Here at the north sea, people are trying to protect the land from the sea. This aim exists for centuries. The beach area protects to land. But, during heavy winter storms, a beach can be removed easily by wind and waves. Thus, in some areas the people set these lines of poles in the tidal area to reduce the speed of the water movement. So, some particles are able to settle near the poles and over time salty meadows grow. That’s a very sensible area, but very valuable for many birds.
In the above image, the meadow is still growing. During high tide the water circles the gras areas and builds uncountable tiniest islands. Over time, more and more grass will grow and avoid water coming here during a regular flood. Only very hight tides will be able to over flood the grass again. The bigger the meadows are and the longer the distance for the ocean is to cover, the less waves are able to fight against the dikes. That’s how protecting the land works.