Lithodynamics and protection of the cliff coast at Jastrzebia Góra Wieslaw Subotowicz

Transcription

1 Lithodynamics and protection of the cliff coast at Jastrzebia Góra Wieslaw Subotowicz In the geological structure of the Jastrzebia Góra cliff (whose height reaches 30 m above sea level) appear mainly deposists of Vistulian Glaciation (Fig. 1). Besides the three levels of the tills and dividing them intermoraine formations represented mainly by fluvioglacial sand, the glacilimnical deposits are worthy of special attention. They consists of varved clay with sand laminations. The intermoraine sandy formations and the glacilimnical deposits are wet. The groundwater occuring in them appears on the cliff face in the form of seepage springs. Its activity inside the cliff massif is after abrasion, the second major factor responsible for landslide formation.the water weakens the ground bed, especially the clay, and in effect determines the generation, the type and the range of the landslide phenomena. An analysis of the geodynamic forms, observed on the cliff at Jastrzebia Góra, shows that both old and new lanslides occur here. Fragments of dead cliff edges and lanslide scars indicate that large landslide phenomena took place at the end of the XIX-th and the beginning of the XX-th century (Fig. 2). At that time an extreme storm surges were recorded. These surges were the main direct cause of the cliff activation on such large scale. The range of landslides that followed reached several dozen meters. The permanently proceeding abrasion resulted in the formation of an abrasion escarp. The rate of its destruction for the period is 0.94 m/year. Simultaneously, a steady degradation of the landslide processes are observed. Old colluvia, resting on the abraded step, become more active. This process is evident by the deflection, and later overturning, of the beach lift tower. The tower was built in It worked for only three years between 1966 and In 1982 it became destroyed. It is expected that total destruction of the remaining fragments of the landslide steps will occur by the year Then the whole cliff will become active, and the predicted range of a large landslide will be about 50 m. It should be pointed out that besides the discussed cliff, the coast consists of the undercoast (bottom) and the beach, and the beach forms a continuation of the undercoast during storm surges. The undercoast consists of the matrix bed, built mainly of glacilimnical clay, and of a sandy dynamical bed. The thickness of the dynamical bed reaches from 1.5 to 2 m, locally 5 m. Two sand bars are formed in the bed. The first the inner-bar, occurs at a distance of a dozen to several dozen meters from MSL waterline. It is characterized by a large variability of form and position, and is associated with small and medium waves. The second, the outer-bar, was formed under conditions of extreme storm waves at theturn of the XIX-th and XX-th century. It is located at a distance of m from the waterline, and is associated with the abrasion escarp formed during those storms. At present, the escarp is buried. Both in the interbar zone and on the seaward slope of the second bar, are observed areas of exposed matrix bed continuously growing. This indicates a negative balance of coastal sediments accumulated in the undercoast and on the beach in the form of the dynamic bed. This is the reason for the increasing activity of the investigated coast. The active cliff presents a threat, in particular to the building objects situated in its close neighbourhood, and also to the town it self. Hence, there arises a question, wheter the cliff coast under consideration should be protected. If yes, the problem ought to by analysed in a complex and interdyscyplinary way. The project of a coast protection system should involve all aspects, especially its lithodynamics, which does not only mean the lithodynamical processes shapning the cliff coast of Jastrzebia Góra, but it also includes the sections adjacent to it (Subotowicz 1991; Fig. 3). The development of the coast takes place in a specific geological environment. The lengths of coast which are composed of formations more resistant to abrasion, i.e. tills and clays, are convex towards the sea, while lengths consisting mainly of sandy formations are concave. A segment of cliff coast of one km at Jastrzebia Góra and the coast of Rozewie Cape are convex fragments of coast. They are responsible for the development of the coast from Karwia to Rozewie. It is primarily them that should be protected. In Rozewie there is already a sea wall, while at Jastrzebia Góra there should be made a similar protecting construction. At this point it is necessary to be aware of the fact that the neighbouring fragments of the coast, especially from the east (the transport of the coast rubble from the west to the east), during the first stage will undergo intensive abrasion. According to the theory of the phase development of the cliff coast, variable in time and space (Subotowicz 1982), the abrasion process is expected to disappear, or even there is likely to take place an entire stabilization of cliffs and reconstruction of beaches along the unprotected sections. 67

