Impact of the port of Wladyslawowo on the shores of the Hel Peninsula

Oddziaływanie portu we Władysławowie

The discussion about the negative impact of the port of Wladyslawowo on the shores of the Hel Peninsula has been going on for almost 90 years. In the media space, an image has even become established indicating that the existence of the port is the cause of the occurrence of severe coastal erosion in the Kuznica area (12 km east of it). Recently, there have been claims that it should be demolished. Based on an analysis of the literature on the subject [1-6], I will try to provide an objective picture of the actual impact of this investment on the shores of the Hel Peninsula.

Natural processes of seabed and coastal reconstruction

The sandy, multi-reef coastal zones of the seas and oceans are characterized by continuous natural remodeling. Many times, on a multi-year basis, fluctuations of up to several hundred meters in the position of the shoreline and accompanying changes in the depth of the bottom, the enlargement (or reduction) of the beach area and the size of the dunes are observed along the same stretch of shore.

The sequence of events that leads to natural coastal reconstruction begins in the open sea, where waves, after reaching the coastal zone, undergo refraction (turn towards the shore), and finally, mainly in the vicinity of the reefs, break. This triggers a number of processes, of which, from the point of view of shore and seabed reconstruction, the most important is the longshore current. In the simplest terms – this current can be imagined as an underwater river that moves parallel to the shore above the crowns of the revetments. Importantly, depending on the current sea level, this is done closer to or further from the beach.

In the conditions of the coastal zone of the southern Baltic Sea, during the biggest storms, these speeds can reach up to 1.5 m s-1. Sometimes this underwater river, moving close to shore, measures up to 500 meters wide. The ongoing uninterrupted process triggers mass transport of sediments, mainly sand, in the coastal zone, causing consequent remodeling of the shore and seabed.

Remodeling processes of the seabed and seashore in the vicinity of port breakwaters

Built in the coastal zone of the sea, any impermeable structures cause disruption to the natural processes of sediment transport. In the simplest terms, on the side of the structure from the direction from which sand is mainly moved (in Polish conditions this is the western direction) there is deposition of carried sediment in the shadow of the western breakwater, and thus shore accumulation (beach widening). On the other hand, on the opposite side of the breakwaters (in Polish conditions – on the eastern side of the port) there is shore erosion, and therefore a reduction in the width of the beach.

Many years of observations, carried out on the sandy shores of the seas and oceans, show that if an impervious structure is located approximately perpendicular to the shore then the longshore extent of its impact, depending on the intensity of debris transport, is a value of three to five times its offshore length. Thus, if, for example, breakwaters baffle the coastal zone for a length of 400 m, then disturbance of the seabed and shoreline reconstruction (accumulation on the western side and erosion on the eastern side) should be expected for a length of 1200 – 2000 m along the shore.

General characteristics of the Hel Peninsula

The Hel Peninsula was formed from sands from the eroded shores of the Swarzewska Kepa, which formerly reached far to the north, and from the eroded shores lying west of Rozewie. Formed in this way several thousand years ago, the Hel Peninsula now ranges in width from 0.3 – 0.4 km (in 1984 it was only 0.1 km) to a maximum of 3 km and covers an area of 32.3 square kilometers.

Nearly half of its area (45%) lies below an ordinate of +2.5 meters above sea level, meaning the peninsula is fairly flat. In the coastal zone, the intensity of average annual accidental sediment transport is directed from west to east and is about 100,000m3/year. The construction of the Hel Peninsula of sandy, loose material makes its shores particularly susceptible to continuous natural redevelopment. On the other hand, the small width and height are the cause of shoreline scouring in heavy storms and high water levels.

Erosion processes on the Hel Peninsula before the construction of the port in Wladyslawow

Based on archival data, four stages can be distinguished in the history of the peninsula.

The first is the period up to the end of the 16th century, when the Peninsula existed as a rather complex creation, about which, however, little can be said today.

