Bringing the beach into the laboratory

Posted 1 August 2008

Ian Turner in front of the DELTA flume wave machine

A million litres of water, 500 tonnes of gravel and a wave machine the size of a two-storey building are currently being used by an international team of coastal researchers - including Dr Ian Turner of the UNSW Water Research Laboratory (WRL) - to recreate and simulate a full-scale 'beach' within the laboratory.

BARDEX - standing for BARrier Dynamic EXperiments - is a collaboration between researchers at the universities of Plymouth, Algarve, Birmingham, UNSW, Hamburg, and Southampton. Experiments have recently been conducted during the European summer months of June and July to observe and measure the response of coarse sediment beaches to changing tide, wave and groundwater conditions.

Led by Principal Investigator Dr Jon Williams of Plymouth University, the overall objectives of the BARDEX team are to examine barrier overtopping and overwash processes at the proto-type scale, and to investigate the role of back-barrier lagoon water-levels and groundwater fluxes on the stability of beaches.

Funded by the European Union through the 'HYDROLAB III' program, BARDEX is taking place within the Delta flume in the north-east of The Netherlands, a facility maintained and operated by Deltares (Delft Hydraulics).

Constructed in the late 1970s and still one of only two experimental hydraulic facilities of its size anywhere in the world, the wave tank is 240 m long, 5 m wide and ranges from 7 m to 9.5 m in depth. Maximum wave heights of up to 2.5 m can be generated, enabling researchers to simulate full-scale coastal processes under controlled laboratory conditions.

A system of 4 pumps capable of supplying 100 litres of water per second can control water levels for 'ocean' and 'lagoon' conditions to a tolerance of 10mm. This allows different sea-level, tide and beach groundwater conditions to be simulated.

Collaborative work with the BARDEX experimental program at UNSW is led by Dr Ian Turner, Deputy Director Research at the Water Research Laboratory, School of Civil and Environmental Engineering. He is responsible for formulating and managing one of the five BARDEX work packages, entitled 'WP2: Barrier Groundwater'.

Working closely with Professor Gerd Masselink of Plymouth University, leader of the 'WP3: Swash Sediment Transport' package, the WRL research team is examining swash volume asymmetry, boundary layer modification and vertical stresses exerted to surficial sediments. These processes are all potentially caused by through-bed groundwater in/out flow at the beachface.

The use of gravel in these experiments demonstrates sediment transport mechanisms associated with fluid infiltration-exfiltration through the beachface. Experimental equipment installed by the UNSW WRL and University of Plymouth team measures a range of hydrodynamic, sediment transport and morphological parameters. Sampling rates of 4 Hz enable the examination of the physics of fluid flow and sediment movement on a wave-by-wave time-scale.

The Water Research Laboratory (WRL) is a major research facility of the UNSW School of Civil and Environmental Engineering, and the largest hydraulic laboratory in Australia. The facilities at WRL - including several wave flumes and a large wave basin all capable of both regular and irregular wave generation - are in constant demand for use in a broad range of fundamental and applied research projects.

The opportunity provided by BARDEX for collaboration with researchers at another international hydraulic research facility is providing exciting new opportunities for the exchange of knowledge and expertise.

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