Satellite-observed flood indicators are related to riparian vegetation communities

Abstract

In riverine ecosystems, flood disturbances govern the distribution and assembly of vegetation communities. However, anticipated connections between disturbance regimes and habitats often cannot be numerically described as the quantification of disturbances remains challenging. This work presents a novel approach to numerically characterize disturbance patterns in a spatially and temporally explicit way. For this, a dense time series of flood extents was created applying a semi-automated water detection approach to multispectral optical satellite data (Landsat 4, 5, 7, and 8; Sentinel-2) to an 8-km stretch of the alpine Lech River in Tirol, Austria. Twelve multitemporal metrics referred to as Flood Indicators (FIs) were derived and compared to habitat classes formed by vegetation communities as observed in field campaigns in July 2020 and 2021.The FI values indicated high disturbance intensities for areas with early successional habitat classes, whereas little to no disturbance were related to late successional classes. This is in accordance with the presumed successional pathway of riverine vegetation communities. We observed numerous significant differences in FI values among early successional classes, supporting the assumption that flood disturbance is a dominant factor shaping the corresponding habitats. In late successional stages, the FI values differed less among the vegetation classes, pointing that other processes are more important in shaping the vegetation community in these stages.The observed relationship between vegetation communities and the satellite-derived disturbance measures underlines the potential of the presented approach to characterize riverine disturbance regimes. Given the global availability of satellite data, the approach should be easily transferable to other study areas.

Keywords

• Time series
• Flood regime
• Disturbance
• Remote sensing
• Braided river
• Biogeomorphic succession