BARDEX LOGBOOK 20/06/08 - 25/06/08

Friday 20/06/08
Arrived at the flume around 09:30 hrs. Received a safety briefing and were shown around. Unloaded the van, placed all scaffolding in the flume and organised the logging cabin.

Saturday 21/06/08
Installed all scaffolding and mounted all bed-level sensors, and also some bits of the swash rigs.

Sunday 22/06/08
Finished installing instruments and connecting them to computers in logging cabin. Also conducted the first survey in the flume (elevations of bed-level sensors and two benchmarks for resectioning) and constructed the offshore rig.

Monday 23/06/08
Tidied up around the flume and set swash rig instruments at correct elevations. Installed video camera and marked location on flume wall. Ian and Peter wrote instructions for Daniel to log instruments. Jon played around with offshore instrumentation. Flume was filled to 2.5 m, which took quite a long time (most of the day).

Tuesday 24/06/08
Placed four video GCPs on the flume wall and surveyed them in. Also surveyed in three video GCPS in the flume (sun shields of bed-level sensors 10, 20 and 30) and additional video GCP on the walkway op of drain. Deltares start their surveys by place wheel on base plate with known elevation (4.5 m). This base plate was also surveyed in and a linked file (bardex_linked_file.csv) was created with a large number of benchmarks inside and outside the flume with the datum the same as the one used by Deltares.
The groundwater run with a low lagoon level was carried out (Series A2). On problem that became apparent was that lowering the lagoon level too fast, causes a very steep hydraulic gradient at the back of the barrier, resulting in water to pour out, inducing sediment transport and channelling. The low ground water run was carried out with ocean level at 2.5 m and lagoon level at 0.8 m; a lower lagoon level is considered too risky. The run lasted four hours, after which the hydraulic gradient through the barrier was still slightly convex and not really approaching linear. However, the pump rate out of the lagoon, i.e., flow through the barrier, appeared reasonably stable. Several problems were identified in the data, the most serious one was the relatively large water level fluctuations in the ocean, due to the pumping routine not being sufficiently fine-tuned.

Wednesday 25/06/08
Today the run with the default wave conditions is planned (Series B1), with Hs = 1 m and Tp = 4.5 s. In the morning UoP set-up the logging, surveyed the tops of bed level sensors and took sediment photos (bed level sensors 8 – 44, two photos each). Still need to do calibration – will do a dry and a wet. Deltares were trying to sort out some pump and wave issues.
Waves were tested first in a series consisting of 20 mins Hs=0.5m, 5 mins of 0.80m and 5 mins of 1m waves. Then a series of runs of varying lengths at Hs=1m were carried out, reprofiling after each run.
Video was logged throughout. Sediment photos of the ‘wet bed’ were taken at the end.
Format of profile files:
· %B1GFN1.SEQ = a lot of logging and instrument information
· %B1GFN1.OUT = some logging and file name information
· %B1GFN1.DAT = binary data file
· %B1GFN1A1V1.OUT = a mixture of information (e.g., statistics, eps. Test)
· %B1GFN1PRF.ASC = data file in ascii; dodgy data at the end due to lifting out of the water of the wheel
· %B1GFN1PRF.DAT = binary data file
· %B1GFN1PRF.SEQ = some logging information
· %B1GFN1PRF.EPS = eps of profile
· %B1GFN1A1V1PRF.EPS = eps of profile change relative to original profile
Several problems occurred during Series B1:
· It was very difficult to keep the water level in the ocean constant at 2.5 m using the automatic pump system, whilst at the same time suppressing reflection at the paddle, because both respond to changes in the water level. Also with turning the reflection off it was difficult to keep the ocean level steady. Controlling the pumps manually was better, but the operator has to stay on the ball. The amount of water pumped out of the lagoon, should be the same as the amount of water to be pumped in the ocean, and by setting the pump percentage for the ocean the same as the one for the lagoon helps greatly in maintaining a steady water level.
· Stopping and starting the waves causes the wave set-up in the beach groundwater table to drop and fall. This is not ideal when one is interested in the beach groundwater table through the barrier. However, the groundwater table at the front of the barrier, especially in the swash zone, responds very quickly to turning waves on and off, and for the morphological response it should not make much of a difference whether waves are turned on and off or not.
· The main rig only occasionally received deep swashes and should really be moved 2 m down the beach. Rig 1 should be moved up by 2 m.
· Inspection of the Deltares data showed that the EMCM only recorded velocities of up to 1 m/s. This should be changed to deal with the stronger velocities.
· Tone hour of waves (1000 waves) was not sufficient to achieve equilibrium. We need to run at least 2000 waves.