ResumenPara dar respuesta a los requerimientos en materia de aguas definidos en las directrices, reglamentos y recomendaciones existentes en la legislación española, los cuales están mayoritariamente basados en directivas europeas, se ha desarrollado una herramienta de modelización numérica del flujo de agua en lámina libre en 2 dimensiones. La herramienta, llamada Iber, combina un módulo hidrodinámico, un módulo de turbulencia y un módulo de transporte de sedimentos, y utiliza el método de volúmenes finitos para resolver las ecuaciones correspondientes. Al módulo de cálculo se le ha adaptado una interfaz que se basa en el software de preproceso y posproceso GiD, desarrollado por CIMNE. El resultado es una herramienta de modelización numérica del flujo de agua y sedimentos en ríos y estuarios, que utiliza esquemas numéricos avanzados especialmente estables y robustos en cualquier situación pero especialmente adecuados para flujos discontinuos y, en concreto, para cauces torrenciales y regímenes irregulares.AbstractThe recent requirements of Spanish regulations and directives, on their turn based on European directives, have led to the development of a new two dimensional open channel flow modelling tool. The tool, named Iber, combines a hydrodynamic module, a turbulence module and a sediment transport module, and is based in the finite volume method to solve the involved equations. The simulation code has been integrated in a pre-process and post-process interface based on GiD software, developed by CIMNE. The result is a flow and sediment modelling system for rivers and estuaries that uses advanced numerical schemes, robust and stable, which are especially suitable for discontinuous flows taking place in torrential and hydrologically irregular rivers

This paper presents the decoupled hydrological discretization (DHD) scheme for solving the shallow water equations in hydrological applications involving surface runoff in rural and urban basins. The name of the scheme is motivated by the fact that the three equations which form the two‐dimensional shallow water system are discretized independently from each other and thus, the numerical scheme is decoupled in a mathematical sense. Its main advantages compared to other classic finite volume schemes for the shallow water equations are its simplicity to code and the lower computational cost per time step. The validation of the scheme is presented in five test cases involving overland flow and rainfall‐runoff transformation over topographies of different complexity. The scheme is compared to the finite volume scheme of Roe (1986), to the simple inertia formulation, and to the diffusive wave model. The test cases show that the DHD scheme is able to compute subcritical and supercritical flows in rural and urban environments, and that in overland flow applications it gives similar results to the second‐order scheme of Roe with a lower computational cost. The results obtained with the simple inertia and diffusive wave models are very similar to those obtained with the DHD scheme in rural basins in which the bed friction and topography dominate the flow hydrodynamics but they deteriorate in typical urban configurations in which the presence of supercritical flow conditions and small‐scale patterns boost the relevance of the inertial terms in the momentum equations.

The transport of wood material in rivers has been the subject of various studies in recent years. Most research has focused on the ecological and geomorphologic role of wood, its recruitment processes and spatial distribution in streams. In this study, we focused on wood transport dynamics, and we have developed a numerical model to simulate wood transport coupled with a two-dimensional (2D) hydrodynamic model. For this purpose, wood drag forces were incorporated as additional source terms into the shallow water equations, which are solved together with wood transport by using the finite volume method. This new tool has been implemented as a computational module into ‘Iber’, a 2D hydraulic simulation software. The new module analyzes the initial motion threshold of wood based on the balance of forces involved in the wood's movement, and computes the position and velocity of differently shaped logs using a kinematic approach. The method also considers the interaction between the logs themselves and between the logs and the channel walls or boundaries. Flume experiments were used in a straight channel with obstructions to validate the model's capacity to accurately reproduce the movement of floating logs.