Modeling arboreal vegetation-induced friction and its influence on river flooding using a two-dimensional model

Extensive research on vegetation flow resistance at the laboratory scale has yielded numerous formulations for determining vegetation friction coefficients. However, implementing and validating these equations at the river scale is often complex due to the lack of data on vegetation features and flow characteristics during floods, resulting in a limited number of field application studies. In this research, we use the Telemac-2D hydrodynamic model in a new case study to evaluate the performance of five vegetation friction formulations applied to arboreal vegetation. Employing vegetation data acquired through field surveys and LiDAR, along with flow data collected during one of the highest peak floods recorded on the Piave River, we built a two-dimensional (2D) river model. This model considers existing arboreal vegetation and terrain conditions to compare observed water surface elevations (WSE) during the flood with those simulated using vegetation friction equations. Our findings reveal that all tested equations perform similarly in all simulations. While these equations overestimated WSE throughout most of the flood, they accurately predicted levels at the highest peak and its proximity. Additionally, we explore several vegetation scenarios, varying density and percentage of area covered by arboreal vegetation, to assess their effect on water levels and flood risk.