2 REFERENCES Subotowicz, W., Lithodynamics of cliff coast in Poland (in Polish). Ossolineum. Subotowicz, W., Protection of the cliff coast along the Jastrzebia Góra - Rozewie section (in Polish). Inzynieria Morska i Geotechnika, 4 Fig. 1. Longitudinal geological section of the cliff at Jastrzebia GóraThe Warta stage: 1 - grey till. The Vistulian stage: 2 - yellow-brown till, 3 - fluvial sand, 4 - glacilimnical clayand sand, 5 - fluvioglacial sand, 6 - grey till, 7 - fluvioglacial sand and gravel, 8 - brown till, 9 - clay, silty clay, 10 - silty and loamy sand. The Holocene: 11 - dune sand. TL dating by Z. J. Olszak from Gdansk University Fig. 2. Geological cross-section of the cliff at Jastrzebia Góra. Interpretation as Fig

3 Fig. 3. Transformation of cliff coast in the section at Rozewie - Jastrzebia Góra 69

4 Hel Peninsula - relief, geology, evolution Anna Tomczak Hel Peninsula is an important part of the Polish coast. It is long, low and relatively flat. In effect, it is specially vulnerable to storm waves and surges. It is important too from geological point of view, because of Holocene deposits of exceptionally large, about 100 m thickness. Besides the Hel Peninsula is neither a typical bay bar or spit, though it extends far towards the deep sea. From the north Hel Peninsula contacts directly with the open sea, while from the south it contacts with the deep Puck Bay and shallow Puck Lagoon. Bathymetry is shown in Fig. 1. The length of the Peninsula is 36 km, and its width is between about 200 m and 3 km. The west part of the Peninsula is narrow and relatively flat. Terrain height is here 1-2 m above sea level. Higher reach only tops of coastal dunes, which only at some places attain the height of 1-13 m above sea level. The south-east part is decidedly wider (1-3 km), with a more differentiated relief. It also differently formed in its inner and outer parts. Inside this part of the Peninsula, terrain level is between 3 and 5 m, and the relief has a clear orientation. Forms run from north-west to south east, forming several alternating zones: regular long embankments, and irregular low hillocks. These are zones connected with the growth and elongation of the Peninsula. In the outer part of the Peninsula there is a belt of high dunes, reaching 20 m above sea level. Dunes of similar height appear also on the Puck Bay side, over a length of about 4 km. Geographical problems met with on the Hel Peninsula are complex. They were topic of many publications (Pawlowski 1922, Pazdro 1948, Rosa 1963, 1984, Baczyk 1963a, 1963b, Rudowski 1979, S³omianko 1986, Musielak 1989). In spite of the several important questions still have not found satisfactory explanations. Geological investigations of Hel Peninsula have a 100 year history. During that time about 50 boreholes were made, very nonuniformly distributed and of much varying depth. In most cases they are hydrological borings near Jastarnia, Jurata and Hel. With respect to gaining knowledge about Quaternary stratigraphy their value is very differentiated. Up to this time, only six profiles were stratigraphically investigated (Samsonowicz 1935, 1938, Sandegren 1935, 1938, Dmoch Wilczynski 1972, Bohr, Sokól 1972, Bogaczewicz- Adamczak 1982, Bogaczewicz-Adamczak, Zukowska 1990, Tomczak, Kramarska, Krzyminska, Zaborowska, Zachowicz 1990). Stratigraphic divisions not always are univocal, some require verification. Hel Peninsula require further research. They are continued by the State Geological Institute, Branch of Marine Geology. The research involves surface relief, geological build, biostratigraphy, and radiocarbon chronology. Many new data have been obtained in that nearly 50 14C dates. Three new borings of about 100 m depth were made. Their stratigraphic analysis is not yet finished. The presented here geological crosssection is the 1990 version (Tomczak 1990, 1993), in the future certain correlations are quite possible. The geological structure of the Hel Peninsula is shown in Fig. 39. Mesozoic formations are present in the substratum. The top of the Jurassic is at about 200 m, and of the Cretaceous at about 100 m depth. There are denivelations in the primary Cretaceous surface, caused by late erosion. The Tertiary appears only in the west part of the Peninsula, and is displaced together with Mesozoic deposits along a line of probable dislocation. Pleistocene deposits are present in the substratum of the whole Peninsula. However they are in two horizons: they lie higher at the root, and lower near the tip of the Peninsula. Pleistocene appears mainly as water accretion forms, sand prevail. Till forms only several thin and noncontinuous laminations. This results in difficulties in stratigraphic definition of the different Pleistocene series. There is a marked bipartiteness at the line of the covered slope near Kuznica. Such structure of the substratum caused that the Holocene series is fully developed only in the east part of the Peninsula, where its thickness reaches 100 m. In the west part there are Holocene deposits only of the Littorina period, forming a relatively thin cover m thickness. Subdivision of the Holocene deposits have been determined basing on biostratigraphic and sedimentological investigations. Pre-Ancylus, Ancylus, Mastogloia, Littorina and Post-Littorina series have been distinguished (Tomczak et al. 1990). Lithologically, the three first series are muds and very fine sand. The two upper ones are medium and fine sand. Predominant species of fauna and Diatom appear only in the lower parts of the profiles, and disappear at the depth of about 40 m. Probably they were destroyed. In the general picture of the geological structure some problems are omitted, i.e.: identification of Tertiary rafts, redeposition of sediments and origin of organic admixtures, differences in depth of horizons of each of Holocene series, difficulties 70

