Comparison of measurements and models of bed stress, bedforms and suspended sediments under combined currents and waves

This study presents an analysis of data collected in an embayment off a sandy beach protected by shore parallel breakwaters. Observations were carried out over a forty day period including spring and neap tidal cycles and low and high wave activity. Measurements were collected on the waves, currents, bedforms and suspended sediments and these were used to derive estimates of the bed shear-stresses, ripple dimensions, reference concentrations and suspended sediment profiles. The aim of the present study was to use the measurements to assess commonly employed empirical formulations applied to sediment modelling in the coastal marine environment. Assessments are made of four ripple predictors, two formulations of reference concentration and power law and exponential suspended sediment shape functions. In some cases predicted parameters are well represented during low wave conditions, whilst other parameters are better predicted under high wave events. The outcome from the work is an evaluation of the predictive capability of the selected empirical formulae at the sandy location and discussions on the comparison between the observations and predictions.

► We present simultaneous measurements of hydrodynamics, suspended sediments and bedforms. ► Assessment of four ripple models, two reference concentration models and two suspended sediment shape functions was done. ► Reference concentration may not be as strongly coupled to the ripple steepness as suggested previously. ► Power law shape provided the better fit to suspended sediment concentration data. ► Importance of bedforms and suspended particle size data for sediment formulations is shown.