Then, the period from the 16th to the end of the 18th century, when, most likely, the continuity of the peninsula was repeatedly interrupted by randomly formed isthmuses, and then naturally reconstructed, as can be read on old maps. However, it should be remembered that their reliability – in our contemporary understanding of the principles of cartography – requires in-depth critical analysis.

The third stage covers the period from the beginning of the 19th century. until the construction of the Port of Wladyslawowo, when the peninsula underwent significant transformations. The first documented shoreline fortifications in the form of bands (structures laid parallel to the shore with the purpose of preventing beach erosion) were built at this time.

In the interwar period, before the construction of the port in Wladyslawow, the peninsula was fortified in many places, including. Due to the strong blurring of the edges. A comparison of the position of the shoreline and dunes in different years shows that between 1910 and 1938 the shore receded by 23.4 meters, a process that took place at a rate of 0.84 meters/year. For this reason, bands were built in the area of Chalup, Kuźnica and Jastarnia.

The fourth, conventional period of the peninsula’s “life” is the time from the construction of the port until today.

Construction of the port in Władysławowo

After the then government of the Second Republic decided to build a port in Wladyslawowo, both in the parliament and in the press at the time, a heated discussion took place, during which critical remarks were made about the advisability of locating the new investment at the base of the Hel Peninsula. This is because it was believed that the built port would contribute to increased coastal erosion, which could even lead to a break in the continuity of the coastline. According to these opinions, sand transported by waves and currents from west to east will be stopped by the harbor breakwaters and will not reach the shores of the peninsula, leading to catastrophic erosion and, consequently, even to its detachment from the European mainland (it would become an island).

Construction of the port began in March 1936 and was completed in the fourth quarter of the following year, when the first boats arrived. The official opening ceremony took place on May 4, 1938.The built breakwaters entered the sea for about 400 meters. The course of the main isobaths was approximately parallel to the shore at the time.

Reconstruction of the seabed and seashore in the immediate vicinity of the port of Wladyslawow

In the period July 1935 – October 1936 (during construction), the processes of rebuilding the seabed and shoreline were taking place in the immediate vicinity of the breakwaters. Depth changes also occurred over the next two years after the work was completed, i.e. May 1936 to March 1938. (Figures 1, 2).

In the diagrams, it can be traced that in the two years after the breakwaters were built, there was constant shoreline reconstruction on the west side of the port. Moved by the longshore current, sand was deposited on the western breakwater, resulting in the widening of the beach.

image 19
Fig. 1. Changes in bottom depth since July 1935. By October 1936. [6]
image 20
Fig. 2. Changes in bottom depth since May 1936. through March 1938. [6]

Over the next 40 years, the process of beach widening, and therefore sand deposition on the west side of the harbor, continued (Figure 3). A comparative analysis of the position of the shoreline in 1935 and 1975 clearly shows a significant accumulation of beach on the western side.

image 21
Fig. 3. Comparison of shoreline positions in 1935 and 1975 in the vicinity of the port of Wladyslawowo [6].

Interestingly, if one compares the position of the shoreline in 1975 (Figure 4) with its position as seen in the 2022 satellite image (Figure 4), it is clear that there has been no significant displacement of the shoreline. Does this mean that the longshore current has stopped carrying sand?

image 13
Fig. 4. Photo of the current location of the shoreline in the vicinity of the Port of Wladyslawow (Source: https://sipam.gov.pl/geoportal)

The rate of retention of sand transported by longshore currents gradually decreased over time. During the first eight years after the construction of the breakwaters (from 1937 to about 1945), the bottom was rebuilt as a result of gradual shoreline growth, which caused the reefs, which in 1935. were parallel to the shore, from about 1945. have become parallel to the western breakwater. As a result, the longshore current, which flowed behind the reefs parallel to the shore at a great distance from the harbor, swung increasingly seaward as it approached, flowing parallel to the western breakwater.

