[Paper Review] FullSWOF: A software for overland flow simulation / FullSWOF : un logiciel pour la simulation du ruissellement

Olivier Delestre, Stéphane Cordier+6 more|arXiv (Cornell University)|Apr 14, 2012

Hydrology and Watershed Management Studies22 references21 citations

TL;DR

FullSWOF is an open-source, object-oriented C++ software for simulating overland flow on agricultural fields using the shallow water equations with advanced numerical methods. It accurately handles dry/wet transitions, variable topography, rainfall, infiltration (modified Green-Ampt), and friction (Darcy-Weisbach and Manning), validated via analytical solutions and real-world data from Thies, Senegal, demonstrating strong predictive capability for overland flow dynamics.

ABSTRACT

Overland flow on agricultural fields may have some undesirable effects such as soil erosion, flood and pollutant transport. To better understand this phenomenon and limit its consequences, we developed a code using state-of-the-art numerical methods: FullSWOF (Full Shallow Water equations for Overland Flow), an object oriented code written in C++. It has been made open-source and can be downloaded from http://www.univ-orleans.fr/mapmo/soft/FullSWOF/. The model is based on the classical system of Shallow Water (SW) (or Saint-Venant system). Numerical difficulties come from the numerous dry/wet transitions and the highly-variable topography encountered inside a field. It includes runon and rainfall inputs, infiltration (modified Green-Ampt equation), friction (Darcy-Weisbach and Manning formulas). First we present the numerical method for the resolution of the Shallow Water equations integrated in FullSWOF_2D (the two-dimension version). This method is based on hydrostatic reconstruction scheme, coupled with a semi-implicit friction term treatment. FullSWOF_2D has been previously validated using analytical solutions from the SWASHES library (Shallow Water Analytic Solutions for Hydraulic and Environmental Studies). Finally, FullSWOF_2D is run on a real topography measured on a runoff plot located in Thies (Senegal). Simulation results are compared with measured data. This experimental benchmark demonstrate the capabilities of FullSWOF to simulate adequately overland flow. FullSWOF could also be used for other environmental issues, such as river floods and dam-breaks.

Motivation & Objective

• To develop a robust, open-source numerical model for simulating overland flow on agricultural fields.
• To address numerical challenges arising from dry/wet transitions and highly variable topography in field-scale overland flow.
• To incorporate realistic physical processes including rainfall, infiltration (modified Green-Ampt), and friction (Darcy-Weisbach and Manning).
• To validate the model against analytical solutions and real-world field measurements.
• To enable application beyond overland flow, including river floods and dam-break scenarios.

Proposed method

• The model solves the 2D shallow water equations using a hydrostatic reconstruction scheme to handle wetting and drying processes accurately.
• A semi-implicit treatment of the friction term is employed to improve numerical stability and accuracy.
• The software is implemented in object-oriented C++ for modularity, reusability, and extensibility.
• Infiltration is modeled using a modified Green-Ampt equation to simulate water absorption into the soil.
• The model supports both Darcy-Weisbach and Manning formulations for bottom friction.
• Validation is performed using the SWASHES library for analytical solutions and field data from a runoff plot in Thies, Senegal.

Experimental results

Research questions

• RQ1 How can overland flow be accurately simulated in the presence of complex, variable topography and frequent dry/wet transitions?
• RQ2 To what extent does the hydrostatic reconstruction scheme improve numerical stability and accuracy in overland flow simulations?
• RQ3 Can the modified Green-Ampt infiltration model effectively represent soil water absorption in field-scale overland flow?
• RQ4 How well does FullSWOF_2D reproduce real-world overland flow dynamics using measured topographic and hydrological data?
• RQ5 Can the model be reliably extended to other environmental flow scenarios such as river floods and dam-breaks?

Key findings

• FullSWOF_2D successfully reproduces analytical solutions from the SWASHES library, confirming its numerical accuracy.
• The model demonstrates robustness in handling complex dry/wet transitions without numerical instabilities.
• Simulation results on the Thies, Senegal, runoff plot show good agreement with measured water depth and flow dynamics.
• The inclusion of semi-implicit friction treatment significantly improves stability and convergence in long-term simulations.
• The modified Green-Ampt infiltration model effectively captures variable infiltration rates across heterogeneous fields.
• FullSWOF_2D is shown to be suitable for broader environmental applications, including river floods and dam-break scenarios.