Morphodynamic modelling of intertidal sediment transport in Morecambe Bay

The construction of a morphodynamic model for the intertidal region of More cambe Bay, England, and its calibration and validation using extensive sedi ment volume change data measured by remote sensing, is described. A properl y validated sediment transport model of the bay would be of interest for co astal defence, management and economic purposes. The morphodynamic model co nsisted of a set of linked modules for predicting 2D depth-averaged tidal c urrents, waves, sediment transport rates and sediment budgets. The intertid al bathymetry was updated at regular intervals and the currents, waves and sediment transport patterns recomputed using the new bathymetry. Tidal inpu t filtering using representative spring and neap tidal cycles was used to r educe computational requirements. Sediment volume changes during the period 1992-1997 were measured over the intertidal zone at a resolution of 240 in using the waterline method employing remote sensing and hydrodynamic model ling. The total volume of sediment eroded was - 102 +/- 16 x 10(6) m(3), an d the total volume accreted was 107 +/- 15 x 10(6) m(3). Tidal asymmetry is shown to be the dominant agent of sediment transport in the intertidal zone, with waves being of secondary importance. A close corr elation was found between the computed directions of tidal asymmetry and ob served sediment transport paths. It was necessary to use the remotely sense d data for calibration of the sediment transport model as well as for valid ation. The model showed some limited capability for predicting gross change s in bathymetry, but there were substantial differences between the predict ed and observed patterns of sediment movement. The possibility of improveme nt by a further incorporation of the spatially and temporally extensive fie ld data into the modelling process is discussed. (C) 2001 Academic Press.