The Preliminary Flood Risk Assessment in Tornionjoki- Muonionjoki River Basin
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In cooperation with: The preliminary flood risk assessment in Tornionjoki- Muonionjoki river basin Table of Contents 1 Background .....................................................................................................................................3 2 Description of the river basin district...........................................................................................5 2.1 Hydrology .................................................................................................................................7 2.2 Population and land use ........................................................................................................ 12 2.3 Land use planning ................................................................................................................. 15 2.4 Protected areas and cultural heritage ................................................................................... 17 2.5 Flood protection and the use of the river basin ..................................................................... 19 3 Floods in history .......................................................................................................................... 21 3.1 Observed floods .................................................................................................................... 21 3.2 Estimation of effects caused by observed floods in present situation ................................... 26 4 Possible floods in future and flood risks .................................................................................. 27 4.1 Effect of climate change ........................................................................................................ 27 4.2 Effect of other long time scaled development on flood risks ................................................. 28 5 Using GIS-data in flood risk estimation .................................................................................... 30 6 Identifying the flood risk areas .................................................................................................. 32 6.1 Empirical knowledge and earlier reports ............................................................................... 32 6.2 Flood risk to human health and security................................................................................ 32 6.3 Flood risk to essential services for community ...................................................................... 33 6.4 Flood risk to environment and to cultural heritage ................................................................ 34 6.5 Threat of flood caused by water structures ........................................................................... 35 7 Flood risk areas that were pointed out ..................................................................................... 37 8 Sources ........................................................................................................................................ 39 9 Annexes ........................................................................................................................................ 41 Annex 1. Hydrological information Annex 2. Protected areas and cultural heritage Annex 3. Summary in North Sámi The preliminary flood risk assessment in Tornionjoki-Muonionjoki river basin 2 1 Background Finnish Act for flood risk management (620/2010) and decree on flood risk management (659/2010) came into force in summer 2010. The purpose of the law is to decrease flood risks, to prevent and reduce harmful consequences caused by floods and promote the preparation for floods. Another pur- pose is to reconcile the flood risk management and other management of the river basin taking the sustainable use of water resources and the needs for environmental protection into account. Besides means of water management attention is especially paid to land use planning, building guidance and rescue services. The goal of flood risk management is to reduce harmful consequences to human health and safety. By the Act and Decree EU's Directive on Floods is implemented in Finland. The flood risk management consists of preliminary flood risk assessment, nomination of possible sig- nificant flood risk areas, preparation of flood hazard and flood risk maps and also preparation of flood risk management plans. In preliminary flood risk assessment (deadline 22.12.2011) areas, that may suffer major damages from flooding, are found out. To those possible significant flood risk areas flood hazard maps and flood risk maps (deadline 22.12.2013) and flood risk management plans (deadline 22.12.2015) are prepared. In flood hazard maps the extent and the water depth of flood are presented by using certain flood frequency. Flood risk map describes possible damages caused by a flood, those damages are for example the amount of inhabitants that suffer from consequences and sites that are harmful for environment. In flood risk management plans the actions that reduce the flood risks are presented. Concerning river floods the flood risk management plans are prepared for river basins where exist one or more possibly significant flood risk area. The preliminary flood risk assessment creates an important basis for flood risk management. In Fin- land the preliminary flood risk assessment of river basins and shore areas are taken care by Centres for Economic Development, Transport and the Environment (ELY-centre). Municipalities are responsi- ble for assessment of flood risks caused by storm water. According to the Act, the preliminary flood risk assessment is done by using available information about occurred floods and development of climate and hydrology; and also the climate change in future should be taken into account. In assess- ment information about occurred floods and possible floods in future and their harmful damages are gathered. The preliminary flood risk assessments are based on information that already exist, major new researches aren't done. The preliminary flood risk assessment is done by river basins and the assessment of flood risk from sea flooding is done by ELY-centres' operating regions. The ministry of agriculture and forestry accepts the significant flood risk areas in river basins and shore area by the proposal from ELY-centre. The goal of the preliminary flood risk assessment is in Finland to find the significant flood risk areas defined in the Finnish Act for flood risk management (620/2010) When estimating the significance of the flood risk area next mentioned from general point of view adverse possible consequences caused by flood are taken into account: 1) adverse consequence to human health or security 2) long-term interruption of essential services like water or energy distribution, telecommunica- tions, road traffic or other related services 3) long-term interruption of economical actions that secures the essential services of commu- nity 4) long-term or extensive adverse consequence to environment 5) irreparable adverse consequence to cultural heritage The preliminary flood risk assessment in Tornionjoki-Muonionjoki river basin 3 The decree1 that implements the flood directive in Sweden has come into force in October 2009. Ac- cording to decree the state authority that is responsible for preliminary flood risk assessment (PFRA) in MSB (Myndigheten för samhällsskydd och beredskap). PFRA in Sweden will be done by river basin districts. The structure of PFRA will probably be like in Finland, but not so detailed. Hearing in PFRA will not be arranged in Sweden. Besides PFRA, MSB will produce flood hazard maps. Provincial gov- ernments (Lännstyrelser) will prepare flood risk maps and flood risk management plans. 1 http://www.notisum.se/rnp/sls/sfs/20090956.pdf The preliminary flood risk assessment in Tornionjoki-Muonionjoki river basin 4 2 Description of the river basin district The Torne River basin district reaches from the coast of the Bothnian Bay to the top of the so called arm of Northern Lapland (Picture 1). On the Swedish side the Torne River basin is part of the Bottenvikens River basin district. The River basin district consists of two main rivers, Torne River flow- ing from Sweden and Muonio River flowing along the border between Sweden and Finland. Those two rivers connect each other approximately 10 km above Pajala. The total length of the river from Kilpisjärvi (MW 473 m) to the Bothnian Bay is approximately 520 km and from Torneträsk (MW 342 m) to the Bothnian Bay 180 km. The length of Torne River from Muonionjoki to the sea is 180 km and the total fall of height is 126 m. Before connecting Torne River the length of Muonionjoki is 230 km and the total fall of height within that distance is 205 m. Könkämäeno, the upper part of Muonionjoki, flows from Kilpisjärvi via the highland falling height 142 m within the river length of 90 km before connecting to Lätäseno. (Puro-Tahvanainen et al. 2001) River Tornionjoki-Muonionjoki is one of four big non-regulated rivers in Sweden and one of two big non-regulated rivers in Finland. Picture 1. Torne River basin district and national frontiers. There are 171 lakes, which area is over 50 ha, on the Finnish side and 250 lakes (area over 50 ha) on the Swedish side of the Tornionjoki-Muonionjoki river basin The biggest lakes are Miekojärvi, Kilpisjärvi, Iso-Vietonen, Raanujärvi, Jerisjärvi, Iso Lohijärvi and Äkäsjärvi on the Finnish side and Torneträsk, Råstojaure, Sautusjärvi, Rautasjaure and Puostijärvi on the Swedish side (See annex 1). Typical to lakes on the