R. Rivis

Natural Development and Human Activities on Saaremaa Island (Estonia) in the Context of Climate Change and Integrated Coastal Zone Management

The coastal zone is a crucial environment that is experiencing pressure from a wide variety of different agents and interests. Many sandy beaches high in recreation value are suffering from increasing erosion, and the shoreline is receding in these areas despite of tectonic land uplift. Sediment deficit is evident in many places. One key problem in recent decades has been a rapid increase in the number of holiday houses built as close as possible to the seashore. Unlike in the Nordic countries, where major coastal settlement expansion took place after WWII, almost the entire coast of Estonia was, until 1991, proclaimed a Soviet border zone in which activities were strongly restricted. A revival in coastal land use and a rapid increase in coastal settlement have occurred over the last 15–20 years. This paper focuses on Climate Change impacts, natural and artificial changes on the coast of Saaremaa Island associated with increasing pressure and conflicting interests. We also examine the advantages and disadvantages of existing legislation regulating land use within the Estonian coastal zone in the context of integrated coastal zone management. The paper ends with an outlook.

Changes on coasts of western Estonia and Russian Gulf of Finland, caused by extreme storm Berit in November 2011

The study is analyzing the meteorological parameters, hydrodynamic conditions and coastal changes caused by extreme storm known as Berit, which travelled across the Baltic Sea from 27th to 29th of November in 2011. Wind speed on West Estonian islands reached to 19,7 m/s (gusts 29 m/s), 20,4 m/s on the northern coast (gusts 27 m/s) and 15 m/s (gusts 20 m/s) on the Russian Gulf of Finland coast. Sea level at Pärnu reached to 110 cm, 142 cm at Narva-Jõesuu and +190 cm near St Petersburg (outside from the Flood Protection Facility). Shorelines, scarp positions and beach profiles were measured at the end of summer in several sites along Estonian coast and Russian Gulf of Finland coast. Two researchers spent the whole duration of the storm in Harilaid Peninsula and recorded changes in shoreline, scarp positions and beach profiles. Wave run-up and sea-levels were also recorded. All the measurements were carried out using DGPS with the accuracy of 1 cm in vertical and horizontal scale. Russian study site was measured a few days after the storm. In order to assess variations in forcing conditions during the storm a wave hindcast was performed using a SMB-type wave model. Calibrated against the field measurements, the model is forced by wind data, and it calculates significant wave parameters for a chosen location. Significant wave height 1.5 km off the Kelba study site was 2.8 m and maximum waves reached to 4.4 m. The first results indicate that 1.5 m high sandy scarp in Cape Kiipsaare receded up to 4 m. The loss of sand was ca 6 m3 per 1 m of shoreline. The speed of recession was around 0.6 m/h during the peak of the storm. The length of gravel-pebble spit at Kelba increased and new gravel ridges in the proximal part reached to 2.8 m. In the Russian part of the eastern Gulf of Finland as a result of storm and flood the scarp up to 2 m high was formed along 15 km of dunes of the northern coast (Komarovo, Repino). It was the first strong erosion event observed after extreme dunes damage during autumn 2006-winter 2007.

Field experiments with different fractions of painted sediments to study material transport in three coastal sites in Estonia

ABSTRACT Tõnisson, H., Suursaar, Ü., Kont, A., Orviku, K., Rivis, R., Szava-Kovats, R. Vilumaa, K., Aarna, T., Eelsalu, M., Pindsoo, K., Palginõmm, V., Ratas, U. 2014. Field experiments with different fractions of painted sediments for studying material transport in three coastal study sites in Estonia. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 229–234, ISSN 0749-0208. Our current understanding of the morphodynamics in swash and surf zones is limited due to their turbulent and irregular nature. The importance of this zone to sediment transport led us to perform a sophisticated field experiment using painted sediments. Sediments collected locally from beach ridges were sorted into the following diameters: 1–2 5 cm, 2.5–5 cm and 5–10 cm. The sediments were painted, amassed in piles and placed at 0.5–10 m depths in three sites near the Estonian coast. The locations were recorded with GPS devices and photographed. The sediment piles placed in the sea were monitored at least once after an intense storm or once before and after the storm season. Some sediments were placed on the shoreline and monitored daily for a shorter period. Hydrodynamic parameters were also measured or hindcasted during the experiment. We found that wave breaking during storms can take place even at 6 m depth, but mostly between 2–4 m depth. Sediment fractions between 1–10 cm diameters can be transported over 20 m towards the shore. Even sediment piles at 10 m depth were moved 2–4 m, but towards the open sea. Sediments accumulated on the shoreline moved up to 3 m/hour along the shore and approximately 350 m during three months. We also found that calm periods can be more influential in places where regular vessel-generated waves wash the shores. As vessel-generated waves often approach from a different angle than natural waves, they can cause notable erosion during the periods when natural waves are weak or absent.

Relationship between coastline changes and dynamics of coastal ecosystems of Tahkuna Peninsula, Estonia

The coastal zone as a boundary between sea and mainland is characterized by different landscape types with high biodiversity. Global climate change is one of the most significant factors that is causing changes on coastal area. The climate warming during the last decades has been evident in the Baltic Sea region. The effects of climate change on seacoast can be seen in the changes of sea level, coastal hydrodynamics and ice conditions as well as in human actions. On regional and local level the change of coastal landscape generally depends on shoreline stability. Most vulnerable to erosion are densely populated coastal areas with cities. The coastal erosion is an increasing problem, it also causes reducing and damaging coastal communities including habitats of NATURA 2000. During the last decades, the coastline and morphology of sandy beaches have noticeably changed at Tahkuna Peninsula. Different methods have been used for landscape investigation. Landscape changes were studied by using maps of different periods and analysed with computer programs. Method of landscape complex profile was used as a basis for research. The aim of the study was to find relationships between coastline changes and dynamics of coastal ecosystems. Due to the intensive erosion the study area with habitats of sandy beaches (1210, 1640), embryonic, white, grey dunes (2110, 2120, 2130) has decreased. Repeated surveys in the eastern part of peninsula (Tõrvanina) show the disappearance of a 45-m-wide strip of land during 1976-1998. The eroded deposits are partly transported to the south where the sandy spit is rapidly elongating, there takes place development of new plant communities. Changes along the coast are result of combination of natural processes and human influence (Lehtma harbour). The study area has a high nature conservation and recreational value. Therefore it is essential to continue monitoring and to improve the planning processes in these vulnerable areas.

