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Title: Morphodynamic impacts of a tidal barrage in the Mersey Estuary
Author: Carroll, Benjamin John
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2012
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This study examines both the short and long-term impacts a tidal barrage would have on sediment transport, under combined waves and tidal conditions in the Mersey Estuary and Liverpool Bay, and thus the corresponding morphological changes. The TELEMAC model suite is used for the numerical prediction, including the 2D hydrodynamic module (TELEMAC-2D) coupled with the sediment transport model (SISYPHE) and the wave propagation model (TOMA WAC). A new scheme has been developed to simulate the operation of a barrage within the Mersey Estuary, with comprehensive hydrodynamic calibration using the most recent field data. Model results indicate that the construction of a tidal barrage across the Mersey Estuary (under ebb mode energy generation) significantly alters the natural movement of the tide; effectively reducing the tidal range and increasing the low water level 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 predicted to alter the siltation rate under the complex spring-neap tidal cycle. Total-load transport residuals for non-cohesive sediments identify that under the present hydrodynamic regime, the Mersey Estuary is a net exporter of sediments, thus resulting in a noticeable increase of the tidal volume capacity in recent years. However, model results have identified that the implementation of a barrage within the estuary would reverse the net sediment pathway, with there being significant accretion upstream of the barrage. Under the new morphodynamic regime created through the implementation of the barrage, it is likely that sediments would continue to accrete within the impoundment area of the scheme for the entirety of its operational lifetime. With the Mersey Estuary potentially becoming a substantial sink for sediment, it would be feasible to assume that the coastline to the north of the estuary would experience a reduction in its source of marine sediment. Various factors influencing the long-term morphological changes in the Mersey Estuary are also reviewed based on the model results presented in this research. Furthermore, the impacts of a tidal barrage on the coastline, and the possible combined influences of sea level rise and the barrage structure are also explored
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available