A gis based approach for flood risk mapping
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1) The national flood information system of Finland brings together essential flood information in a single GIS-based user interface, promoting flood risk assessment and response planning. 2) The EXTREFLOOD II project aims to develop flood risk mapping methods to make risk assessment more effective, including indicating potential adverse consequences of flooding under various probabilities. 3) Flood risk mapping in Finland utilizes flood hazard maps, land use data, building databases, and other datasets to assess numbers of people and economic assets potentially affected by flooding.
A gis based approach for flood risk mapping
- 1. Mikko Sane,Tanja Dubrovin, Mikko Huokuna firstname.lastname@environment.fi Finnish Environment Institute, P.O. Box 140, 00251 Helsinki, Finland www.environment.fi/syke www.environment.fi/floodmapping A GIS based approach for flood risk mapping – extending the national flood information system The national flood information system of Finland, estab- lished in 2006, brings together the essential information on EXTREFLOOD II floods under a single user interface. The system is based – the flood risk mapping pilot on GIS and Web technology and contains various types of flood information. It promotes flood risk assessment, flood- • EXTREFLOOD II research project aims to develop meth- proof land use planning, and rescue operation planning. ods, which enable more effective flood risk assessment in Evidently, it increases public awareness about flood risk Finland. and ensures that the experiential flood knowledge is trans- • One of the main objectives is to develop flood risk map- mitted for the younger generations. Interactivity with oth- ping as a part of the national flood information system. er information systems and GIS datasets eases the mainte- nance and provides a basis for further needs, such as de- • According to the flood directive (2007/60/EC) flood risk velopment of flood risk maps. maps should indicate potential adverse consequences of flooding under several probabilities as a minimum in terms of Flood information types in the ◦ indicative number of inhabitants potentially affected, present flood information system ◦ type of economic activity of the area potentially affected, Flood observations (water level and discharge) Point ◦ installation which might cause accidental pollution in case of flooding and Historic flood maps Polygon ◦ potentially affected protected areas. Point Simulated flood scenarios (water level and discharge) Polyline Flood Hazard Map Flood hazard maps Polygon ▲ An example of the user interface of the Flood Flood Risk Flood Risk Map Management Plan Information System. Polygon Flood Vulnerability Dam break flood hazard maps ◄ Types of flood information in the Flood Information System Point and formats of the information. The arrows denote the Minimum allowed building site levels processing of the information in flood mapping and flood Flood mapping provides a good foundation for efficient flood-risk Polygon management. management. Initial GI-data for • Flood hazard map ◦ a fundamental information for flood risk Examples of flood risk/vulnerability layers flood risk mapping mapping in Finland • SLICES - Separated Land Use/ Land Cover Information System ◦ more classes in the built up area than in the CORINE Land Cover • Building and apartment database (RHR) ◦ e. g. purpose of use and ◦ number of people living in apartment • Environmental database (VAHTI) ◦ activities which require an environmental permit license ◦ will or may cause environmental pollution or degradation ◦ e. g. IPPC-activities (Integrated pollution prevention and control directive 96/61/ EC) and ◦ water intake structures • Nature protection database ◦ e. g. Natura 2000 –areas related to the Water Framework Directive (EU-wide network of nature protection areas) Statistic as tables to the database for each flood scenario from each area HQ 1/250, HQ 1/250, • Other national databases, e.g. ground water protected area protected area 0-0.5 m 0-0.5 m 0.5-1 m 0.5-1 m sea level N60+0,40 m sea level N60+0,40 m 1m 1m areas (POVET), polluted soil (MATTI), - Areas (ha) of land use of - Number of buildings Total Total Flood hazard map of Pori (on general back- Flood Flood each SLICES land use type of each type (RHR) topographic database (e. g. electricity ground map). Flood hazard maps show the ar- Apartment house area 7 15 2 10 34 Detached houses 627 891 615 1 034 3 167 eas which could be flooded including the prob- network), beaches (EU) and cultural heritage Small-house area Holiday cottage area 95 141 11 23 96 13 164 0 497 47 Row houses Apartment houses 14 22 68 109 36 2 118 29 309 89 Sport and leisure facilities 23 40 56 20 140 Holiday cottages 79 239 51 1 370 ability of flooding and the degree of danger (in Commercial ja administrative units 7 6 1 12 25 Commercial, office and transport 45 55 33 84 217 Finland usually water depth). Usually produced • Local vulnerability information Industrial and depot units 17 11 4 19 51 Health care 3 5 1 0 9 Transport units 38 25 8 20 91 Sport and leisure 9 4 1 9 23 flood scenarios in Finland: 1/20a, 1/50a, 1/100a, ◦ all the information cannot be found Community management units Agricultural areas 6 452 9 871 6 921 6 27 101 2 345 Educational buildings Industrial buildings and depots 7 43 1 38 0 14 6 50 14 145 Forest areas 154 220 194 146 715 Fire and rescue services buildings 0 0 0 1 1 1/250a and 1/1000a. from the databases Total of each water depth zone 810 1 361 1 302 498 3 971 ha Agricultural buildings 7 6 1 5 19 Other buildings 197 263 194 331 985 - Number of inhabitants (RHR) 998 3 617 5 766 5 153 15 534 inhabitants Total of each water depth zone 1 053 1 606 1 021 1 668 5 348 buildings Town of Pori – the most significant flood risk area in Finland The town of Pori is located at the mouth of the Kokemäenjoki river in the southwest Fin- land. About 15 000 people is living in the flood prone area. The river is known for harm- ful winter floods. There used to be ice break up jams almost every spring in Pori, but the risk for spring ice jams decreased after the watershed regulation was started about 40 years ago. However, the climate change studies imply that winter discharges are going to increase significantly in the river. The available regulation capacity may be too small in order to decrease discharges and by this way to avoid the problems caused by frazil ice during the cold winter periods. ► Ice jam in the centre of Pori in January 1975. Large areas were flooded, caused a lot of dam- age for housing and industry, because of a partial ice break up after a warm and rainy winter period (Photo: Kari Syrjälä).