rhadint@it.student.pens.ac.id RISK-LEVEL ASSESSMENT SYSTEM ON BENGAWAN SOLO S FLOOD PRONE AREAS USING AHP AND WEB GIS H A R I S R A H A D I A N TO A R N A FA R I Z A JAUA R I A K H M A D N U R H A S I M ICT-ASIA 2015 25-26 May 2015 SEARCA, Los Banos, Laguna, Philippines D E PA R T MEN T O F I N FO R M AT I CS A N D COMPUTER E N G I N EERING E L EC T RONICS E N G I N EERING P O LY T EC HNIC I N ST I T UTE O F S U R A BAYA
CONTENTS Introduction Background Problem Idea Theory Result Future Works
Indonesia as Disaster Supermarket Country Indonesia Data and Information, National Disaster Management Authority (BNPB)
Frequent Disaster in Indonesia Indonesia Data and Information, National Disaster Management Authority (BNPB)
Bengawan Solo River Basin The longest river in Java, it is approximately 600 km in length Located on East Java and Central Java Province, Indonesia. It is comprised of 17 Regencies and 3 Cities In 2007, the Bengawan Solo river basin flooded Central and East Java, causing around $170 million economic damage.
Flood Prone Areas in East Java
The Impact of Flood Floods are considered to be the most common natural disaster worldwide during the last decades. Their consequences are not only environmental but economic as well, since they may cause damages to urban areas and agricultural lands and may even result in loss of lives (Merz et al. 2010). Indonesia Data and Information, National Disaster Management Authority (BNPB)
Problems The national government has created a de-centralized structure to prepare and respond to disasters and climate change. However, these structures are often lacking and funding is frequently diverted from preparation and mitigation to emergency response, and many lack the organizational capability necessary to mitigate disasters. The increase in floods and their destructive results worldwide require an ongoing improvement on identification and mapping of flood hazard. (Kundzewicz and Kaczmare 2000; Ebert et al. 2009).
Idea Build web-based risk-level assessment system that comprehend hazards, vulnerabilities, and capacities summarized in risk analysis and integrated with Geographical Information System so it can map the region based on its risk level
Disaster Risk Assessment R : Disaster Risk H : Hazard Threat V : Vulnerability C : Adaptive Capacity General Guidelines for Disaster Risk Assessment, National Disaster Management Authority (BNPB)
Flood Risk Assessment Indicators used for semi-quantitative risk analysis will be selected based on the suitability and availability. The formula described above still apply, but will contain an index value not real value. In analogy Human Development Index (HDI) of the UNDP, to make the index comparable at least in the dimensions, the index used in the analysis were converted into a value between 0 and 1, where 0 is the minimum value of the original indicator, and 1 is the maximum value. In the case of the low numbers are many and varied in amount sometimes high, will be converted logarithmic (Log10) than linear conversion. The core of the risk mapping methodology for a tree structure indicator, where risk index forming the root end of the analysis. General Guidelines for Disaster Risk Assessment, National Disaster Management Authority (BNPB)
Analytic Hierarchy Process In the semi-quantitative analysis, particularly about the lack of information about factors sensitivity is compensated by a weighting factor. Best weighting factors obtained through consensus of expert opinion. A methodology appears to a consensus such is the Analytic Hierarchy Process (AHP). This methodology has been developed by Thomas L. Saaty began in 1970, and was originally intended as a tool for decision-making. AHP is a measurement methodology through comparison pairwise and depend on the judgment of experts to gain scale priority. This is the scale that measures the relative form. Comparisons are made with using the absolute rating scale, which represents how much the indicator dominating the other with respect to a particular disaster. General Guidelines for Disaster Risk Assessment, National Disaster Management Authority (BNPB)
The Hierarchy
Percentage of Impact Area Number of Population Exposure Number of Population Exposure per District East Java Contingency Plan on Bengawan Solo Flood, National Disaster Management Authority (BNPB)
Risk Value As explained earlier, the Risk map has been prepared based on an index of hazard, vulnerability and capacity. Modifications should be made to the above formula so it can be used in semiquantitative. Multiplication with a capacity inverted (1-C) performed, rather than division with C, to avoid high value in the case of extreme values of the low value of C, or error in terms of the empty values of C. The result of multiplying the index must be corrected by showing the root of 1 / n, for regains its original dimensions General Guidelines for Disaster Risk Assessment, National Disaster Management Authority (BNPB)
Risk-Level Division Furthermore, the values that were derived from were grouped into three risk levels. This classification was done by using the optimization method of classes distribution natural breaks (Jenks 1967). The Jenks optimization method, also called the Jenks natural breaks classification method, is a data classification method designed to determine the best arrangement of values into different classes. This is done by seeking to minimize each class average deviation from the class mean, while maximizing each class deviation from the means of the other groups. In other words, the method seeks to reduce the variance within classes and maximize the variance between classes.
Result
Conclusion There are three level risk-level on Bengawan Solo s flood-prone areas based on the analysis of hazards, vulnerabilities, and capacities There are 5 low-risk districts, 17 medium-risk districts, and 14 high-risk districts on the flood-prone areas
Future Works Flood prediction and forecating system Evaluation and upgrading the system Assessment on the following disaster when the flood occured
References Indonesia Data and Information, National Disaster Management Authority (BNPB) Merz B, Kreibich H, Schwarze R, Thieken A (2010) Assessment of economic flood damage. Nat Hazards Earth Syst Sci 10:1679 1724 Kundzewicz W, Kaczmare Z (2000) Coping with hydrological extremes. Water Int 25:66 75 Ebert A, Kerle N, Stein A (2009) Urban social vulnerability assessment with physical proxies and spatial metrics derived from air- and spaceborne imagery and GIS data. Nat Hazards 48:275 294 Jenks G (1967) The Data Model Concept in Statistical Mapping. Int Year b Cartogr 7:186 190 General Guidelines for Disaster Risk Assessment, National Disaster Management Authority (BNPB)
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