Input from Finland, Sweden and Norway
Flood hazard mapping
Finland:
We suggest that flood hazard maps for national river basins should be made only for the areas which have damage potential and the need of them should be left to the Member States to decide. OK for Sw.
Norway: selection of rivers for mapping should be made with a risk approach. Current risk and expected risk in the future. See data below which clearly identifies that large part of the country is uninhabited. Further development will be in connection to the already inhabited areas. The cost of mapping all rivers would exceed by far the current cost of floods, which is some 15 - 20 mill euros per year in average.
Large areas of Finland are uninhabited: The average population density of 17 persons per sq km, the figure may be compared to the one of the Netherlands (about 460) or Germany (about 230). Many river reaches and lakes are more or less in their natural state and floods do not cause any damages. It is also not expected that those areas will be densely populated in the future. Similar for Norway: se population map below.
The discussion document for the Drafting Group meeting (as it is now) defines flood hazard mapping to be the only instrument which can be used to define if flood risk maps and flood risk management plans should be made for a certain area. It means that flood hazard maps should be done for all areas. In our case we would have to study all the uninhabited lake and marshland areas as well.
According to Finnish legislation the risk of flood or landslide shall be taken into account when building in shore areas. The local environment authorities give statements about the lowest allowed base heights, which corresponds to 100 - 200 years flood height. Because of those statements, numerous lakes and rivers have been studied. Therefore flood elevation information is available and useful, even if it is not presented as floodprone areas on maps. Building on flood areas can be controlled without the need to prepare flood maps for the whole catchment areas.
Is also the same in Sweden we have the Planning and building act where it says that the land used for buildings should be appriopriate for that concerning the people’s health, property and environment.
Similar for Norway: The Planning and Building Act states that natural hazard must be at an acceptable level. NVE has issued a guideline which defines “acceptable hazard” differentiated according to hazard (flood) type and type of asset. Through governmental control this is an effective instrument to control municipal planning.
There are also different other mechanisms which protect the undeveloped or less developed areas. Areas above the tree line will in general not be allowed for development. Large parts of the country are affected by a variety of Protection Plans: National Parks etc. Of particular interest is the Protection Plan towards further hydropower development. Within 100 m distance from the river, there are restrictions on development which may reduce the environmental values.
Finland facts
The map below, in which the Southern part of Finland is presented, gives an idea of the Finnish hydrology. Some 10 % of the inland area is covered by water. The number of lakes larger than 1 ha (10000 m2) is about 56 000. The total shoreline length of these lakes is about 130 000 km. If we include also the smaller lakes ( area > 500 m2) the total number of lakes is about 188 000 and the total length of the shoreline is about 215 000 km. The total length of all rivers in Finland is estimated to be around 20 000 km. Quite large part of Finland (about 30%) is marshland. When snow melts water is retained by marshland areas. However, no harm is caused by this natural "flooding".
Sweden facts
Area450 000 sq km
Coastline7 600 km
Max distance north-south 1 574 km
Max distances east west499 km
The country is sparsely populated. With about 9 million inhabitants,the average number of people per square kilometer is only 20 (slightly more than 50 per sq. mile). 1,7 million Swedes live in or around the capital of Stockholm. 50 % of the population are living in 3% of the total area.
Land use
Forests 54%
Mountains16%
Cultivated land 8%
Lakes and rivers 9%
Marshlands and mires~30 % some parts are forested
92 400 lakes that are larger than 0.01 km2
11 000 drainage basins within the country
5 new water districts and authorities were estab
lished during 2004.
Current flood mapping:
From 100000 km of river length, some 10000 km
are prioritised for mapping. This work started 1998
and to date some 6750 km are mapped.
Population and river systems.
The figure below shows the distribution of the population within the country and also shows some of the major river systems. Somewhat misleading due to the interval of population classes.
Map below show the amount of surface water within Sweden. The maps shows the watersupply in 1000 m2/person and year, 50-250 1000 m2/person and year in the darkblue area and 10-50 1000 m2/person and year in the light blue area.
Norway facts
Area: 324000 km2
Population: approx 4.5 mill
Average population density: 14.8 per km2
The map below shows the population density in squares of 1 km2. All white areas are unpopulated.
Land use:
Mountainous,
area above tree line: 44%
Forest: 38%
- “Productive forest”: 23 %
- “Unproductive forest”: 15 %
Glaciers, lakes and rivers: 7%
Marsh land: 6%
Farm land: 3%
Developed (buildings and roads): 1%
The map shows how land use is
distributed across the country:
Length of rivers.
From maps in scale 1: 1000000: 53000 km rivers.
The length of rivers will de different dependant upon what map scale is used.
The table below shows how this varies for 3 catchments. We see that river length from 1: 50000 maps is 3-4 times that from map scale 1: 1000000.
Map scale/Catchment / 1: 1 000 000 / 1:250 000 / 1:50 000
Glomma
(41971 km²) / 17120 km / 30655 km / 53182 km
Drammen
(17112 km²) / 7461 km / 15359 km / 26152 km
Skien
(10811 km²) / 5242 km / 10295 km / 19119 km
The map below shows Telemark county (see Norway population map for location). The drainage system has been taken of from map scale 1: 1 000000, densely populated areas (> 200 people and less than 50 meters between houses), and reaches which will be mapped through the ongoing national mapping program.
Current flood mapping:
The flood inundation mapping program was started 1998. In total 1100 km of rivers are prioritised for this very detailed mapping. To date approx 600 km has been mapped. The program will finish by 2007. A decision has not yet been made whether the mapping will be extended, in case with reduced level of detailing.
Flood plains in Norway are in general small. From the finished flood maps, we have identified the average width of the flooded area to be approx 300 m, i.e. 150 m on each side of the river. It should be noted that this covers the areas with the widest flood plains. As we move upstream and into smaller rivers, the floodplains will get much smaller.