5 in distinguishing of the Yoldia series, etc. Each of these problems could be a separate subject. Evolution of the Peninsula took a different course in its west and east parts. Genetically, the west part is of land type, and developed together with adjoining from the west land which is here formed into isolated highlands and stream-way valleys. Only 6,900 years ago, on that peat, occurring now 9-12 m below sea level, was being formed. Peat of that age was recently found at Cha³upy and Kuxnica and also at some places in the Puck Lagoon (Kramarska, Uscinowicz, Zachowicz 1994). The land became flooded only due to the Littorina transgression. At the same time, during the whole Holocene, intense accumulation proceeded in the neighbouring on the east sea area, i.e. the west part of the Bay of Gdansk was being filled with sediments. Stabilisation of sea level about 1-2 m below today's level caused that, as an extention of land, a peninsula started to grow, at first short but gradually becoming longer. 14C dates of peat indicate that 5,640 years B.P. Hel Peninsula reached at least to Jurata. Dates 3,000 and 1,760 years B.P. (Fig. 2.) indicate further eastward growth of the Peninsula. The Hel Peninsula attained its present shape about 1,000 years ago, when sea level rose, during a relatively short time, by about 1,5 m, reaching today's position. This is proven by archaeological data and also by a thin peat layer of age 1,600 to years B.P. During the sea level rise, coastal parts of the Peninsula became permanently flooded. Remains of these are the shallow which are easily traced in the bathymetry on the inner side of Hel Peninsula (Fig. 1). The root of the Peninsula was displaced southward with marine erosion of adjoining from the west moraine highland. Because of that the west part of the Peninsula was always low and easily given to storm flooding. This state has not changed significantly until today. However, interesting conclusions result from analysis of old maps. They are three 1:10,000 and 1:50,000 old maps of the west part of the Peninsula, the oldest 300 years old. They show 45 places in which storm waves penetrated into the Peninsula. This means an average of 2 inflows appear always at the same places. In the meantime some of them were stopped or made more narrow. Comparison of the maps with the present-day cartographic image of the Peninsula shows an amazing similarity of all characteristic features of the topography and shape of the coast line (Tomczak 1991, Tomczak, Domachowska 1992, Tomczak, in print). Proportions between the western, narrow part of the Peninsula and its wide eastern one, remain unchanged, which indicates the natural processes have not changed. The seaward coast in the western part of the Peninsula is a "transit segment" along which material is displaced, but does not accumulate. Thus there is no sand for the forming of dunes. The Peninsula remains narrow and low. A positive balance of sediments, with all the consequences (larger width, high dunes, wide beach), is observed starting from Jurata. At the tip gradual elongation occurs, cartographically documented since The conclusion may be drawn that geological conditions guarantee survival of the Peninsula. If it was subjected to progressive destroyal, it would have disappeared a long time ago. REFERENCES Baczyk, J., 1963a. Geneza Pólwyspu Helskiego na tle rozwoju Zatoki Gdanskiej. Dokumentacja Geograficzna, 6, Baczyk, J., 1963b. Genese de la presqu'ile de Hel sur la base du developpement du Golf de Gdansk. Baltica, 1, Bogaczewicz-Adamczak, B., Nowyj diatomowyj analiz osadocznoj tolszczi Gelskogo poluostrowa. Peribalticum, 2, Bogaczewicz-Adamczak, B., ukowska, A., Okrzemki kopalne z osadów w Juracie. Przewodnik LXI Zjazdu Polskiego Towarzystwa Geologicznego, Bohr, R., Sokól, M., The fossil diatom flora from the sediments of the Hel Peninsula. Guide- Book of the Excursions. Subcomm. of the INQUA, Sopot, Kramarska, R., Uscinowicz, S., Zachowicz, J., Late Glacial and Holocene evolution of Puck Lagoon, Gdañsk Bay. In: A Baltic Symposium, The Baltic past, present and future. Abstract volume, Stockholm. Musielak, S., Uwagi dotyczace genezy Pólwyspu Helskiego w swietle nowszych danych. Studia i Materialy Oceanologiczne, 54, Pawlowski, S., Charakterystyka morfologiczna wybrzeza polskiego. Poznan, Pazdro, Z., Pólwysep Hel i jego geneza. Technika Morza i Wybrzeza, 1-2, Pazdro, Z., Hel Bay bar and cliff of the Swarzewo isolated moraine plateau. VIth Congress INQUA. Guide-Book of the Excursion, Part I.,

