Water Resour Res. 2016 Aug;52(8):6621-6642. doi: 10.1002/2015WR018491. Epub 2016 Aug 27.

Assessment of a numerical model to reproduce event-scale erosion and deposition distributions in a braided river.

Water resources research

R D Williams, R Measures, D M Hicks, J Brasington

PMID: 27708477 PMCID: PMC5042110 DOI: 10.1002/2015WR018491

Abstract

Numerical morphological modeling of braided rivers, using a physics-based approach, is increasingly used as a technique to explore controls on river pattern and, from an applied perspective, to simulate the impact of channel modifications. This paper assesses a depth-averaged nonuniform sediment model (Delft3D) to predict the morphodynamics of a 2.5 km long reach of the braided Rees River, New Zealand, during a single high-flow event. Evaluation of model performance primarily focused upon using high-resolution Digital Elevation Models (DEMs) of Difference, derived from a fusion of terrestrial laser scanning and optical empirical bathymetric mapping, to compare observed and predicted patterns of erosion and deposition and reach-scale sediment budgets. For the calibrated model, this was supplemented with planform metrics (e.g., braiding intensity). Extensive sensitivity analysis of model functions and parameters was executed, including consideration of numerical scheme for bed load component calculations, hydraulics, bed composition, bed load transport and bed slope effects, bank erosion, and frequency of calculations. Total predicted volumes of erosion and deposition corresponded well to those observed. The difference between predicted and observed volumes of erosion was less than the factor of two that characterizes the accuracy of the Gaeuman et al. bed load transport formula. Grain size distributions were best represented using two

Keywords: DEMs of Difference; Delft3D; braiding; gravel bed river; morphological modeling; terrestrial laser scanning

References

1. Water Resour Res. 2016 Aug;52(8):6621-6642 - PubMed

Publication Types

• Journal Article