BARDEX LOGBOOK 26/06/08 - 27/06/08

Thursday 26/06/08
Series A1: high lagoon (3.8 m), mean sea level (2.5 m). Pump on lagoon side again manually controlled by GM. An equilibrium groundwater profile was achieved and maintained for one hour. Over this hour both the lagoon and ocean water level was kept within 1 cm from the required level. Water levels were also manually recorded (see Table for measurements taken at 11:30; more in notebook). On the basis of these data a hydraulic conductivity of 0.11 m/s was computed. For information, during the period with stable water levels, the lagoon-in pump was working at 40% and the ocean out pump at 50%. The water level profile through the barrier is slightly convex.

After the groundwater test it was attempted to flatten the beach by hand. After 10-15 minutes shovelling, it was decided not to carry on. Because the beach was very disturbed, one hour of waves were run (Hs = 1 m; Tp = 4.5 s). The beach did not recover completely, but it looked good enough. This run was also logged by Deltares (SeriesA11).
Other activities:
· Rig 2 (main rig) was moved 2 m down the beach and Rig 1 was placed in its stead. The buried pressure sensors were also moved, but the cable was too short – needs sorting tomorrow.
· Sediment calibration photos were prepared and taken.
· Andre began work on preparing tracer for overwash experiments (orange, blue, and green)
· High impact PT prepared and tested at home.
· Found out that the origin for the Deltares profiles is 117.3 m.


Friday 27/06/08

Arrived at flume and sea level 0.5 m too high so after Deltares instruments had been zeroed the water was pumped back out. The cable for the subsurface pressure transducers was lengthened and an extra cross piece added to the scaffold frame in order for these PTs to log into the main logger at the main rig (which is now the seawards most rig – see yesterday’s entry). Series BB1: repeat of Series B1, but with smaller waves: Hs = 0.8 m, Tp = 4.5 s, ocean level = 2.5 m, lagoon level = 2.5 m. UoP and UNSW sensors were started at c. 10:30am, and the video approx 10:38. The waves were started approx 10:48. Waves for 1.5 hours and sequential surveys (5mins, 5mins, 5mins, 5mins, 10mins, 10mins, 15mins, 15mins, 20mins). The random waves run was followed by 5 mins of monochromatic wave conditions. Instruments were adjusted after every wave run.

· An interesting observation was that 5 mins of monochromatic waves caused significant erosion of the mid and upper beachface.
· Did calibration catalogues for two different digital grain size techniques, on both wet and dry images. Found out that both are suitable, and a hybrid of the two will be used from now on. The dry and wet sediments have a very different optical signature so the images will be inspected by eye before analysis, and the correct calibration catalogue used accordingly
· A normal run will now take this template. An hour or so is required in the morning for the Deltares staff to sync clocks, start the run, programme the wave steering signal, check water levels, and pump if necessary. Then 1 hours of waves are required to equilibrate the profile before the test run is carried out with the design wave. After 1.5 hours of the test condition, separated by profiles at 5, 10, 15, 20, 30, 40, 55, 70, and 90 mins. Afterwards, 5 mins of monochromatic waves should be sent down the flume, followed by a final survey. This will enable ensemble averages of the swash/hydrodynamic parameters to be calculated.
· Profile data %BB1EN1PRF.asc is suspect.
· Lower EMCM pair (+3 and 6 cm) looks broken.