Waves, currents and their relationships with coastal processes near Kelba Spit (Saaremaa Island) on the basis of RDCP measurements

A 5-month long record on currents, waves and other hydrological variables was obtained by means of Recording Doppler Current Profilers (RDCP) 1.5 km off the Kelba spit of Saaremaa Island over a period from December 2006 to May 2007. A parallel study of coastal changes was based on orthophotos and the measurements of beach ridges, as well as on the GPS measurements made in 2005, 2006 and 2007 to identify changes in the shoreline and scarp contours and positions. The results suggest that the major changes in coastline at Harilaid Peninsula occur mainly during infrequent but strong storms, e.g. such as the January storm (Gudrun) in 2005. During the measurement period, a strong storm event occurred, too. At Vilsandi station, the maximum wind speed reached 23 m/s (gusts up to 33 m/s) on 15 January 2007 and the maximum sea level at Ristna tide gauge reached 171 cm. The RDCP mooring site fell into accumulation zone, where downward fluxes dominated and fine sand settled. The currents at the RDCP location were not large, but the significant wave height reached 3.2 m in the 14 m deep mooring site and the maximum wave height was 4.6 m. It appeared that in Estonian coastal waters, the Doppler-based vertical velocity measurements reflect the site-dependent equilibrium between resuspension and sedimentation. The GPS measurements taken between summers 2005, 2006 and 2007 show that the tip of the Kelba spit has shifted from north back to north-east. As a result of the single storm, the distal part of the spit has advanced by 50-60 m and its area has increased by 4500 m2. At Cape Kiipsaare, as it also has happened during previous large storms, a clear retreat of the shoreline in the western, north-western (30-50 meters), and north-eastern parts has occurred.

Regional variation in the dynamics of Estonia's coastal landscapes

ABSTRACT Ratas, U., Rivis, R., Kont, A., Tõnisson, H., Vilumaa, K., Anderson, A., Szava-Kovats, R.,2014. Regional variation in the dynamics of Estonias coastal landscapes. In: Green, A.N. and Cooper, J.A.G. (eds.), Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 139–144, ISSN 0749-0208. The coastal landscapes of Estonia are young (less than 10,000 years old). Their development is affected by the Baltic Sea, by pre-existing geomorphology and by regional tectonic uplift. Since emerging from the sea ~5,000 years ago, the coastal landscapes have been evolving under regressive sea conditions. The landscape diversity is greatest on coasts with variable topographies and those exposed to wind and waves. Low and flat parts of the coast, which are seasonally inundated, exhibit less variable landscapes. Landscape changes in coastal areas no longer affected directly by the sea have been caused largely by human activity. Abrupt socio-political and economic changes over the last century led to a cessation of traditional land use during the Soviet era with urban sprawl and expansion of recreation areas after re-independence in the beginning of the 1990s. The aim of this paper is to analyze the structure, formation conditions, and the velocity and extent of change in coastal landscapes (for both natural and human-induced impacts) along different coastal regions of Estonia. The Estonian coast can be divided into four distinct regions: 1) Gulf of Finland; 2) Baltic Proper; 3) Gulf of Livonia and 4) Coast of Väinameri, making it possible to compare the influence of sea exposure, geological structure, vegetation, soil productivity, age of human settlements and character of land use on the development of coastal landscapes. The results of the current study are applicable to coastal conservation, to the development of sustainable coastal land use and to the facilitation of transnational tourism.

Analysis of shore changes between August 2008 and August 2009 and their relationship to hydrodynamic conditions on Kelba Spit, Saaremaa Island, Estonia

The study is focused on a gravel-pebble spit in Kelba. It is a dynamic region in the magnitude and velocity of hydrodynamic and shore processes, where historical changes in shoreline position reflect the changes in wind and wave climate. The region has probably the roughest wave climate along the Estonian coast. In order to assess the changes in shoreline and configuration of shore formations, the study sites in Saaremaa have been regularly examined since the 1960s. The study of coastal changes was based on orthophotos and GPS measurements. Sonar and leveling surveys were carried out in 2008 and 2009 to assess changes in the volume of deposits. Recording Doppler Current Profiler was deployed near Kelba Spit from December 2006 to May 2007 to measure hydrodynamic variables. In order to assess variations in forcing conditions during the study period (2008-2009) a wave hindcast was performed using a SMB-type wave model for Kelba. Calibrated against the field measurements, the model is forced by wind data from Vilsandi station, and it calculates significant wave parameters for a chosen location. The sea level data from Ristna mareograph was also used. Changes in the area of the study site reached 7800 m2 during that period. Erosion made up nearly 2/3 of the changes. Accumulation in volume reached 9200 m3 while loss of the sediments was only 6100 m3. 95% of accumulation took place in the distal part of the spit while 60% of erosion appeared in the proximal part. The year of 2008 started with stormy, ice-free conditions. Although there were no remarkable single storms or storm surges, the wave activity on average was among the strongest over the last two decades. The shore changes were faster than the annual average of the last decade showing that rapid shore changes may happen even without extreme storm events.