Characterizing Flood Impact on Swiss Floodplains Using Interannual Time Series of Satellite Imagery

Abstract

Pressure on the biodiversity of ecosystems along many rivers is growing continuously due to the increasing number of hydropower facilities regulating downstream flow and sediment regimes. Despite a thorough understanding of the shortterm processes and interactions at this hydro-biosphere interface, long-term analyses of the impacts on floodplain dynamics are lacking. We used inter-annual Landsat 4, 5, 7 and 8 time series to analyze the effects of hydrological events on floodplain vegetation in four mountainous floodplains in the Swiss Alps. Using a spectral mixture analysis approach, we demonstrate that the floodplain vegetation dynamics of mountainous rivers can be recovered at a spatial resolution of 30 meters. Our results suggest that interactions between floods and floodplain vegetation are complex and not exclusively related to flood magnitude. Of the four reaches analyzed, only data gathered along the submountainous reach with a quasi-natural flow regime show a clear link between remotely sensed vegetation indices and floods. In addition, our 29-year time series shows a continuous upward trend in vegetation indices along the floodplains, strongest in the reaches affected by hydropower facilities. The approach presented in this study can be easily replicated in other mountain ranges by providing available flow data to verify the impact of hydropower on floodplain vegetation dynamics.

Long-Term Response of Floodplain Meadow Normalized Difference Vegetation Index to Hydro-Climate and Grazing Pressure: Tamir River Plains, Mongolia

“…Monitoring the establishment and recovery of vegetation in floodplains is essential for assessing the management needs of flow regimes and the success of restoration initiatives in river systems worldwide [35][36][37]. Empirical evidence about the differences in hydrologic and edaphic conditions along slopes, both geographically and temporally, is insufficient.…”

Detecting abrupt change in land cover in the eastern Hindu Kush region using Landsat time series (1988–2020)

“…Recent literature shows that Landsat time series have been used in studies on glacier dynamics, detecting glacial lakes, their expansion, and associated floods in different mountain regions such as HKH, Central Asia, and European Alps (Huang et al 2018;Ma et al 2021;Veh et al 2018;Yan et al 2018;Zheng et al 2019). In addition, changes in a forest in wetland areas of China were investigated, and flood impact on Swiss floodplains was also analyzed (Milani et al 2020;Wu et al 2020). However, we found that no studies are using Landsat time series to analyze abrupt changes in a dry mountain region, such as the eastern Hindu Kush.…”