Consequence of DTM Precision for Flood Hazard Mapping: A Case Study in SW Finland

Authors

• Petteri Alho
• Hannu Hyyppä
• Juha Hyyppä

Keywords:

Flood mapping, DTM, LiDAR, Finland

Abstract

Spatial information on floods, which includes inundation maps and estimations of flood damage are essential tools for the creation of effective plans for both flood protection and mitigation. In flood modelling, the accuracy of the model geometry used has a remarkable impact upon flood mapping. Therefore, in this study, flood hazard mapping was undertaken with two existing DTM (digital terrain model) products and a high-precision LiDAR-based DTM. Their characteristics were evaluated with respect to flood hazard mapping. An accuracy assessment of these digital terrain models and their applicability for one-dimensional flood inundation mapping clearly showed that LiDAR DTM topography was the most applicable. Although the 10×10 m DTM from the Finnish National Land Survey could be utilised to show where flooding might occur for very coarse flood mapping surveys, these were not suitable for more exact estimations of flood boundaries. Nevertheless, some inaccuracies in riverbank topography were also found using the LiDAR-DTM. Hence, to study detailed hydrological processes such as short-term channel dynamics, this particular DTM could be further improved by additional data.