Vegetation destruction during an extreme flood: Multilevel modelling of an entire river in southern Korea

Abstract

Human‐induced climate change causes extreme weather events, and flooding induced by heavy rainfall in the riparian system is no exception. The southern Korean Peninsula witnessed record‐breaking rainfall during the summer of 2020, resulting in an extreme flood event that caused extensive damage to the riparian ecosystem along the Seomjin River. This study was aimed at identifying the composite factors of riparian vegetation destruction along the entire river. Based on a spatially explicit multilevel approach, it was found that large‐scale geomorphic characteristics (i.e., alternation of plain and valley topographies) appeared to be essential determinants of hydraulic characteristics of the channel (e.g., shear stress and specific energy), which were the leading causes of vegetation destruction. Moreover, at small spatial scales, several trees situated upstream of a vegetation patch protected other plants on the patch from the direct hydraulic impact of the flood, thereby serving as ‘shield’ trees. These findings indicate that scale‐dependent fluvial biogeomorphic processes take place during extreme flood events; hence, identifying the optimal scales of these processes and associated factors could help in further understanding riparian hydrology from a biogeomorphic point of view. This study suggests that hydrologists consider both geomorphological and ecological factors when studying hydrological processes.