Artificial Nourishment Schemes along the Polish Coast and Lagoon Shores between 1980 and 2020, with a Particular Focus on the Hel Peninsula

Abstract

This article reviews the literature covering the period from 1965 to 2020 dedicated to the issue of artificial beach nourishment along the Polish coast, with a particular focus on the Hel Peninsula. The primary sources used in this work include 34 reports from unpublished case studies and projects implemented by the Department of Maritime Hydrotechnics, Maritime Institute in Gdańsk, between 1971 and 2020. This paper also presents detailed information about the total fill volume in cubic meters of dredged material deposited along the Polish coast and lagoon shores in 1980–2020. During these 40 years, approximately 40.5 million m³ of sediment was deposited along the Polish coast and lagoon shores. Particular consideration was given to beach fills along the Hel Peninsula, which was at actual risk of breaking in its basal and central sections after intense storms at the turn of 1988 and 1989. The survey materials collected enabled the assessment of the coastal morphodynamics of the peninsula under the Coastal Protection Program through the prism of changes in the fill volume along the coastal sections, which were replenished with material coming from submarine deposits. The peninsula’s stability was also assessed, taking into account the ongoing climate change. Moreover, this article discusses the proposed rules and terms for protecting the Polish coast by way of artificial nourishment.

1. Introduction

The Polish Baltic coast spans 510 km and is built by sands, gravels, and till, with a predominant dune coast. The area experiences its most significant development during storm surges, driven by the direct impact of wind-generated waves. Consequently, abrasion processes affecting beaches, dunes, and cliffs can be observed here, and along the majority of the Polish coastline, coastal erosion tends to prevail over processes involving marine and aeolian accumulation [1,2,3,4]. One of the methods of technical coastal protection against erosion and storm flooding is artificial beach nourishment with sand imported from the seabed [5,6,7,8,9]. In this method, sand is collected from a selected offshore or onshore source area and transported to the coastal section to be replenished. Then, the sand is placed along this coastal section to increase the width of the beach, construct or reconstruct the dune ridge, or make the shoreface shallow. This solution allows for maintaining the natural values of the coast and its recreational functions, which are of leading significance for the development of coastal communes, with the coastal zone’s resistance to erosion being substantially increased. Beach nourishment is usually applied along coasts with strong erosion tendencies. Sand deposited on such coasts will also be subject to erosion. Under the influence of hydrodynamic conditions, the artificially developed beach and dune profile gradually incorporates into the natural profile. For example, certain amounts of sediment move from the embankment created as a result of nourishment to the shoreface and accumulate in sandbanks, which are a very important barrier to waves reaching the coast.

A beach (or beach and dune) fill formed as a result of artificial nourishment matches the natural landscape and poses no obstacle to recreation. The effect of the fill is quite the opposite—it enables the formation of a wide and high beach, which, at the same time, enhances the protective functions. The changed lithodynamics in the coastal zone of the sea in the region of beach reclamation are a deliberate effect and an aim of the project, which is to reduce the coastal and foreshore abrasion in the nourished area.

Beach nourishment can be launched relatively promptly to respond to a coastal event, e.g., immediately after a beach is washed away in a storm. Technical constraints mainly refer to the amount of time needed for replenishment. They are related to storm periods and result from extreme waves and wave run-ups observed at that time. Such conditions prevent the operation of dredging equipment.

Undoubtedly, the basic disadvantages of this method include the relatively low durability of the artificial fill and the need to provide sediment of appropriate grain size. Artificial beach nourishment may result in negative environmental effects, at first appearing mainly in the area of sediment collection from the seabed, such as temporary water turbidity [10], seabed height differences causing accumulation of pollutants, and noise which scares birds, fish, and mammals away. This may be followed by covering up the habitats of nearshore flora and fauna in the replenished area, and sediment may be transported inland if its grain size is too small. Changes in the nearshore morphology may lead to the establishment of transverse underwater barriers, disruptions to the bedload movement and changes in wave motion and current distribution. Similarly to other protection measures, diverse disruptions or effects on the marine environment and biocoenoses can be identified. However, in the case of artificial nourishment, they are space- and time-limited only. Habitats which become covered up usually revive naturally after some time [11]. Despite its drawbacks, coastal protection with artificial beach nourishment is beneficial primarily because it is the only method which imitates natural ecosystems and imposes the least harm to the natural environment [12,13]. These features are going to increasingly determine the value and opportunities to rapidly apply individual methods of coastal protection.

The protective actions being taken are a reaction to the process of coastal erosion, which has intensified since the late 19th century. The Polish coastline is exposed to various threats stemming from escalating climate change and accelerated sea level rise. The balance of coastal changes has shown that the average rate of shoreline erosion between 1875 and 1979 was −0.1 m/year, with land losses estimated at −36.6 thousand m²/year. From 1960 to 1983, this process further accelerated, with the shoreline moving at an average speed of −0.5 m/year, and in 1971–1983 at −0.9 m/year. Over the previous century, erosion processes affected 61% of the coastline, increasing to 72% over twenty years, and 74% over thirty years [14].

One of the significant factors accelerating erosion processes is the observed rise in sea levels, increased frequency of storm surges, and, locally, the influence of anthropogenic factors [9]. High water levels caused by storms can threaten inhabited areas, human life, valuable material assets, and cultural heritage. The rise in the Baltic Sea level by 0.2 m/100 years has determined an increase in the erosion rate over a century and necessitated an extension of protective measures. According to the Special IPCC Report on the Ocean and Cryosphere in a Changing Climate [15], the average sea level rose at a rate of approximately 3.6 mm/year from 2006 to 2015. The latest data indicate that over the last decade, the rate of sea level rise has increased to 4.8 mm/year [16]. The IPCC report [15] forecasts that the sea level rise in the last two decades of the 21st century will likely be 29–59 cm for RCP2.6 (meeting the commitments of the Paris Agreement—temperature rise of 1.5 °C) and 61–100 cm for RCP8.5 (continuing emissions practically unchanged). The expected rate of sea level rise will accelerate depending on greenhouse gas emission scenarios. The IPCC authors predict that the average global sea level rise rate will reach 15 mm/year by 2100 and exceed several centimetres annually in the 22nd century.

According to the experts from the Polish Academy of Sciences, the observed long-term trend in sea level rise in the Baltic Sea is similar to the global trend, as confirmed by satellite measurements. Forecasts for the Polish coast do not significantly deviate from global predictions. However, regarding the sea level rise relative to the local seabed, the influence of vertical movements of the Earth’s crust must be considered. Preliminary results indicate a lack of vertical movements on the western edges and in the central part of the Polish coast, with a decrease of about 1 mm/year in the Gdańsk Bay area and even 2 mm/year in the Żuławy region. This could accelerate the relative sea level rise by another 10–20 cm per century, increasing the threats associated with sea level rise to include more extensive areas, including important locations such as Gdańsk, Żuławy, or the Hel Peninsula [17]. The scenarios for sea level changes along the Polish coast, developed as part of the Climate Project [18] which is based on the changes in the regional atmospheric pressure field simulated by the ECHAM5 model, and taking into account global sea level changes, have shown that the average annual sea level for 2011–2030 at all stations along the Polish coast will rise by about 5 cm compared to the reference period of 1971–1990. This increase depends on the assumptions of the developmental pathways.

The scenarios developed for 2081–2100 indicate a significant increase in the average sea level compared to the average values for the reference period of 1971–1990. The scale of changes depends on the emission scenario. The smallest increase is associated with the B1 emission scenario (high dynamics of economic growth with the dominance of services and information technologies) and will be about 20 cm. For the A2 emission scenario (a polarised world with significant population growth, slow economic development, and slow technological change), the predicted increase in the average sea level reaches about 28 cm [18]. Changes in sea level in the second half of the 20th century, as published under the Climate Project, are significant—by the end of the 20th century, the average sea level rose by about 10 cm in Ustka, 8 cm in Łeba, and 14 cm in the North Port of Gdańsk. It increased at a rate of about 2 cm per decade [18].

Although the significance of climate-induced sea level rise is expected to increase over time, additional significant factors such as storm surges, which pose a threat to both dune and cliff coastlines, should be considered when forecasting and assessing the impact of sea level on the coastal zone.

