Abstract:

Artificial beach nourishment is one of key methods preventing coastal erosion and flooding, acting in support of the maintenance of much-disturbed coastal environments and their much-desired recreational functions.

Beach fills have been implemented since the 1930s, though relevant conceptual studies in Poland were elaborated in the 1960s and 1970s. These summarised the worldwide experience focusing on the rational implementation of beach fills in Poland. Recommendations at that time included a maximisation of the use made of sand dredged from navigation channels and canals, with a view to this being used to nourish abraded beaches near ports.

In 1978, sand by-passing was implemented successfully at the Dźwirzyno and Rowy fishing harbors, with regular dredging of the approach channels and harbour canals being combined with the pumping of a water-sand mixture on the lee (eastern) side of breakwaters. These systems have remained operational through to the present day. The largest fills were generated in the 1994‑1996 period; being ca. three times greater than the volume of sand dumped offshore.

Between 1980 and 2014, 32.2 M m³ of sand were deposited along the Polish coast and lagoon shores. This offered partial compensation of the reduced nearshore sand deficit, and served to increase resilience of beaches and the backshore in the face of erosion and inundation, while also helping with the contamination of beaches due to uncontrolled emissions in the course of events of the latter type. More than half of the total fill volume was deposited along the offshore coast of the Hel Peninsula, where a comprehensive scheme for coastal protection was implemented between 1989 and 1995. The Peninsula, and particularly its root and central part, are among sites in Poland most vulnerable to erosion, often subject to catastrophic inundation threats.

Following Poland’s adoption of the Coastal Protection Act 2003 (see the Dziennik Ustaw Official Journal of Laws of 2016, item 678), fills became the most popular coastal‑protection measure. Between 2004 and 2014 this measure was resorted to predominantly along offshore stretches of the Hel Peninsula, and at beaches adjacent to open sea ports on their lee (eastern) sides (including harbours from Łeba along to Dziwnów).

Fills were also performed along the shores of the Gulf of Gdańsk, where erosion processes have accelerated in recent decades; and at the open-sea beaches near Jarosławiec, Ustronie Morskie and Niechorze. The latter installations operated in support of existing protection schemes. Comprehensive protection of the soft cliff between Rewal and Trzęsacz was also inaugurated, the background erosion tendencies ongoing their having coincided with anthropogenic activities causing disruption to local geodynamic processes. Since the time of adoption of the Coastal Protection Act, a total fill volume of 10.5 M m³ has been deployed, see Table 1. This represents about one-third of all the filling done from 1980 until 2014.

Many positive changes are to be identified along the open-sea coast of the Hel Peninsula, on which more than 17.5M m³ of sand were deposited in the years from 1989 through to 2014, cf. Table 1, Figs. 3, 4 and 5. The large fill volumes achieved during the first 5 years of implementation of the protection scheme along the Peninsula resulted in rehabilitation of the nearshore seabed to such an extent that follow-up re-nourishment only needed to assume a lesser intensity. Morphometric parameters along the nourished beaches allow for them to be classified as very highly resilient in the face of hydrodynamic forces.

Since erosion tendencies prevail in Poland’s coastal zones, any cessation of beach fills may result in a gradual loss depletion of the level of safety achieved. Thus, annual deposition of several hundred thousand m3 of sand along the offshore beaches of the Hel Peninsula continues to represent an absolute necessity if the current level of resilience is to be maintained.

Reduction of nearshore sand deficits by way of beach filling represents the only method of preventing negative beach responses. Re-nourishments are determined by hydrological and morphodynamic factors, and should gain incorporation into the protection actions being planned by coastal authorities. There can be no doubt that the experience acquired thus far can provide for successive optimisation of the method under consideration, with a view to level of protection efficacy being raised, even as respect for environmental sustainability is also achieved.

Keywords: sztuczne zasilanie, brzeg morski, erozja, deficyt osadów strefy brzegowej, kubatura osadów

Helena Boniecka [helena.boniecka@im.umg.edu.pl], Uniwersytet Morski w Gdyni, Instytut Morski

Abstract:

The aim of the work described here has been to analyse contemporary changes along the shore along the central part of the Vistula Sandbar located on the Baltic’s south coast. There, breakwaters are being installed to protect the canal cut that has been under construction since 2020 (fig.1). Shoreline changes involving both dunes and beaches have been predicted to arise following construction of breakwaters, which will obviously influence the dynamics of the previously natural shore of the Sandbar. Factors exerting an influence on these have been presented by reference to the results of field research done in the 2003‑2020 period.

