Aquifers formed in the wetland area around the closed lacustrine chalk mine at Mierzyno (northern Poland) are distinguished by a specific groundwater flow system, the main component of which is lateral flow and ascent seepage from the deep aquifer to the ground surface. In investigating the origin of the uncontrolled groundwater outflows and the phenomenon of progressing spring pools, field and laboratory work, as well as model studies of groundwater flow, allowed assessment of damage to the soil and aqueous environment. These occurred due to defective reclamation of post-mining areas, as a result of which the natural hydrodynamic balance in the groundwater was disturbed. Artesian pressure in the deep aquifer caused layer interruption at the boundary of the lacustrine chalk deposit. In consequence, strong uncontrolled outflow of groundwater occurred, and the accompanying spring pools are changing their position as a result of headward erosion. So far, the amount of washed-out carbonate sediment exceeds 5,600 m3.
Research by the Polish Geological Survey has been carried out along the southern Baltic coastal zone over a distance of 38 km. The Baltic Sea is classified as non-tidal, and its southern coasts are built entirely of weakly lithified sedimentary rocks. These deposits form three main types of coast, namely cliffs, barriers and alluvial coasts (wetlands), with the research focusing on the first two. Methods including remote sensing, mapping (geological, hydrogeological), offshore survey (bathymetric and geophysical measurements), laboratory analyses and modelling revealed a number of natural hazards. These are, respectively: (1) permanently occurring hazards, causing material damage such as: landslides, coastal erosion and seabed erosion; (2) incidental hazards such as dune breakage and storm surge overflow and (3) hypothetical threats that may occur in the future, such as hydrogeohazards defined here as flooding resulting from groundwater level rise or more rarely, earthquake threats.
W artykule przedstawiono sposób wykonania analizy ryzyka na potrzeby ustanowienia strefy ochronnej ujęć wód podziemnych w Gdańsku. Została ona wykonana na podstawie dodatków do dokumentacji hydrogeologicznych. Konieczne było przeprowadzenie prac terenowych, badań laboratoryjnych oraz modelowych. Na tej podstawie wytypowano główne czynniki zagrażające ujęciom wód podziemnych. Analiza ryzyka została opracowana z wykorzystaniem matryc oceny ryzyka, uwzględniających zależność prawdopodobieństwa wystąpienia zagrożenia od jego skutków.
EN
The article presents the method of risk assessment for the purpose of establishing a protection zone for underground water intakes in Gdańsk. It was made based on additions to hydrogeological documentations. It was necessary to carry out field works, laboratory tests and model tests. On this basis, the main factors threatening the groundwater intakes were selected. The risk analysis was developed using risk assessment matrices, taking into account the dependence of the likelihood of a threat on its effects.
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