Friday, 25 July 2008
Because I know you all want to see some overwash ...
The final run of E6 (24/07) - sea level 3.625m, lagoon level 3.25m, 6s 1m waves
BARDEX LOGBOOK: 23/07 - 24/07
Wednesday 23/07/03
Series E3 – tide (3.25 upwards in increments of 0.125), plus constant lagoon (3.25m) . Hs=1m, Tp=4.5s
Water pumped into the system to achieve the high sea and lagoon levels. Lagoon level not steady – have to keep manually overrirding it to pump out faster than is achieved on automatic - +/- 8cm of desired level – no-one sure why. Water levels being topped up during the run – during the profiling/instrument adjjustements the water can be pumped in from the canal.
3.25, 3.375, 3.5, 3.625, 3.75m
Saul realised that the reason why the vectrino slave has consistently less data than the master, even though their settings are the same and they are properly synchronised, hitherto unrealised. The reason is that the new Toshiba laptop that the instrument logs into turns its hard drive off after 10 minutes of ‘inactivity’ – he set it to a longer time, so hopefully from now on the problem is solved...
Series E4 – lengthy discussions as to how to proceed. The initial idea was to start with the profile configuration as it is, set the lagoon to 3.5 and sea level to 3.5, and change the wave height (steadily increasing in 5cm increments from 0.8m to 1.3m – the new achievable height considering the elevated sea level).
However, it was noted that this is a juncture at which it would seem prudent to test the reproducibility of the test sequence with respect to observed morphological changes. The changes over E3 were classic cut and fill from low to high, resulting in sedimentation near the crest landwards of the breakers, and erosion near and seawards of the breakpoint. Thus it would be interesting to allow the tide to fall back to 3.25m, with the same wave conditions as before and the same lagoon level. It would be very interesting to see if the profile change observed over E3 would reverse. The idea then would be to repeat E3, pushing the tide back up again to 3.75m. Scientifically speaking, this would give us an opportunity to test a classic hydrodynamic versus morphodynamic hypothesis – because we are sending the same waves down every run, and controlling the sea and lagoon levels, if the profile change occurs exactly in reverse on the ebb, and indeed the same as E3 on the subsequent flood, then hydrodynamic and hydraulic conditions are controlling the profile development. If not, then profile change is very sensitive to morphodynamic feedbacks in the form of sensitivity to the sequence of change. It may also be interesting to overlay the hydrodynamic time series from the instruments on the offshore rig, to see how well they match
The material overwashed in the previous run is lost from the system, and we can carry on with overwash experiments with long period waves tomorrow.
E4 started approx 13:00 with sea=3.625.
Cilia noticed that on one of the pumps at high lagoon level, when the pump becomes submerged and draws in air, the flow meter stops working momentarily. This is only a problem when the lagoon is high, and means that the data for these runs will be noisy – we will need to try to filter this signal out at a later date. In the meantime, the technicians will try to fix the problem for tests from now on, and also try to measure the level at which it starts to become a problem.
Finished the run. The low tide profile (3.25m) was remarkably similar to the start profile at the start of E3, and on the subsequent rising tide (a repeat of E3), the sequence of change was remarkably and satisfyingly similar, except for some more overtopping at high tide which was inevitable.
Still big problems with the video record – very interrupted from the second camera – tomorrow will stand by it all day to keep an eye on it, and log using avi capture software rather than wmv.
Noted that there was quite strong alongshore sediment size grading – significantly finer on the west (rig) side compared with the centre and east side, so did 2 lines of sediment photos (west and centre) instead of the usual 1.
Thursday 24/07/08
High pressure sensors redeployed so one is on top of the other – it was noted l;ast night that the pressures measured are not as high as expected – Torsten believed it was because, even though the sensors are sited correctly, that the sediment and water are buffering the pressure. So this time we are trying one PT slightly out of the still water level, and one slightly below at the same location, to compare the pressure records from each
The offshore rig is still a little bit far from the action, but not in closure depth. The slope just seaward of where the waves are breaking is too steep to have the rig stable, but we will reassess later today
Middle rung of bed level sensors (24 to 39) raised slightly so they are more than 30cm from bed again. Resurveyed in, but large errors on resectionning so will redo after E5 run
Series E5 – SWL=3.5m, lagoon=3.25m, Hs increasing from 0.8m in increments of 0.1m to a possible 1.3m
Note that a few waves (2-3 mins?) were sent down the flume in error at the start before E5 began
Run finished approx 12:30. Max wave height achieved 1.3 – started to break off the paddle so decided to stop. Response of the beach was to steepen more – waves breaking and destroying themselves so little overtopping.
Landwards EM reconfigured so has some vertical flexibility
Tracer deployed. BLS and HF PTs resurveyed
Series E6 – lagoon=3.25, tide 3.25-3.625, Hs=1m, Tp=6, start 13:42
For all these overwash runs, the EMs get buried very quickly during the runs, but if we had them too high they may not record any velocities at all. Its a tough call to make, but we consistently place them at 3cm above the bed
3.25, 3.375, 3.5, 3.625 – significant overwashing on run 4 (3.625) – to back of barrier. Seepage also significant at the back despite high lagoon level, because of the waves, so deciosion taken to stop there
Beach was very 3d – overwash occurred primarily on the western (rig) side. So we did a full 3D total station survey from the level of the seawards benchmark to the lagoon. Also a 3D sediment photo survey was undertaken at the same time
Series E3 – tide (3.25 upwards in increments of 0.125), plus constant lagoon (3.25m) . Hs=1m, Tp=4.5s
Water pumped into the system to achieve the high sea and lagoon levels. Lagoon level not steady – have to keep manually overrirding it to pump out faster than is achieved on automatic - +/- 8cm of desired level – no-one sure why. Water levels being topped up during the run – during the profiling/instrument adjjustements the water can be pumped in from the canal.
3.25, 3.375, 3.5, 3.625, 3.75m
Saul realised that the reason why the vectrino slave has consistently less data than the master, even though their settings are the same and they are properly synchronised, hitherto unrealised. The reason is that the new Toshiba laptop that the instrument logs into turns its hard drive off after 10 minutes of ‘inactivity’ – he set it to a longer time, so hopefully from now on the problem is solved...
Series E4 – lengthy discussions as to how to proceed. The initial idea was to start with the profile configuration as it is, set the lagoon to 3.5 and sea level to 3.5, and change the wave height (steadily increasing in 5cm increments from 0.8m to 1.3m – the new achievable height considering the elevated sea level).
However, it was noted that this is a juncture at which it would seem prudent to test the reproducibility of the test sequence with respect to observed morphological changes. The changes over E3 were classic cut and fill from low to high, resulting in sedimentation near the crest landwards of the breakers, and erosion near and seawards of the breakpoint. Thus it would be interesting to allow the tide to fall back to 3.25m, with the same wave conditions as before and the same lagoon level. It would be very interesting to see if the profile change observed over E3 would reverse. The idea then would be to repeat E3, pushing the tide back up again to 3.75m. Scientifically speaking, this would give us an opportunity to test a classic hydrodynamic versus morphodynamic hypothesis – because we are sending the same waves down every run, and controlling the sea and lagoon levels, if the profile change occurs exactly in reverse on the ebb, and indeed the same as E3 on the subsequent flood, then hydrodynamic and hydraulic conditions are controlling the profile development. If not, then profile change is very sensitive to morphodynamic feedbacks in the form of sensitivity to the sequence of change. It may also be interesting to overlay the hydrodynamic time series from the instruments on the offshore rig, to see how well they match
The material overwashed in the previous run is lost from the system, and we can carry on with overwash experiments with long period waves tomorrow.
E4 started approx 13:00 with sea=3.625.
Cilia noticed that on one of the pumps at high lagoon level, when the pump becomes submerged and draws in air, the flow meter stops working momentarily. This is only a problem when the lagoon is high, and means that the data for these runs will be noisy – we will need to try to filter this signal out at a later date. In the meantime, the technicians will try to fix the problem for tests from now on, and also try to measure the level at which it starts to become a problem.
Finished the run. The low tide profile (3.25m) was remarkably similar to the start profile at the start of E3, and on the subsequent rising tide (a repeat of E3), the sequence of change was remarkably and satisfyingly similar, except for some more overtopping at high tide which was inevitable.
Still big problems with the video record – very interrupted from the second camera – tomorrow will stand by it all day to keep an eye on it, and log using avi capture software rather than wmv.
Noted that there was quite strong alongshore sediment size grading – significantly finer on the west (rig) side compared with the centre and east side, so did 2 lines of sediment photos (west and centre) instead of the usual 1.
Thursday 24/07/08
High pressure sensors redeployed so one is on top of the other – it was noted l;ast night that the pressures measured are not as high as expected – Torsten believed it was because, even though the sensors are sited correctly, that the sediment and water are buffering the pressure. So this time we are trying one PT slightly out of the still water level, and one slightly below at the same location, to compare the pressure records from each
The offshore rig is still a little bit far from the action, but not in closure depth. The slope just seaward of where the waves are breaking is too steep to have the rig stable, but we will reassess later today
Middle rung of bed level sensors (24 to 39) raised slightly so they are more than 30cm from bed again. Resurveyed in, but large errors on resectionning so will redo after E5 run
Series E5 – SWL=3.5m, lagoon=3.25m, Hs increasing from 0.8m in increments of 0.1m to a possible 1.3m
Note that a few waves (2-3 mins?) were sent down the flume in error at the start before E5 began
Run finished approx 12:30. Max wave height achieved 1.3 – started to break off the paddle so decided to stop. Response of the beach was to steepen more – waves breaking and destroying themselves so little overtopping.
Landwards EM reconfigured so has some vertical flexibility
Tracer deployed. BLS and HF PTs resurveyed
Series E6 – lagoon=3.25, tide 3.25-3.625, Hs=1m, Tp=6, start 13:42
For all these overwash runs, the EMs get buried very quickly during the runs, but if we had them too high they may not record any velocities at all. Its a tough call to make, but we consistently place them at 3cm above the bed
3.25, 3.375, 3.5, 3.625 – significant overwashing on run 4 (3.625) – to back of barrier. Seepage also significant at the back despite high lagoon level, because of the waves, so deciosion taken to stop there
Beach was very 3d – overwash occurred primarily on the western (rig) side. So we did a full 3D total station survey from the level of the seawards benchmark to the lagoon. Also a 3D sediment photo survey was undertaken at the same time
Wednesday, 23 July 2008
The D series - cumulative and incremental change in profile
From top to bottom, series DD1, D2 and D3. The upper panel in each figure is cumulative change relative to initial profile (every 15 minutes of waves at varying tidal heights, always low to high and back to low). Red indicates relative accretion and blue indicates erosion. Y axis increase landwards, and profile number corresponds with increasing time.