6 Rosa, B., O rozwoju morfologicznym wybrzeza Polski w œwietle dawnych form brzegowych. Studia Societatis Scientiarum Torunensis, C2, Rosa, B., Rozwój brzegu i jego odcinki akumulacyjne. W: Augustowski, B. (ed.) Pobrzeze Pomorskie. Ossolineum, Rudowski, S., The Quaternary history of the Baltic, Poland. Acta Universitatis Uppsalensis, Uppsala, Samsonowicz, J., Nowy otwór swidrowy na Helu. Sprawozdania PIG, 8(3), Samsonowicz, J., Uber das Quartar und den Untergrund des Quartars in polnische Sudbalticum nach neuen Tiefborungen in Jurata und Karwia. Geol. Foren. Forhandl., 60(4), Sandegren, R., O kopalnej mikroflorze z wiercenia na Helu i o zmianach postglacjalnych poziomu Baltyku. Sprawozdania PIG, 8, Sandegren, R., Uber die fossile Mikroflora aus den Borungen bei Bad Hel und Jurata auf der Halbinsel Hel. Geol. Foren. Forhandl., 60(4), Slomianko, P., Problemy ochrony brzegów Pólwyspu Helskiego na tle ogólnych prawidlowosci rozwoju kos. Prace Instytutu Morskiego, 696, Tomczak, A., Budowa geologiczna i rozwój Pólwyspu Helskiego w swietle najnowszych badan. Przewodnik LXI Zjazdu Polskiego Towarzystwa Geologicznego, PIG, Tomczak, A., Morfogeneza Pólwyspu Helskiego. W: Program i streszczenia referatow, I Zjazd Geomorfologów Polskich, Poznan, Tomczak, A., The Hel Peninsula - relief, geology, evolution. Guide-Book of the excursion. The Baltic -IIIth Marine Geological Conference, Sopot, Tomczak, A., (in print). Przelewy sztormowe w zachodniej czesci Pólwyspu Helskiego na mapach z lat 1694, 1818 i 1844 a rzezba wspólczesna. Studia i Materialy Oceanologiczne, 2. Tomczak, A., Domachowska, I., O ksztalcie Pólwyspu Helskiego w czasach historycznych w swietle zródel kartograficznych. Przeglad Geologiczny, 8, Tomczak, A., Kramarska, R., Krzyminska, J., Zaborowska, K., Zachowicz, J., Nowy otwor wiertniczy w Helu w swietle badan litologicznych, biostratygraficznych i radioweglowych. Przewodnik LXI Zjazdu Polskiego Towarzystwa Geologicznego, PIG, Genesis and development of the Puck Lagoon 72