Wind action on the sea surface and changes in atmospheric pressure cause sea level fluctuations along our coast of up to several tens of centimetres within a few hours or days. These are accompanied by seiches, which can change the water level by several tens of centimetres, and tides, which for most areas of the Baltic Sea do not exceed 2–5 cm. Storm surges are the greatest threat to the coastal zone, during which the relative sea level can temporarily rise by several tens of centimetres, and in extreme cases, even by 2 metres [19]. For example, from 1947 to 2007, 252 storm surges (+70 cm above average levels, i.e., 500 cm) were recorded on the Polish coast, with 70 of them being surges above 600 cm. The highest number of high surges (≥600 cm N.N.) occurred in Kołobrzeg—53 surges, and the lowest in Władysławowo—27. They occurred 40 times in Gdańsk. The number and strength of storm surges noticeably increased from two to six annually in the mentioned period. The highest numbers of storm surges are observed on the western coast (ibid). Also, in 1960–2010, the distribution of the annual number of storm surges at water gauge stations along the Polish coast showed an increasing trend (e.g., Gdańsk from 1.3 to 3.0 annually on average; Kołobrzeg from 1.9 to 3.3; Władysławowo from 1.8 to 2.8) [20]. Within 30 years, storm surges are likely to become more frequent in Central Europe and the Baltic region than in the past [17].

As a result of these events, in areas where the built-up and urbanised coastal zone is threatened by the effects of sea level rise, a need emerges to protect the health, life, and property of people, as well as infrastructural objects of social or economic nature, through the protection of coastal and adjacent land areas, including the method of artificial nourishment, which is the subject of this article.

Coastal protection schemes using the artificial nourishment method have been applied worldwide since the 1930s [21]. The first interventions covered the USA coast, where over 60 beach fill projects were implemented until 1952 [6]. After 1960, artificial beach nourishment began to be used on a larger scale in the United States [22,23,24] and other countries as well, including the following: Germany, The Netherlands, Great Britain, France, Portugal [12,21,25,26], Australia [27], China [28,29], and Brazil [30]. Most beach fill projects were implemented to protect the coast against erosion and to ensure flood safety by way of filling the sediment deficit along the protected shore sections and channel walls [12]. Some of the projects were not associated with protection needs but were aimed at improving the recreational conditions by increasing the width of the existing beaches (France, Brazil) or acquiring new areas for investment purposes (The Netherlands). The results achieved were not always satisfactory. This was the case when only the underwater zone was nourished. Now, after decades of gaining experience, the efficiency of the artificial nourishment method has increased significantly. The concept and development of beach nourishment have been thoroughly investigated [12,31]. Additionally, post-nourishment evaluation, as a crucial element of beach nourishment projects, has received considerable focus, typically encompassing three main aspects: the physical [32], ecological [13], and economic impacts [12,33]. Considering the above, peer-reviewed research was found to be scarce in a literature review regarding the artificial beach nourishment implemented along the Polish Baltic coast. This paper, therefore, attempts to fill this research gap by presenting the trends observed in this process in Poland and the experience gained in this field over the last 40 years. The results are mainly based on a specialised literature review, which includes case studies and reports from selected projects implemented by the Department of Maritime Hydrotechnics, Maritime Institute in Gdańsk in 1971–2020. The distinctiveness of the provided materials stems from their exclusive publication in Polish through the Internal Publications of the Maritime Institute in Gdańsk. Until now, these materials have been mostly accessible in printed form at the institute’s library. Taking the above into account, the results presented in this paper make an important contribution to the knowledge of artificial beach nourishment along the southern Baltic Sea coast. Furthermore, this study places significant emphasis on the artificial nourishment of the Hel Peninsula shores, where this method plays a particularly crucial role in coastal protection.

2. Materials and Methods

To explore the topic of artificial beach nourishments along the Polish coast, an extensive literature review was conducted. We sought information on the following topics: (1) case studies for specific locations along the Polish coast, (2) general information about artificial beach nourishments performed in Poland, and (3) data regarding the total fill volume of the fill material used in this process. A literature review conducted in scientific databases (Scopus, Web of Science) did not yield sufficient results. By using the keyword ‘beach nourishment’, we identified studies covering this issue worldwide. However, only a few focused on the Polish coast. Conversely, the Polish shoreline has been extensively researched in terms of geology or aeolian processes [1,2,34]. To fulfil the purpose of this paper, we reviewed the specialised literature, the main source of which was the Library of the Maritime Institute in Gdansk. The findings included works performed at the Department of Maritime Hydrotechnics and the materials systematically collected at the library since the 1960s and 1970s (

Table 1. Summary of the studies of artificial beach nourishments along the Polish coast and lagoon shores. Studies carried out at the Maritime Institute in Gdańsk in 1965–2020.

No.	Study Location	Ref.	Authors and Year
1	Trzęsacz	[35]	Boniecka, H., Cylkowska, H., Gajda, A. & Gawlik, W. (2011)
2	Rewal	[36]	Boniecka, H., Cylkowska, H., Gajecka, A. & Gawlik, W. (2008)
		[35]	Boniecka, H., Cylkowska, H., Gajda, A. & Gawlik, W. (2011)
3	Łeba	[37]	Boniecka, H., Gajda, A. & Staniszewska, M. (2013)
		[38]	Mierzyński, S. Cieślak, A., Kowalski, T., Michowski, A., Semrau, I. & Skurczyński, M. (1971)
4	Mrzeżyno	[39]	Boniecka, H., Gajda, A., Gawlik, W. & Kaźmierczak, A. (2016)
5	Kołobrzeg	[40]	Jednorał, T. (1974)
		[41]	Kowalski, T., Gruszczyński, B., Grunwald, A., Semrau, I., Cieślak, A. & Niespodzińska, L. (1971)
		[42]	Skurczyński, M., Michowski, A. & Potylicki, W. (1974)
6	Koszalin Bay	[43]	Jednorał, T. (1987)
7	Władysławowo	[44]	Kowalski, T. (1977)
8	Ustka	[45]	Semrau, I., Cieślak, A., Gruszczyński, B., Kowalski, T., Michowski, A., Subotowicz, W. & Zawadzka-Kahlau, E. (1978)
9	Darłówko	[46]	Semrau, I. & Kowalski, T. (1969)
10	Dziwnów	[47]	Skurczyński, M. (1967)
11	Wicie	[48]	Boniecka, H.; Cylkowska, H.; Gajda, A.; Budnik, M. (2020)
12	Międzywodzie	[49]	Boniecka, H., Gajda A., Budnik M. (2019)
13	Hel Peninsula	[50]	Boniecka, H. (ed.). (2011)
		[51]	Cieślak, A., Boniecka, H., Michowski, A., Niemkiewicz, E., Semrau, I. & Zawadzka-Kahlau, E. (1990–1995)
		[52]	Gajewski, L. (1996)
		[53]	Michowski, A. (1979)
		[54]	Semrau, I., Kowalski, T. & Cieślak, (1974)
		[55]	Semrau, I., Kowalski, T. & Michowski, A. (1979)
14	Vistula Lagoon	[56]	Michowski, A. (1978)
		[57]	Skurczyński, M., Kowalski, T., Michowski, A. & Semrau, I. (1972)
		[58]	Słomianko, P. (1965)
15	general studies regarding the Polish coast	[59]	Cieślak, A. & Mierzyński, S. (1978)
		[60]	Dubrawski, R. (ed.). (2008)
		[61]	Dubrawski, R. & Zawadzka-Kahlau, E. (ed.). (2006)
		[62]	Michowski, A. (1980)
		[63]	Mierzyński, S. (1983)
		[64]	Mierzyński, S. (1987)
		[65]	Mierzyński, S., Cieślak, A., Gorski, J., Kowalski, T., Michowski, A. & Semrau, I. (1983)
		[66]	Prognoza oddziaływania na środowisko dla zmiany programu wieloletniego na lata 2004–2023 pn.: “Program ochrony brzegów morskich” ustanowionego ustawą z dnia 28 marca 2003 r. o ustanowieniu programu wieloletniego “Program ochrony brzegów morskich” (2015)
		[6]	Semrau, I. (1979)

). Moreover, relevant data were provided by the maritime offices in Gdynia, Słupsk, and Szczecin, which are units of maritime administration responsible, among other things, for the performance of activities related to coastal protection, including artificial nourishment of the coastal zone. Research and analyses conducted by other institutions of science, including the Polish Geological Institute and the Institute of Water Engineering of the Polish Academy of Sciences, and data from enterprises in the realm of beach filling were also utilised in this paper. These materials, next to the other existing literature, were used to discuss the progress of activities related to the implementation of artificial nourishment projects along the Polish coast (Figure 1).

