Tide, wave and suspended sediment modelling on an open coast - Holderness

An intensive series of observations off the Holderness coast was followed b y a related set of modelling applications. Observations included: aircraft and satellite remote sensing, H.F. and X-band radar, ship surveys and in si tu instruments on the sea bed and at the sea surface. These observations ai med to monitor, over three successive winter periods, the dynamics and sedi ment distributions in the vicinity of this rapidly eroding coastline, Assoc iated modelling applications included components simulating: (i) tides and surge currents; (ii) wave evolution, (iii) vertical distributions of turbul ence and SPM (suspended particulate matter) and (iv) resulting spatial patt erns of sediment transport in the region. Simulations of tidal currents confirmed the accuracy of such models, given accurate fine-resolution bathymetry and appropriate boundary conditions. Ne w developments of WAM, the spectral wave model required for fine-resolution applications in shallow water (described by Monbaliu et al, [Monbaliu, J., Padilla-Hernandez, R., Hargreaves, J.C., Carretero Albiach, J.C., Luo, W., Sclavo, M., Gunther, H., 2000. The spectral wave model WAM adapted for app lications with high spatial resolution. This volume.]) are tested here. A n umber of additional features pertaining to shallow water are revealed inclu ding the sensitivity to specification of wind directions and the excessive temporal spreading of short-lived distant events. Likewise, the application of the generic single-point models for vertical profiles of turbulence and SPM (described by Baumert et al. [Baumert, H., Chapalain, G., Smaoui, H., McManus, J.P., Yagi, H., Regener, M., Sundermann, J., Szilagy, B., 2000. Mo delling and numerical simulation of turbulence, waves and suspended sedimen t for pre-operational use in coastal seas. This volume]), are tested and al so shown to be appropriate for simulating localised resuspension of SPM. Th is simulation also illustrates how, in shallow water (< 15 m), tidal and wa ve dynamics interact with significant mutual adjustments and with first-ord er influence on stress at the sea bed and thereby erosion and suspension pr ocesses. Some preliminary simulations of net sediment movement are included, involvi ng an integration of the above effects. These simulations emphasise how, in all but the shallowest water, the mobility of coarse grain sediments is li mited to occasions of extreme waves. By contrast, the movement of fine sedi ments follows that of the residual tidal current streamlines, i.c., primari ly longshore with attendant cross-shore dispersion. However, significant va riation between closely-spaced observations indicates the irregularity and complexity of such distributions. It is concluded that because of the inabi lity to prescribe the spatial distribution of available surficial sediments (including size distributions) such simulations can only be expected to re produce the essential statistical characteristics of SPM concentrations. Th e availability of extensive remote sensing or in situ data can help to circ umvent this problem. (C) 2000 Elsevier Science B.V. All rights reserved.