Steady nonuniform shallow flow within emergent vegetation

摘要: Surface flow redistribution on flat ground from crusted bare soil to vegetated patches following intense rainfall events elevates plant available water above that provided by rainfall. The significance of this surface sustaining vegetation in arid and semiarid regions is undisputed. What disputed the quantity spatial distribution redistributed water. In ecohydrological models, such nonuniform flows are described using Saint-Venant equation (SVE) subject a Manning roughness coefficient closure. To explore these assumptions most idealized setting, flume experiments were conducted rigid cylinders representing with varying density. Flow was induced along streamwise x direction adjusting free height H(x) between upstream downstream boundaries mimicking nonuniformity encountered nature. natural settings, variations arise due contrasts infiltration capacity ponded depths during storms. measured values interpreted SVE augmented progressively elaborate approximations representation. simplest approximation employs friction factor derived drag (Cd) for isolated locally (but not globally) uniform upscaled rod density varied across experiments. Comparison modeled suggested “naive” approach overpredicts H(x). Blockage then incorporated into model calculations but resulted underestimation Biases suggest Cd must be beyond what local or bulk Reynolds number predicts. Inferred Cd(x) exhibited near-parabolic shape peaked densest canopy cases. outcome summarized resistance formulation may beneficial modeling runon-runoff processes shallow slopes SVE.