The materials used in the case of the Hel Peninsula included, above all, the studies by Semrau et al. [54,55], the annual efficiency assessments for the nourishment operations performed [51] and the findings of the coastal monitoring carried out by the Maritime Office in Gdynia since 2004.

3. Results

3.1. Artificial Beach Nourishment Interventions Performed along the Polish Coast

The first case studies in Poland devoted to the issue of beach filling were conducted at the Maritime Institute in the 1960s and 1970s. They included discussions on the worldwide experience gained in this regard [5,6]. The activities conducted at the Maritime Institute at that time, and later on, were devoted to the principles of artificial nourishment design including the methods of selecting the fill material, issues of basic importance for reasonable nourishment, such as identification of hydro- and lithodynamic processes. In particular, the characteristics of the material forming the coastal zone were studied, and identification of the resources of potential sand deposits suitable for artificial nourishment and defining the rules of their exploitation [43,55,63,64,65,67,68,69] were among the chief activities.

Many works of the Maritime Institute dating back to the 1960s and 1970s suggested using artificial nourishment with sand to reinforce the eroded coastal sections, as a rule, adjoining the ports on their eastern sides. These concepts referred to, among others, Darłówko [46], Dziwnów [47], Kołobrzeg [40,41,42], Ustka [45], and Łeba [38]. Moreover, artificial nourishment of the Vistula Lagoon shores was taken into consideration [56,57,58]. Different methods of beach filling and opportunities to apply them to protect the lagoon shores were analysed.

What was proposed for replenishment of the abraded near-port shores was the maximum use of spoil from systematic dredging of the port canals, fairways, and roadsteads, which was carried out because of constant sanding up of these bodies of water [59,62,64].

In 1978, in the area of the entrance to the fishing ports in Rowy and Dźwirzyno, dredging spoil from the fairway and port canal began to be successfully transported using a pipeline to the beach on the leeward side of the port breakwaters. The nourishment systems installed at that time have been operative until the present day.

Various types of sedimentation tanks located at sea in the vicinity of sanded port approach fairways are used for temporary storage of the fill material. They are also used to intercept, at least to some extent, sediments transported by sea waves and currents, from which the bedload is periodically obtained and transported to the leeward side. This solution was applied in the region of the ports of Władysławowo, Łeba, and Darłowo [37,44,70,71].

Using dredging spoil for artificial nourishment is one of the major methods of acquiring sediment for the protection of the coastal sections adjoining the ports on their eastern sides. With sediment transport predominantly occurring in one direction along the Polish coast of the Baltic Sea [72], the port breakwaters extending into the sea run across the bedload flow, which results in the roadsteads and port fairways becoming sanded up. Blocked bedload leads to a permanent sand deficit along the sections of the coast adjoining the ports on their eastern sides. The adverse impact of breakwaters on the coast has been observed in the form of erosion of the adjoining sections with a length of approximately 3 km [73].

A good example is the breakwater in the port of Władysławowo, which was built in the 1930s and impedes the supply of sediment to the Hel Peninsula, being one of the reasons for its decay, and hindering natural restoration of the devastated spit. The first attempts at artificial nourishment of the peninsula shores were made in 1982–1987. However, the use of small amounts of fill material along short coastal sections did not bring satisfactory results. Because of the disastrous condition of the peninsula’s base after the intense 1988/1989 storms, which put the peninsula at risk of breaking in its basal and central parts, a decision was made to start a massive nourishment project, which was implemented in 1989–1995. As the results achieved in terms of protection were temporary, artificial nourishment of the Hel Peninsula’s shores has been continued until the present day.

The volume of the dredging material obtained in 1990–2008 in the roadsteads and open sea ports in Łeba, Ustka, Darłowo, and Kołobrzeg was over 6.85 million m³. Apart from other operations carried out in the coastal zone, such an amount of material dredged from roadsteads and ports significantly disturbed the nearshore sediment balance. Since the mid-1990s, substantial amounts of material coming from fairways and port canals have been deposited on the adjacent eastern sections of the coast. Thanks to this, sediment transport has been partially restored and the resistance of the coastal zone to erosive impacts from the sea has increased [61]. Unfortunately, certain amounts of the material dredged from the port approach fairways are still deposited in dumping sites at sea, in non-active zones, instead of being used for replenishment of the eroded near-port coastal sections. In the above-mentioned period, only 43% of the dredged material was used to nourish the coastal zone. The remaining part was deposited in dumping sites. The greatest amount of dredged material was used in coastal zone nourishment in 1994–1996 when as much as three times more sediment was deposited on the coast than in offshore dumping sites [74].

In 2019, as part of the modernisation of the approach fairway channel to the Northern Port in Gdańsk under the Operational Program Infrastructure and Environment for the years 2014–2020, nearly 4 million m³ of sand, extracted during the deepening of the waterway to the Gdańsk Northern Port, were deposited on the Pomeranian beaches. The beaches were widened by 40 m on average and locally by up to 100 m.

It should be highlighted that dredging spoil is not always suitable for beach nourishment because of the degree and nature of its pollution or the sediment composition (aggregate muds, clays, and very fine-grained sands), as beach filling requires the use of fill material of adequate size and quality, i.e., appropriate type and grain size. However, no clear criteria have been established so far for using dredging spoil in artificial beach nourishment [74].

Another constraint involves the location of the sand source area. In light of the experience gained in the field of seabed geological identification and the nourishment projects implemented so far, it has been established that sediment can be dredged from offshore borrow pits situated on the southern Baltic slope, if the water depth at the borrow pit location is ≥12–15 m and the distance between the borrow pit and the shore is not less than 3 km [36,75,76].

In the research on nearshore hydrodynamics and lithodynamics as subject to artificial nourishment and in the assessment of the results obtained in the field of protection, a significant role was also played by the Institute of Hydro-Engineering of the Polish Academy of Sciences. Here, attention should be paid to the studies by Basiński [77], Pawluk [78], Skaja et al. [79], Basiński and Szmytkiewicz [80], Kaczmarek et al. [81], Ostrowski and Skaja [82], and Pruszak et al. [83]. The basic synthetic information about artificial nourishment projects implemented along the Polish coast and lagoon shores until 2020 is presented in

Table 2. Artificial beach nourishments along the Polish coast and lagoon shores between 1980 and 2020. Own work based on the data collected by the Department of Maritime Hydrotechnics and provided by the maritime offices in Gdynia, Słupsk, and Szczecin and the company PRCIP sp. z o.o.

