openKARST: Assessing flooding dynamics in karst aquifers with a resolution-aware modeling tool

We present a newly developed flow and transport simulator for karst systems, designed to model complex flow dynamics and tracer transport in large-scale networks. Based on the Saint-Venant equations, the simulator integrates advanced hydraulic modeling and particle tracking to investigate how conduit geometry and network structure influence flow and transport behavior. It supports both steady-state and transient conditions, under free-surface and pressurized flow. Turbulence is modeled via the Darcy-Weisbach equation with classical friction formulations, and validation includes analytical solutions and the extensive Ox Bel Ha cave system.

Using 3D lidar-derived geometries, we build high-resolution network models to study how geometric simplification, through resolution reduction, affects flooding signals. Downscaling reduces the number of conduits and averages properties such as diameter and roughness, which can mute or eliminate bottlenecks that control flow and hydraulic gradients. This leads to a more homogenized flow regime, altering the timing, magnitude, and spatial distribution of flooding.

These findings have direct climate relevance. As extreme rainfall events intensify under climate change, understanding karst aquifer responses becomes critical for flood prediction and water resource management. Simplified models may underestimate the role of geometric complexity in buffering or amplifying flood signals. Our work highlights the trade-offs between computational efficiency and predictive accuracy, emphasizing the need for resolution-aware modeling when assessing climate-driven impacts on vulnerable karst systems.