75. The sum of 1.5 and 0.75 is 2.25. Because the output raster from Weighted Overlay is integer, the final value is rounded to 2.

b. Landslide Vulnerability Determination

Determination of landslide vulnerability considers parameter that has potential vulnerability to landslide hazard. The potential vulnerability is determined based on possible locations generate victims when landslide occured. The locations like that are lands that are used as settlement, because settlement areas represent that there are human populations in the area. The human populations can become to be victims if landslide occured. So all of settlement landuse are considered to be the vulnerable area, while all of landuse except settlement are considered to be the no vulnerable area. To operate this mapping using data query operation.

c. Landslide Risk Determination

To produce landslide risk map considers landslide hazard map and landslide vulnerability map. The area has landslide risk when the area is a vulnerable area to landslide hazard and located in landslide hazard area. But if the area is a no vulnerable area to landslide hazard, although located in landslide hazard area, so the area has not landslide risk. And if the area located in no hazard area, either vulnerable area or no vulnerable area to landslide hazard, so the area also has not landslide risk. Risk area has the levels of risk based on the levels of hazard. If the area is a vulnerable area and including in high landslide hazard area, so the
area also including high landslide risk area. To operate this mapping using vector overlaying operation.















E. Conclusions
1. Determination of landslide hazard areas is done by considering the parameters that
influence the landslide occurrence, each of those parameters has a weight factor that
describes the level of influence on the the landslide occurrence.
2. Hazard area mapping using weighted overlay analysis due to the weighted factors and
restricted rules consideration.
3. Result of landslide hazard area mapping shows that the potentially landslide hazard in
study area have percentage of 47.12% of total area.
4. The most extensive high level of landslide hazard is located in the Girimulyo district,
Kulonprogo (with percentage 36.66% of the entire area has high hazard).
5. To determine the risk map, it is needed information about the vulnerability map, the
vulnerability map is a map of the location of settlements which represent exciting
conditions of vulnerable populations to disasters occured.
6. Based on the hazard map and vulnerability map, risk map can be compiled using vector
overlay analysis due to it will be analyzed geometric size, related area measurement.
7. Result of landslide risk area mapping shows that the potentially landslide risk in study area
have percentage of 39.84% of total area.
8. The most extensive high level of landslide risk is also located in the Girimulyo district,
Kulonprogo (with percentage 52.46% of the entire area has high risk).

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