Physical Flood Vulnerability Assessment using Geospatial Indicator-Based Approach and Participatory Analytical Hierarchy Process: A Case Study in Kota Bharu, Malaysia

Ismaila Usman Kaoje,Khamarrul Azahari Razak,Muhammad Zulkarnain Abdul Rahman,Tze Huey Tam,Mohd Radhie Mohd Salleh,Nurul Hazrina Idris,Wan Nurul Mardiah Wan Mohd Rani

doi:10.3390/w13131786

Abstract

The most devastating flood event in Kota Bharu was recorded in December 2014, which affected several properties worth millions of dollars and thousands of homes. Damage to physical properties, especially buildings, is identified as a significant contributor to flood disasters in Malaysia. Therefore, it is essential to address physical flood vulnerability by developing an integrated approach for modeling buildings’ flood vulnerability to decrease the flood consequences. This study aims at developing a flood vulnerability assessment approach using an indicator-based model (IBM) for individual buildings in Kota Bahru, Kelantan, Malaysia. An intensive literature review and expert opinions were used to determine suitable indicators that contribute to the physical flood vulnerability of buildings. The indicators were grouped into three components, i.e., flood hazard intensity (I), building characteristics (C), and effect of the surrounding environment (E). The indicators were further refined based on expert opinions and Relative Importance Index (RII) analysis. Based on their contribution to the Malaysia local building flood vulnerability, priority weight is assigned by the experts to each of the selected indicators using the participatory Analytical Hierarchy Process (AHP). A spatial database of buildings in Kota Bharu is developed through field surveys and manually digitizing building footprints from satellite imageries. The identified indicators and their weight are added to each building footprint. The Weighted Linear Combination (WLC) aggregation method combined the weight of indicators into a vulnerability index and maps. The results of a physical flood vulnerability were validated using building damage information obtained through interviews with the community that experienced previous flood in the study area. The result showed that about 98% of the study area’s buildings have either moderate or low vulnerability to flooding. The flood vulnerability map has an overall accuracy of 75.12% and 0.63 kappa statistics. In conclusion, the IBM approach has been used successfully to develop a physical flood vulnerability for buildings in Kota Bharu. The model contributes to support different structural and non-structural approaches in the flood mitigations process.

Highlights

In recent decades, there has been a significant increase in the frequency, intensity, and magnitude of flood events in different parts of the world [1,2]
The buildings vulnerability Index (VI) presented in this study provides a scale of criticalities for individual buildings that will be severely affected at the occurrence of 100-year flood events
This paper modeled the building vulnerability index using an indicator-based approach

Summary

Introduction

There has been a significant increase in the frequency, intensity, and magnitude of flood events in different parts of the world [1,2]. In a large floodplain area, avoiding floods occurrence is challenging. Communities within flood-prone areas are adapted to the floods by reducing its impacts [1]. One of the cost-effective ways to manage and adapt to floods are through a flood risk assessment. This could be conducted by analyzing the probability of flood occurrences (hazard) and its (vulnerability) potential consequences [3]. The flood depth and extent are the most important variables to assess flood probability [4,5]. The vulnerability assesses the potential susceptibility consequences of the hazard to the exposed physical elements [6]

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Conclusion