Ecohydraulic Modeling with RIVER2D – a Canadian Contribution to Worldwide E-Flow Regimes

Establishing e-flow regimes (i.e. environmental, in-stream, or ecological flow regimes), is a key consideration in sustainable water resources development.  The most sophisticated e-flow methods to date are those based on hydrodynamic and habitat modeling.  Ecohydraulic relationships between water depths, velocities, substrates and habitat suitability are complex.  These relationships are affected by river morphological features, hydrological and ice regimes, as well as habitat preferences for various aquatic species, including fish.  The Canadian ecohydraulic model, “River2D” (www.river2d.ca), introduced in the early 1990s, has contributed to E-flow challenges and remains public domain software.  A large body of literature reflects the wide use of this two-dimensional, depth-averaged, finite element model for simulations around the globe, from the tundra to the tropics.  Although in most of these studies the “River2D” was used for e-flows, in many cases the model was used for habitat improvement, replacement or management.  Strategies developed for data collection, boundary conditions, use of “breaklines”, discretization of main features and large in-river objects, computational mesh generation, model calibration, output results and model verification are reviewed.  Case studies which illustrate challenges, limitations, and lessons learned are highlighted, while areas of future development directions, particularly in biological and morphodynamic areas are suggested.