Phase 2 of DynaRev

DR0 waves are running today, and on the whole it went smoothly! After lunch the vectrinos decided to bury themselves in the sediment, time to jump in again... However, after 4 weeks of wading into this freezing cold murky river water, Jen came down and said he had some waders. Where were these at the beginning?! Sorry Daniel and Gerd for sacrificing yourselves to the water, we had waders the whole time...Oh well, better late then never, thank you Jen! I definitely rocked the outfit.

We are still ahead of schedule, completing 4 hours of waves (fig.2) so we can relax over the weekend... We will continue DR0 on Monday.  

Figure 1 - Me getting ready to do some DIY on rig 1.

Figure 2- Original cross-shore profile including profile DR0-7, the last run of today (4 hours). The sandbar is already taking shape and the beachface has begun to erode.

Figure 3 - Schematic diagram of the DynaRev experiment, including rig 1 and 2, 3D scanner, LiDARS, ADVs, an original beach profile and a profile from SBO-14, to get a visual of where the instruments are in respect to the sandbar. 

Re-shaping

So the last two days we've had 'off', and when I say off we actually had to move a tonne of sediment! But it was nice to do something different. So we have re-shaped the beach back to how it was originally (or as close as we could get to it), and we shall be running wave SB0 again (but this time it's called DR0, Dynamic Revetment). Once this has been completed and we're happy that the beach is stable the revetment, finally, can be installed! All the tests we completed in the first half of the experiment will be done again, but obviously with the revetment in place this time, and this is so we can compare the two beaches (one with the revetment, one without).

And just like magic...(or 13 hours of manual labour) the beach is flat as a pancake, instruments have been re-measured and tightened, ready for waves in the morning! 

After the storm

Sandy Beach Accretion waves (SBA1). (SRP) This morning on rig 1, as it had ended up being down, I jumped in the flume once again. The water temperature is not getting any warmer, no surprise, it is refreshing when I come out! SRP fixed, time to carry on with wave run SBA1, and just in time for lunch!

Looks like all this data collection is taking its toll on someone! 

Figure 1,2,3 (SB1, SBE1, SBE2 and SBA1), you can see the beach profile changing over time. As expected, the erosive waves (SBE) significantly erode the beach face. The sandbar builds up and SBE waves. SBA waves cause it to be erode but ripples form in its place.

This is one of the most important aspects of the experiment. Fingers crossed all goes to plan!

Figure 1 -Cross-shore profile of the beachface. Includes the first full profile of the experiment (blue). Up to a meter of sand has eroded over the course of the experiment. 

Figure 2 - Cross-shore profile of the sandbar. Sandbar is migrating offshore and accreting waves are causing the bar to erode and form ripples.

Figure 3 - Overall cross-shore profile. You can see an inner trough forming at ~254 m as a result of accreting waves.

Storm a-brewin'

Wave runs SBE1 and SBE2 (Sandy Beach Erosion) commenced today. The wave height (originally 0.8 m) increased to 1.0, then to 1.2 m, with an increasing wave period (originally 6.0 s) of 7.0 to 8.0 s. Very exciting stuff! In the video below, a very large wave breaks at around 38 seconds in. 

Everything was going smoothly, the waves were getting higher and we were running ahead of schedule. However, obviously, this would not last long as we managed to over heat the wave paddle and break it. I guess we will not be getting those 1.3 m waves ...

Nonetheless the wave paddle trooped on with 1.2 m waves and the profiles were as expected. Erosion occurred after each run on the beach face (fig. 2) , and the sand bar is migrating seawards (fig.3).  Now that the waves are bigger, water depth has decreased at the sand bar, therefore when the waves break, this energy from the undertow forces sediment back (seawards), hence why we can see the bar gradually retreating. 

The OBS's on rig 2 have also gone a bit crazy, and the data produced looked as if something was blocking the sensors. Reluctantly I jumped into the FREEZING water and i couldn't find anything wrapped around it. However, there were quite a few pebbles on the seabed, meaning they could be being suspended up by the current  or the instruments are being bombarded by pebbles. Either way, hopefully tomorrow we shall get some nice data completing tests Sandy Beach Accretion (SBA1), and we'll try not to break the wave machine!

Figure 1 - Full cross-shore profile.

Figure 2 - Cross-shore profile of the beach face, eroding with every run. (BE11 to 13 = SBE 1) (BE14 to 18 = SBE2).

Figure 3 - Cross-shore profile of the sand bar, showing the front of the bar is eroding and the back of the bar is accreting, migrating seaward

Wave run SB4

Test SB4 1 to 11 is now complete, and it shows some interesting results; the beach face is eroding, apart from the final 3 hour run where SB4-11 shows accretion (fig.1). However, as expected the sand bar is slowly migrating landwards, with a significant difference again in SB4-11 (purple). On the whole though the bar doesn't seem to be moving much! 

Apart from this all the instruments are running smoothly, we're having slight issues with the vectrinos being buried in the sediment, so every now and again one of us jumps into the murky waters in the flume and adjusts the rigs. 

There's also been some casualties, myself and Emily managed to both break our glasses! Luckily mine were fixable, however Emily's were not... May they rest in peace. 

Figure 1 - Run SB4 1 to 11, a zoomed figure of the beach face.

Figure 2 -  Run SB4 1 to 11, a zoomed figure of the sand bar.

Figure 3 -  Run SB4 1 to 11, a full profile.

It's time to jump in the flume!

It was a scorching 35 degrees in the flume today, and so I couldn't resist but to go for a swim... It was quite refreshing despite the look on my face, although I did have to do some maintenance on rig 1. We raised the rig up 8 cm on the leg as the vectrino and EMCM was buried in the sediment. This is due to the foot of the leg creating a huge scour hole, resulting in the whole rig to drop. We are trying to think of a more effective solution, however until then we will just have to go swimming and adjust the height. 

Today's activities included raising the sea level once more another 10 cm, making the sea level 4.9 m. The profiles have shown a significant difference between the first run (SB4_1) and the last run (SB4_4), with the bar edging landwards by ~90 cm. As well as this figure 1 appears to be indicating that the mega ripples are migrating back, seawards.

Again the beach face continues to erode (fig.2), more so after SB4_2 (40 mins), and the berm is gradually being built up. 

Sea level = 4.9 m

Wave height = 0.8 m

Wave period = 6.0 s

Figure 1 - Cross-shore profile of test SB4_1 to 4 (4 hours), showing the elevation of the outer sand bar and mega ripples.

Figure 2 - Cross-shore profile of test SB4_1 to 4, showing the elevation of the beach face and berm.

Figure 3 - Cross-shore profile of test SB4_1 to 4 of the elevation of sediment across the whole beach.

Sea level is rising

Flume re-filled, this time with an increase of 0.1 m, making the sea level now 4.8 m. The sand bar carries on migrating seawards, until the last run (SB3_6, in green), the bar starts to migrate landwards. Erosion occurring on the beach face is larger between the first 3 runs, but this decreases once the 60 minute wave sets run and the beach becomes stable.

Sea level = 4.8 m
Wave height = 0.8 m
Wave period = 6.0 s

Beach profile showing the elevation of sediment of test SB3 (sandy beach 3).

A zoomed in version of the sand bar and mega ripples (SB3).

A zoomed in version of the beachface and berm (SB3).