The section of the Sandbar under discussion (the middle part, at km 18‑25, fig. 1, 2) has so far shown only limited accumulation trends. Plate 1 presents different relief of the foredunes caused by storm surges and aeolian processes. The wind regime for 2001‑2017 features the more marked presence of wind from the W and SW sector. Aeolian accumulation caused by such westerly winds is rebuilding the beach and dune in the investigated area (fig. 6‑8). The strongest winds are those from the NW that arise during the autumn-winter period.

The orientation of the sandbar coast ensures that erosion in the course of storm surges is different. The middle part of the Vistula Sandbar is only eroded during the highest storm surges (fig. 3). Over the research period, it was possible to observe erosion of various types caused by storm surges recorded in Gdańsk. Since 2003, there have been several storm surges featuring a water level higher than 1.2 m AMSL. Each such surge ensures severe erosion of dunes (as in 2004, 20006, 2007, 2012, 2017 and 2019). Storm erosion is a major factor in dune development: the higher the surge, the higher the levels of water run up and coastal erosion (fig. 4). During the highest surges (featuring water of H>1.2 m AMSL, the run-up is of almost 4 m AMSL. The mean rate of retreat at the base of the foredune is 3‑4 m, while the maximum reaches 7‑8 m.

In the periods between storms, the areas at the bases of dunes increases by 0.8 to 1.5 m/y. Reconstruction of the dunes took place up to 2‑3 years after a major storm surge. The sand building foredunes is fine and medium (average 0.20‑0.21 mm). There are fines sands along the whole Vistula Sandbar, while beach dune sand is coarser. The coarsest sand is the type that builds the beach ridge (0.3‑0.4 mm). This type of material comes from the cliffs of the Sambian Peninsula located in the NE part of the Gulf of Gdańsk. Plants scattered across the beach ensure aeolian accumulation on the upper beach.

Beach height is often higher than the highest water run-up during storm surges, with this serving to safeguard dunes against erosion. Beach width is almost widest on the investigated part of Sandbar (other than at the mouth of the Vistula delta), exceeding 41 m on average (figs. 1C and 5).

The foredune dynamics are not great (figs. 6 and 7). However, there are more major increases in years lacking storm erosion, with the height of foredunes exceeding 4‑5 m. Neighbouring sections of coast lack such foredunes, however – meaning that erosion is more marked there than along the Sandbar’s central stretch.

The area under study is one of two accumulating sections of the Vistula (the second being in the Vistula Delta). Analyses show that breakwaters constructed will block sediment transport on both the shore and the beach. All aeolian sediment will accumulate on the western side of the Canal that is to be completed (at km 26‑25). There will be new dune growth and beach widening. Sand will not be transported eastwards (at km 23‑18 and further east to Krynica Morska). Dunes will not develop in this section, and that will ensure the development of erosive tendencies. The erosion of dunes will take place on the eastern side of breakwaters and may exceed 0.5 to 1.2 m/y (fig. 8). Annual rates of erosion will depend on the number of strong storm surges with sea level H > 1 m. Such surges occur more frequently than they did in the 20^th century.

Keywords: dynamika plaż, rozwój wydm, erozja sztormowa, akumulacja eoliczna, przekop Mierzei Wiślanej

Tomasz Arkadiusz Łabuz [tomasz.labuz@usz.edu.pl], Uniwersytet Szczeciński, Instytut Nauk o Morzu i Środowisku

Abstract:

Previous studies identified regions of Poland privileged in terms of their wind energy resources, given that they are in areas in which energy values exceed 750 kWh/m²/year at 10 metres above ground level. These are mainly the Baltic coast, the Suwałki region, the ranges of mountains and hills called Bieszczady, Beskid Śląski and Beskid Żywiecki, and central Wielkopolska and Mazowsze. Comparing these results with research over an analyzed period, the author concludes that there has been a certain displacement of energy-privileged areas. The coast remains the most advantageous area from the point of view of new developments in wind energy, but central and eastern Podkarpacie is no longer as favourable as, for example, the Sudety Mountains, with the same being true of the comparison between the Suwałki Region and Warmia. Finally, the privileged area in central Poland “shifted” north-north-east, from Wielkopolska towards Kujawy and the northern part of Mazovia.

The comparison of the results for individual seasons (warm and cold) allows for the conclusion (based on both measurement and model data) that, due to the location of Poland, dominant wind directions, and maximum velocities achieved in different seasons, average wind speed and the value of generated wind energy are much greater during the (October-March) cold season. On the other hand, the warm season (April-September) contributes to resources of wind energy to a much more limited extent.

The basic input data for the programmes for the assessment of wind-energy resources (especially the “older” ones whose development began before 2000) were the results of measurements at Meteorological Stations. Exemplary evaluations of this kind used to be prepared with the aid of a Danish model called WAsP (the Wind Atlas Analysis and Application Program). This made it possible to produce wind-energy calculations on the basis of data from synoptic stations.

