Author(s): Bettina N. Bockelmann
Linked Author(s):
Keywords: River restoration; Meandering channel flow; Sedimenttransport; Initiation of motion; Numerical models; River models; HECRAS; HEMAT
Abstract: At present, very little information is available about the design and maintenance of ‘natural' river restoration schemes, combining both hydraulic and morphological conditions. This combined field and numerical modelling study seeked to redress this situation by first using two computer modelling tools: The 1-D model HECRAS for predicting velocities and water depths longitudinally and the Research Centre's 2-D, finite volume model HEMAT, which was applied for several meanders taking account of the cross-sectional velocity and depth distributions. An additional program was developed to determine the necessary sediment size to prevent the initiation of sediment motion. The program calculated the values for specifying the critical Shields parameter from the results of the two numerical models and, in a next step, the critical sediment sizes. The models were applied to a 4 km reach of meandering stream. Monitoring started immediately after the river had been reinstated over a disused ‘open cast' coal mine in Wales, UK. The ‘natural'design, with the aim to maximise habitat creation, required that bed armouring material of the smallest size possible was used. The numerical models correctly predicted water depth and velocity distributions. The calculated critical sediment sizes closely identified regions where erosion was occurring. The 1-D model and the 2-D model segments of the curved sections can be linked into one modelling tool, which has the potential to define hydro-morphodynamic effects on habitat creation by integrating the stream ecology.
Year: 2001