The Runoff Potential Index: Upland-lowland differentiation

This MATLAB toolbox implements a 3D physics-based simulation for surface water runoff analysis, designed to support the Runoff Potential

Methodology for agricultural drought vulnerability assessment. The toolbox provides real-time visualization of water flow dynamics over terrain, demonstrating how landscape morphology controls water redistribution patterns between upland and lowland zones.

The Runoff Potential Index Simulation Toolbox is the computational implementation of research findings from the doctoral thesis "Crop Modeling to Identify Drought Adaptation Strategies for Rainfed Rice in Drought-Prone Regions." This toolbox addresses critical limitations of existing topographic indices (particularly TWI) in low-gradient agricultural terrains by providing a curvature-based approach for identifying drought-vulnerable versus resilient zones.Key Features:

• 3D Terrain Modeling: High-resolution grid-based terrain representation with customizable spatial resolution
• Physics-Based Water Simulation: Gravity-driven water movement with lateral diffusion effects
• Real-Time Visualization: Dynamic animation of water flow and accumulation patterns
• Runoff Index Calculation: Automated computation of terrain-based runoff potential
• Agricultural Focus: Specifically designed for low-gradient terrains where microtopographic variations (20-80 cm) control water retention
• Animation Export: Frame-by-frame output for scientific visualization and presentation

Scientific Applications:

• Drought Vulnerability Assessment: Identify water-retentive lowland zones vs. drought-vulnerable upland areas
• Precision Agriculture: Support field-scale water management decisions
• Landscape Analysis: Quantify morphological water retention potential in agricultural systems
• Educational Tool: Demonstrate hydrological processes in terrain-mediated water redistribution

Technical Specifications:

• Grid Resolution: Configurable (default 200×200 cells)
• Vertical Resolution: 0.1m layers
• Simulation Timeline: Customizable time steps
• Output Format: Sequential frames with water volume data (mm)
• Visualization: 3D surface plots with water distribution overlay

This toolbox extends beyond traditional slope-dependent indices to provide a framework for agricultural drought preparedness in rainfed systems, particularly valuable for rice production systems vulnerable to water stress during critical phenological stages.Research Context:

Developed as part of comprehensive research on the Runoff Potential Index (RPI), a curvature-based terrain metric that addresses specific limitations of slope-dependent indices for agricultural drought vulnerability assessment. The RPI formula: RPI(x,y) = ∇²z / (|∇z| + ε) integrates local terrain curvature with slope magnitude to quantify morphological water retention potential, enabling regional-scale vulnerability mapping through upland-lowland differentiation.

Author: Edgar S. Correa

Research Area: Dynamic Systems Modeling / Agricultural Drought Vulnerability Assessment

Institution: [Pontificia Universidad Javeriana, School of Engineering, Bogota Cra. 7 No. 40-62, 110311 Bogota, Colombia/ UMR AGAP Institut, Univ. Montpellier, CIRAD, INRAE, Institut Agro, Montpellier, France]

Thesis Chapter: Final chapter of "Crop Modeling to Identify Drought Adaptation Strategies for Rainfed Rice in Drought-Prone Regions"

Original Version: June 10, 2025