Applied Sediment Dynamics – Boat Work and Modelling Results

In order to validate the model of Southampton Water (see here) produced in week one of Applied Sediment Dynamics it was necessary to collect field measurements. Boat work was carried out over three days during the second week of the course on the RV Bill Conway and RV Callista using a range of techniques and equipment in both the Solent and Southampton Water.
Current velocity measurements were taken using an ADCP and three Valeports 808 units (electromagnetic current metres) mounted to weighted frames and deployed on the sea bed (also logging pressure, and optical backscatter). Four additional pressure transducers were also deployed at various locations within the study area. In addition temperature and salinity profiles were taken using a CTD, whilst the vertical distribution of sediment was measured using modified Helley-Smith sand traps, and Niskin bottle water samples at various depths.  Finally, the grain size at various locations were sampled using van Veen grab sampling which were later analysed in the NOC’s sediment lab. The grab samples were dried and placed in the furnace in order to carry out a loss on ignition test to calculate the organic content. Sediment samples were also sieved to determine the mean and median grain size, the sorting, skewness and the kurtosis; and examined in a settling column.
It was concluded that our model successful represented reality through a range of statistical tests including correlation and linear regression along with visual comparisons. This was then taken forwarded in order to consider the implications of building a dredge channel to the northeast of the Bramble Bag sandbar. However, comparisons between the hydrodynamics pre and post dredge suggested that there would be very little change following the dredging of a channel and any changes would be localised. This in turn implied that there will be very little changes to the sediment dynamics in the region, although there could be wider social, economic and environmental implications.
Overall, Applied Sediment Dynamics was an extremely enjoyable and thought-provoking module. It provided a valuable introduction to modelling and experience of working as a consultant on a realistic problem with the pressures of deadlines and data availability whilst trying to conclude as accurately as possible.

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