Qualitatively, a similar pattern emerges - morphological change is assymetric with the tide, and becomes more so when the lagoon levels become high or low. In addition, the consistent theme is one of sediment convergence, especially on the ebb tide (presumably when the groundwater table is super-elevated?), and positive feedback - once features form, they grow. Series DD1 and D2 have nice examples of berms stranded by the ebbing tide. Series D3 has the best example of sedimentation through sediment convergence
Profile response D2 and D3
Tests D2 and D3 looked at profile response with a tide and fixed low and high lagoon level, respectively. The major point of note is that whereas initial and end profiles on D2 were similar, the same was not the case for D3 (high lagoon). It seems that the high lagoon promoted substantial net offshore sediment transport, qualitatively similar to both C6 and C4, although here the zones of erosion and accretion were more substantial. I think it could be conclusively said that high lagoon levels promote offshore sediment transport, as expected.
Profile response D1 - first tidal run; and DD1 - the same experiment repeated with a 15min longer flood and 15min longer ebb tide
We saw significant differences in profile response between D1 and DD1. D1 and DD1 were essentially the same experiment (2.5m lagoon, tide between 1.75 and 3.25m), 0.8m waves, 4.5s period. The only difference between them was the rate at which the tide flooded and ebbed, being a 75 minute flood and ebb on D1 and a 90 minute flood and ebb on DD1.
As you can see, the profile responses were quite different. The profile of DD1 at the beginning was very much the same as at the end (see the next post for the differences over the tidal run) - apart from some crestal accretion, the two profiles were virtually identical. However, the profile at the end of D1 was very different to the beginning, with offshore sediment transport in the region of wave breaking and profile accretion/flattening offshore. The tide pushed up a similar lens of sediment at the crest
Sensitive to the initial profile, or the shape of the tidal curve? It is likely that the initial profile DD1 had equilibriated to the wave/tide conditions, which explains the lack of subsequent net change
Profile response C5 and C6
The profile response (before/after) of series C5 and C6 (longer period waves, low and high lagoon respectively). As with the runs with shorter wave periods, a low lagoon level promoted beachface accretion. The profile change associated with a higher lagoon level (C6) was less substantial, with some crestal accretion and relative depletion in the region of wave breaking (exit point effect?). C6 destroyed the subtidal ripple field
Profile Response C3 and C4
Sorry guys, realised that I've been a little thin on outputs recently. This and the following few posts have the profile change after the tests.
This is the difference between C3 and C4 (short period waves, low and high lagoons, respectively). The low lagoon level promoted onshore sediment transport and beachface accretion, whereas the high lagoon level promoted more offshore sediment transport and accretion in the region seaward of wave breaking
BARDEX LOGBOOK - 18/07 to 22/07
Friday 18/07/08
Another D-Day in the Deltagoot. The water required for today’s run (D3 – high lagoon plus tide) was pumped in over night.
Major concerns today over first the level of the buffer, then the rates at which we can achieve pumping out of the sea (so concerns over first the time it takes to achieve a low sea level to start the run, and then the length of the ebb tide later on the experiment). The pump which pumps water from the buffer to sea was working against the pump which pumps the water from the sea to buffer (because the buffer was so high the head above the pump was prohibitively high), so the ramp down to low tide was very long, and concerns that the system was at stretching point for the ebb tide to happen within the desired 90 minutes. An option was to lower the level of the lagoon, or to increase the length of either the whole tidal curve to keep it symmetric but within the limits of the pumping system, or to have an asymmetrical tide. It was decided that none of these options was desirable, because it would mean re-runs of at least yesterday’s test (and possibly more). Thus we asked for another solution to be found – the pump from buffer to sea was disabled, which helped the sea level drop, but still it was not fast enough for our ebb tide rate. Other options were considered including opening the release gate at the end of the flume to drain water out on the ebbing tide, thus aiding the speed at which we could achieve the ebb, using smaller pumps. It was felt that these pumps were not strong enough to make a noticeable difference.
By this point, there were fears over the stability of the front of the barrier because of a long delay in the start of the experiment, with high lagoon levels and low sea levels. So it was decided to start the run (pumping issue not a problem on the flood tide), and in the meantime wait for the pumping company to bring an extra submersible pump, to aid the ebb tide. At some point on the flood tide the pump would have to be reactivated in order to achieve a smooth flood tide, and we hope that the extra pump on the ebb would make the difference.
Pump reactivated on flood tide, and it worked well to keep the sea level stable.
Did first half of D3 (until high tide, until which point the problems with pumping out fast enough would not be realised), then installed 2 new pumps, ready for the ebb tide on Monday morning. In consequence, overwash rigs would have to be reconfigured on Mon afternoon, in order to record the swash on the remainder of D3.
Jon and Saul still trying to clear data from the srp using dos commands, problem is there are permissions set – no-one at the moment knows how to remove the directories, and Jon is awaiting response from Marine Electronics. Discovered that files can be accessed and deleted through internet explorer (ftp to there rather than through windows explorer or DOS, as before) – all instruments reprogrammed to sample from tues morning at 9am.
Monday 21/07/08
Because some water had to be drained from the flume in order for the pump installation on Friday, and because the technicians forgot to refill, the first part of Monday morning was spent reintroducing the lost water to the flume, before the rest of D3 could begin. Then delay when wave paddle overheated. In meantime, we put the offshore rig back in. Started run at 10:45 approx (series D33)
Computer in control room was not switched on for timings file (seq) for series D33 – clocks reset, and new run started – ‘Series D333’ approx 13:15. At the start of D333, there’s 2 mins of ‘accidental waves’ at the start, and camera not in position. Afterwards, no problems to the end of the run.
Response of the profile was to cut back from the beachface and accretion offshore. The elevated groundwater table made a significant difference to the dynamics of the beachface.
Meanwhile, offshore rig moved – landward side rotated off the wall – will have to be replaced.
In the afternoon, the swash rigs were reconfigured. The two suspect EMs (red cyclinder) were removed. The remaining 4 EMs were configured on their own at 4 different locations from barrier crest to lagoon mid-slope, each with a PT. The central logger was turned around and moved ~2m landwards. The two EM cyclinders were moved to over the break in slope at the lagoon side. None of the bed level sensors were touched. All instruments were cleaned and surveyed in using a total station. The offshore PT was moved ~3m landwards, and the 3 infiltration/exfiltration PTs were moved landwards to the crest. The atmospheric PT was repositioned higher, on the top of the flume wall. The remote control was also strapped higher to avoid submersion.
The video camera was tilted downwards, and the profiler carriage was moved to a new position for the runs, some 10m or so back, in order to catch the back of the barrier. This video camera now has a field of view stretching from the lagoon water line at 2.5m, to the barrier crest. The second video camera will be logging for the shorelines, and activity seawards.
Torsten from Hamburg installed 2 high frequency (1kHz) pressure transducers near the likely breakpoint, mounted on a scaffold pole which could be easily moved between wave runs if necessary to catch the plunging face of the wave
Tuesday 22/07/03
Series E1 – varying sea level (2.5 to 3.625 in increments of 0.125m). Hs=1m, Tp=4.5s
The response of the beach was cutback of the crest face, and accretion of the crest of the barrier. The barrier is now thinner than at any point previously. A decision was taken not to reset the barrier because it would be impossible by hand, and long period waves would now only serve to overwash the barrier. Crestal accretion was achieved through infiltration-enhanced runup limit, but overwash sensu-stricto was not achieved.
Series E2 – constant sea (3m) and lagoon level (2.5m), varying wave height (1.05 in 0.05 to 1.2 m). The run was stopped when waves breaking off the paddle, and therefore dissipating energy before they arrived at the beach. Afterwards it was realised that probably the maximum wave height acheived was 1.15 +/- 5cm.
Sediment photos taken at end.
Still gaps in the video record during runs because the video camera keeps going onto ‘demo mode’ and i haven’t figured out how to turn that off. I can’t be there to tend to the video camera all the time, so asked the profile technicians to keep an eye on it for me, but still not perfect
Another D-Day in the Deltagoot. The water required for today’s run (D3 – high lagoon plus tide) was pumped in over night.
Major concerns today over first the level of the buffer, then the rates at which we can achieve pumping out of the sea (so concerns over first the time it takes to achieve a low sea level to start the run, and then the length of the ebb tide later on the experiment). The pump which pumps water from the buffer to sea was working against the pump which pumps the water from the sea to buffer (because the buffer was so high the head above the pump was prohibitively high), so the ramp down to low tide was very long, and concerns that the system was at stretching point for the ebb tide to happen within the desired 90 minutes. An option was to lower the level of the lagoon, or to increase the length of either the whole tidal curve to keep it symmetric but within the limits of the pumping system, or to have an asymmetrical tide. It was decided that none of these options was desirable, because it would mean re-runs of at least yesterday’s test (and possibly more). Thus we asked for another solution to be found – the pump from buffer to sea was disabled, which helped the sea level drop, but still it was not fast enough for our ebb tide rate. Other options were considered including opening the release gate at the end of the flume to drain water out on the ebbing tide, thus aiding the speed at which we could achieve the ebb, using smaller pumps. It was felt that these pumps were not strong enough to make a noticeable difference.
By this point, there were fears over the stability of the front of the barrier because of a long delay in the start of the experiment, with high lagoon levels and low sea levels. So it was decided to start the run (pumping issue not a problem on the flood tide), and in the meantime wait for the pumping company to bring an extra submersible pump, to aid the ebb tide. At some point on the flood tide the pump would have to be reactivated in order to achieve a smooth flood tide, and we hope that the extra pump on the ebb would make the difference.
Pump reactivated on flood tide, and it worked well to keep the sea level stable.
Did first half of D3 (until high tide, until which point the problems with pumping out fast enough would not be realised), then installed 2 new pumps, ready for the ebb tide on Monday morning. In consequence, overwash rigs would have to be reconfigured on Mon afternoon, in order to record the swash on the remainder of D3.
