Flood mapping using LIDAR DEM. Limitations of the 1-D modeling highlighted by the 2-D approach

Nowadays, the use of 2-D fully dynamic models represents the most reliable approach for flood inundation and flood hazard studies, especially in complex applications. However, 1-D modeling is still a widely used approach due to the reduced computational time and cost. The introduction of LIDAR technique has stimulated a more detailed topographic description of river reaches. As a result, this huge amount of topographic data can lead to significant improvements in the 1-D computations. Therefore, the main purpose of this paper is to realize how the improvements in the topographic description can reduce the difference between 1-D and 2-D models, highlighting at the same time the critical aspects and the limitations of 1-D approach in the hydraulic simulation as well as in the spatial representation of the results. The analysis presented in the paper refers to two actual case studies for which terrestrial and airborne LIDAR DEMs were collected on purpose. The results of those applications show that the use of 1-D models requires a greater hydraulic skilfulness than the use of 2-D model.