Aug 16, 2021 Finland

Hydrological corrections for all of Finland

  • New releases

As streams and rivers make their way through the landscape they pass through culverts and under bridges. These culverts and bridge-underpasses are not visible from above and hence they are not part of the Finnish elevation model that has been created through aerial surveys.

When analysing floods the absence of culverts and bridges cause significant inaccuracies in the computed flow paths and flood maps. Previously SCALGO Live users in Finland had to create hydrological corrections in workspaces - a cumbersome task especially when working with large areas.

To help our Finnish users we have recently completed a project to produce a set of so-called "hydrological corrections" that map culverts and bridges across all of Finland. Using these corrections in the SCALGO Live analysis engine we can more accurately model how water flows in rivers and streams thereby creating much more accurate flood maps.

To develop the hydrological corrections, we identified intersections between waterways and other structures such as, roads and railroads. Each correction follows a line in the river network from Maastotietokanta with end points adjusted to match flow paths in the elevation model.

Below we illustrate the effect of hydrological corrections through selected examples.

Flow paths

With the new hydrological corrections the flow paths in SCALGO Live can run under roads through culverts. This provides for significantly more realistic flow paths without having to first create the corrections in a workspace.

Roads and other structures in the elevation model disrupt flow paths but with hydrological corrections flow paths can run through culverts.

Flooded areas

The lack of hydrological corrections often creates artificially flooded areas in places where water naturally runs below a road but where the elevation model simply records the road as a barrier. Putting in the hydrological correction ensures that water can flow freely under the road and thereby removes the flooded area. Tip! Use the profile tool to have a closer look at how the culverts are placed in the terrain.

Artificially flooded areas are created in places where flow paths are cut off by roads. The hydrological corrections ensure that water can flow through culverts without artificially flooding the area behind the road.


Nationwide hydrological corrections make it easier than ever to instantly map accurate catchments and sub-catchments.

Watersheds that cross roads are instantly mapped using the watershed-tool in SCALGO Live.

Helena Åström,