Stone breakwaters at Sarbinowo beach on the Bay of Pomerania, West Pomeranian Voivodeship, Poland
Stone breakwaters at Sarbinowo on the Bay of Pomerania. Photo: CC BY-SA 4.0, via Wikimedia Commons.

The Role of Hard Structures on Sandy Coasts

Hard engineering structures on the Polish Baltic coast serve two overlapping purposes: protecting harbour entrances from wave action and sedimentation, and defending beaches and dunes that front urban areas, tourist resorts and infrastructure. The distinction matters because harbour breakwaters are designed primarily for navigational safety, but their placement inevitably alters the sediment transport regime of the adjacent coast, often causing erosion downdrift.

Poland's coast has been subject to systematic engineering since at least the 19th century, when harbour works at Świnoujście, Kołobrzeg, Darłowo and other ports were constructed or extended. The post-war period saw additional harbour development and an expansion of shore protection works driven by the growth of coastal tourism. The result is a heavily managed coastline where natural sediment circulation has been substantially altered.

Types of Structures in Use

Harbour Breakwaters

The largest structures are the harbour entrance breakwaters (falochrony portowe) at Świnoujście, Kołobrzeg, Darłowo, Ustka, Łeba, Władysławowo and Gdańsk/Gdynia/Sopot. These are typically rubble-mound structures with armour layers of natural stone or concrete units, extending several hundred metres to over a kilometre seaward. Their primary function is to create a navigable channel in the surf zone, but they interrupt longshore sediment transport completely in the littoral drift direction, causing sand to accumulate on the updrift side and starve beaches downdrift.

Groynes

Groynes (ostrogi) are structures built perpendicular or at a slight angle to the shoreline. On the Polish coast they are constructed from natural stone (typically granite transported from Scandinavia or the Sudetes) arranged in rubble form. A groyne field — a series of groynes spaced at intervals of one to three times groyne length — is the typical management response to an eroding beach frontage in front of a settlement.

The effect of a groyne field is to trap sediment moving in the longshore direction, widening the beach in the protected zone while reducing supply to the area downdrift of the last groyne. The stone breakwaters visible at Sarbinowo, shown in the photograph above, are an example of this type of structure deployed along an open beach with no harbour. Similar groyne fields appear at Mielno, Kołobrzeg (outside the harbour), Niechorze and Łeba.

Submerged Reefs and Geotextile Tubes

More recent interventions at several sites on the Polish coast have used low-crested or submerged offshore structures and geotextile elements (synthetic tubes filled with sand or gravel) placed at the dune base or on the shoreface. These are intended to reduce wave energy reaching the beach without fully blocking longshore transport.

A documented example is the Rowy site (between Ustka and Łeba), where a geotextile tube was installed at the dune base in 2014 and supplemented by artificial submerged reefs in 2016. Monitoring data published in Geosciences (MDPI, 2020) recorded the changes in beach morphology, aeolian sediment flux and dune development following these interventions. The findings showed that the reef arrangement altered wave breaking patterns and affected the delivery of sediment to the foredune.

Satellite view of Hel Peninsula (Mierzeja Helska), a narrow sand bar separating the Bay of Puck from the Baltic Sea
Hel Peninsula (Mierzeja Helska) from Landsat, 2000. The peninsula's narrow sections are particularly vulnerable to storm overwash. Image: NASA/USGS, public domain, via Wikimedia Commons.

Sediment Bypassing and Management Approaches

Because hard structures interrupt the sediment budget, their construction at one location typically requires compensatory measures elsewhere. In the Polish practice, this is addressed through beach nourishment (refulacja): dredging sand from offshore or from updrift accumulation zones and placing it on eroding beaches. Several kilometres of beach at Kołobrzeg, Ustka and Władysławowo have been nourished in this way.

Nourishment is a recurrent rather than permanent measure; placed sand disperses over time through wave action and longshore transport, and the beach reverts toward its pre-nourishment condition within years. The maintenance cycle, frequency and volume of material required are documented in project reports held by the Regional Water Management Boards (Regionalny Zarząd Gospodarki Wodnej) and by the Coastal Research Station in Lubiatowo, operated by the Institute of Hydro-Engineering of the Polish Academy of Sciences (IBW PAN).

Hel Peninsula and Structural Vulnerability

The Hel Peninsula's geometry — a narrow sand bar between 100 and 3,000 metres wide and 35 kilometres long — makes it structurally dependent on maintaining sufficient dune and beach volume. Historical records indicate the peninsula has been breached by extreme storms on several occasions over the past centuries, temporarily reverting to an island chain. The Polish coastal administration (currently the Maritime Office in Gdynia, Urząd Morski w Gdyni) treats the peninsula as a priority area for shore protection, with a series of groynes, beach nourishment operations and dune management measures in place.

Regulatory Framework

Shore protection structures in Poland fall under the jurisdiction of the three Maritime Offices (Urzędy Morskie) in Gdynia, Słupsk and Szczecin, which administer the coastal zone under the Act on Maritime Areas of the Republic of Poland (Ustawa o obszarach morskich RP). Construction of new structures requires environmental impact assessment and authorisation. Projects within Natura 2000 areas must additionally pass the Habitats Directive appropriate assessment procedure.

Main Harbour Breakwater Locations

  • Świnoujście – western end of the coast, Oder estuary port, long breakwater arms
  • Kołobrzeg – major tourist port and marina on the central coast
  • Darłowo – smaller harbour with documented downdrift erosion effects
  • Ustka – port with adjacent beach affected by groyne management
  • Łeba – small harbour adjacent to the Słowiński National Park dune system
  • Władysławowo – harbour at the base of the Hel Peninsula
  • Gdańsk / Gdynia – largest port complex, Northern Port (Nowy Port) and Gdynia main harbour

References

  • Maritime Office in Gdynia. Shore protection programme documentation. umgdy.gov.pl
  • Rotnicka, J. et al. (2020). Impact of Sea Shore Protection on Aeolian Processes. Geosciences 9(4), 179. mdpi.com
  • Musielak, S., Łabuz, T. et al. (2012). Dynamics of the Polish Baltic Coast. IBW PAN, Gdańsk.
  • Pruszak, Z., Zawadzka, E. (2008). Potential implications of sea-level rise for Poland. Journal of Coastal Research 24(2), 410–422.
  • Polish Geological Institute – Coastal geology data. pgi.gov.pl