Development of an ecohydraulics model for stream and river restoration

At present, very little information is available about the design and maintenance of 'natural' river restoration schemes, combining hydraulic and ecological conditions. This field and numerical modelling study sought to redress this situation. A unique data set, containing hydraulic, substrate, and ecological parameters was collected over a three-year period for a 3 km meandering section of the Afon Morlais, a small river in West Wales, UK. The reach was investigated commencing immediately after it had been reinstated over a disused opencast coal mine, with the aim being to evaluate the overall success of the restoration scheme and for calibration and validation of the ecohydraulics model developed in this study. Surveying results showed that the river bed was stable and chemical data analysis indicated that the water quality was good. Macroinvertebrates were collected and taxa also showed good water quality. A computer modelling tool was used and further developed to investigate the dependence of habitat creation on hydrodynamic factors. The two-dimensional finite difference model Depth Integrated Velocitiy and Solute Transport (DIVAST) was applied to several meanders, taking account of the cross-sectional velocity and depth distributions. A curvilinear computational mesh was applied. DIVAST was then linked with the stream ecology; through macroinvertebrate suitability and two-dimensional velocity, bed shear stress and the consequential habitat distributions of two macroinverbrate species were predicted. The integrated modelling tool enabled habitat predictions to be made and addressed current design guidelines for enhanced recolonisation processes in river regeneration projects. (C) 2004 Elsevier B.V. All rights reserved.