CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of theEstonian Academy of Sciences.
Engineering
Volume 50 No. 2June 2001
Guest editorial;83–84
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Heiki KRANICH
Hydrodynamical andgeological investigations of possible deep harbour sites in north-westernSaaremaa Island: Overview and conclusions; 85–98
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Jüri ELKEN, JüriKASK, Tarmo KÕUTS, Uno LIIV, Rein PERENS, and Tarmo SOOMERE
Abstract. Saaremaa is the largestEstonian island located to the west of Estonian mainland. A new deep harbour, needfor which is stated in the Saaremaa County development plan, is possible onlyin the north-western part of the island that is environmentally sensitive andbelongs partly to the area of Vilsandi National Park. This part of the islandis known as wintering area of Steller’s Eider and the sanctuary for seals.Environmental impact assessment of the harbour site selection indicatedenvironmental risks at all the considered sites. Discussion of the assessmentresults led to additional hydrodynamical and geological investigations of thethree harbour location alternatives on the Tagamõisa Peninsula: Undva(Uudepanga Bay), Suuriku-Kuriku (entrance of Tagalaht Bay), and Vaigu (centralpart of Tagalaht Bay). The investigations contained geological and hydrographicfield work and modelling of currents and waves. The results revealed that dueto dominating cyclonic circulation and small current speeds in the UudepangaBay, the risk of oil pollution from the Undva harbour to nearby VilsandiNational Park is rather low. The risk of polluting Steller’s Eider winteringarea in the north from the harbour site is somewhat higher, but still small.Vaigu has a favourable wave regime, but the bedrock is covered by a sand layeramounting to 10 m thickness. The waves exceed critical value for sandmovement frequently, indicating the need for repeated dredging of shipchannels. In addition, contaminant dispersal from Vaigu has the worst pattern.Suuriku-Kuriku has been found the most suitable location for the deep harbour.The expected tough wave regime is not so critical because the high-wave winddirections are rather seldom. As a location of the deep harbour, Undva wasfound somewhat less favourable and Vaigu considerably less favourable.
Key words: Saaremaa Island,harbour, environmental impact assessment, geological setting, currents, waves,oil drift, sediment transport, hydrogeological conditions, modelling.
Comparison ofgeological settings at possible deep harbour sites, north-western SaaremaaIsland; 99–125
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Jüri KASK, Helle PERENS, Rein PERENS, Sten SUUROJA,and Andres KASK
Abstract. The investigationscarried out on Tagamõisa Peninsula (north-western Saaremaa Island, WestEstonian Archipelago) were aimed at finding the deep harbour site with mostfavourable hydrogeological and geological conditions. Three possible sites werestudied: Undva on the eastern coast of Uudepanga Bay, and Suuriku-Kuriku andVaigu on the western coast of the Tagalaht Bay. The investigations show that inspite of active shore processes between Suuriku and Kuriku cliffs, geologicaland hydrogeological conditions for establishing the deep harbour are somewhatmore favourable in this area than at Undva (dredging volumes as well as theamount of filling material needed for jetties and quays were not considered).At Undva dredging would be more work-consuming and to obtain fresh high qualitydrinking water is more complicated. Vaigu is less favourable because in theharbour basin area a thick layer of sand occurs on the seafloor.
Key words: deep harbour, Saaremaa Island, geologicalsetting, bathymetric surveying, soil properties, hydrogeological conditions.
Variability of currents in bays of Tagalaht and Uudepanga; 126–140
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Tarmo KÕUTS and Janek LAANEARU
Abstract. The variability of thehydrodynamical fields in the sea around the Tagamõisa Cape, the north-westerncoast of the Saaremaa Island, has been investigated from August to November 2000 measuring currents and stratification. The timeseries of the forcing parameters, such as the sea level, wind, and currents arepresented, and the primary relationships between them have been established.The horizontal fields and the progressive vector diagrams of the currents areconstructed. The measured currents in the Tagalaht Bay are significantlydependent on the forcing factors and reveal predominantly a two-layercharacter. During the dominating southern winds the surface flow to the north,which carries water out from the bay, is compensated by the undercurrent,causing in such a way intensive ventilation of the bay. The two-layershallow-water model was used to calculate the vertical structure of thecurrents by integrating the equation of motion through upper and lower layersand eliminating the local sea level forcing term. In the Uudepanga Bay thedominating southern winds cause anticlockwise circulation and the currentsreveal predominantly the one-layer structure.
