Progressive surface waves generate oscillatory flows and sand fluxes along the sea bed in the wave boundary layer. The primary research aim of the SANTOSS project was to establish a new ‘ semi-empirical’ model for the resulting net sand transport in this layer for a wide range of wave- , wave +current and sediment conditions. Existing data from experiments conducted in The Netherlands, the UK and elsewhere were brought together for the first time to create the best possible set of existing large-scale data on oscillatory sand transport rates. New experiments were carried out i) in the Aberdeen Oscillating Flow Tunnel to study sand transport processes under acceleration-skewed oscillatory flows and ii) in the Grossen Wellen Kanal in Hannover to study the transport processes under progressive surface waves. With the new data and with the help of selected process-based numerical models new insights were obtained in the flow mechanisms responsible for additional onshore transport as found i) under acceleration–skewed waves, and ii) under progressive surface waves in the sheet flow regime.
These insights were used together with the new database for the development of the new transport model. The transport model was extensively tested and optimized for different flows (wave shapes and currents), sediment sizes and bedform regimes (ripple and sheet flow regime). The final model shows a better performance and has a wider validity range than existing models.
The question of sand transport and the resulting morphological evolution of the coastal zone are fundamental to all major coastal management, coastal defence and coastal environment policies. End-users of the research include coastal engineers, coastal zone managers and coastal scientists working in coastal authority institutions, consultancy firms, large hydraulics research laboratories and universities. The User Committee of SANTOSS comprised a number of Dutch and UK institutions and consultancy companies. They played a vital role in (i) defining the structure of the general sand transport module, (ii) integrating the general module within coastal modelling systems and (iii) testing the behaviour and use of the module for various practical scenarios. During the project a prototype of the new transport model was implemented and tested in coastal modeling systems of Deltares and HR Wallingford. The implementation and testing process of the final transport model is expected to be carried out in 2010-2011 in a continuing collaboration between researchers and users. A wide dissemination of the new sand transport formula is achieved and will be achieved further in the future through The Netherlands Centre for Coastal Research (NCK), the UK’s COZONE network as well as trough conference and journal publications.