Modeling river bed evolution in natural alluvial streams

A numerical model, suitable for prediction in bed evolution of natural alluvial rivers is presented. It is based on an original conservative formulation of one-dimensional shallow water equations, including a new treatment of source terms. The present model has been tested versus several literature test cases and experimental data. The simple MacCormack explicit finite-difference numerical scheme is used and a semi-coupled procedure has been adopted. The model herein proposed shows an improved stability and favorable results, comparing to the classical conservative form of balance governing equations First fixed-bed test cases are modeled, in order to check model response in presence of rapidly varying flow and non prismatic channels. Afterward various mechanisms of bed evolution in different water regime conditions are investigated, in order to verify model response in case of erosion, deposition, bed morphology evolution and embankment overtopping. Model results are compared with experimental data showing satisfactory agreement.