No.	Area	Artificial Nourishments until 2003			Total Artificial Nourishments (until 2020)
		Start Point of the Nourished Section	End Point of the Nourished Section	Total Fill Volume (until 2003)	Start Point of the Nourished Section	End Point of the Nourished Section	Total Fill Volume (until 2020)
		Shore Mileage [KM H]	Shore Mileage [KM H]	Thousand m3	Shore Mileage [KM H]	Shore Mileage [KM H]	Thousand m3
1	Vistula Lagoon	22.70	25.50	3955.7	22.60	25.50	4202.0
		29.43	32.75		29.43	32.75
		41.65	44.27		41.65	44.27
		60.40	67.37		58.90	59.00
		67.50	70.00		60.40	67.37
		78.70	81.30		67.50	70.00
		85.35	85.55		78.70	81.30
		87.05	87.25		84.40	87.30
2	Stegna-Sztutowo	-	-	0	n/d	n/d	516.0
3	Górki Wschodnie	n/d	n/d	-	58.4	59.0	160.5
					58.75 1	59.00
4	Gdańsk-Sopot	-	-	0	70.20	75.50	1028.8
					72.00	~74.50
5	Gdynia-South	79.40	80.85	385.2	79.40	80.85	503.2
		-	-		80.3	80.80
		83.03	83.53		83.03	83.53
		84.53	85.28		84.53	85.28
6	Puck	113.90	114.50	137.6	113.90	114.50	147.8
		116.40	116.50		114.60	114.70
		-	-		116.40	116.50
7	Hel Peninsula (Gdańsk Bay side)	48.00	48.30	228.8	44.30	46.00	244.3
		48.40	48.84		48.00	48.30
		51.70	53.00		48.40	48.84
		54.70	55.40		51.70	53.00
		59.20	59.50		54.70	55.40
		63.30	63.50		59.20	59.50
		67.10	67.20		63.30	63.50
		-	-		67.10	67.20
	Hel Peninsula (campsites)	2 campsites		10.3	8 campsites in 2004–2012		33.4
8	Hel Peninsula (seaward side)	0.00	4.60	13,165.4	0.00	4.60	19,433.8
		5.90	8.40		3.80	7.80
		8.80	13.80		5.90	8.50
		14.40	17.20		8.80	13.80
		17.90	19.40		14.40	20.50
		21.50	23.50		21.50	23.50
9	Jastrzębia Góra-Ostrowo-Karwia	-	-	0	133.50	135.50	2367.8
					134.60	135.50
					135.50	136.10
					136.10	136.80
					140.45	140.60
10	Łeba	181.60	183.00	484.3	180.50	183.54	1337.0
11	Rowy	216.97	217.47	254.8	216.97	219.00	717.4
12	Ustka	231.94	233.40	1077.9	230.95	233.4	2062.0
13	Jarosławiec	-	-	0	253.65	254.3	270.0
					255.32	255.73
14	Wicie	-	-	0	260.49	261.19	137.9
15	Darłowo	268.50	269.60	559.9	267.50	270.20	1145.8
16	Sarbinowo	-	-	0	305.60	306.30	44.5
17	Ustronie Morskie	-	-	0	319.00	319.90	251.2
18	Sianożęty	-	-	0	321.60	323.0	100.0
19	Kołobrzeg	330.40	331.67	598.2	328.90	330.28	933.6
					330.40	331.83
					333.30	334.00
					333.50	33.80
20	Dźwirzyno	345.00	345.50	228.9	344.00	344.60	481.0
					345.00	345.50
21	Mrzeżyno-Rogowo	351.40	352.26	98.0	350.50	352.26	743.0
					350.95	352.00
22	Niechorze	-	-	0	365.20	367.20	368.0
					366.00	367.00
					368.10	368.80
23	Niechorze-Rewal	-	-	0	368.55	369.70	150.0
24	Rewal-Trzęsacz	-	-	0	369.70	370.20	1138.0
					369.75	371.35
					370.20	373.50
					371.80	373.80
25	Pustkowo	-	-	0	374.00	375.00	113.0
26	Dziwnów- Dziwnówek	391.08	391.40	122.0	385.40	388.30	1211.0
					388.10	389.00
					388.30	390
					389.00	390.40
27	Międzywodzie	-	-	0	391.80	392.80	284.0
					392.50	393.05
					392.80	394.00
28	Szczecin Lagoon Nowe Warpno	n/a	n/a	255.0	n/d 2	n/a 2	255.0
29	Szczecin Lagoon Brzózki Warnołęka	n/a	n/a	150.0	n/d 2	n/a 2	150.0
Total		-	-	21,702.8	-	-	40,530.0

Notes: ¹ A total of 80 thousand m³ were deposited on the Messina Spit as part of reconstructing the fairway on Wisła Śmiała. ² There is no chainage defined for the Szczecin Lagoon.

. This compilation is divided into two parts. The first part only covers nourishments carried out until 2003, and the second part presents total nourishments until 2020. This division stems from a significant shift in the approach to coastal protection after 2003, with the enactment of the Act of 28 March 2003 on the establishment of the long-term ‘Coastal Protection Program’ (Journal of Laws, No. 67 of 18 April 2003, item 621 as amended [84]). Additionally, projects under the Operational Program Infrastructure and Environment for the years 2014–2020, Priority Axis II, Environmental Protection, including adaptation to climate change, began to be implemented. As no relevant data are available, the table fails to present the first nourishments carried out at the end of the 1970s. The artificial beach nourishment sites along the Polish coast are presented in Figure 2.

In 1980–2014, a total of approx. 32.2 million m³ of sediment was deposited along the Polish coast and lagoon shores. The nourishments covered over 80 km of the coast, of which a large number of sections required repeated interventions. Along the Gdańsk Bay shore, in the area of Stegna-Sztutowo, Górek Wschodnich, Jelitkowo, Sopot, Gdynia, Puck, and the bayward shore of the Hel Peninsula, approximately 2.6 million m³ of sand was deposited, which partially reduced the nearshore sand deficit. A large nourishment project was carried out in 2019 in the Jelitkowo and Stegna-Sztutowo areas, where material extracted during dredging works on the modernised fairway to the Northern Port was used. As part of this project, 1.06 million m³ of sediment was incorporated into the shoreline of these two sections of the bay. In the aforementioned period, along the open sea coast between Łeba and Międzywodzie, approximately 11.5 million m³ of sandy sediment was deposited, which to some extent reduced the nearshore and backshore sediment deficit, thus contributing to the reduction in the risk of erosion and storm flooding of the developed hinterland. Almost half of the total fill volume covered the seaward shores of the Hel Peninsula, where a comprehensive protection project was implemented in 1989–1995. Artificial beach nourishments have been carried out in this area until the present day. Only in 2015–2020, along the particularly eroded sections of the Hel Peninsula shore (km H 0.10–1.10; 3.8–7.8; 10.2–12.3; and 17.8–19.0), the volume of artificial nourishment exceeded 1.8 million m³ of sand. This sand originated from subsea accumulations of sandy sediments and dredging works on the approach fairways to the ports of Władysławowo and the Northern Port in Gdańsk.

Until the end of the 1980s, along the open sea coast, single artificial nourishment operations were implemented only in the region of Kołobrzeg and Ustka. However, the created embankments were small in size, and their parameters were not adjusted to the prevailing morpho- and lithodynamic conditions. They were soon washed away, leaving no permanent effects on the shore or in the shoreface. Only in the 1990s did the available technical opportunities allow for applying nourishments on a larger scale, particularly when hard protection proved to be insufficient. Artificial beach nourishment and dune restoration began to be used along abraded sections overshadowed by port breakwaters and, most often, along sections representing high use values and situated in the vicinity of holiday resorts. For this purpose, sediment from the dredging of roadsteads and port canals was used. Near-port areas in Łeba, Rowy, Ustka, Darłowo, Kołobrzeg, and Dźwirzyno were replenished repeatedly. In 1990–2003, approximately 3.2 million m³ of sand was deposited on the central coast beaches. On the western coast, at that time, beaches were nourished and dunes were restored in two protected areas, i.e., Mrzeżyno and Dziwnów, with 0.22 million m³ of sediment being deposited. Moreover, nourishments covered the eroded shores of the Szczecin Lagoon in the region of Nowe Warpno, Trzebież, Brzózki and Warnołęka, where 0.4 million m³ of sediment was deposited.

Since 2003, when the coast began to be protected under the act on the establishment of the long-term “Coastal Protection Program”, the artificial nourishment method has often been chosen to complement hydrotechnical procedures. In 2004–2020, beach nourishments were carried out mainly along the seaward shores of the Hel Peninsula and near-port sections situated on the eastern side of the breakwaters of the open sea ports of Łeba, Rowy, Ustka, Darłowo, Kołobrzeg, Dźwirzyno, Mrzeżyno, and Dziwnów.

Beach filling also covered the shores of Gdańsk Bay, where the process of erosion has accelerated over the last decades and where the shores in the area of Jastrzębia Góra, Ostrowo, Karwia, Jarosławiec, Wici, Ustronie Morskie, and Niechorze were nourished to support the existing protection systems. Moreover, a comprehensive protection project began to be implemented along the cliff section of the coast between Rewal and Trzęsacz, where the erosive activity of the sea overlaps with the cliff’s geodynamic processes, resulting both from natural and anthropogenic conditions. To reduce the risk of further erosion of the cliff’s foot and wall, artificial beach nourishment was applied, which was followed by placing riprap to protect the foot of the cliff against the impact of waves at high sea levels.

