Developing a functional form of particle interception in vegetated environments

Abstract:

There is a growing body of literature seeking to evaluate particle interception in vegetated, aquatic environments; however, it is difficult to compare results of these studies due to large variation in flow regime, particle size, vegetation canopy density, and stem configuration. This work synthesizes data from these studies and develops a functional form of particle interception efficiency (ƞ) as a function of stem Reynolds number (Re_s), stem diameter, vegetation frontal area, particle-collector radii ratio, flow velocity, and kinematic viscosity. We hypothesized this functional relationship based on the physics of flow around cylindrical objects, and we tested this hypothesis by synthesizing data from 84 flume experiments reported in the literature and in-house flume experiments. Contrary to our hypothesis, data from different Re_s ranges followed a single functional form for particle interception. In this form, ƞ varies strongly with Re_s, flow velocity, stem diameter, and frontal area, and weakly with particle-collector radii ratio. This work will enable more accurate modeling of the flux terms in sedimentation budgets, which can inform ongoing modelling and management efforts in marsh environments. For example, we show that by integrating the new functional form of particle interception into established models of marsh elevation change, direct particle interception may account for up to 20% of total elevation change in a typical, silt-dominated marsh ecosystem with emergent vegetation.