7 Fig.1. Hel Spit: Elements of geomorphology on the background of bathymetry of the surrounding sea. 1- morainic plateau, 2- pradolina floor, 3- Spit area covered by low aeolian forms, 4-area covered by high foredunes, 5-storm ridges slightly reshaped by the aeolian processes. Running kilometres of the Polish shoreline are marked from east to west; running kilometers of the Hel Spit are market separately Fig. 2. Simplified geological cross-section along the Hel Peninsula J - Jurassic, Cr - Cretaceous, Tr - Tertiary, 1 - Pleistocene undivised; Holocene deposits: 2 - Pre-Ancylus, 3 - Ancylus, 4 - Mastogloia, 5 - Littorina, 6 - Post-Littorina, 7 - accretion-lines of the youngest part of Hel Peninsula, 8 - fault, 9 - selected sites with 14 C dating 73

8 Coast changes of the Hel Spit over the last 40 years Kazimierz Furmanczyk Changes that have affected selected elements of the Hel Spit coastal zone over a period of nearly 40 years have been described on the basis of an analysis of aerial photographs at a scale of 1: taken in 1957 and Examples of photos from these two yese two years covering the Jurata region are presented in Fig and Fig On the basis of such photographs photomaps of the coastal zone of the spit were made at a scale of 1: using the autogrammetric method. The map shows both constant and variable elements occuring in the zone. For comparison the dune baseline was chosen, assuming changes in its location to be indicative of the general tendency in coast development. The magnitudes of these changes were determined, and the results are presented in Fig The analysis shows that the Hel Spit can be divided into three parts differing in the magnitgude and derection of change in the location of the dune baseline. The western part of the spit, from the 0 to 19 th km, despite its coastal protection in the form of groins along the first 12 km, is an area with clear predominance of abrasion, with a maximum change of 55 m near the 11 th km and 43 m near the 4 th km. The second, middle part of the spit, from the 19 th to 31 st km, is characterised by big changes caused alternately by abrasion and accumulation. The maximum change due to abrasion occurs near the 24 th km and amounts to 64 m, while acumulatin has brought about the biggest changes on the 25 th and 29.5 th km amounting to 45 m and 47 m respectively. The third, eastern part, from the 31 st km to the tip pf the spit, is predominantly characterised by accumulation, with the maximum increment of about 105 m. An analysis was then made of variations in the dune baseline in less than a year, from September 1991 till May 1992, using aerial photographs processed and magnified to a scale of 1: The results are shown in Fig It was the period of an exceptionally high dynamisc of change in the coastal zone. Abrasion section definitely predominated along th whole length of the spit shore, with variations in the dune baseline of 25 m in several places, and on the 24 th km even of 40 m. Accumulation-dominated sections were almost exclusively those where artificial beach nourishment was taking place. These sites are shown in Fig It is worth nothing that while the dune baseline definitely tends to retreat, there are fragments where its position has not altered. This fact corroborates the existence of "nodal" points observed and described earlier. To sum up, we can state what follows: 1. The domination of abrasion in the western section of the Hel Spit coastal zone is largely the effecgt of checking the west-east lonshore driff as a results of the construcion of the Wladyslawowo harbour in the 1930 s. This tendency has prevailed over nearly 40 years despite such coastal protection measures as groins. It should be mentioned that even betore the harbour had been built, there used to be communication difficulties at the root of the spit caused by the destruction of dunes and the sea overglowing to the other side of the strip of land. 2. The heavy abrasion of the coast along the whole spit shown in the 91/92 diagram of yearly change was due to aviolent storm associated with a catastrophic surge that took place in January During that storm in many places sea water penetrated to the woods in section devoid of dune protection. At the root the water overflowed to the other side of the spit causing damage to the railway. Another disastrous storm surge occurred in January 1993, with similar effects. In 1989 to the coastal protection measures was added artificial beach nourishment in the most threated places, thanks to which abrasion has lessened there. The tendency, however, has remained. 74

