The Blue spot model - development of a screening method to assess flood risk on highways

A method to assess flood risk on Danish national roads in a large area in the middle and southern part of Jutland, Denmark, was developed for the Danish Road Directorate. Flood risk has gained renewed focus due to the climate changes in recent years and extreme rain events are expected to become more frequent in the future. The assessment was primarily based on a digital terrain model (DTM) covering 7500 square kilometers in a 1.6 x 1.6 m grid. The high-resolution terrain model was chosen in order to get an accurate estimation of the potential flooding in the road area and in the immediate vicinity, but that means a high requirement of the methods, hardware and software applied. The outcome of the analysis was detailed maps (as GIS layers) illustrating the location of depressions with depths, surface area and volume data for each depression. Furthermore, preferential flow paths, catchment boundaries and ranking of each depression were calculated. The ranking was based on volume of depressions compared with upstream catchment and a sensitivity analysis of the runoff coefficient. Finally, a method for assessing flood risk at a more advanced level (hydrodynamic simulation of surface and drainage) was developed and used on a specific blue spot as an example. The case study shows that upstream catchment, depressions, drainage systems, and use of hydrodynamic calculations have a great influence on the result. The upstream catchment can contribute greatly to flooding.


  • English

Media Info

  • Media Type: Web
  • Features: Appendices; Figures; Illustrations; Maps; References; Tables;
  • Pagination: 40
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 01486606
  • Record Type: Publication
  • Source Agency: Danish Road Directorate
  • ISBN: 9788792094667
  • Files: ITRD
  • Created Date: Jul 11 2013 8:20AM