Limiting the development of riparian vegetation in the Isère River: A physical modelling study

Nicolas Claude,Clément Leroux,Marion Duclercq,Kamal El Kadi Abderrezzak,Pablo Tassi,A Paquier,N Rivière

doi:10.1051/e3sconf/20184002015

Abstract

Physical modelling experiments are conducted to investigate if a modification of the Isère River (French Alps) hydrology by changing dams management is able to foster riverbed morphodynamic and, thus limiting riparian plant development. The experimental setup is a 1:35 scale, undistorted movable bed designed to ensure the Froude number similarity and initial conditions for sediment particle motion. The physical model is 35 m long, 2.6 m wide, with a sand mixture composed of three grain size classes. Two runs with different flow and bed load conditions are simulated. Preliminary results show an intense riverbed activity when the system reaches a dynamic equilibrium state. Under these conditions, bar mobility is strong enough to limit vegetation encroachment only when water discharges are higher than the discharge of a 5-years flood during more than 10 days. These results indicate that the hydrological characteristics of the Isère River and the actual configuration of the hydropower structures could be not able to release annually the flow conditions needed to control riparian plant development.

Highlights

Many rivers worldwide have been strongly modified during the 19th and 20th centuries by human activities, such as channelization, sediment dredging and damming [1]
The objective is to propose a modification of the current river hydrology, mainly controlled by dams, to foster riverbed morphodynamic and, to limit the riparian plant development
The physical model is 35 m long, 2.6 m wide with a sand mixture composed of three grain size classes (D16 = 0.65 mm, D50 = 1.4 mm and D84 = 2.3 mm)

Summary

Introduction

Many rivers worldwide have been strongly modified during the 19th and 20th centuries by human activities, such as channelization, sediment dredging and damming [1]. The colonization of the active channel by plants increases the flood risk due to a reduction of the flow conveyance of the river [9], and degrades the ecological status of the river by a homogenization of the habitat diversity [10]. Regular removing is necessary to limit plant encroachment in anthropized rivers, which constitute a non-perennial and expensive solution Under this context, new management options have emerged such as environmental flows which correspond to artificial floods aiming at restoring mobility of bed materials and bars in order to limit vegetation encroachment within river channels, and maintain a diverse habitat [12, 13]

Methods

Results

Conclusion