9 Fig. 1. Classification of Hel Peninsula coast, s changes in period of time years. Fig. 2. Jurata (Hel Spit). Upper parts of photos: subaqueous longshore bars in the open sea foreshore zone. Lower parts of photos: Puck Bay. 75

10 Concept of Hel Peninsula coast protection Andrzej Cieslak A. CAUSES OF PRESENT AND FUTURE COASTAL EROSION AND FLOOD RISKS Seaward side Erosional character of the Baltic wave climate: Causes parallel displacement of coastline and of morphological forms (sand-bars, beach, dune), with no significant reduction of these forms. Breakwater of Wladyslawowo harbour: Causes qualitative and quantitative change in sediment transport at port profile, reducing the transport eastwards of the port. In effect: a) In a perspective of several decades - completely destroyed sand-bar system, which stabilizes the existing coastline, then dune degradation and appearance of direct risk of flooding by sea during storm surges along 20 km of the Peninsula; periodical of permanent breaking of the Peninsula will become possible, especially at its root part. b) In longer term (over 100 years) - gradual change of coastline orientation (deflection southwards) of the whole peninsula, decrease of the peninsula's volume and highly probable shortening; in effect the presently relatively stabile coast of the Gulf of Gdansk may become active. The presence of breakwaters caused also a change in the distribution of areas of accretion and erosion along the Peninsula. Bottom morphology: Oblique to coastline troughs in the bottom, appearing at depths exceeding 10 m. It is not known whether they are stationary or do they move. Their geological build is uncertain. By concentrating hydrodynamic energy they generate additional local erosion of the coast, i.e. cause increased risk of sea-floods. Hydrotechnic structures on the Peninsula coast (groynes): Cause a change in longshore sediment transport within a narrow belt adjacent to the beach, and local restructuring of the bottom. Downstream of each groyne system appear systematically growing erosion bays. Action of groyne systems, especially in conditions of a nontidal sea and in longer term, is insufficiently investigated and is subjected to some reasonable doubts. Probably, with time groynes begin to have a negative, or at best zero, influence on coastal stability - also within the groyne systems. Climate change: Increase of frequency and strength of storms, longer periods of higher filling of the Baltic, sea level rise (according to IPCC- CZM up to 30 cm in 40 years and 110 cm in 100 years). In effect: a) Due to increased frequency and intensity of storms, processes transforming the coastal zone will be strengthened, i.e. the trend to move the coastline southward will increase. b) The risk of sea-flood along the first 20 km of the Peninsula will become higher; at year 2030 terrain below +1.8 m will become endangered, and by below +2.6 m. Pollution of the sea: Resulted in disappearance of sea plants, which once stabilized the foot of the active zone of sea bottom and dissipated some of the energy arriving at the coast. In effect the whole coastline is retreating, seeking a new equilibrium. Bayward side Storm surges in the bay, especially during winds from SW: In extreme cases water level at the Peninsula may exceed +1.0 m. Additionally, due to wave runup, water may reach cm higher. In effect there is a danger of flooding of areas below +1.4 m by overtopping waves; areas below +1.0 to +1.1 m are in danger of flooding due to groundwater level rise during high water levels in the Puck Bay. Pressure of ice on coast under wind action: Can result in cutting off of dykes, driving of ice sheets into the soil and damaging or destroying unprotected buildings and installations located too close to waterfront, local blocking or even damaging of the road. Climate change: Danger of flooding areas below: till m - due to wave runup, and +1.3 to due to periodical groundwater level rise; till m - due to wave runup, and +2.1 to m - due to periodical groundwater level rise. B. CONCEPT OF PROTECTION Seaward side Assuming that the Hel Peninsula is to exit in its present shape, and that its functions are to be 76