Jon and Saul still trying to clear data from the srp using dos commands, problem is there are permissions set – no-one at the moment knows how to remove the directories, and Jon is awaiting response from Marine Electronics. Discovered that files can be accessed and deleted through internet explorer (ftp to there rather than through windows explorer or DOS, as before) – all instruments reprogrammed to sample from tues morning at 9am.
Monday 21/07/08
Because some water had to be drained from the flume in order for the pump installation on Friday, and because the technicians forgot to refill, the first part of Monday morning was spent reintroducing the lost water to the flume, before the rest of D3 could begin. Then delay when wave paddle overheated. In meantime, we put the offshore rig back in. Started run at 10:45 approx (series D33)
Computer in control room was not switched on for timings file (seq) for series D33 – clocks reset, and new run started – ‘Series D333’ approx 13:15. At the start of D333, there’s 2 mins of ‘accidental waves’ at the start, and camera not in position. Afterwards, no problems to the end of the run.
Response of the profile was to cut back from the beachface and accretion offshore. The elevated groundwater table made a significant difference to the dynamics of the beachface.
Meanwhile, offshore rig moved – landward side rotated off the wall – will have to be replaced.
In the afternoon, the swash rigs were reconfigured. The two suspect EMs (red cyclinder) were removed. The remaining 4 EMs were configured on their own at 4 different locations from barrier crest to lagoon mid-slope, each with a PT. The central logger was turned around and moved ~2m landwards. The two EM cyclinders were moved to over the break in slope at the lagoon side. None of the bed level sensors were touched. All instruments were cleaned and surveyed in using a total station. The offshore PT was moved ~3m landwards, and the 3 infiltration/exfiltration PTs were moved landwards to the crest. The atmospheric PT was repositioned higher, on the top of the flume wall. The remote control was also strapped higher to avoid submersion.
The video camera was tilted downwards, and the profiler carriage was moved to a new position for the runs, some 10m or so back, in order to catch the back of the barrier. This video camera now has a field of view stretching from the lagoon water line at 2.5m, to the barrier crest. The second video camera will be logging for the shorelines, and activity seawards.
Torsten from Hamburg installed 2 high frequency (1kHz) pressure transducers near the likely breakpoint, mounted on a scaffold pole which could be easily moved between wave runs if necessary to catch the plunging face of the wave
Tuesday 22/07/03
Series E1 – varying sea level (2.5 to 3.625 in increments of 0.125m). Hs=1m, Tp=4.5s
The response of the beach was cutback of the crest face, and accretion of the crest of the barrier. The barrier is now thinner than at any point previously. A decision was taken not to reset the barrier because it would be impossible by hand, and long period waves would now only serve to overwash the barrier. Crestal accretion was achieved through infiltration-enhanced runup limit, but overwash sensu-stricto was not achieved.
Series E2 – constant sea (3m) and lagoon level (2.5m), varying wave height (1.05 in 0.05 to 1.2 m). The run was stopped when waves breaking off the paddle, and therefore dissipating energy before they arrived at the beach. Afterwards it was realised that probably the maximum wave height acheived was 1.15 +/- 5cm.
Sediment photos taken at end.
Still gaps in the video record during runs because the video camera keeps going onto ‘demo mode’ and i haven’t figured out how to turn that off. I can’t be there to tend to the video camera all the time, so asked the profile technicians to keep an eye on it for me, but still not perfect
Tuesday, 22 July 2008
Monday, 21 July 2008
I'm very proud of my white box
The least hi-tech of our instruments, this white box was constructed by yours-truly, and at least judging by this photo, I'm obviously very proud!
I feel a Zingg coming on!
Nicole and David measuring the dominant three axial dimensions of pebbles. I feel a zingg diagram coming on! Great work guys ...
Step on my blue suede shoes
... and that's an order private! Saul jamming with the BARDEX posse in the eveningtide
BACK IN THE FLAT - can anyone suggest a song to accompany it?
I need suggestions for a song to accompany this video we made on saturday - the singer is me, and the subject is the other two.
Sunday, 20 July 2008
BARDEX LOGBOOK 17/07 - 18/07
Thursday 17/07/08
Series D2 – low lagoon level run first because not enough water in the system for a high lagoon run. Will need to be pumped in tonight.
Began approx 10:30. Sea level 1.75—3.25m over 90 mins, lagoon level 1.5m
Some issues in the morning stabilising water level in the lagoon, but eventually stabilised to a satisfactory +/- 2cm. Some concerns over the stability of the lagoon at 1.5m at high tide (sea level = 3.25m) because of the head difference, but decided to continue and see what would happen at high tide – because the earlier tests were done with 1.5m, it is desirable to keep this lagoon level for comparative purposes.
Offshore rig data downloaded. Subsurface PTs reset. Offshore EMs adjusted. Swash rigs and bed level sensors logged as usual. Sediment photos at end. No problems with video.
File split into D2 and D22 because the wave machine was switched on and off by mistake, causing problems in the wave paddle, and new run file was set up for the rest of the experiment.
File D222 is the run logged overnight (again logging the seepage, and groundwater response back to equilibrium)
Friday 18/07/08
Another D-Day in the Deltagoot. The water required for today’s run (D3 – high lagoon plus tide) was pumped in over night.
Major concerns today over first the level of the buffer, then the rates at which we can achieve pumping out of the sea (so concerns over first the time it takes to achieve a low sea level to start the run, and then the length of the ebb tide later on the experiment). The pump which pumps water from the buffer to sea was working against the pump which pumps the water from the sea to buffer (because the buffer was so high the head above the pump was prohibitively high), so the ramp down to low tide was very long, and concerns that the system was at stretching point for the ebb tide to happen within the desired 90 minutes. An option was to lower the level of the lagoon, or to increase the length of either the whole tidal curve to keep it symmetric but within the limits of the pumping system, or to have an asymmetrical tide. It was decided that none of these options was desirable, because it would mean re-runs of at least yesterday’s test (and possibly more). Thus we asked for another solution to be found – the pump from buffer to sea was disabled, which helped the sea level drop, but still it was not fast enough for our ebb tide rate. Other options were considered including opening the release gate at the end of the flume to drain water out on the ebbing tide, thus aiding the speed at which we could achieve the ebb, using smaller pumps. It was felt that these pumps were not strong enough to make a noticeable difference.
By this point, there were fears over the stability of the front of the barrier because of a long delay in the start of the experiment, with high lagoon levels and low sea levels. So it was decided to start the run (pumping issue not a problem on the flood tide), and in the meantime wait for the pumping company to bring an extra submersible pump, to aid the ebb tide. At some point on the flood tide the pump would have to be reactivated in order to achieve a smooth flood tide, and we hope that the extra pump on the ebb would make the difference.
Pump reactivated on flood tide, and it worked well to keep the sea level stable.
Did first half of D3 (until high tide, until which point the problems with pumping out fast enough would not be realised), then installed 2 new pumps, ready for the ebb tide on Monday morning. In consequence, overwash rigs would have to be reconfigured on Mon afternoon, in order to record the swash on the remainder of D3.
Jon and Saul still trying to clear data from the srp using dos commands, problem is there are permissions set – no-one at the moment knows how to remove the directories, and Jon is awaiting response from Marine Electronics. Discovered that files can be accessed and deleted through internet explorer (ftp to there rather than through windows explorer or DOS, as before) – all instruments reprogrammed to sample from tues morning at 9am.
Series D2 – low lagoon level run first because not enough water in the system for a high lagoon run. Will need to be pumped in tonight.
Began approx 10:30. Sea level 1.75—3.25m over 90 mins, lagoon level 1.5m
Some issues in the morning stabilising water level in the lagoon, but eventually stabilised to a satisfactory +/- 2cm. Some concerns over the stability of the lagoon at 1.5m at high tide (sea level = 3.25m) because of the head difference, but decided to continue and see what would happen at high tide – because the earlier tests were done with 1.5m, it is desirable to keep this lagoon level for comparative purposes.
Offshore rig data downloaded. Subsurface PTs reset. Offshore EMs adjusted. Swash rigs and bed level sensors logged as usual. Sediment photos at end. No problems with video.
File split into D2 and D22 because the wave machine was switched on and off by mistake, causing problems in the wave paddle, and new run file was set up for the rest of the experiment.
File D222 is the run logged overnight (again logging the seepage, and groundwater response back to equilibrium)
Friday 18/07/08
Another D-Day in the Deltagoot. The water required for today’s run (D3 – high lagoon plus tide) was pumped in over night.
Major concerns today over first the level of the buffer, then the rates at which we can achieve pumping out of the sea (so concerns over first the time it takes to achieve a low sea level to start the run, and then the length of the ebb tide later on the experiment). The pump which pumps water from the buffer to sea was working against the pump which pumps the water from the sea to buffer (because the buffer was so high the head above the pump was prohibitively high), so the ramp down to low tide was very long, and concerns that the system was at stretching point for the ebb tide to happen within the desired 90 minutes. An option was to lower the level of the lagoon, or to increase the length of either the whole tidal curve to keep it symmetric but within the limits of the pumping system, or to have an asymmetrical tide. It was decided that none of these options was desirable, because it would mean re-runs of at least yesterday’s test (and possibly more). Thus we asked for another solution to be found – the pump from buffer to sea was disabled, which helped the sea level drop, but still it was not fast enough for our ebb tide rate. Other options were considered including opening the release gate at the end of the flume to drain water out on the ebbing tide, thus aiding the speed at which we could achieve the ebb, using smaller pumps. It was felt that these pumps were not strong enough to make a noticeable difference.
By this point, there were fears over the stability of the front of the barrier because of a long delay in the start of the experiment, with high lagoon levels and low sea levels. So it was decided to start the run (pumping issue not a problem on the flood tide), and in the meantime wait for the pumping company to bring an extra submersible pump, to aid the ebb tide. At some point on the flood tide the pump would have to be reactivated in order to achieve a smooth flood tide, and we hope that the extra pump on the ebb would make the difference.
Pump reactivated on flood tide, and it worked well to keep the sea level stable.
Did first half of D3 (until high tide, until which point the problems with pumping out fast enough would not be realised), then installed 2 new pumps, ready for the ebb tide on Monday morning. In consequence, overwash rigs would have to be reconfigured on Mon afternoon, in order to record the swash on the remainder of D3.
Jon and Saul still trying to clear data from the srp using dos commands, problem is there are permissions set – no-one at the moment knows how to remove the directories, and Jon is awaiting response from Marine Electronics. Discovered that files can be accessed and deleted through internet explorer (ftp to there rather than through windows explorer or DOS, as before) – all instruments reprogrammed to sample from tues morning at 9am.
