Hierarchical Structure of The Criteria

4.2 Hierarchical Structure of The Criteria

Hazard vulnerability criteria used in this research are shown in Table 4.7. The classification of criteria including source of classification standard is discussed in detail in sub 4.1. Table 4.7 Hazard vulnerability criteria for mud volcano Vulnerability Characteristic Z1 Z2 Z3 Z4 Subsidence crack width limit in mm 5 - 15 1 – 5 1 No crack Bubble gas ♦ Methane 14 5.3 - 14 0.1 – 5.3 0.1 ♦ H 2 S PPM 30 10 – 30 0.13 - 10 = 0.13 ♦ CO 2 10 2 - 10 0.1 - 2 0.1 Flooded Area frequency 2 1-2 May occur Not likely to occur Water quality Storet -30 -11 to -30 -1 to -10 The alternative for this research is in the context of vulnerability class. The rab d into four groups which is Z1 High hazardous zone, Z2 Moder vulne le class is divide ate hazardous zone, Z3 Low hazardous zone and Z4 Not Impacted Zone. The hierarchical structure of the criteria for this research is shown in Figure 4.1. 57 Figure 4.1 Hierarchical structure of the criteria 4.3 r 2007 and February 2008. The criteria maps for this study were classified as relative to hazard class Table 4.7 and consist of six maps which are subsidence criterion map, methane gas criterion map, hydrogen sulfide gas criterion map, carbon dioxide gas criterion map, mud flooded area criterion map and water quality criterion map. Criterion Map The hazard impact in the study area is very dynamic. This research is limited to the data obtained from November 2007 until March 2008. The subsidence criterion map, simulation of flooded area and field data of bubble gas concentration are observed for one period February to march, while the water concentration data are observed for two periods i.e. Novembe 58

1. Subsidence Criterion Map

The subsidence criterion map for this research is obtained from BPLS. Figure 4.2 shows subsidence criterion map that is classified based on the impact with reference to walls crack width. The greatest part is categorized as very low impacted area to subsidence not impacted area. The hazard area of subsidence can be found in the Western part and Eastern part of the mud pond which formed a ring of class from high to low. The high subsidence hazard class covers larger areas than the other hazard class in the Eastern part, while in the Western part is dominated with low hazard area. The highest subsidence occurs in the centre point of mud gushing, but this area is not analyzed for this reseach. Figure 4.2 Subsidence criterion map

2. Bubble Gas Criterion Map

The data about concentration of gas CH 4 , H 2 S, and CO 2 for each bubble are obtained from BPLS. These data were recorded by HSE Health and Safety Environment team. Recently, the bubble that still active is 36 from 86 bubbles that ever appear, while the active bubbles that contain gasses are only 20 bubbles. 59 The plotting of bubble point location that contains gas is shown in Figure 4.3, while the concentration of gases is presented in Appendix 1. Figure 4.3 The plotting of bubble gas points The process to generate bubble gas criterion map is shown in Figure 4.4. Figure 4.4 The process of generating bubble gas criterion map 60 The proposed process uses the information of percentage of volume or PPM value of each gas. The value is classified using the information about hazard class zone. The area of each zone is generated by spatial buffering each gas point at certain distance i.e. 750 m for methane gas, 500 feet for hydrogen sulfide gas and 200 m for carbon dioxide gas. Figure 4.5 shows bubble gases criteria map consisting of methane gas, hydrogen sulfide gas and carbon dioxide gas. Figure 4.5 Bubble gas criteria maps map is classified based on the effect on humans. The area surrounding mud pond with buffer distance 500 feet is categorized as medium hazard area due to the accumulation of this gas that has rotten eggs smell. This gas did not exist in each bubble, but only a small number of bubbles contain this gass. Carbon Dioxide gas criterion map is classified based on the effect on humans. The level of this gas is dominated by safe concentration for almost all of Methane gas criterion map is classified based on the flammable limit of this gas. The areas from North-Western part to South-Eastern part of mud pond are dominated by low to medium hazard class, since almost all areas in Northern part and Western part of mud pond are categorized as very low hazard area. Hydrogen Sulfide gas criterion 61 the study areas and the concentration categorized as medium and low for cover area in Siring and Mindi villages.