The nourishment of the Vistula Lagoon shores consisted mainly of forming levee forelands to support the protection of low areas against sea flooding. The total volume of artificial nourishment during the Coastal Protection Program operation period amounted to approximately 18.8 million m³ (Table 2), constituting over 45% of the nourishment carried out between 1980 and 2020.

Since 2004, the implementation of beach fill projects along numerous coastal sections has been preceded by the preparation of guidelines allowing for more effective nourishment and achievement of the planned protection results. These guidelines, which are based on thorough analyses of the condition of the coastal zone and assessment of tangible and intangible values of the beach hinterland, define the shape and location of the designed embankment, and the volume of sand necessary to obtain a safe coastal profile, taking into consideration the degree of mismatch between the sediment obtained from the deposits and the nearshore native sediment. The basis for assessing the condition of the coastal zone and foreshore in the area of the planned artificial nourishment consists of tachymetric–bathymetric measurements conducted for documentation purposes and the results of the coastal zone monitoring. The project documentation includes a nourishment plan (work organisation plan), cross-sections of nourished areas every 100 m, a bill of quantities—the quantity of sand in one cubic metre per one metre of the beach, and recommendations (e.g., [35,36,39]).

It should be emphasised that, according to Polish legislation, for undertakings that may potentially have a significant impact on the environment, such as artificial nourishment, it is required to obtain a decision on environmental conditions. This decision specifies the environmental conditions for the implementation of the undertaking. An application for an environmental impact decision must include an environmental information form (EIF). The EIF is for assessing potential environmental hazards, natural and landscape values, as well as the impact on human health. It determines the types of work technologies and environmental protection solutions. An important element is presenting the assessment of the impact of the implementation on the environment and Natura 2000 sites/objects of protection.

3.2. Costs of Artificial Beach Nourishment in Poland

The basis for estimating the costs of implementing artificial nourishment was an analysis of previous protective actions carried out in Polish coastal areas since 2004, i.e., since the enactment of the law establishing the long-term Coastal Protection Program. Since 2004, the provisions of the law have determined the expenditures necessary to protect the coastline from erosive sea activities, of course, in areas where the condition of the coastal zone indicated such a need. Importantly, the law ensured funding for the program from the state budget and extra-budgetary funds during its validity period. The law also specified the maximum limit of state budget expenditures for the entire implementation period of the program from 2004 to 2023, amounting to PLN 911,000. The planned expenditures for the implementation of tasks provided for by the program (artificial nourishment, coastal fortifications, artificial nourishment with supporting structures, monitoring, and research to determine the current state of the coastal zone) could not be less than PLN 34,000 in individual years. The limit on state budget expenditures specified in the law did not include funds from the EU under the Operational Program Infrastructure and Environment 2014–2020.

The cost of nourishing one cubic metre of beach sand has changed over the years. This is influenced not only by the changing economic situation on a national scale but also by the increase in fuel prices in global markets, and the rising costs of operating nourishment enterprises (employee wages, machine usage costs, fuel costs, and taxes). The final price of a cubic metre of sand is also affected by the cost of its extraction, transportation from the extraction site to the material deposition site, and the cost of the deposition itself. The increase in competition in the dredging market is also significant, especially for large-scale nourishment projects. Competition is an important element in market functioning, shaping the real behaviours of economic entities.

In the first year of the program’s implementation, the cost of depositing one cubic metre of sand on the coast ranged from PLN 10.00 in Rowy and Dźwirzyno to PLN 20.50 in Łeba, Ustka, and Kołobrzeg. On the Hel Peninsula, the cost of one cubic metre of sand was PLN 15, while in the Kuźnica-Jastarnia region, it was lower by PLN 2. In subsequent years, this cost increased due to inflation and rising operating costs of nourishment enterprises. In 2018, on the Hel Peninsula, it ranged from PLN 31.0 to 34.5 per one cubic metre, while in the open sea area—from Łeba to Kołobrzeg, it was the highest, averaging PLN 48.5 per one cubic metre of material refloated onto the beach.

Based on previous analyses, it can be concluded that the cost of sand deposition depends on the volume of nourishment per one metre of the beach. As the volume increases, the cost of refilling one cubic metre of sand on the beach decreases. In 2011, the cost of nourishing one metre of the beach was around PLN 2000–3000. This cost has increased in recent years to around PLN 3000–4500, depending on the local conditions of the designated nourishment area. Assuming that about 70 km of the coastline in coastal towns requires replenishment of sediment deficit and achieving a sufficiently wide beach for recreation every 3 to 5 years, in 2011, the estimated amount necessary for nourishment implementation ranged from PLN 140 to 210 million. Currently, it has increased to PLN 210–315 million. Of course, such amounts exceed the state budget capabilities. Therefore, artificial nourishment is not implemented all at once along the entire coastline. The decisions on implementation are based on the condition of the coastal zone of the invested sections, which remains closely related to the increase in the activity of wind–wave phenomena and changes in atmospheric circulation, shaping both the rate of sea level rise and the extent of coastal erosion.

The selection of sections for artificial nourishment is also influenced by previous implementations of coastal belts, which after their execution require reinforcement of the coastal zone with sediment within their influence range. The largest expenditures are incurred on the Hel Peninsula, where, due to strong erosive processes in its nascent and central parts, artificial nourishment is carried out annually. During the program’s implementation period from 2004 to 2012, over PLN 27 million was spent, while in 2015–2018, this cost amounted to about PLN 31 million. Bearing such large financial outlays for artificial nourishment of the peninsula’s shores is necessary due to the existence of factors weakening the effects of artificial nourishment, including constant predispositions to erosion in certain shoreline areas, sediment outflow towards the cape, and the persistence of erosive tendencies in the surf zone. This is the only method upon which its lithodynamic equilibrium and the maintenance of the coast safety standard at the Tp = 100-year level depend, as well as the safety of the Gdańsk Bay coasts, for which the peninsula forms a natural protective barrier.

3.3. Nourishment of the Hel Peninsula Shores

Artificial nourishment plays a particularly significant role in the protection of the Hel Peninsula shores (Figure 2b). The hydrodynamics and lithodynamics, including erosion and sand accumulation in the area of the Hel Peninsula, have been studied for a long time. As a result, this section of the coast is relatively well diagnosed as regards hydrodynamic impacts, morphological characteristics, and susceptibility to erosion of its fragments [4]. Thanks to the surveys, measurements, and numerical simulations that have been carried out, information has been obtained on the wave motion, currents, and sediment transport, which made it possible to identify in detail the morpholithodynamics of the Hel Peninsula shoreface [85,86,87]. The modelling of hydrodynamic conditions proved the occurrence of maximum currents with an NW wind. With a wind blowing from this direction, the longshore transport towards the east and the on–offshore transport towards the northeast are the most intense [88]. Along the section between Władysławowo and Kuźnica, there is flow diversity related to the seabed topography. The seabed forms with embankments slanting to the shore and depressions distort the longshore sediment transport, causing increased coastal erosion along the basal section to as far as Kuźnica [52,89,90]. The modelling of lithodynamic processes proved the relationships between the seabed forms of the peninsula and the seabed transformation in extreme storm conditions [90]. The changes in the location of the shoreline and the dune base in different survey periods were addressed in the publications by Furmańczyk and Musielak [91], Furmańczyk [92], Zawadzka-Kahlau [14], and Stachurska [93]. Based on the data obtained, the authors confirmed that abrasive processes prevail at the narrow base of the peninsula, erosion and accumulation interchange in the central part, and accumulation processes predominate in the eastern part. All the periods analysed by the authors indicate a similar spatial arrangement of the coastal changes on the Hel Peninsula.

As early as the 1970s, it was indicated by the Maritime Institute [54,55] that the only solution to counteract the adverse processes of erosion observed along the peninsula may be artificial nourishment of the beaches, dunes, and the shallow shoreface.

