Abstract
This study examines an innovative Coastal Reservoir (CR) technique as a feasible solution for flood adaptation and mitigation in the Brisbane River Estuary (BRE), Australia, which is vulnerable to coastal flooding. The study analysed the operation of a CR by using the MIKE 21 hydrodynamic modelling package. The 2D hydrodynamic model was calibrated and validated for the 2013 and 2011 flood events respectively, with a Nash-Sutcliffe coefficient (Ens) between 0.87 to 0.97 at all gauges. River right branch widening and dredging produced a 0.16 m reduction in water level at the Brisbane city gauge. The results show that by suitable gate operation of CR, the 2011 flood normal observed level of 4.46 m, with reference to the Australian Height Datum (AHD) at Brisbane city, could have been reduced to 3.88 m AHD, while under the improved management operation of the Wivenhoe Dam, the flood level could be lowered to 4 m AHD at Brisbane city, which could have been reduced with CR to 2.87 m AHD with an overall water level reduction below the maximum flood level. The results demonstrated that the innovative use of a CR could considerably decrease the overall flood peak and lessen flood severity in the coastal city of Brisbane.
Highlights
Worldwide many people are presently exposed to the effects of coastal floods [1]
The Brisbane River requires some innovative solutions for flood control and adaptation and this study has investigated a Coastal Reservoir (CR) for downstream storage with dredging and widening of the river’s right branch, and control gates for flood mitigation
This paper is structured as follows: Section 2 describes the case study area, the Brisbane River estuary; Section 3 explains the Brisbane flooding, the hydrodynamic model, the data requirements and methods, and includes a brief explanation of a CR and gates; Section 4 describes and discusses the results of the hydrodynamic model calibration and validation along with the CR simulations; and Section 5 discusses conclusions drawn from this research, its relevance to Brisbane, and its wider applicability
Summary
Worldwide many people are presently exposed to the effects of coastal floods [1]. Coastal flooding is likely to become more common globally in the future [2] due to runoff generated by significant rainfall events [3,4], raised ocean levels, or a combination of both, and other aspects such as urban development, increase in population and land subsidence [5,6], which are causing a substantial risk to life in coastal areas [7,8]. The existing studies have mainly considered dams on the upstream catchments, channel deepening and tidal gates or barriers for flood adaptation These measures do not suffice for flood adaptation in the coastal city of Brisbane. The lower Brisbane River requires innovative flood mitigation options downstream of the Wivenhoe Dam to avoid flooding and damage to life and property. The Brisbane River requires some innovative solutions for flood control and adaptation and this study has investigated a Coastal Reservoir (CR) for downstream storage with dredging and widening of the river’s right branch, and control gates for flood mitigation. This paper is structured as follows: Section 2 describes the case study area, the Brisbane River estuary; Section 3 explains the Brisbane flooding, the hydrodynamic model, the data requirements and methods, and includes a brief explanation of a CR and gates; Section 4 describes and discusses the results of the hydrodynamic model calibration and validation along with the CR simulations; and Section 5 discusses conclusions drawn from this research, its relevance to Brisbane, and its wider applicability
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