Urban Flood Vulnerability and Risk Mapping Using Integrated Multi-Parametric AHP and GIS: Methodological Overview and Case Study Assessment

Yashon Ouma,Ryutaro Tateishi

doi:10.3390/w6061515

Abstract

This study aims at providing expertise for preparing public-based flood mapping and estimating flood risks in growing urban areas. To model and predict the magnitude of flood risk areas, an integrated Analytical Hierarchy Process (AHP) and Geographic Information System (GIS) analysis techniques are used for the case of Eldoret Municipality in Kenya. The flood risk vulnerability mapping follows a multi-parametric approach and integrates some of the flooding causative factors such as rainfall distribution, elevation and slope, drainage network and density, land-use/land-cover and soil type. From the vulnerability mapping, urban flood risk index (UFRI) for the case study area, which is determined by the degree of vulnerability and exposure is also derived. The results are validated using flood depth measurements, with a minimum average difference of 0.01 m and a maximum average difference of 0.37 m in depth of observed flooding in the different flood prone areas. Similarly with respect to area extents, a maximum error of not more than 8% was observed in the highly vulnerable flood zones. In addition, the Consistency Ratio which shows an acceptable level of 0.09 was calculated and further validated the strength of the proposed approach.

Highlights

According to [1], floods are among the most recurring and devastating natural hazards, impacting upon human lives and causing severe economic damage throughout the world
The ranking and prioritization process is the main purpose of Analytical Hierarchy Process (AHP) based multi-criteria decision making
To determine the objectives and formulate the decision making process, sixteen experts comprising of four hydrologists, four engineers and eight end-users were asked to give their assessments and judgments regarding the variables related to flooding and their significances in terms of weights, out of the six factors analyzed

Summary

Introduction

According to [1], floods are among the most recurring and devastating natural hazards, impacting upon human lives and causing severe economic damage throughout the world. It is understood that flood risks will not subside in the future, and with the onset of climate change, flood intensity and frequency will threaten many regions of the world [2]. The potential for flood casualties and damages is increasing in many regions due to the social and economic development, which imply pressure on land-use, e.g., through urbanization. Flood hazard is expected to increase in frequency and severity, through the impacts of global change on climate, severe weather in the form of heavy rains and river discharge conditions [4]. The current trend and future scenarios of flood risks demand for accurate spatial and temporal information on the potential hazards and risks of floods

Objectives

Results

Discussion

Conclusion