Between 1978 and 1987, many experimental nearshore seabed nourishments were carried out along the Hel Peninsula. The dredging spoil from the fairway to the port of Władysławowo, which was previously dumped at sea at large depths, was used to fill the seabed areas situated at a depth of approximately 3–5 m at a distance of 150–200 m from the shoreline. The nourished sections differed in length (between 70 and 1000 m) and were located between KM H 3.4 and KM H 13.45. The volumes of the fill material deposited differed significantly, and they were between 440 thousand m³ (1980) and 32.4 thousand m³ (1987). These experiments were aimed at verifying whether the condition of the coast in this region would improve permanently after filling the seabed depressions occurring near the shore (150–200 m from the water line) [53,79].

However, they did not bring the expected positive results. The low effectiveness of this method was the consequence of using too little sand in relation to the sediment deficit and carrying out reclamation in the most active part of the shoreface. Therefore, these works were not continued until 1989. Since that time, the beach and the shallow shoreface, as well as, potentially, the dune, have been nourished.

Because of the intensified erosion of the Hel Peninsula shores in the 1980s and the risk of its breaking, a resolution of the Economic Committee of the Council of Ministers (108/89) was adopted in 1989, under which a comprehensive protection scheme was launched for the Hel Peninsula, including large-scale artificial nourishment of the backshore and the beach with large amounts of sand. In the beginning, the two most eroded coastal sections were nourished, i.e., KM H 0.0–4.6 and 9.5–13.7, which was followed by replenishment of other sections between the base of the peninsula and Jurata (KM H 23.5) (Figure 3 and Figure 4).

In 1989–1995, approximately 8.34 million m³ of sand was deposited on the seaward shores of the Hel Peninsula—between KM H 0.0 and as far as KM H 22.8. This was the largest artificial dune coast nourishment project on the Polish coast. Along the coast with a total length of 13.8 km, beaches and dunes were restored and the assumed parameters of the so-called “Hel Peninsula standard” were achieved, which ensured the security of the dune hinterland in the event of a 100-year storm [51].

In 1989–1995, artificial nourishments were carried out to eliminate the risk of the eroded backshore breaking, as well as to stabilise the lithodynamic processes occurring in the coastal zone, enlarge the coastal (beach) terraces, and extend the sandbank zone.

The most intense fill projects were implemented near Chałupy and Kuźnica, where the highest sediment deficit and the risk of flooding in the narrow devastated dune hinterland were observed. In 1989–1995, along the basal section of the coast, i.e., KM H 0.0–4.6, 17 nourishment projects were implemented with 3.37 million m³ of sediment being deposited. In the same period, along another strongly eroded section, i.e., KM H 9.55–13.73, a total of seven nourishments were carried out with 3.13 million m³ of sediment being deposited on the dunes, the beach and the near shoreface, of which over one-third was deposited along the section KM H 10.6–13.6. The remaining amount of sand, i.e., 1.84 million m³, was deposited near Jastarnia and Jurata. Since 1995, the area subject to nourishment has been gradually extended. Until 2003, dunes and beaches along a coastal section with a total length of nearly 18 km were restored with the use of approximately 13.2 million m³ of sand in total.

Since 1995 until today, artificial nourishment has been carried out to fill in the deficiencies and establish material reserves in the shoreface, which ensures the security of the coast in the event of a storm with a probability of occurrence of once per 100 years. The most significant erosion still affects the base (km H0.0–5.5) and the central part (km H 9.5–19.5). Implementing long-term artificial nourishment projects, especially along the sections of the Hel Peninsula shore heavily damaged by offshore storms, results in the restoration of dunes and beaches, ensuring the safety of the hinterland. The results obtained in the field of coastal protection of the Hel Peninsula with artificial nourishment allow for better environmental management, securing the peninsula against climate change and planning better use of the nearshore zone.

In the beginning, the sediment used was imported from the Puck Bay seabed and the sedimentation tank in the port of Władysławowo. Subsequently, since 1995, and because of the need to consider the ecological aspects, the substantial mismatch between the fill material from the Puck Bay seabed (the necessity to increase the material volume between two- and five-fold in relation to the sediment deficit), and new technical opportunities, the material used was imported from a submarine deposit near Rozewie and a submarine deposit in the central part of the Hel Peninsula near Jastarnia. These were the first attempts at using the fill material adjusted to the native material and the wave and current conditions prevailing in the area to conduct nourishment. According to the experience gained so far, beach filling taking into consideration average storm conditions requires the use of a material with a grain diameter median of 0.25–0.5 mm. Such a material will be gradually washed away, depending on the variable hydrodynamic conditions.

In 2011, geological and bathymetric documentation was prepared on the collection of material for artificial nourishment of the prospective area “Hel Peninsula” situated in the shallow water zone of the Baltic Sea, in the vicinity of Chałupy and Kuźnica, between KM 6.5 and KM 16.0 of the Hel Peninsula shore, including the report on the environmental impact of dredging and filling works [35,94]. The surveys and in-house studies conducted resulted in the identification of accumulations of sand suitable for beach nourishment. Six deposit fields were designated with an area ranging from 0.26 to 1.33 km², irregularly distributed in different zones of the analysed region.

Currently, the sand used for beach nourishment is mainly collected from the field near Kuźnica and Jastarnia, the “Rozewie” field, and the sedimentation tank and the fairway to the port of Władysławowo. In 2019, approximately 0.28 million m³ of material, originating from the modernisation of the waterway to the Northern Port in Gdańsk under the Operational Program Infrastructure and Environment for the years 2014–2020, was deposited on the coast shore in the Kuźnica area.

In total, between 1989 and 2020, over 19.4 million m³ of sand was deposited on the seaward shores of the Hel Peninsula (Table 2, Figure 2b). The artificial nourishment projects covered beaches and dunes with a length of 22.8 km between Władysławowo (KM H 0.00) and Jurata (KM H 23.50), i.e., nearly 63% of the length of the seaward section of the Hel Peninsula.

3.4. Analysis of the Results of Artificial Nourishment along the Seaward Shores of the Hel Peninsula

The distribution of the nourishments along the Hel Peninsula depended, among other things, on the level of risk to which the facilities and areas situated in the beach hinterland were exposed. Hence, the additional concentration of nourishments near Władysławowo, Chałupy, Kuźnica, and Jastarnia.

The particularly large fill volume (over 2.8 million m³) along the first kilometre of the peninsula (KM H 0.0–1.0) results from very intense erosion along this section of the shore. The erosion processes in the basal part of the Hel Peninsula (KM H 0.0–4.20), which are related to the bedload deficit caused, among other things, by the impact of the breakwaters at the port of Władysławowo, are intense enough to prevent any permanent increase in the volume of nearshore sediment resulting from large-scale beach nourishment, which can only contribute to the maintenance of its comparative lithodynamic balance. Fixed predispositions to erosion in specific coastal areas are also connected with the occurrence of nearshore tunnel valleys running at an angle of 25–27° to the shoreline [95]. Their location influences the occurrence of areas of permanent coastal and seabed erosion (the so-called structural erosion), and, thereby, the need for the accumulation of artificial nourishments of the coastal zone in these areas.

The distribution of the fill volumes along the eroded section of the Hel Peninsula (KM H 0.0–23.5) in individual years of the period of 1989–2020 (Figure 5) is related to the implementation of the above-mentioned resolution of the Economic Committee of the Council of Ministers. Particularly, intensive nourishment interventions were carried out in 1989–1993. This was also a period of high storm activity, which contributed to the artificial beach being washed away and the artificial dune being undermined. The sediment from embankments was discharged from the shore within circulation cells of different sizes. This form of sediment transport from embankments is attributed to gravity and rip currents [96]. After 1995, the number of storm days in the southern Baltic Sea decreased significantly, which was conducive to higher persistence of the fill material. The exceptions were the years 2002–2004, when the number of storm days in the southern Baltic Sea was 10–11 [97]. In November 2004, in Władysławowo, a storm surge was recorded, with a maximum sea level rise of 644 cm, which was the absolute maximum for 1951–2014. Under such intense hydrodynamic conditions, erosion rates increased again in the morphological zones within the sections with established erosive tendencies, which entailed the need for increasing the fill volumes along these sections. In 2004–2005, the annual average fill volume was 702 thousand m³/year. In the following years, these annual values were substantially lower. The average value for 2006–2014 was not more than 400 thousand m³/year. Hence, a conclusion can be drawn that the large fill volumes in the first years of the comprehensive protection scheme for the Hel Peninsula shore resulted in effective restoration of the shore, so that the nourishments carried out in the following years could be much smaller in scale. A thesis can be proposed that the reduction in the fill volume (Figure 6) was also the consequence of the knowledge acquired during the implementation of the first nourishments, as well as the decreased number of storm days after 1995. Thanks to the experience gained during the first years of the comprehensive protection scheme for the peninsula [51], artificial nourishment has, to some extent, become optimised.

