3. Methodology.

Flowchart of methodology.

Evaluation of the layer such as soil, elevation, slope, geology and landuse is important to order identify the possibility of landslide. Classification are based on the table given as show in appendix, every layer have their own attribute and an information which need to trough several process for GIS application able to analyze and produce the result based on the criteria needed. For this methodology, its show, how GIS application produce a map which show location low risk and high risk possibility landslide occur.

Classes number 1 has choose as well as low risk of possibility landslide and number 5 show the high risk possibility of high risk possibility landslide. The procedure of process as show in number 3.1 until 3.9. And the table classes show in appendix.

start create tin tin to raster

create aspect map

feature to rasterreclassify

grouping the layer

weighted overlay end

3.1 Preparation new map layer.

I. Set Kertau RSO Malaya (Meters) in layers.II. Add data.

i. Boundary.ii. Soil.

iii. Geology.iv. Landuse.v. Countour.

Figure 3.1 New Map Layer.

3.2 Create TIN layer and Convert to Raster.

Tin layer refer to triangulated irregular network (TIN) where includes topological relationship between points and neighboring triangles. Because interpolation of the input TIN surface occurs at regular intervals, some loss of information in the output raster should be expected. How well the raster represents the TIN is dependent on the resolution of the raster and the degree and interval of TIN surface variation. Generally, as the resolution is increased, the output raster more closely represents the TIN surface. Because the raster is a cell structure, it cannot maintain the hard and soft break line edges that may be present in the TIN. Step to create and convert:

I. Create Tin.II. Convert Tin to Raster.

Figure 3.2 Raster from TIN layer.

3.3 Spatial Analysis-Slope.

Figure 3.3 Slope.

Spatial analysis for slope analyst the raster layer and create an information slope level. Where the input is raster layer. As we can see, every colour differentiate value of slope, and the red colour is show highest value.

3.4 Aspect Map.

To show direction and degree of slope terrain, then Aspect Map created. Where, Aspect Map provide with colour such red, orange, yellow and etc. for categories symbol and degree of slope mapped with saturation color for to show the difference brightness of steepness.

Figure 3.4: Aspect Map.

3.5 Feature to Raster.

The map needed to convert are,I. Soil Map.

II. Geology Map.III. Landuse Map.

Feature to raster is conversion change the map into the raster image and then all the information contained

3.6 Reclassify for Slope, Elevation & Aspect Map.

Reclassify means change the original value of classes to classify value we refer to standard table as show in appendix.

Figure 3.6 Elevation Reclassification.

The image above, show map of elevation with class’s number 1 to 5. Where indicated number 5 more than 20 degree. Thus it’s rejected.

3.7 Reclassify Soil, Geology and Landuse map.

For soil, geology and landuse Map, the field chosen must follow the table reclassify given. Example Soil Map, we need classify for information about geology activity, such as name igneous activity, Silurian-Ordovician, Devonian, Triassic, Tertiary, Jurassic-Cretaceous, Permian and Carboniferous, Quaternary. And the classes show in table in appendix.

Figure 3.7: Attribute name NAMA_SIRI needed to reclassify for Geology Map.

For landuse classification, the information such as Sungai, Perkampungan Campur and etc are classify from class number 1 to 5. Where the possibility of landslide occur is consider. Class number 5 show high possibility of landslide. And

class number 5 is rejected.

3.8 Make new group layer.

The aim of made grouping, is to make easier to identify of job have done and make easier to continue next process.

There have three grouping, based on what process their have. Group layer Raw Data, for original layer. And weighted overlay data, group layer are group layer which will use to overlay process.

Figure 3.8 Group Layer.

3.9 Weighted Overlay.

Weighted overlay is final process for this report, to identify which area accepted and rejected based on the classification has done.

Figure 3.9 Weighted Overlay

The figure show, a map of natural activity. Green colour indicate for high risk, and not suitable for any development, including construction TNB Tower, because possibility of landslide is high.

Appendix.

Aspect Weightage

Table Weightage for Soil Series

Batang Merbau-Munchong 4 Batu Anam-Durian 4 Batu Anam-Melaka-Tavy 4Batu Hitam-Tepus-Sungai Amin 5

Briah-Tanah Liat Organan & Muck 5

Bungor-Durian 4

Bungor-Munchong 4 Chengai 5 Chenian 3Cherang Hangus-Lubok Kiat 5 Durian-Melaka-Tavy 4 Durian-Munchong-Bungor 4 Gajah Mati-Munchong-Melaka 4

Harimau-Tampoi 5 Holyrood-Lunas 5

Hutan-Semberin 3 Jempol 4 Kangar 3Kelau-Kawang 1 Kranji 1 Kuala Brang-Kedah-Serdang 4Kuantan 5 Kulai-Yong Peng 5 Kundor-Sedaka-Kangkong 5Langkawi 1 Lubok Itek-Lubok Sendong 4 Marang-Apek 4Marang-Batu Anam-Bungor 4 Munchong-Serdang 4 Munchong-Seremban 4Pohoi-Durian-Tavy 4 Prang 4 Rengam-Bukit Temiang 1Rengam-Jerangau 3 Rengam-Kala 1 Rengam-Tampin 1Rudua-Rusila 5 Sedu-Parit Botak-Linau 5 Segamat-Katung 5Selangor-Kangkong 5 Serdang-Bungor-Munchong 4 Serdang-Kedah 4Sogomana-Sitiawan-Manik 5 Tanah Bandar 5 Tanah Curam 5Tanah Gambut 5 Tanah Liat Organan & Muck 5 Tanah Lombong 5

Tasik & Kolam 5 Telemong-Akob-Lanar Tempatan 1

Telok-Guar 5

Tok Yong-Chempaka-Lundang 4

Tualang-Idris 5

Weightage for slope and elevation.

1 2 3 4 5 RejectSlope 0 – 5 5 - 10 10 - 15 15 - 20 - >20

Elevation 0 – 150m

150 – 250m

250 – 350m

350 – 1000m

>1000m -

Influence factor for weightage overlay.

LHM(HUMAN) %

LHM (NATURAL%

Elevation map 40 50

Slope map. 25 40Aspect map 10 10

Geology map. 10Soil map. 10

Landuse Map 5