Generation of 1D channel networks for overland flow simulations on 2D complex domains

Conventionally two-dimensional (2D) models are used to simulate 2D overland flow with a non-overlapping 2D computational mesh. However, 2D models are not computationally efficient when applied to large domains. Due to their computing efficiency, one-dimensional (1D) models can be used to simulate 2D overland flows by replacing 2D computational meshes with 1D computational channel networks with topography described by closely-spaced transverse cross sections that fully cover the whole domain. Channel networks must enforce the basic physical laws of gravity-driven flows ensuring water flow paths converge and connect from high to low elevations. This manuscript presents a novel algorithm to generate channel networks following two principles, a geometric principle and a hydrologic principle. The geometric principle requires that the generated channel network covers the whole study domain without overlaps or intersections, while the hydrologic principle requires that the generated channel network follows the local steepest slope. Correspondingly, the proposed generation algorithm includes two main processes: (1) the extraction of channel network using a terrain slopecalculation-based delineation algorithm; and, (2) the generation of cross sections with varying channel widths determined by considering topographic complexity, the hydrological correctness, and computational requirements. The proposed cross section generation algorithm is described using several 2D geometrically complex domains at the laboratory scale, and is also applied to a natural watershed. An overflow simulation on a 2D domain with obliques walls using a 1D model demonstrated the effectiveness of the proposed generation algorithm for 1D channel networks of 1D model.