3. Mud Flooded Criterion Map

T he area of impact can be roughly defined based on the impact of past floods UNDP, 2005. T he area of mud flooded for this reseach is obtained from simulation of mud overflow area by BPLS combined with flooded area generated from IKONOS serie field survey. The simulation map shows the area that has the posibility to be affected by mud flow, om im shows that the areas have ever been affecte s image obtained from CRISP and while the flooded area generated fr age d by mud overflow. Figure 4.6 The process of generating mud flood frequency criterion map The information of mud flood frequency and dam failure is obtained from BPLS. This research uses the assumption that the impacted area ever flooded by 62 mud overflow is classified as high hazard area. The process to generate mud flood criterion map is shown in Figure 4.6. The proposed process overlay mud overflow simulation map and mud flooded area. The map resulted is then classified according requirement as listed in Table 4. 4. Figure 4.7 shows the mud flooded area criterion map of the study area. This figure shows the class hazard from very low to high. The condition in the field shows that the mud overflow has high possibility to occur in the future, therefore the area surrounding the embankment with low hazard class might become medium or high hazard area. Figure 4.7 Mud flooded criterion map

4. Water Quality Criterion Map

The area of water quality for this reseach is acquired by interpolating GPS data plot. The plotting of water observation point location is shown in Figure 4.8, hile the physical and chemical data of water samples is presented in Appendix 2. w 63 Figure 4.8 The plotting of water observation points The process of generating water quality map is shown in Figure 4.9. Figure 4.9 The process to generate water quality criterion map 64 Plotting data from field survey is interpolated using Invers Distance Weighted n to o n area of er quality based on point survey. The area then is classified based on the stored class to obtain water quality map. interpolatio btai wat Water quality criterion map Figure 4.10 shows the water quality criterion map of the study area. According to Storet classification, most of the area is categorized as D class heavy polluted, followed with C class polluted and only small area that fulfil the standard water quality. The pollution of water in this area is mostly caused by mud waste from land surface but not by intrusion of mud gushing to the surface usat Lingkungan Geologi, 2007. 4.4 airwis parison of ility a using Fuzzy AHP approach is the crisp PCM obtained from expert judgment. The experts that give their judgment in atrix PCM represent all elements of the society such a Figure 4.10 P Crisp P e Com Matrix The input vulnerab ssessment form of Pairwise Comparison M s The National Sidoarjo Mudflow Mitigation Team BPLS, Settlement Agency of Sidoarjo, Centre of Environmental Geology, academic disaster 65 researchers and the public as a victim of Lapindo mud. Each of the elements gave their judgment based on their view, their knowledge and their experience on real condition of the study area. The judgment from each expert was combined to achieve single crisp PCM for all criteria. he preference of expert is performed for criteria weighting matrix and vulnerability rating ove M of criteria weight is displayed in Tab Cri for cr eighti Criteria e le looded ter Quality T r each criterion matrix. The crisp PC le 4.8. Table 4.8 sp PCM iteria w ng Subsidenc Bubb Mud F Wa Subsidenc 3 13 e 1 12 1 Bubble 2 1 12 12 Mud Flood 2 ed 3 2 1 Water Quali 2 1 ty 3 12 Table 4.8 s s the rat lative preference over two criteria of mud volcano. The expert present highest preference f ud flooded and water quality, llowed by bubble and finally subsidence. how e of re or m fo Table 4.9 shows crisp PCM of subsidence criterion relative to vulnerability class. The crisp PCM for the other criterion is presented in Appendix 4. Table 4.9 Crisp PCM for subsidence criterion to vulnerability class Subsidence Z1 Z2 Z3 Z4 Z1 1 4 6 8 Z2 14 1 3 5 Z3 16 13 1 2 Z4 18 15 12 1 66 As shown in Table 4.9, Z1 is given preference 4 times than Z2, 6 times than Z zzy AHP Approach in Vulnerability Analysis 4.5.1 F PCM from AHP is fuz by using triangular membership which has three values fuzzification is pe ed ove ia weig ix and ting matrices within the values ing fro to 9 as in Tab . The fuzzified of risp PCM for criteria weight matrix is displayed in Table 4.10. zzified Pairwise Comparison Matrix C 3 and 8 times than Z4. It implies that zone 1 has the highest preference compared to the other zones.

4.5 Fu