Exploring marsh surface canopy dynamics - A discussion of laboratory methods

The complex interactions between marsh surface vegetation, hydrodynamics and the settling of suspended sediments in marsh surface waters are poorly understood. An improved understanding of the role of vegetation in modulating marsh surface hydrodynamics and mass settling fluxes, at the canopy scale, may improve current abilities to explain spatio-temporal variations in erosion/deposition and may be of benefit to morphodynamic prediction. In this paper, an experimental methodology is discussed which uses a large annular flume and Doppler Velocimetery to addresses the influence that a dense Spartina anglica canopy (1000 stems m^-2) has on time-averaged hydrodynamics and suspended sediment dynamics. The construction of artificial S.anglica mimics, which have geometric and dynamic similarity with prototypical vegetation, is outlined and illustrative velocity profiles measured in laboratory flows through this mimic canopy are presented. The flow response is shown to be produce vertical profiles of velocity statistics that are similar to a number of previously published studies which use real or artificial vegetation. The implications of flow modification by submerged S.anglica on the flocculation and settling of Suspended Particulate Matter is discussed as the basis of further research.