EP004-0006
Quantifiable effects of vegetation on river meander morphology and dynamics
Monday, 7 December 2020
Poster
Alvise Finotello, University of Venice, Department of Environmental Sciences, Informatics, and Statistics, Venice, Italy, Alessandro Ielpi, Laurentian University, Harquail School of Earth Sciences, Sudbury, ON, Canada, Eli Lazarus, University of Southampton, Geography & Environment, Southampton, United Kingdom, Massimiliano Ghinassi, University of Padua, Padua, Italy, Luca Carniello, University of Padua, Civil, Environmental and Architectural Engineering, Padua, Italy, Mathieu Gaetan Andre Lapotre, California Institute of Technology, Pasadena, CA, United States, Serena Favaro, University of Padova, Civil, Environmental, and Architectural Engineering, Padova, Italy and Andrea D'Alpaos, University of Padova, Department of Geosciences, Padova, Italy
Abstract:
Vegetation has long been thought to be a necessary condition for the development of river meanders, leading to the assumption that meandering channels could form only in vegetated landscapes. Flume experiments have also demonstrated that vegetation facilitates the transition from multi- to single-thread rivers, promoting relatively narrow and deep channels with low width-to-depth ratios. However, increasing emprical evidence and physics-based modelling indicate that meandering rivers can also develop in landscapes devoid of plant life, where other cohesive agents, such as mud, provide the bank strength required to sustain meandering planforms. Recent remote-sensing observations prompt unanswered questions regarding the role of vegetation in the morphodynamics of meandering rivers.
Here, we analyze the morphology and dynamics of a set of actively meandering rivers characterized by different density of riparian vegetation, using high-resolution measurements and multivariate statistical analyses of migration rates and meander form descriptors derived from aerial and satellite images.
Our analyses suggest that vegetation has a perhaps more subtle and complex influence on the morphodynamics of meandering rivers than previously thought. For vegetated rivers, we consistently observe reduced rates of channel migration along the length of actively migrating reaches; previous observations were limited to the apices of individual meanders. We also find that the absence of vegetation appears to limit the growth of tight and highly sinuous meander bends, thereby modifying the relation between width-adjusted migration rates and channel curvature typically observed in vegetated, freely meandering alluvial systems. This effect produces quantifiable differences in the aggregate morphological characteristics of vegetated and unvegetated meandering rivers, opening new avenues for the effective classification of paleo-vegetation density from fluvial planforms and the prediction of meander dynamical behaviors from remote sensing.
