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Determining the Impact of a Flood Event: Flood Hazard Mapping and Modelling of Ba River, Fiji

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Thesis(12.15 MB)

Date

2023

Authors

Supervisor

Case, Bradley
Petterson, Michael

Item type

Thesis

Degree name

Master of Science

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Volume Title

Publisher

Auckland University of Technology

Abstract

Fiji faces recurrent flood events, making it crucial to prioritize efforts in reducing flood risk and its impact. With limited resources available to prepare, respond, and recover from flooding, creating a flood hazard map becomes a vital tool in identifying high-risk areas. By mapping potential flood locations, communities can be better protected, and emergency resource allocation and decisions can be improved. Additionally, such maps can aid in town planning efforts, reducing the risks posed to people and infrastructure. The Ba Town vicinity, located on the western part of Viti Levu, Fiji’s main island, is a highly flood-vulnerable area. With a rise in the urban population due to increased commercial and industrial activity and the expansion of the town boundary, Ba Town presents a greater flood risk to people and the economy. This thesis aims to create a flood hazard map and examine flood risk areas using three methodologies. The three methods are: i) Multicriteria Decision Analysis (MCDA) using the Height Above Nearest Drainage (HAND) method; ii) flood mapping using Synthetic Aperture Radar (SAR) imageries on the Sentinel Application Platform (SNAP) software; and iii) simulating a one-dimensional flood in Hydrologic Engineering Centre’s River Analysis System (HEC-RAS) for flood extent. The most suitable flood inundation result is generated from the HAND method and is categorized into five risk levels: very high, high, medium, low, and very low. The results are analysed in three zones and against flood heights and land use land cover present in each zone. The results from the HAND method were satisfactory and showed areas at flood risk and supported the field validation data from the National Disaster Management Office. The results from SAR and HEC-RAS methods can be calibrated, and output can be further improved with more accurate input data parameters of the study site. The highlight of this study's findings is the successful development of a flood hazard map using the HAND method, categorizing flood risk levels, and validating results against field data. This comprehensive approach empowers decision-makers in Ba Town to prioritize mitigation efforts, allocate resources effectively, and implement targeted measures to protect vulnerable communities and critical infrastructure from the increasing threat of recurrent flooding. By providing valuable insights into flood-prone areas and enhancing disaster preparedness, this research contributes significantly to Fiji's resilience against climate-induced hazards and supports sustainable urban development in flood-prone regions.

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http://hdl.handle.net/10292/16773

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Masters Theses