Modeling vegetation controls on fluvial morphological trajectories

Walter Bertoldi1, Annunziato Siviglia2, Stefano Tettamanti1, Marco Toffolon1, David Vetsch2, and Simona Francalanci3
1Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy, 2Laboratory of Hydraulics, Hydrology and Glaciology VAW, ETH Zurich, Zurich,Switzerland, 3CERAFRI Center of Research and Advanced Education for Hydrogeological Risk Prevention, Retignano di Stazzema, Italy

Abstract

The role of riparian vegetation in shaping river morphology is widely recognized. The interaction between vegetation growth and riverbed evolution is characterized by complex nonlinear feedbacks, which hinder direct estimates of the role of key elements on the morphological evolutionary trajectories of gravel bed rivers. Adopting a simple theoretical framework, we develop a numerical model which couples hydromorphodynamics with biomass dynamics. We perform a sensitivity analysis considering several parameters as flood intensity, type of vegetation, and groundwater level. We find that the inclusion of vegetation determines a threshold behavior, identifying two possible equilibrium configurations: unvegetated versus vegetated bars. Stable vegetation patterns can establish only under specific conditions, which depend on the different environmental and species-related characteristics. Froma management point of view, model results show that relatively small changes in water availability or species composition may determine a sudden shift between dynamic unvegetated conditions to more stable, vegetated rivers.

 

Article first published online: 21 OCT 2014 on Geophysical Research Letters

Url: http://dx.doi.org/10.1002/2014GL061666