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.

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).