11 maintained, protection activities should fulfill the following objectives: Stop disadvantageous transformation of the coastline, i.e.: a) reconstruct longshore sediment transport, which became disrupted by Wladyslawowo breakwaters, b) rebuild the sand-bar system along the Peninsula, c) restore sea plants. Provide a system of protection against sea-floods in accordance with assumed safety standard (because of lacking legal regulations in this respect, a 100-year storm situation was assumed). Maintain and even enhance recreational value of beaches. In order to realize these objectives the following are necessary: a) By-pass system at Port of Wladyslawowo. The volume of by-passed sediments should be of the order of 200,000 to 300,000 m 3 annually. The system started operating in 1992, and should be operated as long as the port exists. b) Artificial beach nourishment of about 1 mln m 3 annually until The nourished sand is necessary to rebuild the sand-bar system and to build up the dunes and beaches to safety standard requirements. c) Along especially vulnerable stretches - hard revetments built into the dunes. Such a structure should be built, among others, along the first 2 km of the Peninsula. d) After maintenance nourishment. It is evaluated that annually this will amount to ca. 200,000 to 300,000 m 3. e) Reduction of coastal zone pollution in order to reintroduce marine vegetation. c) Protection of vulnerable objects and installation by revetments. C. FINAL REMARKS With developing climate change and sea level rise, parameters of the dunes and dykes should be appropriately increased. Therefore sufficient reserve areas must be set aside, and a program of protection system development must be worked out. Additionally, for the interior of the Peninsula: a) a concept of a drainage system of areas with terrain below +2.5 m must be worked out, and appropriate land reserves for such a system must be set aside; b) for the area of the Hel Peninsula special house, road, installation, etc. construction standards should be worked out and enforced, also regional development plans should be revised. Probably the main source of sand arriving from the west at the port Wladyslawowo profile is the area between the port and Cape Rozewie. In time the erosional nay, developing now between these two points, will arrive at some equilibrium shape. Supply of sediments to the by-pass system will diminish and then nearly stop, though energy supply to the Peninsula coastline will remain unchanged. By that time a significantly different protection system will have to be ready along the seaward coast of the Hel Peninsula. Finally, some remarks on the possibilities of reacting to the described processes - in terms of Coastal Zone Management and coastal protection are made. It is assumed that at least 80% of sand supplied within points a) and b) should in effect of wave and current action be taken away from the beach and help restore the Ist and IInd sand bar. Bayward side Protective measures should fulfill the following objectives: Protect living areas and roads against flooding. Protect living areas, roads, installations and dykes against ice action. The following are necessary: a) Dykes to +2 m along inhabited areas. b) Protection of waterward slope of dykes against ice action. 77

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