Thursday, 17 July 2008
Sediment size so far (B1 to DD1)
Filled contour plot of the sediment size of the beachface during the past weeks. Along the bottom is the sample location (underneath every bed level sensor), and along the y axis is the series/experiment, before or after. Lighter shading indicates relatively coarse sediment sizes
BARDEX LOGBOOK 14/07 - 16/07
Monday 14/07/08
JW asked us to delay deployment of rig – SRP settings need to be changed in order to minimise echo problems.
Levels brought back down in lagoon to 2.5m. Sea level brought down to 1.75m. No problems in the front of the barrier with seepage.
Series A3 started approx 10.30am. It was calculated that the pumping out takes 78% of the time as pumping in, however this estimate was based on only half the tidal run performed on Friday, and the system is nonlinear, so in reality it is hard to estimate the required pumping rate on the ebb required to make the tidal curve perfectly symmetrical. Also probably not good the pumps on flood work at 100%, especially when the wave runs begin. Wave paddle movements etc will make difference to the tidal curves. So today’s run controlled using a txt file which specifies the water level every minute – each row is a minute, and the figure is the level the sea should be, and the pumps work at a given percentage to achieve that level. A 150 minute flood and ebb was specified, plus 30 mins of still stands either side, so the tidal curve is
30 mins at 1.75m
150 mins to 3.25m
30 mins at 3.25m
150 mins to 1.75m
30 mins at 1.75m
The total run is thus 490 minutes or 8 hours.
UNSW bed level sensors were logged throughout – to catch the bed for the first time at low tide, and interesting to compare the water levels with the tidal levels and the pt records
It is likely the pumps can work at least twice as fast, so the wave runs should be:
[30 + 75 + 30 + 75 + 30] or 4 hours total. Perhaps the sequence should then be:
[30, profile, 25, profile, 25, profile, 25, profile, 30, profile, 25, profile, 25, profile, 25, profile, 30]
Assuming each profile takes 10 minutes (8*10=80 minutes), the run length will then be 5 hours 20 mins
Alternatively, cut the still-stands down to 15 mins
[15+75+15+75+15] = 275min run (4.5 hours) and profile every 15 mins during the flood and ebb
[15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile]
Assuming each profile takes 10 minutes (13*10=130 minutes), the run length will then be 6 hours 45 mins. This latter sequence seems preferable.
New attachment added to wave following staff so wave followers can reach the troughs of the waves at low tide.
SRP and ADV reprogrammed to start with new settings tomorrow 9am. Instruments altered on offshore rig – SRPs lowered to 1m from bed, lower vectrino raised 10cm.
Trial of camera set up to log breaking waves over offshore rig on tidal runs. Powered from survey cabin and logged onto spare laptop using firewire cable and firewire PCMCIA card. Cilia to order an external hard drive to store the extra video data. This video set up may also come in useful for the overwash experiments – different/extra angle of view.
Some discussions regarding wave sequence during the tidal runs. Decided to keep Hs constant at 0.8m – previously was discussed that wave height could be allowed to vary with the tide (tidal modulation) but it was decided that the experiments should only vary one thing at a time (lagoon level), and keep the rest constant.
Tuesday 15/07/08
Series D1 – sea level 2.5, lagoon level 2.5, tide varying 1.75—3.25. Tidal ramp over 75 mins, with 15 mins LT and 15 mins HT.
Offshore rig logging. Gerd arrived for a day
Decision was made not to have the 15 mins of waves at the LT following the ebb tide, because it would build a LT berm and the profile would thus not be primed for the following test run.
Sediment photos before and after. Swash rigs not logged but bed level sensors logged.
Some problems with the rig camera all day – could not charge and log at same time – eventually realised had to take the battery out when running on mains power. Also problems with the video stream. So the record of waves over the offshore was patchy to say the least.
Run was stopped about 13:20 when the wave paddle filter flooded. Pumps working too hard to achieve a steady sea level on the flood tide– decided to re-run this series tomorrow with a longer flood and ebb, so the pumps have more time to respond to the sea-level variations
After run, middle line of bed level sensors raised (a couple on the berm crest too low to record) – also in readiness for the tidal and overwash runs.
Gate/Buffer seepage was logged overnight – series D1A. Jon arrived in evening
Wednesday 16/07/08
Series DD1 – lagoon 2.5m, sea level 1.75—3.25 over 90 mins on flood and ebb. Extra 15 mins means extra profile (so 6*15 on flood and 6*15 on ebb)
Offshore rig once again logging. Resolved issues with rig camera – not a firewire logging problem at all – camera goes onto demo mode after a while. Needs to be looked on – touch screen touched every 10 minutes or so. Also logging laptop timestamped with the other video laptop, which receives its time over a wireless network from gps. Tried to log with avi files but too big, and unable to log with compression, so carry on with wmv files. Have a special program to load these files into matlab.
11:10 swash rigs put back into position and logged. Just offshore rigs
After run, offshore rig removed. Does not need to be deployed until Monday so have time to download and reprogram for a longer run during the overwash experiments.
Sediment photos at end
Gerd left. Oscar and Ana arrived from Portugal
JW asked us to delay deployment of rig – SRP settings need to be changed in order to minimise echo problems.
Levels brought back down in lagoon to 2.5m. Sea level brought down to 1.75m. No problems in the front of the barrier with seepage.
Series A3 started approx 10.30am. It was calculated that the pumping out takes 78% of the time as pumping in, however this estimate was based on only half the tidal run performed on Friday, and the system is nonlinear, so in reality it is hard to estimate the required pumping rate on the ebb required to make the tidal curve perfectly symmetrical. Also probably not good the pumps on flood work at 100%, especially when the wave runs begin. Wave paddle movements etc will make difference to the tidal curves. So today’s run controlled using a txt file which specifies the water level every minute – each row is a minute, and the figure is the level the sea should be, and the pumps work at a given percentage to achieve that level. A 150 minute flood and ebb was specified, plus 30 mins of still stands either side, so the tidal curve is
30 mins at 1.75m
150 mins to 3.25m
30 mins at 3.25m
150 mins to 1.75m
30 mins at 1.75m
The total run is thus 490 minutes or 8 hours.
UNSW bed level sensors were logged throughout – to catch the bed for the first time at low tide, and interesting to compare the water levels with the tidal levels and the pt records
It is likely the pumps can work at least twice as fast, so the wave runs should be:
[30 + 75 + 30 + 75 + 30] or 4 hours total. Perhaps the sequence should then be:
[30, profile, 25, profile, 25, profile, 25, profile, 30, profile, 25, profile, 25, profile, 25, profile, 30]
Assuming each profile takes 10 minutes (8*10=80 minutes), the run length will then be 5 hours 20 mins
Alternatively, cut the still-stands down to 15 mins
[15+75+15+75+15] = 275min run (4.5 hours) and profile every 15 mins during the flood and ebb
[15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile, 15, profile]
Assuming each profile takes 10 minutes (13*10=130 minutes), the run length will then be 6 hours 45 mins. This latter sequence seems preferable.
New attachment added to wave following staff so wave followers can reach the troughs of the waves at low tide.
SRP and ADV reprogrammed to start with new settings tomorrow 9am. Instruments altered on offshore rig – SRPs lowered to 1m from bed, lower vectrino raised 10cm.
Trial of camera set up to log breaking waves over offshore rig on tidal runs. Powered from survey cabin and logged onto spare laptop using firewire cable and firewire PCMCIA card. Cilia to order an external hard drive to store the extra video data. This video set up may also come in useful for the overwash experiments – different/extra angle of view.
Some discussions regarding wave sequence during the tidal runs. Decided to keep Hs constant at 0.8m – previously was discussed that wave height could be allowed to vary with the tide (tidal modulation) but it was decided that the experiments should only vary one thing at a time (lagoon level), and keep the rest constant.
Tuesday 15/07/08
Series D1 – sea level 2.5, lagoon level 2.5, tide varying 1.75—3.25. Tidal ramp over 75 mins, with 15 mins LT and 15 mins HT.
Offshore rig logging. Gerd arrived for a day
Decision was made not to have the 15 mins of waves at the LT following the ebb tide, because it would build a LT berm and the profile would thus not be primed for the following test run.
Sediment photos before and after. Swash rigs not logged but bed level sensors logged.
Some problems with the rig camera all day – could not charge and log at same time – eventually realised had to take the battery out when running on mains power. Also problems with the video stream. So the record of waves over the offshore was patchy to say the least.
Run was stopped about 13:20 when the wave paddle filter flooded. Pumps working too hard to achieve a steady sea level on the flood tide– decided to re-run this series tomorrow with a longer flood and ebb, so the pumps have more time to respond to the sea-level variations
After run, middle line of bed level sensors raised (a couple on the berm crest too low to record) – also in readiness for the tidal and overwash runs.
Gate/Buffer seepage was logged overnight – series D1A. Jon arrived in evening
Wednesday 16/07/08
Series DD1 – lagoon 2.5m, sea level 1.75—3.25 over 90 mins on flood and ebb. Extra 15 mins means extra profile (so 6*15 on flood and 6*15 on ebb)
Offshore rig once again logging. Resolved issues with rig camera – not a firewire logging problem at all – camera goes onto demo mode after a while. Needs to be looked on – touch screen touched every 10 minutes or so. Also logging laptop timestamped with the other video laptop, which receives its time over a wireless network from gps. Tried to log with avi files but too big, and unable to log with compression, so carry on with wmv files. Have a special program to load these files into matlab.
11:10 swash rigs put back into position and logged. Just offshore rigs
After run, offshore rig removed. Does not need to be deployed until Monday so have time to download and reprogram for a longer run during the overwash experiments.
