Determining surface resistance to overland flow in semiarid field conditions with low Reynolds numbers using the Crompton framework

Abstract

Shallow water flow on semiarid hillslopes with shrubs or cultivated with crops often occurs as laminar flow without concentration. Typically, the flow has a low Reynolds number, usually below 100, and the surface hydraulic resistance generated from the interaction between the soil surface and vegetation that obstructs the flow is governed by the Froude number. This study conducted field experiments on Brazilian shrub and semiarid crop fields and applied the Crompton framework to model hydraulic resistance. The overland flow observed on semiarid hillslopes under crops or natural vegetation always presented Reynolds numbers between 32 and 54, and the flow was laminar and subcritical. By employing the kinematic wave approximation, the Crompton framework was found to model overland flow resistance over semiarid hillslopes with acceptable accuracy.