Key words: Baltic Sea,Saaremaa, bay current circulation, wind forcing.
Modelling of coastalcirculation and oil drift at possible deep harbour sites, north-westernSaaremaa Island; 141–156
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Jüri ELKEN
Abstract. In a short-term projectrelated to the environmental impact assessment of the possible locations of adeep harbour in the north-western Saaremaa Island, Estonia, the oil driftprobability was investigated by applying Lagrangian particle tracking on thecurrents from the coastal circulation model. In a four-step nestedthree-dimensional circulation model, the coarsest grid covered the whole BalticSea area with a 4 mi grid step. One-way nesting with the use of spongelayers refined each subsequent grid by a factor of four, reaching on the finestgrid the 1/16 mi grid step. Due to unstratified conditions in the bays andto the need for computational efficiency, the Bryan–Cox–Killworth model was recodedfor barotropic conditions and implicit timestepping. Calibration run, usingforcing data from the local wind measurements that were near the coastcorrected by fetch dependent wind speed reduction, gave satisfactory agreementwith direct current observations. Using the calibrated model, time series ofthe current patterns were calculated for a 32 week period in 1991 using thegridded wind fields over the Baltic Sea. Further, the oil drift probability wascalculated by recollecting on the grid counter the number of particles reachinga specific grid point after 24 h of drift. If the harbour will be locatednear the Vilsandi National Park, then probability of oil spill drift to thecoasts of the protected territory is low. However, the risk of oil contaminationof the nearby wintering areas of globally endangered Steller’s Eider remains.The Suuriku-Kuriku site was found to be the most suitable harbour location withthe least consequences of oil spill drift.
Key words: coastal circulation,circulation model, oil spill, environmental impact assessment, Baltic Sea.
Wave regimes andanomalies off north-western Saaremaa Island; 157–173
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Tarmo SOOMERE
Abstract. Properties of thesaturated wave field in the neighbourhood of possible sites of the Saaremaadeep harbour during typical (about 15 m/s) and extreme (about 25 m/s)storms, forced by steady winds, are analysed on the basis of the wave modelWAM. The toughest wave regime is at Undva (Uudepanga Bay, probability ofoccurrence of waves exceeding 3 m is 1%), slightly better atSuuriku-Kuriku (0.6%) and the mildest at Vaigu (0.13%). Directionaldistribution of wave heights in typical and extreme storms is highlyanisotropic. The highest waves correspond to NNW storms. Remarkable wave heightanomalies may occur in the neighbourhood of the harbour sites. The anomaliesemerge only during very strong storms and may serve as a major navigationdanger.
Key words: wave modelling,local wave climate, surface waves, wave height anomalies.
Saaremaa deep harbour layout design and computer simulation of the waveclimate and sediment transport; 174–192
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Toomas LIIV and Uno LIIV
Abstract. The layouts for the threeproposed sites for the Saaremaa Island deep harbour were designed at CorsonConsulting. The layouts were designed on the basis of geological, hydrometeorological,and wave and current conditions. Emphasis was given to the impact of the futureharbour on nature. The layouts were used as the basis for wave and velocityfield calculations using program MIKE
21. Wave and velocitycharacteristics were determined for wind directions that are significant forthe harbour sites. SandCalc 2.0 was applied for calculation of wavegenerated shear stresses on the bottom of the seabed around the harbour sitestaking into account the local bed characteristics. The calculated shearstresses were used for the analysis of the sediment processes. The resultsindicate that Suuriku-Kuriku site is the most favourable site for the harbour.The proposed layout protects satisfactorily the harbour basin from most winddirections. The movement of the alluvial material into the harbour basin doesnot generate problems due to the characteristics of the seabed. Calculationshows that at Suuriku-Kuriku less dredging work is needed than at the other sites.
Key words: harbours, wave climate,sediment transport, MIKE 21.