Sediment photos at end
Gerd left. Oscar and Ana arrived from Portugal
Example of sediment size profiles - B1 to C2
Surface sediment size distributions are being routinely monitored using the image processing techniques of Buscombe and Masselink (in press, Sedimentology) and Buscombe (in press, Sedimentary Geology) *shameless plug* Example outputs here for the first runs (black is before a run, red is after a run) - here we have B1, BB1, and C2. Greens are inherited from the first survey. Magentas are inherited from subsequent surveys
Wednesday, 16 July 2008
First Tidal run D1
Test D1 (Series D1: lagoon 2.5m; tide 1.75-3.25m; Hs=0.8m; Tp=4.5s; ARC off)
This test is the first of a series of three with a 1.5-m tide. In hindsight the duration of the tidal cycle was too short (75 min from low to high tide) and the pumps were not able to keep up with the planned rate of tidal rise. A different tidal duration (90 min from low to high tide) will be used for the next three tidal runs. The initial profile was obtained by exposing the end profile of test C4 to 3 min of long period waves (Tp = 10 s) with the water level at 2.5 m. These conditions effectively removed the berm, leaving a relatively featureless slightly convex profile. During the rising tide, the berm build-up and a step developed just below high tide level. The falling tide left the berm stranded and the step migrated down the beach. The contourplots show better the temporal evolution of the beach profile. Of interest is the tidal asymmetry: (1) berm accretion mainly during the rising tide; (2) step development mainly on the falling tide.
Thanks to Prof Hoff for preparing this figure
Monday, 14 July 2008
BARDEX LOGBOOK 10/07/08 - 11/07/08
Thursday 10/07/08
The rest of series C3 [15,15,20,5] was carried out, with the usual profiles, rig adjustments and sediment photos.
Offshore rig removed, data downloaded.
30 mins of design waves for this sequence – 2.5 sea, 2.5 lagoon, Hs=0.8, Tp=3s.
Water levels prepared for the next set of tests –
Then series C4 began (high lagoon 3.5, sea=2.5, hs=0.8, tp=3) and half the run completed
[5,5,5,5,10]. Note that when the series ends unfinished we continue to log the delatres pressure transducers overnight in a separate file (to keep file sizes down!) in order to log the beach groundwater table response back to equillibrium
Friday 10/07/08
Finished series C4 with [10,15,15,20,5mono] waves, with usual rig adjustments, profiles and sediment photos. It has been noted that the 3s waves cause little morphological change compared to 6s period waves, apart from on the monochromatic waves of 3s which cause large erosion (c.5-10cm in 5mins), possibly because the swash excursions are so small with 3s waves, the volume of water contained in them being very small
The 3s waves caused much more obvious sediment grading patterns compared with the longer waves. C4 saw armouring of the beachface, before the monochromatic waves removed the coarse particles on the surface offshore to the breakpoint
Offshore rig reprogrammed to start recording on Monday 9am
Total station survey of all instruments, inc EMs, PTs, camera, weather station, all rig instruments (heights relative to known points on rig).
Five 25cm-long sediment cores taken for geotechnical analysis, and their positions surveyed in. All EMs washed
Lagoon and sea pumped to 2.5m. 3mins of reset waves (1m, 10s) to remove berm in readiness for the nest series.
Trial of A3 started at 15:00. Took 35 mins to raise sea level from 2.5m to 3.25m, pumping in at 100%. Took 25 mins to pump back down again – not symmetrical because of differences in the pumps.
Monday can begin with offshore rig deployment followed by test A3
The rest of series C3 [15,15,20,5] was carried out, with the usual profiles, rig adjustments and sediment photos.
Offshore rig removed, data downloaded.
30 mins of design waves for this sequence – 2.5 sea, 2.5 lagoon, Hs=0.8, Tp=3s.
Water levels prepared for the next set of tests –
Then series C4 began (high lagoon 3.5, sea=2.5, hs=0.8, tp=3) and half the run completed
[5,5,5,5,10]. Note that when the series ends unfinished we continue to log the delatres pressure transducers overnight in a separate file (to keep file sizes down!) in order to log the beach groundwater table response back to equillibrium
Friday 10/07/08
Finished series C4 with [10,15,15,20,5mono] waves, with usual rig adjustments, profiles and sediment photos. It has been noted that the 3s waves cause little morphological change compared to 6s period waves, apart from on the monochromatic waves of 3s which cause large erosion (c.5-10cm in 5mins), possibly because the swash excursions are so small with 3s waves, the volume of water contained in them being very small
The 3s waves caused much more obvious sediment grading patterns compared with the longer waves. C4 saw armouring of the beachface, before the monochromatic waves removed the coarse particles on the surface offshore to the breakpoint
Offshore rig reprogrammed to start recording on Monday 9am
Total station survey of all instruments, inc EMs, PTs, camera, weather station, all rig instruments (heights relative to known points on rig).
Five 25cm-long sediment cores taken for geotechnical analysis, and their positions surveyed in. All EMs washed
Lagoon and sea pumped to 2.5m. 3mins of reset waves (1m, 10s) to remove berm in readiness for the nest series.
Trial of A3 started at 15:00. Took 35 mins to raise sea level from 2.5m to 3.25m, pumping in at 100%. Took 25 mins to pump back down again – not symmetrical because of differences in the pumps.
Monday can begin with offshore rig deployment followed by test A3
Today is A3 (2) - 1st tidal simulation
Today's run will look something like this! Distorted scale. Red squares are bed level sensors, green markers are Deltares instruments, and black squares are video gcps. Red circles are plymouth swash rigs
Today is A3 (1) - 1st tidal simulation
Today's tidal curve.
30 mins at 1.75m, 150 mins up, 30 mins at 3.25m, 150 mins down, 30 mins at 1.75m
This is a symmetrical tide which the pump software has been pre-programmed to perform. It's a very slow tidal run (0.5cm/min or 30cm/hr) compared to the rate at which the pump systems can vary the water levels (at least twice this speed). This way the tide is more realistic in terms of its shape (flood/ebb times relative to slack), groundwater levels in the beach have ample time to respond to the sea levels
BARDEX - the story so far (2)
For every test run (x-axis) the following parameters have been graphed: from top to bottom - Hs, Tp, sea level, and lagoon level
BARDEX - the story so far (1)
BARDEX timeline - series run versus date. Multiple runs of the same series (e.g. C3, C33, and C33) refer to stops and starts in the Deltares measuring system. Subscript 'r' refers to beach profile resets.
Hope this helps to put the runs in some sort of order in your heads!
Thursday, 10 July 2008
Video of offshore rig as it leaves the water
Video courtesy of Amaia Ruiz de Alegria Arzaburu Fernandez Beitialarringoitia Larrea Uribetxebarria
Dan in 70s wetsuit shocker
No experiment would be complete without Dan donning the trusty 'potato skin' wetsuit. Here you see Dan showing off his new 'moins pelage visage', his Dutch (beer and bread) gut, and his gentle effervescence
The amazing sinking sensors
It was to be expected really. The swash rig, equipped with Dr Turner's bed level sensors, is sinking slowly into the sea and algoon. Regular checks made using a total station have confirmed that the rig is sinking up to 3cm into the sea, and up to 2cm into the lagoon, with little change on the dry crest. Regular monitoring is important for subsequent calculations
BARDEX LOGBOOK 09/07/08
Wednesday 09/07/08
EMs and Bed level sensors cleaned with soapy water
Series B2 continued [15, 15, 20, 5mono], rig adjustments and profiles, followed by sediment photos. The response of the morphology to the remainder of the run was to destroy the ripple field completely, and consolidate the small berm which developed at the runup limit, which was much more limited than seen under the longer period waves.
Checks made on EM and PT data from swash rigs. Cleaning seemed to make the improve the data, so this will now regularly happen.
Successful trial of vectrino synching
Bed level sensors surveyed, and change in heights computed – they have sunk by max 3cm at the seawards extent and max 2cm at landwards extent. The dry sensors have remained at approximately the same position
Offshore rig taken out of the water, and reprogrammed for another deployment. Some issues with data collection and downloads on ADV and SRP. The ADV did not collect data successfully because it was not issued with the command ‘deploy’ before deployment. The SRP failed to respond to established routines to download the data, once again.
Offshore rig deployed, and water levels pumped for series C3 to begin – sea 2.5, lagoon 1.5, Hs=0.8, Tp=3
Began series [5,5,5,5,10,10], will finish the run tomorrow. The response of the profile so far has been very mild – very slight accretion of the berm, and little change elsewhere. Once again the data was logged overnight to record the re-equilibriation of the groundwater table before the recommencing of series C3 tomorrow morning.
Little is known about the sediments we are using, so Nicole and David measured the a, b, and c axes of pebbles, for quantification of angularity, using callipers. Deltares will source scales so some proper and independent particle size analysis using sieves can occur
EMs and Bed level sensors cleaned with soapy water
Series B2 continued [15, 15, 20, 5mono], rig adjustments and profiles, followed by sediment photos. The response of the morphology to the remainder of the run was to destroy the ripple field completely, and consolidate the small berm which developed at the runup limit, which was much more limited than seen under the longer period waves.
Checks made on EM and PT data from swash rigs. Cleaning seemed to make the improve the data, so this will now regularly happen.
Successful trial of vectrino synching
Bed level sensors surveyed, and change in heights computed – they have sunk by max 3cm at the seawards extent and max 2cm at landwards extent. The dry sensors have remained at approximately the same position
Offshore rig taken out of the water, and reprogrammed for another deployment. Some issues with data collection and downloads on ADV and SRP. The ADV did not collect data successfully because it was not issued with the command ‘deploy’ before deployment. The SRP failed to respond to established routines to download the data, once again.
Offshore rig deployed, and water levels pumped for series C3 to begin – sea 2.5, lagoon 1.5, Hs=0.8, Tp=3
Began series [5,5,5,5,10,10], will finish the run tomorrow. The response of the profile so far has been very mild – very slight accretion of the berm, and little change elsewhere. Once again the data was logged overnight to record the re-equilibriation of the groundwater table before the recommencing of series C3 tomorrow morning.
Little is known about the sediments we are using, so Nicole and David measured the a, b, and c axes of pebbles, for quantification of angularity, using callipers. Deltares will source scales so some proper and independent particle size analysis using sieves can occur
Wednesday, 9 July 2008
Ripple Profiler 'Data Taster'
Thanks to Charlie for preparing this figure - a typical swath made by UoP's scanning ripple profiler. This makes a scan of the bed every minute, and is currently sitting over a decaying ripple field.
