The observed flood area is an area covered by water from a given flooding event, which is delimited by field observations (marking or filming the edge of the flood zone) or by remote sensing material (aerial photography (still/video recording) or satellite imagery). The flood boundary interpreted can be used to measure the heights of the water levels at a later stage. Satellite images can produce almost real-time observed flood areas.
Flood areas identified are available as flood-specific and interpretative layers. Several layers of maps may be available for the same flooding if it has interpreted flood areas from several satellite and aerial photographs. On the other hand, a flood limit may be available for some older floods, of which only one year is known. The spatial data set also includes the delimitation of the observed/interpreted area (e.g. area delimited by satellite or aerial imagery). In addition, a national compilation covering all territorial demarcations is available.
The material is part of SYKE’s open data (CC BY 4.0).
Description of the material:
Observed Flood (observed/interpreted/detected area):
HavTlv_id Item number/site number
Name Item Name/site name
Year of observation/observation year
Observation time Time of observation (date and time)
DigOrg Digitisation organisation/organisation where the Digitisation was done
DigPohja Digitisation scale or material from which interpretation is made/scale
ChangePvm Date where the item or related information has been modified/date, when the data has been changed or updated
Water-covered area of a given flooding, e.g.
HavTlv_19660503_9999_Vantaa_Aerial photography
HavTlv_id Item number
CovervCategory_id Coverage Class Class:
0 = dry land (not all)
1 = flooded area/flooded area
99 = water body/water body
—9 = data missing/no data
CapitavCategories Coverage class
DigOrg Digitising organisation
DigPohja Digitisation scale or material from which interpretation is made
ChangePvm Date where the object or related information has been edited
For more information:
https://www.ymparisto.fi/tulvakartat
http://www.ymparisto.fi/fi-FI/Vesi/Tulviin_varautuminen/Tulvariskien_hallinta/Tulvariskien_hallinnan_suunnittelu/Tulvakartoitus
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Brief in English
The historical flood maps dataset includes data on detected (observed) floods indicating areas that have been covered by observed floods in some point of time. The historic flood maps can also be produced near real time using satellite images. The observed flood covered area has been Outlined based on a field visits (marking or Photographing the border area of the flood on site) or outlining has been done using remote sensing data (aerial photographs or satellite images). The border data can later be combined with information on water levels on marked water level measuring stations.
Additional information and the flood map service:
https://www.environment.fi/floodmaps
The flood areas detected are delimited on the basis of field observations or aerial photographs/remote mapping material. The reliability and accuracy of the data shall be taken into account in the use of the flood areas identified. In general, the flood areas identified are not accurate enough for a building-specific examination.
The material can be viewed via the Flood Map Service (https://www.ymparisto.fi/tulvakartat). The path of material in the spatial information infrastructure of environmental management: \data\flood\observed. Available via the Flood interface.
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The historic flood map areas were Outlined based on field surveys or aerial photographs/remote sensing data. When using the dataset for planning or management purposes, the uncertainties in the source material, base material and its implications to the accuracy of the flood map need to be taken into account. As a rule the dataset does not have enough high accuracy to make any assumptions on individual buildings.
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