Abstract

Floods are a natural phenomena that causes significant impacts on the communities, economy, built infrastructure and natural environments of Australia. From 1967 to 2013, the direct annual cost of flooding amounted to $943 million (Geoscience Australia). This, coupled with a long term economic and societal impacts and costs that consequent from flooding; it is imperative that responsible authorities pursue an adaptive flooding management approach to mitigate flooding disaster events.

The aim of this report is to provide the Victorian State Government emergency response and management plans for the Greater Melbourne region. The paper provides a synthesis of relevant literature on flood management and Geographic Information Systems (GIS) for flood risk analysis. By applying both sources of information and analysis, this paper explores the appropriate criteria, variables and parameters used in spatial analysis. These variable were provided with weightings to indicate levels of risk to potentially affected areas in the Greater Melbourne Region. With the use of digital elevation models (DEM) and data, flood hazard and risk maps were produced for the general public of Greater Melbourne and relevant authorities responsible for the safety and resilience of communities. This paper addresses the gap in research and risk management analysis for Greater Melbourne, as there is limited scholarly research in this region of Australia concerned with flooding events.

The findings from GIS analysis and review of existing literature contributed to the recommendations for population movement, environmental impact statements, industry response plans and infrastructural management and protection plans. However, despite limitations of data availability and limited experienced in research and analysis, this report contributes to the gap in research and literature of flooding risk analysis and management for Greater Melbourne.

ABBREVIATIONS

Abbreviation

DEM

BOM

GIS

LGA

VICSES

Meaning

Digital Elevation Model

Bureau of Meteorology

Geographic Information System

Local Government Area

Victorian State Emergency Services

INTRODUCTION

Flooding is a natural hazard experienced in Australia nation-wide (Melbourne Water, 2015). Such phenomenons in urban centres cause significant damage to communities, the natural environment, built environment and vital infrastructure networks (M. H., & Middelmann, M. 2007). In Victoria, flooding has many causal factors such as: heavy rainfalls over catchment areas, impervious surfaces, geology, riverine flooding, tidal influences, storm surges and increasing of sea levels due to climate change (M. H., & Middelmann, M. 2007).

Flooding is an experienced and common phenomena for a large portion of Victoria’s population (Ladds, M., Keating, A., Handmer, J., & Magee, L. 2017). The tangible and intangible economic costs of flooding are known to be a significant impact on affected society and on government expenditure (Deloitte Access Economics, 2017); this can include costs of recovery of public infrastructure, transport reconstruction, homes and government supplementary funding such as emergency payments (Deloitte Access Economics, 2017).

In Victoria, the predominant hazards in terms of costs are storms, floods, cyclones and bushfires. Since 2000, Victoria has experienced 40% of Australia’s total disaster loss (Handmer, J., Ladds, M., & Magee, L. 2018). Moreover, the economic costs of natural disasters for Australia will increase to $39 billion per year by 2050 (Deloitte Access Economics, 2017). However, with appropriate knowledge applied for risk management schemes and protocols for emergency response, such impacts can be mitigated (Climatexchange Scotland, 2016). The purpose of this report is to provide the Victorian State Government recommendations on risk management strategies and emergency response plans in areas within Greater Melbourne (Figure 1). The selection site of the Greater Melbourne region for this report is to reduce crisis as seen over the past few years (Figure 2, Figure 3); for example, the flash flooding of inner suburbs and coastal regions part of Greater Melbourne in December 2018 (Herald Sun, 2018). Furthermore, this report explores the risk of flooding inundation due to rising sea levels for the coastal regions of the Greater Melbourne Region, as seen at high levels of risk from findings.

Analysis based on Geographic Information System (GIS) for flood hazard modelling, has been used to understand and identify which populations by Local Government Areas (LGAs) may be exposed to flood hazards at high levels of risk. The methodology of analysis and findings, , found in later sections of this paper, provided sound conclusions to infer appropriate response plans for potentially impacted communities and relevant authorities.

Figure 1: Map of Greater Melbourne Area and land use. ABARES 2017

Flooding Management Definitions

In motive of readers obtaining accurate understanding throughout this report, the following provides basic definitions of concepts concerning flooding management.

Flood

High water levels caused by excessive rainfall, storm surge or dram break that overtop the natural or artificial banks of a stream, creek, river, estuary, lake or dam (Middlemann, M. H., & Middelmann, M. (2007).

Hazard

Flood hazard is the extent of flooding determined by variables such as elevation, geology, rainfall, and flow accumulation (Sui, D. Z., & Maggio, R. C. 1999).

Risk

Chance of something happening that will have an impact on objectives.Risk is measured in terms of a combinations of the consequences of an event and their likelihood. Risk depends on three factors: hazard, exposure and vulnerability (Crichton, D. 1999).

Vulnerability

Degree of susceptibility and resilience of the community and environment to hazards (Middleman, M. H., & Middelmann, M. (2007)

Tangible costs

Cost as a result of the hazard event in which holds a market value. Referring to examples of damage to property, transport infrastructure, telecom infrastructure and vehicles. (Deloitte Access Economics, 2017).

Intangible costs

Direct and indirect damages that can not be easily be quantified. Referring to examples such as death, injury and impact of mental health wellbeing. Includes opportunity cost of the next best alternative use of the resource that is foregone (Deloitte Access Economics, 2017).

Figure 2: Flash Flooding in South Melbourne December 2018 . (Herald Sun, 2018)

Figure 3: Flash Flooding on Punt Road and Swan Street, December 2018 . (Herald Sun, 2018)