Requirements attached to programs of this type of course combined with input data, necessitate generalisation of results or limited applicability to lowland areas with a non-complex orography (mainly given a need to “transfer” the results of calculations from the vicinity of a meteorological station to the place in which the construction of a wind turbine is foreseen. The use of the calculation results of the numerical meteorological model in high spatial resolution allows for such problems to be overcome with no loss of quality or representativeness of results.

This paper presents a comparison of the results of calculations of wind-energy resources based on measurements at meteorological stations and on the basis of the results of the COSMO meteorological model in three basic resolutions in the period 2011‑2019. The results of this work encouraged a conclusion that the products of the numerical meteorological model, especially those launched at high resolution, on a convection-permitting scale, can be deployed successfully in both pure and applied circumstances. Comparison of measurements revealed that, with a view to correct and true-to-reality results being obtained, it was worth increasing model resolution for computational purposes – up to several kilometers, even taking into account the related extension of computing time, as well as the increase in disk space necessary for data storage.

The desirability – in terms of investment – of increasing the heights and sizes of planned wind power plants was also confirmed, as more energy may be obtained in this way. Even as the costs of such structures increase with their heights, the results of the work presented here show clearly that the use of taller power plants (specifically those for which the rotor axis is at the level of 50, 100 or more meters above ground level) offers the chance of a major increase in the gross amount of energy that can be generated. This is due to the change with the mean wind speed linearly with the power profile, while the amount of wind energy obtained depends on the wind speed taken to the third power. Thus, a raising of the level of the rotor axis to a height ten times higher – e.g. from 10 to 100m agl. – on average results in about a fivefold increase in the amount of wind energy obtainable each year.

Keywords: nergia wiatru, model meteorologiczny, rozdzielczość siatki obliczeniowej, profil prędkości wiatru

Andrzej Mazur [andrzej.mazur@imgw.pl], Instytut Meteorologii i Gospodarki Wodnej – Państwowy Instytut Badawczy

Abstract:

As well as serving economic functions, forests in Poland are places of rest and recreation. However, a particular form of the latter, not necessarily coming to mind as a first association, is illegal motorised tourism, which entails entries into forests in or on off-road cars, quads, and cross and enduro motorcycles. With a view to achieving fuller insight into these activities, and the problems they pose, the present article offers the results of analyses as regards the spatial distribution, intensity and characteristics of the phenomenon. The effectiveness of existing tools to combat the practice is then assessed, prior to a presentation of solutions foresters propose, to ensure that infringements of the law are counteracted, even as compromises are arrived at so that the needs of various groups of user of forests are met. Data supporting such an approach to analysis derive from questionnaire-surveying targeted at Poland’s Forest Districts. Some 332 of Poland’s 430 Districts elected to participate in the survey, with the vast majority (as many as 86.45%) recording illegal entries, most often featuring motorcycles or quads, and slightly less often involving off-road cars. This denotes a phenomenon affecting at least 66.74% of Poland’s Forest Districts. Indeed, the phenomenon of illegal motorised tourism in forests is seen to be spread rather evenly across the country, even as certain Forest Districts see this as being among the most important problems faced. Among the 287 affected FDs, 90.59% assess this as a problem that is either growing or maintained at the same level. Manifestations are of both an individual or collective nature (through with the former dominant) and with local people by far the most involved. 42.86% of respondents regarded legal provisions relevant to illegal entry into the forest as ineffective (though 36.24% were of the opposite opinion). Those not satisfied pointed to penalties that are too low, and powers of the Forest Guard that are too limited. While the problem of illegal motorised tourism affects forest areas across the country, FDs’ conviction that locals are the main culprits ensures that preventative measures will mainly be local in scope. That would denote an increased involvement for local authorities in the combating of the practice, as well as educational activity in the direction of the stigmatisation of specific activities, the elimination of tacit public consent for the breaking of the law, and the provisioning of legal alternatives to illegal motorised tourism. While effective combating of a negative phenomenon is sought by foresters, who therefore demand comprehensive amendment of the law, those involved are nevertheless willing to countenance the development of specially-organised routes for off-road driving.

Keywords: turystyka zmotoryzowana, turystyka w lasach, obszary cenne przyrodniczo, Lasy Państwowe, Polska

Dagmara Chylińska [dagmara.chylinska@uwr.edu.pl], Uniwersytet Wrocławski, Instytut Geografii i Rozwoju Regionalnego
Krzysztof Kołodziejczyk [krzysztof.kolodziejczyk@uwr.edu.pl], Uniwersytet Wrocławski, Instytut Geografii i Rozwoju Regionalnego