Modeling rain-driven overland flow: empirical versus analytical friction terms in the shallow water approximation

TL;DR

This study compares empirical and analytical friction models in shallow water simulations of rain-driven overland flow, finding the Poiseuille model most accurate for laminar flow in a controlled flume experiment.

Contribution

It evaluates and compares the effectiveness of Manning, Darcy-Weisbach, and Poiseuille friction models in simulating rain-driven overland flow, highlighting the superiority of the Poiseuille model for laminar conditions.

Findings

Poiseuille friction model yields the best simulation results.

Manning model is unsuitable for this flow type.

Darcy-Weisbach performs well in laminar flow conditions.

Abstract

Modeling and simulating overland flow fed by rainfall is a common issue in watershed surface hydrology. Modelers have to choose among various friction models when defining their simulation framework. The purpose of this work is to compare the simulation quality for the Manning, Darcy-Weisbach, and Poiseuille friction models on the simple case of a constant rain on a thin experimental flume. Results show that the usual friction law of Manning is not suitable for this type of flow. The Poiseuille friction model gave the best results both on the flux at the outlet and the velocity and depth profile along the flume. The Darcy-Weisbach model shows good results for laminar flow. Additional testing should be carried out for turbulent cases.