This article describe Polish coastal dunes and the factors influencing their development. The Polish coast is 500 km long and mainly exposed for a northerly direction. It is a part of the southern Baltic shore. The Polish coast is composed of mostly loose sand, till and peat. Because the coast hardiness is so weak, it is under constant threat from storm surges as well as human impact caused by rapid infrastructure development and the coastal protection measures put in place to try and protect it. These protection measures destabilize the natural coast dynamics and rebuilding process. Almost 85% of the shoreline is built up by sandy aeolian deposits and covered by different dune types. Among them are typical foredunes or inland dunes in eroded coastal areas. The second type of dune coasts are built up by land dunes, which appear on the coast as a result of sea erosion causing land regression. Sometimes dunes can be found over moraine deposits or in front of moraine old cliffs. Nowadays these habitats are heavily threatened by storm surges and human activity. In some places there is an accumulation that leads to new ridge developments. This article describes these issues with an emphasis on the present dynamics of Poland's coastal areas.
The article summarises results of studies conducted along the Baltic Sea sandy coasts by scientists involved in coastal dune research, and presents an attempt to describe the types and distribution of dune coasts. The Baltic Sea coasts feature lower and higher foredunes. The lowland behind the coastal dune belt is covered by wandering or stabilised inland dunes – transgressive forms, mainly parabolic or barchans. The source of sediment for dune development includes fluvioglacial sands from eroded coasts, river-discharged sand, and older eroded dunes. Due to the ongoing erosion and coastal retreat, many dunes have been eroded, and some are withdrawing onto the adjacent land. There are visible differences between the south-eastern, western, and northern parts of the Baltic Sea coast with respect to dune development. The entire southern and eastern coast abounds in sand, so the coastal dunes are large, formerly or currently wandering formations. The only shifting dunes are found at the Polish and the Russian–Lithuanian coasts on the Łebsko Lake Sandbar as well as on the Vistula and Curonian Spits. The very diverse shoreline of the south-western coast experiences a scarcity of larger sandy formations. Substantial parts of the Baltic Sea sandy coasts have been eroded or transformed by humans. The northern part of the Baltic Sea coast features mainly narrow and low sandy coasts (e.g. in Estonia). Further north, sandy dunes are virtually absent.
TheŚwina Gate Sandbar (southern Baltic Sea) is affected by storm surges caused by passages of deep low-pressure systems over the Baltic Sea. The storm surge of 22-25 November 2004, with a maximum sea level of 1.35 m above mean sea level (MSL) as measured at theŚwinoujście gauging station, was one of the most severe storm events in 1993-2007. It produced changes in the coastal relief by inducing significant erosion of the dune shore in the western and eastern subsections of the sandbar area examined. Seawater flooded the beach and flowed over the low ridges, up to 3 m above MSL. As a result, all relief forms below the 3 m level were eroded, and the dunes retreated by an average of 2 to 6 m. The maximum amount of sediment that eroded away amounted to 22 m 3 per 1 m of coastline. This study showed that the magnitude of coastal erosion and retreat is dependent both on the height and the duration of the sea surge.
Climate change is having an undeniable influence on coastal areas. This chapter describes the growing threat of climate change on the Baltic Sea coastline, with an emphasis on field research focused on storm surges and coastal retreat. The main climatic factors driving change in the Baltic Sea coastal zone are wind, waves, storm surges, ice jams and flooding. The cumulative effects of these drivers are also important. For example, a costly coastal protection scheme in one area may result in coastal erosion in another. Natural and man-made coastal features are experiencing unprecedented change; important natural habitats, coastal settlements and local economies are all being affected. The extent of storm surge impacts depends on the exposure of a shoreline to a surge event. The submergent and soft coastal relief of the southern Baltic Sea area is under most threat; the rate of retreat depending on the frequency and strength of the storm surges. The rate of coastal retreat has also increased in recent years due to sealevel rise and loss of beaches. KeywordsCoast erosion Á Threats for coast Á Coast type response for climate change IntroductionThe coastal zone is one of the most dynamic environments in the world, because it is where different geospheres interact. Taking place over a range of timescales, these interactions cause dynamic coastal rebuilding, referred to coastal morphodynamics. The factors responsible for change in the coastal zone may be grouped into geological and geomorphological, hydrodynamic, biological, climatic and anthropogenic factors. The main geological factors-sediment type, arrangement and resistance of sediment structures, and isostasy-are the basis of the morphological processes and the development of coastal relief. Geomorphological processes are influenced by many external forces, including climatic factors such as precipitation rain and wind. They are responsible for the development of typical relief forms and sediment supply. Biological factors mainly concern the influence of plants and are responsible for the development of particular coastal types. Anthropogenic factors refer to many human activities taking place within the coastal zone: settlements, industrial development, agriculture, deforestation and coastal protection. The coastal system is a dynamic complex of sensitive factors and typically responds in a nonlinear morphological manner (Dronkers 2005). The wide range of natural and human influences on the Baltic Sea coastline makes it difficult to identify the specific effects of climate change. Exposure to wind is a key factor for coastal development. Climatic conditions greatly influence the inflow of material to the coastal zone, by determining the amount and origin of terrigenic material supplied to the coastal zone as well as the amount of biogenic material produced and supplied to the sediments. The combination of sea-level rise, land subsidence and isostatic rebound creates both emergent and submergent coasts. Emergent coasts are identifiable by accumulative
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