ABSTRACT
Stage-discharge relations at hydrometric stations with aquatic vegetation vary continuously in time due to the vegetation evolution. Maintaining such rating curves for establishing discharge time series is a challenge. Generally, the curves are adjusted manually as convenient stage-discharge models are missing. To fill this gap, we developed a practical model that accounts for transient changes due to aquatic vegetation. It is restricted to hydraulic controls that can be described by the Manning-Strickler equation for wide rectangular channels. In most situations, aquatic plants induce changes in bed roughness and mainly affect flow resistance. Bed roughness is characterized using a time-varying Manning coefficient, estimated using a friction equation accounting for the vegetation development (growth and decay) and for the plant flexibility (bending). In this paper, we illustrate the need to take into account flow-induced plant bending in the friction equation even though vegetation development remains the main factor affecting the flow resistance.
