Sea Level Rise and Flood Risk Assessment in Itä-Uusimaa

Sea Level Change Affecting the Spatial Development of the Baltic Sea Region, Edited by Philipp Schmidt-Thom. Geological Survey of Finland, Special Paper 41, 95–106, 2006. SEA LEVEL RISE AND FLOOD RISK ASSESSMENT IN ITÄ-UUSIMAA by Heidi Virkki1, Hilkka Kallio2 & Oskari Orenius1 Virkki, H., Kallio, H. & Orenius, O. 2006. ��Sea Level Rise and Flood Risk Assessment in It-Uusimaa.�� Geological Survey of Finland, Special Paper 41, 95–106, 5 figures and 3 tables. The Vulnerability Assessment developed by the SEAREG project consists of an Impact Assessment of sea level rise and flood risk as well as assessing the Coping Capacity of stakeholders and institutions to withstand the future hazard. There are three different mean sea level surface height scenarios for the Baltic Sea up to the year 2100 released by the SEAREG project: high case, medium case (ensemble average) and low case scenario. In the case of It-Uusimaa, the corresponding measures are a sea level rise of 73-75 cm, sea level rise of 21-24 cm and sea level lowering of 24-26 cm. A Vulnerability Assessment was carried out in the It-Uusimaa region, situated on the Gulf of Finland, by interviewing local and regional experts from many different branches. The cities Porvoo and Loviisa represent a local perspective and special attention has been given to local land-use planning. Spatial planning plays an important role in mitigating the impacts of sea level rise and flooding. This has also been recognised on a national level in the report prepared by the Ministry of Agriculture and Forestry on extensive flooding in Finland. This report proposes seven actions on mitigation in case of extensive flooding that would improve and standardize flood control in the whole coun- try. The most central proposals for action aim to ensure a uniform risk level in preventing damage to housing from flooding. An important tool for regulating construction near shorelines is the building code, which in many cases sets a safety margin for building in municipalities. Although the guidance from planning is quite strong in It-Uusimaa and in Finland in general, uniform risk levels are required. Key words (GeoRef Thesaurus, AGI): It��-Uusimaa��, climate change, sea level rise, floods, impact assessment, Porvoo, Loviisa. 1�egional Council of Itä Uusimaa, Porvoo, Finland 2Geological Survey of Finland, Espoo E-mail: [email protected] 1 INTRODUCTION The region of It-Uusimaa lies on the coast Porvoo has about 46 000 inhabitants and Loviisa between Helsinki and St. Petersburg. The whole some 7400, which together constitute more than half region of It-Uusimaa features more than 3500 km of the region’s population. Porvoo and Loviisa are in of shoreline. It-Uusimaa consists of 10 municipali- many respects similar to each other. Both cities are ties, of which Porvoo and Loviisa are the only cities. culturally and historically valuable due to their well- 95 Geological Survey of Finland, Special Paper 41 Heidi Virkki, Hilkka Kallio & Oskari Orenius Fig. 1. Case study area locations of Porvoo and Loviisa. Source: H. Kallio. 96 Geological Survey of Finland, Special Paper 41 Sea Level Rise and Flood Risk Assessment in It-Uusimaa preserved old towns. Central parts of these cities lie in Research Institute does not perform official measur- the vicinity of the water, a river runs through Porvoo, ing in Porvoo. According to the Marine Research and Loviisa lies on the Loviisa bay. Porvoo is famous Institute’s statistics, the sea level in December 2003 for having Finland’s largest oil refinery and Loviisa was the tenth highest in Porvoo since 1928. (Marine for Finland’s first nuclear power plant. It-Uusimaa Research Institute 2004.) is Finland’s second most industrialised region on the Within the SEAREG project, the goal is to in- industrial gross national product scale. crease awareness and identify possible impacts and Since It-Uusimaa is located on the Gulf of Fin- hotspots in the region concerning sea level rise. In land, the sea is an important element for the region. Finland, the problem might be that people under- Central parts of both cities are flood prone even today. estimate the impacts of sea level rise because the In Loviisa, the flood of 1986 is still remembered for scenarios do not appear to be too serious. Still, in an the fact that the sea wall could not withstand the rising actual situation of storm or flood, even an increase seawater. The cellars and basements of houses located of tens of centimeters in the mean sea level may be close to the Laivasilta harbour area in Loviisa were significant. Therefore, it is crucial to get the local seriously damaged. After the flood of 1986, more stakeholders to consider the meaning of sea level rise attention has been paid to flooding in Loviisa and in the region of It-Uusimaa and identify possible lo- the dike has been