Geomorphologist: the natural protective barrier of the Polish coast is at risk

The front dunes are a natural protection of the coast against extreme storm waves. Due to insufficient protection against human pressure, deflation niches are created in the area of ​​the front dunes, which allow waves to penetrate inland during these phenomena - Dr. Maciej Dłużewski told PAP.

On May 20, we celebrate European Maritime Day, which was established by the Council of the European Union in 2008. Its aim is to raise citizens' awareness of the ecological and economic impact of the seas on our daily lives.

The front dune system occurs, among others, in the Łebsko Spit, stretching for about 40 km from a place located west of the town of Rowy to a place located a few kilometres east of Łeba. The front dune ridges play a key role in protecting the Polish coast from storm waves - contributing to coastal abrasion (destruction of the coast by waves).

As geomorphologist Dr. Maciej Dłużewski, professor at the University of Warsaw, told PAP, front dunes are best formed on a wide, sandy beach when the wind is blowing in the right direction - the most favourable is an active wind (with a speed above 5 m/s), blowing obliquely from the sea.

Another key element for the formation and development of front dunes is Ammophila arenaria (common sandgrass). This tall grass (up to 1 m high) growing on the dunes forces a slowdown in the near-surface air flow transporting sand from the beach to the dune, which results in its deposition (accumulation) within the dune and, consequently, an increase in its height.

However, the common sand dune is extremely sensitive to trampling, especially in winter. "A person entering a dune not only creates a problem for the dune itself, but also for the arenaria. We all know that when we trample a lawn in the city, the lawn stops growing. It is similar with the arenaria," explained the geomorphologist.

In places where there are no arenaria, deflation niches are created, i.e. concave landforms created by wind activity. The expert explained that as the niche grows, so-called storm wave gates are created, which will continue to contribute to the abrasion process, and at the same time - the disappearance of dunes.

The professor pointed to the increasing number of extreme storm events as one of the greatest threats to the Polish coast. Due to the fact that the Baltic Sea is a tidal sea, storm surges on our coast are caused by strong winds of the appropriate direction. Particularly large storm waves are created when the wind is from the north and north-east, because the length of the path within which the wave develops is the largest in this case. Then a high and long wave is created, which has a potentially large impact on the shore.

"The wind blowing from these directions for a long time causes significant abrasion of the shores, including the front dunes," the expert added. The autumn-winter period is the time of the greatest abrasion, then the storms are the strongest.

The last extreme storm occurred in January 2025. The Maritime Office in Gdynia reported that the losses within the Polish coast were very large. On the coast, front dunes, beach accesses and tree stands suffered, among others. Local flooding was also recorded. At that time, the Institute of Meteorology and Water Management issued level II and III warnings against rising waters in the northern catchments of the country.

"Unfortunately, we don't talk much about protecting dunes, mainly because we don't realize how long the process of their reclamation is in the event of destruction," said Professor Dłużewski. He noted that, for example, in Northern European countries or the United States, coastal monitoring is carried out much more often, and remedial actions after the storm period are much faster than in Poland.

The destruction of dunes will result in a greater threat to the Polish coast, especially in the era of climate change, when the number of extreme storms is significantly increasing. The geomorphologist emphasized how important it is to preserve the belt of front dunes for the protection of areas located at the back of the dunes. Due to the flooding of land in uninhabited areas, e.g. in national parks, the natural environment of the back of the dunes may change. Built-up areas located at the back of the dunes, most often designated for tourist and recreational activities, should also be protected from the impact of storm waves and, when possible, also through active protection of the front dunes, which constitute a natural barrier even for such large waves.

Science in Poland, Barbara Chmielarz (PAP)

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