3D post-overwash fieldwork

Conversely to the previous fieldwork, on January 30 overwash maximum intrusion on the barrier top was very easy to follow.

Overwash maximum intrusion visible by colour contrast.

Overwash maximum intrusion visible by colour contrast and shell debris.

At the end of this fieldwork we computed the distance that we make holding the GPS antenna and discovered that in a 2 km coastal stretch we walk 14 km!!!!

We had to wait until February 4th to do the bathymetric survey. Our experienced skipper advised us to postpone the survey because of the waves.

This set of data is very good as there is a high confidence on the overwash intrusion and also there is a good match between the lowest points on the topographic survey and the highest points on the bathymetric survey.

Fieldwork without clear overwash evidences

On January 19th, there was a red alert for waves on the Portuguese coast. In the Algarve, Hs reached 4.5 m with maximum wave height exceeding 8 m. We went to Albufeira groin to undertake a fieldwork campaign within another national project (SPACE). An electromagnetic current meter and 5 pressure transducers were deployed, and cool videos were recorded during the overtopping of the coastal structure.
On January 21st, we made a post-storm survey on Barreta Island, expecting serious overwash all over the island.

Top of the barrier, looking westwards.

 However, we found almost no evidences of overwash. What we did find was significant aeolian rework of the barrier surface.

Aeolian ripples on the bare sand surface.

Now the questions are: Did overwash occur? Did sand transport by wind cover overwash evidences afterwards? We think it is difficult to assume that this area was not overwashed under such energetic waves, but we have no way to prove it. The lesson is to try our best to do fieldwork within the next 24 hours after overwash is supposed to occur.

Meanwhile there was a fishing contest in Barreta Island.