heightened a few times. Also, in cal and regional adaptation measures. Furthermore, Porvoo floods are occurring annually. According to it is important to examine the overall relevance of the Marine Research Institute’s statistics since 1928, this hazard in the Finnish context. Contradictory in- the sea level was highest at 1.41 meters above mean formation and a long time scale makes sea level rise sea level in Porvoo. However, in January 2005 the an abstract and distant hazard in the eyes of many new sea level maximum values were observed along people. With the help of the SEAREG project, the the Gulf of Finland. In Porvoo and Loviisa, sea level stakeholders in the It-Uusimaa region have a chance height was measured at 1.70 meters above the mean to consider these matters through their own work and water level. These are only estimates since the Marine perspectives. 2 METHODOLOGY The Vulnerability Assessment in It-Uusimaa was Interviewed experts were chosen among those carried out following the Decision Support Frame who can influence the region’s ability to adapt to sea (DSF) developed by the SEAREG project (Schmidt- level rise. For example, spatial planners in Porvoo Thom P. & Peltonen 2006, this volume). Vulnerabil- and Loviisa, local water works, rescue department ity is determined by the potential of a community to and city functionaries are professionally connected react and withstand a disaster, for example its emer- to the subject. The Regional Environmental Centre of gency facilities and disaster organisation structure Uusimaa gives a regional aspect, as does the spatial like the Coping Capacity (Schmidt-Thom 2005). ��The planning chief of the Regional Council of It-Uusi- Vulnerability Assessment in It-Uusimaa was carried maa. As well, one private person in a potential risk out mainly by interviews. ��The qualitative approach area from each of the cities was interviewed. At the and theme interviews suited the meaning well since time the interviews were made, these private persons the topic is still quite new for many stakeholders. were also city councillors and thus aware of commu- Also, the development of the Vulnerability Assess- nal politics (see complete list of interviewees on page ment was easier due to direct feedback. The original 106). These experts represented a wide range of local idea was also to determine opinions of the decision knowledge from different branches. makers’ but only 1 of the 12 members of the Board Concepts defining Coping Capacity helped to guide of the Regional Council returned the questionnaire the conversation in interviews. The experts were also addressed to them. A questionnaire might have been asked to fill in the Finnish translation of the impact too difficult to answer because the subject is new and matrix, which was designed to estimate the effects of more consideration may have been required before sea level rise on different land�� use categories of the answering. The low response might also indicate the case study area. ��In some cases, for example, when regional decision makers’ interest towards the pos- the opinions between experts differed greatly, the sible sea level rise. 97 Geological Survey of Finland, Special Paper 41 Heidi Virkki, Hilkka Kallio & Oskari Orenius resulting value is based on the mode that is the most the City of Porvoo. The values in the impact matrix popular value (see Table 1 and 2). Consequently, the should not be compared as such, but taken as opinions impact matrix represents the general view of local of individual experts. The values of regional Coping experts. As one can notice later on, the City of Loviisa Capacity are based on the general view derived from received higher values in the impact matrix than several interviews. 3 RESUlts The two most important factors affecting the mean The air pressure, winds, the current inwards and sea level on the Finnish coast are the land uplift and outwards through the Danish Straits and the ice cover the global mean sea level rise. Both of these cause a cause short-term sea level variabilities in the Baltic long-term, trend-like change in sea level – the land up- Sea. The scenarios for short-term sea level variability lift a lowering one and the global mean sea level rise are of practical importance for coastal construction, a rising one (Johansson et al. 2002). There are three planning and safety estimation. In these cases, the different mean sea surface height scenarios for the 21st probabilities for occurrence of extremely high sea century released by the SEAREG project. In the case levels are often of special interest. In Loviisa, the of It-Uusimaa, the high scenario corresponds to a sea sea level rises approximately 50-80 cm on average level rise of 73-75 cm and the medium case scenario once a year and the maximum sea level height has a sea level rise of 21-24 cm.

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