Abstract
LiDAR data has revolutionized the availability of digital elevation models, basis to generate flood inundations. Red LiDAR is the common methodology for scanning terrain, but for hydraulic applications, it cannot penetrate water and thereby lacks river bathymetry. Therefore, using the Red LiDAR terrain for producing flood inundation maps will be accompanied by misleading results. On the other hand, Green LiDAR can penetrate water and provide detailed bathymetry. This study has used the 2D-hydraulic flood simulation; to compare the performances of both LiDAR data in 11 sites in Norway with good available data. Investigations of the associated geomorphological features of the sites were carried out to link the differences in inundations to terrain parameters. It is found that the inundation error continuously decreases as the flood return period decreases in reaches where few flood protection embankments are present. On the other hand, in reaches where substantial flood embankments are built, the error increases until the flood levels overtop the embankments before it returns to a decreasing trend. Moreover, the level of the inundation error was found to be positively correlated with the percentage of the protection coverage and negatively correlated with the bank's slopes. A correction was implemented by subtracting the discharge at the time of the Red LiDAR flight from the flood discharges, and we found this to be difficult in rivers with flood protection works. It is recommended that the use of the Red LiDAR terrains for flood inundation estimations for flat bank reaches subjected to significant flood protection should be cautious. More caution should be provided the larger the extent of the flood protection works that exist in the reach.