BARDEX LOGBOOK 04/07/08 - 08/07/08
Friday 04/07/08
1 hour of .8m, 6s waves with sea and lagoon at 2.5m
Instruments reset, and SRP/ADV downloaded
Cilia sourced a more suitable auger – we will reinstall the PTs on Monday
Series C6 - .8m, 6s, sea=2.5m, lagoon=3.5m (any more and too much water pours out of the beachface and causes rill erosion)
Normal sequence of [5,5,5,5,10,10,15,15,20,5 mins mono]
Response of the beach was to steepen and slight berm accretion. Stabilised very quickly
Matlab worked fine for the video measurements
Lawrence got more information about the wave generation with respect to steering signal, water depth, reflection compensation etc, and started to write a short report on the Deltaflume paddle modis operandi
Andre and Charlie worked on data analysis scripts for the ADV and SRP data, respectively, in order for us to do quick checks on the quality of the data, and also get some information whilst we are here.
No reset – will do the same as yesterday because the profile is steep then flattens considerably in the region of wave breaking. Therefore it is likely that the waves again wont breach the berm sufficiently.
Test run – beach steepened even more, and position of the berm cut back approx 1m.
At start of default waves, PT stick 17.5cm from bed. At end was 17cm off bed. Top PT (-10cm) exposed at surface.
The response of the profile was to erode and steepen the beachface and accrete the berm. Some bedforms started to develop seawards of the breakers around 75-80m (1—2 crests)
Monday 07/07/08
30 mins of Hs=0.8m, 6s, 2.5 sea and 2.5 lagoon. Did desired job of reshaping the profile so the beachface was not so steep. ‘Reset’ run again not desired because waves breaking further offshore, and boundary conditions should ideally not change when wave parameters are not changing (only lagoonal levels)
Instrument heights fixed, sediment photos taken. Top subsurface pt still flush with the bed.
On offshore rig, SRP is 43cm above the Sontek ADV probe bottom to middle axis of SRP. New vectrino (delft) is 25cm above the lower vectrino (soton) probe bottom to probe bottom
PT 12 was replaced. It was quite an effort to dig down through the gravel with the tools provided. Used combination of low lagoon levels, vacuum cleaner, and soil augers to drill down 1.8m, where the replacement pt was installed at 1.8m + 0.18m (1.62m), which was believed to be always below the water table. Insufficient time for the installation of PT 8 so that will occur tomorrow when the offshore rig is replaced in the flume. Only levelled the new PT approximately in order not to waste any more time, so it was approximated, and a uniform offset will be worked out at the end and will be applied to the data once acquired.
Series C5 – 0.8m, 6s, 2.5 sea, 1.5 lagoon
The response of the profile was to move material from breaker zone and seawards of the breaker zone and move it onshore to create uniform sedimentation on the beachface. The bedforms around 75-80m seawards of breakpoint developed into 3—4 distinct crests with spacing of around 1m.
The run finished very late so it was decided to keep the run going over night so the PTs could log whilst the groundwater levels equilibriated, and also to check the levels of the new PT that was installed earlier on but not checked. To prevent the files from becoming too large, the run was stopped and restarted (called seriesC5 and seriesC5a, respectively).
Tuesday 08/07/08
Instruments moved out of way of the forthcoming profile reset
Sediment photos
Barrier profile reset using 10s 80cm waves for 2min. Did not achieve desired effect of berm flattening, so we used rakes and shovels to push the material down the slope. We then sent 10s 1m waves down the flume for 2mins, which pushed a little material onshore, but had the desired effect of flattening the profile sufficiently for runs to continue
With some considerable effort again, PT 8 was reinstalled – the distance from pt sensor to bed was 2.03m.
Some issues with synching one vectrino laptop with time server – not able to do it wirelessly. Resolved by plugging the laptop into the last remaining Ethernet port on the hub of the timeserver laptop
Offshore rig was reinstated into the flume at 72.5m, - fibreglass poles were both 40cm above water surface. Rig placed closer inshore because of interesting ripples (1m wavelength, 30cm height) which had developed in this area (some 5m seawards of breakpoint) over the last 2 experimental runs. Instruments were programmed to start recording at 14:00:00
SRP – 1 minute swaths, continuously as before
ADV – 25Hz, as deployment before
Series B2 began at c.15:00
[5,5,5,5,10,10]. Built a small berm around rig 2. Will finish the run in the morning, and the offshore rig will be removed, checked, and programmed for a longer run
Vectrino trial logging with synchronisation – vectrinos were synced and the master vectrino logged data ok, but the slave did not log data (the file didn’t appear even though it said it was logging in the software). Jon and Dan resolved this problem so a repeat trial will be made in the morning when series B2 gets under way again.
The data from the EMs and PTs looked a little dodgy – blocky. Dan noticed and stopped the data collection momentarily, restarted LabView data acquisition software, and logged again for the rest of the run. Will check the data tonight.
1 hour of .8m, 6s waves with sea and lagoon at 2.5m
Instruments reset, and SRP/ADV downloaded
Cilia sourced a more suitable auger – we will reinstall the PTs on Monday
Series C6 - .8m, 6s, sea=2.5m, lagoon=3.5m (any more and too much water pours out of the beachface and causes rill erosion)
Normal sequence of [5,5,5,5,10,10,15,15,20,5 mins mono]
Response of the beach was to steepen and slight berm accretion. Stabilised very quickly
Matlab worked fine for the video measurements
Lawrence got more information about the wave generation with respect to steering signal, water depth, reflection compensation etc, and started to write a short report on the Deltaflume paddle modis operandi
Andre and Charlie worked on data analysis scripts for the ADV and SRP data, respectively, in order for us to do quick checks on the quality of the data, and also get some information whilst we are here.
No reset – will do the same as yesterday because the profile is steep then flattens considerably in the region of wave breaking. Therefore it is likely that the waves again wont breach the berm sufficiently.
Test run – beach steepened even more, and position of the berm cut back approx 1m.
At start of default waves, PT stick 17.5cm from bed. At end was 17cm off bed. Top PT (-10cm) exposed at surface.
The response of the profile was to erode and steepen the beachface and accrete the berm. Some bedforms started to develop seawards of the breakers around 75-80m (1—2 crests)
Monday 07/07/08
30 mins of Hs=0.8m, 6s, 2.5 sea and 2.5 lagoon. Did desired job of reshaping the profile so the beachface was not so steep. ‘Reset’ run again not desired because waves breaking further offshore, and boundary conditions should ideally not change when wave parameters are not changing (only lagoonal levels)
Instrument heights fixed, sediment photos taken. Top subsurface pt still flush with the bed.
On offshore rig, SRP is 43cm above the Sontek ADV probe bottom to middle axis of SRP. New vectrino (delft) is 25cm above the lower vectrino (soton) probe bottom to probe bottom
PT 12 was replaced. It was quite an effort to dig down through the gravel with the tools provided. Used combination of low lagoon levels, vacuum cleaner, and soil augers to drill down 1.8m, where the replacement pt was installed at 1.8m + 0.18m (1.62m), which was believed to be always below the water table. Insufficient time for the installation of PT 8 so that will occur tomorrow when the offshore rig is replaced in the flume. Only levelled the new PT approximately in order not to waste any more time, so it was approximated, and a uniform offset will be worked out at the end and will be applied to the data once acquired.
Series C5 – 0.8m, 6s, 2.5 sea, 1.5 lagoon
The response of the profile was to move material from breaker zone and seawards of the breaker zone and move it onshore to create uniform sedimentation on the beachface. The bedforms around 75-80m seawards of breakpoint developed into 3—4 distinct crests with spacing of around 1m.
The run finished very late so it was decided to keep the run going over night so the PTs could log whilst the groundwater levels equilibriated, and also to check the levels of the new PT that was installed earlier on but not checked. To prevent the files from becoming too large, the run was stopped and restarted (called seriesC5 and seriesC5a, respectively).
Tuesday 08/07/08
Instruments moved out of way of the forthcoming profile reset
Sediment photos
Barrier profile reset using 10s 80cm waves for 2min. Did not achieve desired effect of berm flattening, so we used rakes and shovels to push the material down the slope. We then sent 10s 1m waves down the flume for 2mins, which pushed a little material onshore, but had the desired effect of flattening the profile sufficiently for runs to continue
With some considerable effort again, PT 8 was reinstalled – the distance from pt sensor to bed was 2.03m.
Some issues with synching one vectrino laptop with time server – not able to do it wirelessly. Resolved by plugging the laptop into the last remaining Ethernet port on the hub of the timeserver laptop
Offshore rig was reinstated into the flume at 72.5m, - fibreglass poles were both 40cm above water surface. Rig placed closer inshore because of interesting ripples (1m wavelength, 30cm height) which had developed in this area (some 5m seawards of breakpoint) over the last 2 experimental runs. Instruments were programmed to start recording at 14:00:00
SRP – 1 minute swaths, continuously as before
ADV – 25Hz, as deployment before
Series B2 began at c.15:00
[5,5,5,5,10,10]. Built a small berm around rig 2. Will finish the run in the morning, and the offshore rig will be removed, checked, and programmed for a longer run
Vectrino trial logging with synchronisation – vectrinos were synced and the master vectrino logged data ok, but the slave did not log data (the file didn’t appear even though it said it was logging in the software). Jon and Dan resolved this problem so a repeat trial will be made in the morning when series B2 gets under way again.
The data from the EMs and PTs looked a little dodgy – blocky. Dan noticed and stopped the data collection momentarily, restarted LabView data acquisition software, and logged again for the rest of the run. Will check the data tonight.
Friday, 4 July 2008
BARDEX LOGBOOK 02/07/08 - 03/07/08
Wednesday 02/07/08
Started with 3 mins of 10s monochromatic waves at SL=3m to remove the berm. Successfully did so
Another deltares PT (#8) has packed up - not good, so Cilia is investigating buying a corer to retrieve and replace it
Charlie and Andre worked on the offshore rig, finishing tests, hanging instruments, and having another go at making a better connection inside the sontek adv for the compass to work. When finished the offshore rig was placed inside the flume, on the western wall near the depth of closure. It took most of the afternoon to do this, including final adjustments to rig design and conversations as to the best location for it.
Sediment samples
Thursday 03/07/08
· Profiler checked it could get past the offshore rig as it was placed yesterday – it could.
