Case Study: Bring back 'the Gap'

Vaughan, Patricia (2020) Case Study: Bring back 'the Gap'. [USQ Project]

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‘The Gap’ was originally a low sand dune which was located within the narrow piece of land between Budgewoi Beach and Budgewoi Lake. The ocean would breach this section of the land and spill over into the lake. In the 1980’s the dune was raised to restrict the ‘wash over’, as it would cause damage to the local road (Budgewoi Rd – A49) (Scott, 2015-2020) The community is divided with its point of view of ‘the Gap’ as they either believe it will improve the lakes flooding issues or it would increase the flooding extents at the lakes edge and low lying areas

This report investigated the effects of local flooding along Budgewoi Rd (A49) if ‘The Gap” was reinstated. The primary objective of this flood study was to develop a model that was able to simulate the ‘wash over’ effect. Once this was developed the model was used to determine the height, length and ideal location for ‘the Gap’.

Collation of historical data and flood information was undertaken. This provided a greater understanding of the area and the effect of changes that were implemented over time. The project utilised a coupled software approach to produce the flooding extents. TUFLOW and QGIS were the chosen software for the modelling aspect. TUFLOW used several text files to set model extents, boundary conditions and rainfall data. QGIS displayed the graphical inputs and outputs (TUFLOW, 2020). 12d software package was used to modify the sand dune height. Eight modified surfaces were created, and each new DEM was referenced in the TUFLOW model. TUFLOW Simulated different combinations of storm surges and estuary flooding events. These included the 1%AEP catchment, 5%AEP ocean, 1% AEP ocean, NEAP tide and June 2007 storm surge. Climate change factors of sea level rises were included in the model, these included 550mm and 910mm increases for the year 2050 and 2100.

The key outcome of this project was a model that simulated the wash over effect. The model ran each storm event at the eight modified dune surfaces heights. From the four modelled scenarios the NEAP tide had very little to no impact on the flood levels whereas the 5% AEP and 1%AEP only started to impact the area when the dune was lowered a minimum of 2.5m. The June 2007 storm surge event had the largest effect on the area as it breached the sand dune at its existing height and the flooding extended into properties north of Coloma St.

The project concluded that by reinstating ‘The Gap’ the flooding within Budgewoi Rd (A49) corridor and surrounding area increased. The community would be at risk of property loss and /or server injury. When climate change was considered this risk increased significantly.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Baillie, Justine
Qualification: Bachelor of Engineering (Honours) (Civil)
Date Deposited: 11 Aug 2021 06:04
Last Modified: 26 Jun 2023 04:53

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