ADCP validation of 3D morphodynamic modelling in clay-bed meandering rivers

Colin Rennie, Parna Parsapour-Moghaddam

Thursday 2 july 2015

11:15 - 11:30h at Africa (level 0)

Themes: (T) Special session, (ST) Acoustic monitoring of flow, turbulence and river discharge

Parallel session: 11F. Special session: Acoustic monitoring of flow, turbulence and river discharge

Three-dimensional (3D) morphodynamic models are now readily available for prediction of velocity fields and erosion/deposition processes. These models can be applied to challenging flows such as tortuously meandering clay-bed rivers. Typically, calibration of such models is achieved by adjusting channel roughness to obtain observed flow stage for a given discharge. However, the complex three-dimensional flow field that drives sediment entrainment and transport is not usually validated. In this paper we utilize a spatially distributed velocity field obtained by intensive surveying with an acoustic Doppler current profiler (aDcp) to improve calibration and validation of a Delft3D morphodynamic model of a torturously meandering clay-bed river. Sensitivity analysis on model parameters showed that eddy viscosity is useful for model calibration. Horizontal eddy viscosity is adjusted to minimize differences between individual measured and modelled point velocities. The predicted results of erosion/sedimentation show how sediment transport processes can be affected by changes in the horizontal eddy viscosity. The validated model can be utilized to estimate boundary shear stress and bed erosion/deposition. The value of calibration/validation using spatially distributed aDcp data is discussed.