Year

2021

Degree Name

Doctor of Philosophy

Department

School of Civil, Mining and Environmental Engineering

Abstract

Floods and droughts are likely to occur more frequently due to the impact of climate change. Floods are the most common and destructive disasters around the globe, which becomes more challenging in coastal areas due to higher population density and associated damage it can cause to infrastructure and communities. The freshwater shortage has become a progressively severe problem in the world, especially in coastal areas due to rapid urbanization and economic growth, particularly in the deltaic areas where rivers and seas meet with fewer dams built. It is necessary to investigate whether the coastal flood disasters can be mitigated and the non-saline floodwater can be captured and stored as a water source to be used in dry years.

In Australia, more than 85% of the population is living in coastal areas, which are exposed to the impact of climate change, particularly in Southeast Queensland (SEQ). SEQ experienced major floods during the years 1974 and 2011. Further, SEQ has experienced ten spells of severe droughts, during the last two centuries, and during Millennium Drought (2001-2009), the water levels in SEQ dams reduced to 17% of the full supply level in the year 2007. After a decade-long millennium drought, the Brisbane River catchment experienced an extreme rainfall event that gave rise to the January 2011 Brisbane flood causing significant property damage and lives lost. The region has a twofold issue of flooding and water shortage. The Brisbane River Estuary (BRE) and Moreton Bay have been selected as the study area to analyze adaptation measures against flood and drought.

The existing hydrological studies have considered flood mitigation measures upstream of the Wivenhoe dam. However, in Brisbane River, almost half the catchment area lies above the Wivenhoe dam and almost half of the area below the dam, and hence the Wivenhoe dam for flood control cannot regulate catchment flows associated with the latter. Obviously, in extreme events like storm surge and when a significant downpour occurs in the lower half of the catchment, the existing counter-measures are not enough to mitigate Brisbane’s flood disasters. Further, without new water storage facilities, the city cannot meet its future water demand in dry years.

This study aims to provide a solution for lower BRE flood disasters and droughts together by using a novel Coastal Reservoir (CR) technique, so when a significant climate event occurs in future, its effects on the regional community are lessened or annulled. The main objective of the study is to investigate the feasibility of the CR in BRE. Numerical software is used to model the impacts of CRs on the twofold issues of freshwater supply and flood adaptation.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.