Hi David, this layer is to prevent the fall of material water is not normal materials are unloaded sacks, iron generally is what downloading these ships in this port site.
If you have very good eyesight, you can see a long damage to the side of the ship, apparently it came into port with that damage.

Is that the normal way to prevent cargo falling in the water between ship and quay?
And she has had a fairly substantial scrape along a previous quay wall.