MORPHODYNAMIC IMPACTS OF A TIDAL BARRAGE IN THEMERSEY ESTUARY

摘要

This paper examines both the short and long-term impacts a tidal barrage has onsediment transport, under tidal conditions in the Mersey Estuary and Liverpool Bay, andhence morphological changes. The TELEMAC model suite is used for the numericalprediction, including the 2D hydrodynamic model (Telemac-2d) coupled with thesediment transport model (Sisyphe) and the wave propagation model (Tomawac). A newscheme has been developed to simulate the operation of a barrage within the estuary,with comprehensive hydrodynamic calibration using most recent field data. Thepreliminary model results indicate that the construction of a tidal barrage across thenarrows of the Estuary for ebb mode energy generation significantly alters the naturalmovement of the tide: effectively reducing the tidal range and increasing the low waterlevel upstream of the structure. Due to the strong flows in the vicinity of the barrage,increased erosion is expected in the narrows. Barrage operation procedures are predictedto alter the siltation rate under the complex spring-neap tidal cycle. Long-term changesdue to the interaction of a barrage and tidal asymmetry are also under consideration withfurther examination of model results within both the Mersey and Dee Estuaries and outerLiverpool Bay.