· EMCM issue resolved – gerd swapped the channels for offshore EMs [1,2] and [3,4] and worked fine – suggests a mistake in main logging cylinder. Velocity profile now achieved but EMs on other two (landwards) swash rigs not working. Will have to reconsider this approach for the later overwash experiments. Note now that corresponding channels for the PTs will now be different. The channels in the data files for the UoP swash rigs are now as follows:
6-7 - +3 main rig
8-9 - +6 main rig
10-11 – auxillary rig 1 (presently not working)
12-13 - auxillary rig 2 (presently not working)
14-15 - +10 main rig
16-17 - +14 main rig
18-21 – for EMs not present
22-onwards = PTs
· PTs and Ems corrected so at same height (for some reason they had been at different heights)
· Series B3 – 0.8m, 6s, 2.5 sea, 2.5 lagoon, [5,5,5,5,10,10,15,15,20,5 mono, reset]. Response was again berm building and beachface steepening
· Offshore rig also logged – vectrino (Southampton) data seemed to be fine, so happy that that is functioning correctly. Logged at 200Hz continuously, Charlie started and stopped each run to coincide with measurement runs. Tomorrow the SRP and ADV will be downloaded and checked
· Offshore rig taken out and placed on the barrier crest. The instruments will be downloaded and reprogrammed for another installation on Monday. The data will be checked to test for any faults etc. It is believed the chosen rig position is desirable.
· Sediment samples
· Lawrence carried out a porosity test on the beach gravel
· Barrier profile reset as yesterday (3 mins of 10s monochromatic waves at SL=3m) – not the desired effect achieved. Instead, crest accretion occurred, breakpoint scour and very little berm erosion. It is thought this is because the previous run had caused some accretion offshore, therefore the area of wave breaking was shallower and waves broke further out. Waves were thus not able to breach the berm, and backwashes were weaker. The result is that the boundary condition for tomorrows run is different from todays, which is not ideal. Preceding tomorrows run therefore we will run an hour of today’s waves (0.8, 6s, lagoon 2.5, sea 2.5m) in order to achieve a better equilibrium with the test run.
· An attempt was made to core a hole in the barrier to replace a broken deltares PT (#12). However, the corer supplied has a head which was unsuitable for the job so another corer head will have to be found.
· Matlab was reinstalled on SRP laptop so an attempt will be made tomorrow to log the video with that as before
The likely sequence of subsequent tests is as follows:
name Sea level (m) Lagoon level (m) Hs (m) Tp (s)
C6 2.5 3.5 0.8 6
C5 2.5 1 0.8 6
B2 2.5 2.5 0.8 3
C4 2.5 1 0.8 3
C3 2.5 3.5 0.8 3
A3 tide 2.5 No waves No waves
Note that A3 needs to go ahead before series D (with tide) takes place. A3 also requires the availability of pump specialists. The hope is that the offshore rig will be placed in the flume on Monday for a week of logging series.
Started with 3 mins of 10s monochromatic waves at SL=3m to remove the berm. Successfully did so
Another deltares PT (#8) has packed up - not good, so Cilia is investigating buying a corer to retrieve and replace it
Charlie and Andre worked on the offshore rig, finishing tests, hanging instruments, and having another go at making a better connection inside the sontek adv for the compass to work. When finished the offshore rig was placed inside the flume, on the western wall near the depth of closure. It took most of the afternoon to do this, including final adjustments to rig design and conversations as to the best location for it.
Sediment samples
Thursday 03/07/08
· Profiler checked it could get past the offshore rig as it was placed yesterday – it could.
· EMCM issue resolved – gerd swapped the channels for offshore EMs [1,2] and [3,4] and worked fine – suggests a mistake in main logging cylinder. Velocity profile now achieved but EMs on other two (landwards) swash rigs not working. Will have to reconsider this approach for the later overwash experiments. Note now that corresponding channels for the PTs will now be different. The channels in the data files for the UoP swash rigs are now as follows:
6-7 - +3 main rig
8-9 - +6 main rig
10-11 – auxillary rig 1 (presently not working)
12-13 - auxillary rig 2 (presently not working)
14-15 - +10 main rig
16-17 - +14 main rig
18-21 – for EMs not present
22-onwards = PTs
· PTs and Ems corrected so at same height (for some reason they had been at different heights)
· Series B3 – 0.8m, 6s, 2.5 sea, 2.5 lagoon, [5,5,5,5,10,10,15,15,20,5 mono, reset]. Response was again berm building and beachface steepening
· Offshore rig also logged – vectrino (Southampton) data seemed to be fine, so happy that that is functioning correctly. Logged at 200Hz continuously, Charlie started and stopped each run to coincide with measurement runs. Tomorrow the SRP and ADV will be downloaded and checked
· Offshore rig taken out and placed on the barrier crest. The instruments will be downloaded and reprogrammed for another installation on Monday. The data will be checked to test for any faults etc. It is believed the chosen rig position is desirable.
· Sediment samples
· Lawrence carried out a porosity test on the beach gravel
· Barrier profile reset as yesterday (3 mins of 10s monochromatic waves at SL=3m) – not the desired effect achieved. Instead, crest accretion occurred, breakpoint scour and very little berm erosion. It is thought this is because the previous run had caused some accretion offshore, therefore the area of wave breaking was shallower and waves broke further out. Waves were thus not able to breach the berm, and backwashes were weaker. The result is that the boundary condition for tomorrows run is different from todays, which is not ideal. Preceding tomorrows run therefore we will run an hour of today’s waves (0.8, 6s, lagoon 2.5, sea 2.5m) in order to achieve a better equilibrium with the test run.
· An attempt was made to core a hole in the barrier to replace a broken deltares PT (#12). However, the corer supplied has a head which was unsuitable for the job so another corer head will have to be found.
· Matlab was reinstalled on SRP laptop so an attempt will be made tomorrow to log the video with that as before
The likely sequence of subsequent tests is as follows:
name Sea level (m) Lagoon level (m) Hs (m) Tp (s)
C6 2.5 3.5 0.8 6
C5 2.5 1 0.8 6
B2 2.5 2.5 0.8 3
C4 2.5 1 0.8 3
C3 2.5 3.5 0.8 3
A3 tide 2.5 No waves No waves
Note that A3 needs to go ahead before series D (with tide) takes place. A3 also requires the availability of pump specialists. The hope is that the offshore rig will be placed in the flume on Monday for a week of logging series.
Thursday, 3 July 2008
BARDEX gravel up close and personal
.JPG)
The gravel used in BARDEX is not beach gravel - it is slightly more angular. However, it is still narrow graded. Sediment samples are being taken before and after each run using controlled photographs of the bed such as this. Already some interesting surface grading patterns are emerging ...profile change - low lagoon vs high lagoon
After similar initial profiles, the response of the barrier to the same wave conditions and sea level, but different lagoon levels. Huge berm accretion under low lagoonal water levels. Comparitively little profile change under high lagoon levels. It might suggest that a seawards-directed hydraulic gradient has little effect on beach stability under 'normal' wave conditions, whereas a landwards-directed seepage promotes berm building. Thanks to Gerd for preparing these figures. Any comments, as always, are welcome
Wednesday, 2 July 2008
3 mins of waves can change the profile like this!
Yesterday the profile was reset to remove the huge berm which had formed after series B1, BB1, C2, and C1, ahead of today's B3 run (long waves). After just 3 minutes of Hs=.8m, Tp=10s waves and high sea and lagoon levels, the profile changed from the red line to the blue line. It was something quite special to witness!! I must admit we were all rather smug after this
Change in beach profile after the first set of waves (B1)
thanks again to Gerd for doing this figure. red line is the initial profile, and blue dashed line is the profile after the first wave run (B1). Good to see sediment continuity is preserved (after all, where else could it go!) - classic cut and fill profile as expected
Measured groundwater table profiles during series A
thanks to Gerd for doing these figures. Shows a phreatic surface we would expect under different lagoon levels. from this we have calculated a value of hydraulic conductivity for a gravel beach - possibly the very first direct measurement of this important parameter
BARDEX LOGBOOK 01/07/08
Tuesday 01/07/08
Series C1 – low lagoon (1m), MSL, Hs=0.8, Tp=4.5 (default waves, compensator on, new steering signal), beginning with an hour of default waves to reset the profile. Again the run ended with 5mins monochromatic default waves
· Gerd and Andy talked about the overwash experiments to come later in the month
· Video logging into avi was improved – dan worked out settings so no dropped frames, no compression, and reliable sample rate. In evening he wrote scripts to cut sequence into 1 minute chunks, properly time-stamped, clearing memory buffers, etc. He also finished the matlab scripts for the bardex sediment sizing, which is giving nice results
· Charlie worked out how to read the srp binary files into matlab
· Worked out that the wave statistics with and without wave reflection compensator were sufficiently different to warrant a new wave steering signal, which we will do from now on. No compensator (Friday, BB1 run 6) versus compensator (Monday, C2 run 6) shows that compensator reduces significant wave height by approx 10%
· The offshore rig was lifted on the barrier crest with the crane, and we began mounting the instruments at the end of the day. Problem with the sontek adv compass – appears to be a loose connection so Charlie and andre worked on that, however by the end of the day it was so hot they couldn’t open the casing to get to the electroinics.
· Srp - Charlie and Andre advised by Marine Electronics to check firewall and protocols, and IP on srp computer. All correct, no access. Found advice online and managed to open ftp site in windows explorer, which meant they could access and save configuration file. However, changing configuration file to ascii still results in binary files being stored. Set to sample 1 sweep per minute from 8am to 4pm on 02/07/08.
· Sontek adv – com pass not initialising. After opening and checking connections could initialise and read compass. However, not for long because next check and problem had reappeared. Deploy without – 25hz, 15min bursts, 10s buffer, from 08:00 on 02/07/08.
· Nortek vectrino working fine.
The response of the beach to series C1 was for the beach to steepen dramatically. One aim in the morning is to try to flatten the beach with a series of long waves, in order to remove the berm
Series C1 – low lagoon (1m), MSL, Hs=0.8, Tp=4.5 (default waves, compensator on, new steering signal), beginning with an hour of default waves to reset the profile. Again the run ended with 5mins monochromatic default waves
· Gerd and Andy talked about the overwash experiments to come later in the month
· Video logging into avi was improved – dan worked out settings so no dropped frames, no compression, and reliable sample rate. In evening he wrote scripts to cut sequence into 1 minute chunks, properly time-stamped, clearing memory buffers, etc. He also finished the matlab scripts for the bardex sediment sizing, which is giving nice results
· Charlie worked out how to read the srp binary files into matlab
· Worked out that the wave statistics with and without wave reflection compensator were sufficiently different to warrant a new wave steering signal, which we will do from now on. No compensator (Friday, BB1 run 6) versus compensator (Monday, C2 run 6) shows that compensator reduces significant wave height by approx 10%
· The offshore rig was lifted on the barrier crest with the crane, and we began mounting the instruments at the end of the day. Problem with the sontek adv compass – appears to be a loose connection so Charlie and andre worked on that, however by the end of the day it was so hot they couldn’t open the casing to get to the electroinics.
