NUMERICAL-SIMULATION OF WIDENING AND BED DEFORMATION OF STRAIGHT SAND-BED RIVERS .2. MODEL EVALUATION

In this paper the numerical model presented in the companion paper is tested and applied. Assessment of model accuracy was based on two appr oaches. First, predictions of evolution of a 13.5 km reach of the Sout h Fork of the Forked Deer River, in west Tennessee, were compared to o bservations over a 24-yr period. Results suggest that although the mod el was able to qualitatively predict trends of widening and deepening, quantitative predictions were not reliable. Simulated widths and dept hs were within 15% of the corresponding observed values, but observed change in these parameters at the study sites were also close to these values. Simulated rates of depth adjustment were within 15% of observ ed rates, but observed rates of channel widening at the study sites we re approximately three times those simulated by the model. In the seco nd approach, the model was used to generate relationships between stab le channel width and bank-full discharge. The model was able to succes sfully replicate the form of empirically derived regime-width equation s. Simulations were used to demonstrate the model's ability to obtain more realistic predictions of bed evolution in widening channels.