A one-Dimensional representation of residual currents in the Severn Estuary and associated observations
Uncles, R.J.; Jordan, M.B. (1980). A one-Dimensional representation of residual currents in the Severn Estuary and associated observations. Estuar. Coast. Mar. Sci. 10: 39-60
In: Estuarine and Coastal Marine Science. Academic Press: London. ISSN 0302-3254; e-ISSN 1878-3023, meer
A one-dimensional hydrodynamical model is used to describe the cross-sectionally averaged Stokes drift and Eulerian residual currents in a section of the Severn Estuary between Porthcawl and Sharpness. Residual variables are computed for periodic M2 tides, and as functions of time during simulated spring-neap cycles. The results for periodic MSUB-2 tides show that the landward directed Stokes drift has a spatially averaged value of 3.5 cm s-1 in the Severn Estuary, which is balanced by seaward flowing Eulerian residual currents. The residual setup of water is determined by the magnitudes of the axial density gradients and friction, with the friction dominating for typical salinity distributions; the landward flow of water due to the Stokes drift contributes to the set-up, which drives the seaward residual currents against the opposing frictional forces. The magnitude of the Stokes drift is determined by the estuary's geometry, the strength of the tidal streams and the friction. The frictional dissipation in the Severn Estuary, which amounts to 3 x 109 watts for M2 tides is balanced by a landward residual flow of energy across the mouth, which is nearly proportional to the Stokes drift at the mouth. The axial residual currents and Stokes drift have maximum and minimum speeds at spring and neap tides respectively. The neap to spring part of the tidal regime is a period of increasing estuarine residual volume and landward flowing Lagrangian residual currents; the reverse is true for spring to neap tides.
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