The beaches on the seaward side of the Hel Peninsula (KM H 0.0–22.80) are, in general, beaches of small and average width (20–40 m). The graph showing the changes in the beach width along the section in question, i.e., from KM H 0.0 to KM H 23.5, between 2004 and 2020 (Figure 7), which is based on the results of the large-scale coastal zone surveys carried out during the reclamation works, accurately presents the relationship between this parameter and the distribution of fill volumes along individual kilometres of the Hel Peninsula shore. As can be seen, the differences in the data as measured in 2014 and the data obtained 10 years earlier (2004) are substantial in many profiles. Simultaneously, the average beach width as of 2014 (39.6 m) only exceeds the average beach width for 2004 (37.6 m) by 2.0 m. Locally, the beach width after nourishment is more than 50 m (Figure 7, Figure 8 and Figure 9), which temporarily classifies these sections as beaches with very high resistance to the impact of hydrodynamic conditions. In 2015–2020, subsequent nourishments improved the sediment balance in locations crucial for maintaining the resilience of the peninsula shore to hydrodynamic factors (Figure 7, Figure 8 and Figure 9). In 2020, based on monitoring measurements, the average beach width was 41.5 m ± 14.04, with maximum widths in the areas of KM H 5.0 (60 m); H 22.0–22.5; H 31.0 (65 m); H 29.0 (75 m), and at the cape, where the beach width reached up to 100 m (KM H 36.0). The base of the peninsula still had narrow beaches, with a minimum at KM H 0.5 (17 m). Up to KM H 4.0, the average beach width in 2020 did not exceed 30 m.

Therefore, it can be stated that the resistance of the Hel Peninsula beach between KM H 0.0 and KM H 23.5 increased in the analysed period (2004–2020). It was improved in the 1990s and has been maintained until the present day.

The shore and shoreface of the Hel Peninsula are still characterised by a semi-stable erosion and accumulation system with a majority of erosive tendencies, which is influenced by the hydro-geomorphological conditions and morphodynamics of the region [14,82,90,98,99]. Depositing such a large amount of sediment in the coastal zone substantially decreased the sediment deficit along the peninsula and enhanced its resistance to the impact of hydrodynamic conditions. The comprehensive nourishment projects implemented along the Hel Peninsula were the subject of intensive research and analyses until 2000. This allowed for the refinement of this coastal protection method, particularly in regards to the determination of the necessary fill volume for obtaining a safe shore and backshore profile in the area to be protected, and the selection of the fill material from potential source sites with grain-size characteristics similar to the native material of the nourished section. The continuation of filling works along the eroded shore sections of the Hel Peninsula is the condition determining the maintenance of the coastal zone’s resistance to a 100-year storm. A storm with a probability of happening once in 100-years in the Baltic Sea is understood as a storm caused by wind with an average speed of 18 m/s blowing from the most unfavourable direction in relation to the shore for 5 h with the simultaneous high sea level.

The morphometric analysis method used to assess the coastal zone’s resistance and the effectiveness of the works conducted also allowed for documenting the existence of the erosion and accumulation system in the coastal zone, and assessment of the morpho- and lithodynamic changes taking place in this system, in the case of artificial nourishment [99,100,101,102].

The experience gained during the implementation of the comprehensive peninsula protection program has been used in other coastal protection projects, and, in particular, in artificial nourishment projects. What has been noticed are the advantages of this method, i.e., counteracting the basic cause of erosion, which is sediment deficit. In the event of project implementation following the developed assumptions, there are no adverse side effects which are typical of permanent reinforcements. Moreover, a social effect (increasing the width of beaches used for recreation) and an aesthetic effect (a beach and dune landscape resembling nature) were achieved.

Because of the predispositions (conditions, characteristics) and strategies of the coastal communes, which are oriented towards tourism development, the existence of wide beaches determines their further development and maintenance of the use value of their recreational facilities.

4. Discussion

Between 1980 and 2020, around 40.5 million m³ of sediment was deposited along the coast and lagoon shores of Poland. A significant portion, over fifty percent, of this sediment deposition occurred along the shores of the Hel Peninsula, which gives an average of 0.5 million m³ annually added to the coastline of 70 km. For comparison, an average of 12 million m³ is deposited annually along the coast of Denmark, which spans a length of 432 km and is recognised as one of the most heavily nourished coasts globally [12]. At present, artificial nearshore and backshore nourishment is a widely applied method of protecting coasts against erosion and storm flooding in Poland and worldwide. Similarly to other methods, it requires improvement, both due to the expected results in the field of protection and minimisation of its environmental impacts.

The nourishment of beaches along the Polish coast follows a structured set of procedures, commencing with the preparation of environmental documentation. This is followed by measurements conducted on the chosen shoreline section intended for recharging. Subsequently, a contractor is selected to execute the process under the “design and build” system. In this system, the contractor develops design documentation and then carries out artificial recharging based on this documentation. The areas where the artificial nourishment method can be optimised are the embankment shape and its parameters (width, the ordinate of the embankment crown, and inclination of the seaward slope), which need to ensure a relevant level of coastal security against storms of specific probability of occurrence. The security level depends on the tangible and intangible values located in the hinterland of the section identified for protection. The question regarding how long a designed embankment needs to be to represent the required parameter values should be answered, and whether the parameters should be represented permanently or over a specific time.

Moreover, when designing an embankment, the natural geometry of the coast in its vicinity should be taken into account. The new shoreline should level out the existing bends, cannot form sharp curves, and should gently adjoin the natural beach. Preservation of the coastal landscape character is one of the major arguments for the application of this coastal protection method. However, another question emerges regarding the size of the beach (dune) embankment, which needs to satisfy requirements in the fields of protection and naturalness at the same time. And, this is another sphere where optimisation can take place.

A factor contributing to the optimisation of the artificial nourishment method will be the development of mathematical modelling of bedload movement in the coastal zone, thanks to the possibility of analysing very numerous variants over a short time. Due to the development of IT techniques, quite significant and rapid progress can be expected in this field.

Another area to optimise artificial nourishment is the monitoring of its results. The role of monitoring as the basic database for nourishment design (also when it comes to follow-up re-nourishment) cannot be overestimated. Measurements should be taken before filling, immediately after filling, and between subsequent nourishments, with a minimum of two measurements per year (in spring and autumn). The current use of drones and other devices, as well as the development of continuous monitoring systems and online data transmission and processing (easier and cheaper measurements), allow for a better assessment of the state of the environment and, thereby, make it possible to choose nourishment parameters that make this process increasingly more effective. Monitoring should also cover the sediment source sites for artificial nourishment, which will enable an assessment of the state of a given deposit (determining the area for exploitation, the seabed morphology, and the state of sand resources). The aim should be making the morpho- and lithodynamic monitoring of the coastal zone in nourished areas obligatory for maritime offices. The importance of monitoring should be increased and the control of its performance should be enhanced. And, this should be the role of independent research units, not the executors of nourishment projects.

According to the forecasts of coastal changes resulting from the increasing sea levels and the increasing frequency of storm surges [61], and the assessment of the nearshore state based on the results of the first monitoring of the Polish coast, which was carried out in 2004–2006, maintaining resistance by 2023 in areas at risk of erosion would require the use of approximately 61 million m³ of sediment [60]. The material needs along the coastal sections with sediment deficit are defined in the artificial nourishment guidelines. These guidelines are based on the assessment of the state of the nearshore and backshore zones, the comparison of the grain-size composition of sediment coming from a deposit and native nearshore sediments, and the level of coastal security required under the regulations [103]. However, the opportunities in this regard are sometimes determined by the funds available to the maritime administration.

