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Using physical model testing to inform coastal design in complex wave environments

Australasian Coasts & Ports Conference, 2023, Sunshine Coast, Queensland

The 10 km stretch of foreshore between two of New Zealand’s largest cities Wellington and Hutt City is a crucial infrastructure corridor combining cycleway, road and rail, as well as sub-surface utilities. Recent storm events have caused significant damage to, and overtopping of, the current rock revetment structure resulting in the rail line being undermined and closed for extended periods. Future proofing the foreshore is integral for the longevity and function of this corridor and the Te Ara Tupua Alliance have been tasked with redeveloping it. Show more…UNSW Water Research Laboratory (WRL) undertook a large physical modelling program (over a 100 individual tests) to assist optioneering for a range of coastal protection designs. 2D flume testing was conducted to assess both the stability and overtopping performance of rock and concrete armoured (modified XblocPlus) revetments and vertical walls equipped with sloped crown walls.
All tests were conducted using irregular wave time series derived from several spectral conditions. Analysis of wave buoy records showed that both wind waves and swell entering the harbour could be expected to impact the project area. As such, sensitivity testing for overtopping was conducted using custom-generated bimodal conditions with different wind/swell ratios. Physical model testing results showed that overtopping volumes were highly sensitive to the long period wave component within the bimodal spectrum.
The findings of this extensive physical modelling program highlight the limitations of standard empirical methods for assessing overtopping under bimodal wave climates, the importance of extending beyond conventional unimodal wave climates when designing coastal structures, and the importance of using on-site wave data to best model potential overtopping volumes and safely optimize designs.
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Categories: Water
Tags: 2023
Author: Blanchard Leandre, Chan Jonathan, Flocard Francois, Paine Michael, Shand Tom D