As a result of the new hydrodynamic equilibrium, the breakwater is no longer an obstacle to the longshore current. As a result, the sand carried by the currents also moved along the western breakwater and was only deposited in the approach track leading to the port. This track has become a kind of natural catch basin, where sand carried along the shore is collected. From there, it’s just a relatively simple technical step of taking sand from the approach track using a dredge and depositing it on the eastern side of the port. This is the procedure that has been used for more than 40 years in Wladyslawow.

Summary

The above analysis allows us to formulate the main conclusions regarding the actual impact of the port of Wladyslawowo on the Hel Peninsula. The banks have always undergone intense erosion and accumulation processes. The construction of the port in its early days actually disrupted the natural sediment transfer paths, but in the second half of the 1940s, the port was built on the basis of the natural sediment transfer paths. There has been self-reconstruction of transport along the breakwaters. As a result, dredging began after World War II to maintain navigational depths in the approach track.

The impact of the existence of the port on the shores of the Hel Peninsula is local, becoming apparent up to a distance of approx. 2 km on the east side and 2 km on the west side of the port. The negative impact of the port on the shores has been offset by the implementation of a system for transferring material taken from the approach track and depositing it on the beaches.

The causes of erosion in the Kuznica area are not related to the existence of the port in Wladyslawowo. Maintaining the shores of the Hel Peninsula now requires, and will continue to require in the future, permanent protection work, regardless of whether the port of Wladyslawow would be decommissioned or left in its current form.

FAQ

Is the port of Wladyslawow causing the redevelopment of the seabed and seashore in its close vicinity?

Yes. The breakwaters of the port of Wladyslawow, which extend into the sea for a distance of about 400 m, cause changes along the seashore for a distance of about 2 km east and 2 km west of the port.

Almost 90 years after the port opened, has the debris flow from before construction work began been restored?

Yes, with technical human participation (silting of the beaches on the eastern side with sand from the approach track), the debris flow has been restored.

Is the port of Wladyslawowo causing shore erosion on the Hel Peninsula a few kilometers east of the port, such as in Kuznica?

Don’t. The port of Wladyslawowo does not cause shore erosion in the Kuznica area.

Dr. Ing. Piotr Szmytkiewicz is deputy director of the Institute of Hydraulic Engineering of the Polish Academy of Sciences, an assistant professor and university lecturer at the Faculty of Oceanography and Geography of the University of Gdansk, and a specialist in water engineering. coastal protection. He is the author of dozens of scientific publications on oceanography and coastal mechanics and engineering. Manager and/or contractor of some fifty marine construction expertise. ORCID.


In the article, I used, among other things. From the works:

[1] Basinski T., Sawicki A., Szmytkiewicz M., 1993. Hel Peninsula – maintain, enlarge or surrender to nature? Marine Engineering and Geotechnics, 6/1993.

[2] Cerkowniak G., Ostrowski R., Szmytkiewicz P., 2014. Climate change related increase of storminess near Hel Peninsula, Gulf of Gdańsk, Poland. Journal of Water and Climate Change, Vol. 6, No. 2.

[3] Kaczmarek L. M., Ostrowski R., Skaja M., Szmytkiewicz M., 1998. Mathematical modeling of sea shore changes at the base of the Hel Peninsula with consideration of artificial recharge. Marine Engineering and Geotechnics, Vol. 19, 1.

[4] Kowalska B., Lendzion J., Miętus M., Ostrowski R., Stanisławczyk I., Szmytkiewicz P., Sztobryn M., Zawadzka-Kahlau E., 2015. Flood and erosion management on a dynamic spit, the Hel Peninsula, Poland.

[5] Różyński G., Lin J.-G., 2021. Can climate change and geological past produce enhanced erosion? A case study of the Hel Peninsula, Baltic Sea, Poland, 115, DOI: 10.1016/j.apor.2021.102852

[6] Szmytkiewicz M., 2003 Assessment of the impact of the port of Wladyslawowo on the shores of the Hel Peninsula. Marine Engineering and Geotechnics, Vol. 24, No. 5,

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