Another important issue is the access to sediment deposits suitable for artificial nourishment projects. Choosing a material as similar as possible to the native sediment in the area to be nourished and the distance between the extraction site and the area to be nourished are of basic importance for achieving the assumed level of effectiveness. When determining submarine deposits of sediment suitable for artificial beach nourishment, many factors should be taken into consideration, the most significant of which are environmental and biocenotic conditions, and the potential impact on Natura 2000 sites situated within the source sites, in their vicinity, and in the spoil deposition area. In conditions where coastal areas are most vulnerable to the effects of climate change, a challenge in implementing this method of coastal protection may lie in insufficient recognition of sediment accumulations on the seabed suitable for artificial nourishment of the shores. Moreover, attention should be paid to the issue of reinforcing the effects of artificial nourishment by way of associating this method with various protective structures. According to the numerical simulations carried out for the geometrical arrangement of groynes along the Hel Peninsula and the typical nearshore bathymetry of the peninsula, the time when the material deposited near the shore in between the groynes stays in place is 30% longer in comparison with the non-built-up shore [83]. The length of groynes is of particular importance for an artificially nourished coast, in which case groynes should extend to the first sandbank, which is conducive to the restoration of the natural sandbank profile and enhances coastal stabilisation [83]. Such simulations should be supported with field research, which would allow for defining the actual impact of groynes and other protective structures on the fill material deposited on the coast.

Because of the recreational needs and requirements (wide beaches and no disruptions to beach leisure in summer), as well as hydrodynamic conditions (wave motion, storm surges), nourishments should be carried out primarily in spring, and preferably, between the first half of April and the first half of June. An embankment created in this period is more likely to stabilise and it will favour recreation. Furthermore, the existing ecological requirements should be kept in mind, including the increased requirements for the chemical and biological purity of the fill material, and the constraints resulting from the need to preserve the natural habitats and species in a non-deteriorated condition as part of national nature conservation forms, including Natura 2000 sites.

Over the last twenty years, and, in particular, since Poland joined the EU, the importance of activities aimed at preserving or restoring the values of the natural environment has increased. And, there has been an increased need to preserve nature. Therefore, a critical attitude has also emerged towards artificial nourishment, its effects, and the methods for its implementation. It should be remembered that the establishment of coastal protection systems, including the application of artificial nourishment, reduces the progress of erosion and contributes to improved quality of the coastal environment and the development of beach ecosystems. The Helcom list of marine biotopes distinguishes, among others, sandy beaches (biotope code: 3.2.1). Beaches are an element of the coastal zone, which plays a very important role, both in terms of protection and cleaning of the marine environment. Their restoration and preservation by way of artificial nourishment contribute to the reduction in the negative response of the coastal system to technical coastal protection and, in the situation of climate change, constitute the basic form of their protection.

Innovative coastal protection solutions include massive beach nourishments, i.e., the artificial creation of extensive sand motors in the coastal zone, which, as a result of free and natural movement of the fill material, replenish the coast over a significantly larger section than the one where the material was originally deposited [104]. In a tideless sea, where the direction of the longshore currents is variable and depends on meteorological forcing, the effectiveness of mega-nourishment would be lower than that achieved in a tidal sea.

Coastal protection structures, both hard and soft ones, should improve the conditions for the protection of natural values by way of reducing the susceptibility of the coastal zone to extreme climate phenomena, including marine flooding in particular. Compliance with the rules of the Integrated Coastal Management will have a positive influence on sustainable management in the coastal zone, preventing its devastation and having a positive impact on natural habitats and human activity (both social and economic). With spatial planning taking into account the boundaries of safe investments, the need to undertake protective actions along further coastal sections will be reduced to locations with developed hinterlands at risk of erosion and marine flooding.

Coastal protection using artificial beach nourishment in line with the new Coastal Protection Program (Journal of Laws 2016, item 678 [105], see also the Act of 25 September 2015 on amending the Act on the establishment of the long-term “Coastal Protection Program”—Journal of Laws of 23 October 2015, item 1700 [106] requires extensive analyses aimed at assessing the effectiveness of the undertaken actions and identification of sandy sediment resources. It also requires that the conditions imposed by the operation of the European ecological network Natura 2000 and other nature conservation forms are taken into consideration. The objective of Natura 2000 sites is to ensure that the major European species and natural habitats are preserved in good state and to prevent their transformation by way of monitoring the condition of the subjects of protection and effective management of individual sites. Consequently, a necessity emerges to protect against devastation (damage) not only in built-up coastal sections with settlement networks, ports, and harbours, including military facilities, but also to protect numerous habitats and species related to the specificity of their occurrence at the meeting point of the land and the sea. Artificial filling of sections at risk of abrasion allows for preserving the habitat of the shifting dunes along the shoreline and restoring them, although admittedly with features of artificially restored dunes, which undergo naturalisation on the condition of not planting them out with alien species [66].

When calculating the costs of artificial nourishment, it is also necessary to consider the costs of documentation and scientific research required for the proper course of the investment process and the assessment of the ecological effects of nourishment. To achieve the intended effects and effectiveness of artificial nourishment, each nourishment project requires assumptions based on tachymetric–bathymetric measurements, which will determine the sediment deficit on the beach and the seabed and estimate the volume of sediment in the collection area necessary to achieve a safe shoreline profile. An integral part of applying this protection method should be monitoring the obtained results, which would allow for the assessment of the shoreline condition and more effective design of maintenance nourishments.

5. Conclusions

The Polish-language literature review, gathered, among others, from the Library of the Marine Institute in Gdańsk, has proven to be a valuable and unique source of information for exploring the topic of artificial beach nourishment along the Polish coast. Artificial beach nourishment is currently the only method causing relatively the least severe side effects to the coastal geomorphological system. It allows for, at least, partial mitigation of the side effects generated by the existing port breakwaters and coastal protection systems, by way of filling the nearshore sediment deficit and improving the coastal zone’s resistance to the impact of hydrodynamic factors. It also improves the recreational values of beaches.

In 1980–2020, approximately 40.5 million m³ of sediment was deposited along the Polish coast and lagoon shores, which allowed for partially filling the nearshore and backshore sediment deficit, contributing to a reduction in the risk of erosion and storm flooding in the developed hinterland and the pollution of the marine environment. More than half of the total fill volume covered the seaward shores of the Hel Peninsula. The Hel Peninsula is one of the most sensitive parts of the coast, where beach fill projects have been implemented since 1989 until the present day.

The effectiveness of large-scale artificial nourishment of the Hel Peninsula’s coastal zone, which has been verified with multiple measurements, became a determinant in accepting this method as the preferred manner of filling the sediment deficit along other coastal sections; in particular, along the coastal sections adjoining the ports on their eastern sides (Łeba, Rowy, Ustka, Dźwirzyno, Mrzeżyno, Kołobrzeg, and Dziwnów) and in the vicinity of protective structures (Jastrzębia Góra, Ostrowo, Ustronie Morskie, Niechorze, Rewal, and Trzęsacz). Since 2003, when coastal protection began to comply with the Act on the establishment of the long-term “Coastal Protection Program” (consolidated text, Journal of Laws 2016, item 678 [105]), artificial beach nourishment has become a widely used method of coastal protection. The total fill volume within the term of the program was approximately 18.8 million m³ of sand, which accounts for 45% of the fill volume in 1980–2020.

Undoubtedly, the development strategies of coastal and lagoon region communes should be amended so that the safe investment zone is allowed for, and their development in areas at no risk of erosion and flooding is preferred, to reduce the scale of risks. Thanks to such actions, the length of coastal sections requiring protection will not increase, and the aesthetic values of the coastal zone will not diminish. However, it should be pointed out that even an environmentally friendly method such as artificial nourishment with sand is still an interference with the prevailing conditions on the coast. It should be applied only to the necessary extent, from the viewpoint of protection against erosion and, additionally, provision of conditions adequate for recreation.

It is estimated that, due to the progressive climate and anthropogenic changes, the complete implementation of the Coastal Protection Program, as regards artificial beach nourishment, requires the use of approximately 61 million m³ of sand with grain size adequate for the sections to be nourished. Under the above-mentioned act, between 2004 and 2023, 196.85 km of the open sea shore were designated for coastal protection using the artificial nourishment method, which could be accompanied by support structures and coastal reinforcements. According to the program, artificial nourishments can be implemented as the sole method of coastal protection in six regions along the coast, and lagoon shores with a total length of 8.5 km.