6 / 2023-11-25 00:37:03

Effects of extreme flood events on river morphology and riparian vegetation

flooding,GEE,Satellite Imagery,River Morphology

In a global climate change scenario, flood hazards triggered by extreme rainfall events are now significantly increasing also in continental regions. Vegetation can have a particularly strong impact on the hydrodynamic process in river channels, where the channel beds are often occupied by plants. This study analyzed the influence of extreme flood events that happened at the beginning of May 2009 and in the middle of November 2014 in the Po River Basin (Italy) on river morphology and riparian vegetation. The investigation was made by comparing changes in the river channel using satellite imagery (Landsat 7 and MOD09GA.061) before and after the selected flood events. Moreover, the Normalized Difference Vegetation Index (NDVI) calculated via Google Earth Engine (GEE) was used as a metric to analyze the changes in the riparian vegetation, which ultimately can influence flood risk. The results showed that most of the vegetation in and around the river channel was destroyed by the floods and the channel had been widened, while the vegetation around and in the river channel was largely restored within half a month and one and a half monthly after the May and November events, respectively. Pointing out the vegetation feedback on floods, this study represents an initial step in evaluating how roughness in river channels varies with riparian vegetation, and how this vegetation influences the hydrodynamic processes during flooding events.