· Srp - Charlie and Andre advised by Marine Electronics to check firewall and protocols, and IP on srp computer. All correct, no access. Found advice online and managed to open ftp site in windows explorer, which meant they could access and save configuration file. However, changing configuration file to ascii still results in binary files being stored. Set to sample 1 sweep per minute from 8am to 4pm on 02/07/08.
· Sontek adv – com pass not initialising. After opening and checking connections could initialise and read compass. However, not for long because next check and problem had reappeared. Deploy without – 25hz, 15min bursts, 10s buffer, from 08:00 on 02/07/08.
· Nortek vectrino working fine.
The response of the beach to series C1 was for the beach to steepen dramatically. One aim in the morning is to try to flatten the beach with a series of long waves, in order to remove the berm
BARDEX LOGBOOK 30/06/08
Monday 30/06/08
Arrived at flume and the water levels were too low in flume and lagoon because of a minor fault in the pumping system. Took an hour to pump the water levels to the required level for today’s series run (high lagoon 4m max, MSL, Hs=.8m Tp=4.5s) – C2. Start-up problems:
· Scouring at the front of the barrier; therefore, lagoon level set to 3.5
· The EMCM at +10 and 14 are now set to +3 and +7, because the lower EMCM pair is not working
· Matlab does not want to initialise on the SRP laptop; Dan is trying to use other laptop. We are now logging every individual segment as an .avi. using open source capture software as an emergency measure. Not great because it drops frames with alarming regularity, it doesn’t time stamp, big files, etc. Played around with sample frequencies – settled on 25 f/s to try to counter the problem of dropped frames, but effectively couldn’t achieve 4Hz as desired. Will have to decompoile and sync with the wave trace record (until fixed). This problem was unresolved by the end of the series, but is imperative to fix this problem this evening.
· Johan pointed out a problem in our methodology of estimating the seepage through the barrier: there is leakage from the buffer to lagoon through the gate, and this leakage is unrecorded. Back-of-the envelope calculations suggest that the seepage through the gate may be up to 10% of the seepage through the barrier.
· [5,5,5,5,10,10,15,15,20 mins] plus 5mins regular waves. Profile after each run, and rig adjustments. The response of the bed was to become very steep at the landwards runup extent, then a shallow slope to the breakpoint
From the 2nd 10 minute run (run 6 or F), the wave reflection compensator (ARC) was turned on because of an estimated 15cm (30s period) standing long wave, calculated from linear wave theory. Initially there was a worry that the use of the compensator would compromise on the efficacy of the pumpos and wave steering mechanism, but by the end of series C2 it was apparent that these fears had not been realised.
· Sediment photos taken at end
· Problems downloading the data from SRPs. Charlie and Andre investigating
· Offshore rig frame lifted by crane to the top of the barrier, ready for instrumentation
Summary
Series C2 (high lagoon) did not make the beach as unstable as expected. Deltares PTs worked fine except 7 and 12 (as usual). 9 looked a bit noisy. The bottom UoP EMs still don’t appear to be working but the others are fine, and the PTs are all fine. The bed level sensors are holding up, although a couple on the crest (sensors 14 and 15) are beyond their minimum range (30cm,) so are currently not sending back useful information. Its a priority to get the video sorted out. The SRP is logging, and working, and we are able to program it. However, we cannot talk to the SRP computer to retrieve data etc in windows explorer. We can do it in DOS, so working on brushing up our DOS knowledge to extract all the files from the ftp site on the srp logger, rather than one at a time. Later, we found that the command ‘mget’ does the job nicely. Also working on either changing the default settings in the configuration file to retrieve data as ASCII rather than binary, or write matlab scripts to read the binary files in
The wave reflection is small on the monochromatic wave runs (5mins at end of program, in order for the ensemble swash statistics) from observation. Managed to get rid of the long period standing wave using the wave reflection compensator, which works really well – eliminated the standing wave completely without compromising the wave steering or pumping system. Lawrence will check the wave statistics of the 2nd 10 mins segments from the series BB1 (Friday) and C2 (today) to see how they compare. If they are very different we will have to think about getting a new wave steering signal generated which takes into account the compensator
Tomorrow we will aim to resolve problems with video and srp, and start mounting instruments on the frame. Someone needs to continually check the pumps – boring job but necessary. Johan knows the mechanics of the pumping system so any problems ask him.
Arrived at flume and the water levels were too low in flume and lagoon because of a minor fault in the pumping system. Took an hour to pump the water levels to the required level for today’s series run (high lagoon 4m max, MSL, Hs=.8m Tp=4.5s) – C2. Start-up problems:
· Scouring at the front of the barrier; therefore, lagoon level set to 3.5
· The EMCM at +10 and 14 are now set to +3 and +7, because the lower EMCM pair is not working
· Matlab does not want to initialise on the SRP laptop; Dan is trying to use other laptop. We are now logging every individual segment as an .avi. using open source capture software as an emergency measure. Not great because it drops frames with alarming regularity, it doesn’t time stamp, big files, etc. Played around with sample frequencies – settled on 25 f/s to try to counter the problem of dropped frames, but effectively couldn’t achieve 4Hz as desired. Will have to decompoile and sync with the wave trace record (until fixed). This problem was unresolved by the end of the series, but is imperative to fix this problem this evening.
· Johan pointed out a problem in our methodology of estimating the seepage through the barrier: there is leakage from the buffer to lagoon through the gate, and this leakage is unrecorded. Back-of-the envelope calculations suggest that the seepage through the gate may be up to 10% of the seepage through the barrier.
· [5,5,5,5,10,10,15,15,20 mins] plus 5mins regular waves. Profile after each run, and rig adjustments. The response of the bed was to become very steep at the landwards runup extent, then a shallow slope to the breakpoint
From the 2nd 10 minute run (run 6 or F), the wave reflection compensator (ARC) was turned on because of an estimated 15cm (30s period) standing long wave, calculated from linear wave theory. Initially there was a worry that the use of the compensator would compromise on the efficacy of the pumpos and wave steering mechanism, but by the end of series C2 it was apparent that these fears had not been realised.
· Sediment photos taken at end
· Problems downloading the data from SRPs. Charlie and Andre investigating
· Offshore rig frame lifted by crane to the top of the barrier, ready for instrumentation
Summary
Series C2 (high lagoon) did not make the beach as unstable as expected. Deltares PTs worked fine except 7 and 12 (as usual). 9 looked a bit noisy. The bottom UoP EMs still don’t appear to be working but the others are fine, and the PTs are all fine. The bed level sensors are holding up, although a couple on the crest (sensors 14 and 15) are beyond their minimum range (30cm,) so are currently not sending back useful information. Its a priority to get the video sorted out. The SRP is logging, and working, and we are able to program it. However, we cannot talk to the SRP computer to retrieve data etc in windows explorer. We can do it in DOS, so working on brushing up our DOS knowledge to extract all the files from the ftp site on the srp logger, rather than one at a time. Later, we found that the command ‘mget’ does the job nicely. Also working on either changing the default settings in the configuration file to retrieve data as ASCII rather than binary, or write matlab scripts to read the binary files in
The wave reflection is small on the monochromatic wave runs (5mins at end of program, in order for the ensemble swash statistics) from observation. Managed to get rid of the long period standing wave using the wave reflection compensator, which works really well – eliminated the standing wave completely without compromising the wave steering or pumping system. Lawrence will check the wave statistics of the 2nd 10 mins segments from the series BB1 (Friday) and C2 (today) to see how they compare. If they are very different we will have to think about getting a new wave steering signal generated which takes into account the compensator
Tomorrow we will aim to resolve problems with video and srp, and start mounting instruments on the frame. Someone needs to continually check the pumps – boring job but necessary. Johan knows the mechanics of the pumping system so any problems ask him.
Introducing ... the dutch square tree!
This square-trunked tree was found in the tiny village (sorry, city!) of Vollenhove. Thanks to Martin for spotting this little fellow, nestled in amongst his more regular brothers! Apparently the square tree is in response to a European Union directive which means that, from now on, we can fit more trees in a box
Instruments mounted onto offshore frame
after a few glitches with instruments (compass not responding in the Sontek ADV; not being able to retrieve data from the SRP logger ftp site; not being able to send the computer a mofified version of the configuration file, etc, etc), the instruments are finally being mounted onto the offshore rig. thanks Charlie and Andre for all your techy work! Another language to add to your CV - DOS (it's a dead language though, roll over Bill Gates! - probably more useful than esperanto, however) ;)
Check out my bad self
Thanks Chris for that wonderful phrase!so the latest is this - the team at the moment is me, Gerd, Shunqi (arrived last night and instantly put everyone in a good mood!), lawrence, charlie, and andre. Gerd is currently liasing with the technical staff about today's run (B2 I believe - long period 6s waves, medium sea and lagoon levels - 2.5m) . We are chopping and changing between series B and C in response to the morphology of the beach - we do not want to oversteepen too early, but more of that later in the daily notes.
Lawrence is working on calculating the throughputs through the system - there are losses of water from the lagoon into the reservoir, and also from evaporation etc, that are not recorded therefore currently not accounted for. he has also been working with gerd and myself in examing wave statistics with and without wave reflection compensators being turned on during runs.
I have been manning the instrument rigs, doing sediment samples, logging video, taking notes and checking all logging computers during runs. During runs, one person is required to ensure water levels on sea and lagoon are kept to within 1cm of how we want them, which involves constant monitoring and occasional manual adjustment using Delft's sophisticated pumping software (Its so sophisticated no-one knows how it works, really!). the automatic wave reflection compensator is doing a fantastic job
Charlie and Andre have spent the past two days ironing out some technical issues with the offshore rig instrumentation, all of which is (fingers-crossed!) currently resolved - again, see the daily notes for more information. they are currently fixing instruments to the rig, which is currently sitting on top of the beach
Andy B left yesterday, and he and Gerd had some interesting and useful discussions about the experimental programme for the overwash experiments
The previous two days we've had technical problems galore - see the diary for more details! yesterday we ran series C1 (low lagoon, MSL, default waves). Gerd has some graphs to show, and informs me he will load them up later.
A word of warning to arrivals in the next week or so - its really hot and sunny so bring hats and suncream!
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