Analysis of storm surge and tidal resonance in the Bristol channel

The Bristol Channel is located in the south-west coast of Great Britain, which has the second largest tidal range in the world. Despite a number of previous studies which have been undertaken in the Bristol Channel, its complex tidal dynamics are not yet fully understood, in particular given its resonant nature and presence of large storm surges. This was the motivation for development of a simplified two-dimensional model to simulate the tidal flows and storm surges in the Bristol Channel. In the tidal resonance study, a small two-dimensional model has been developed using the discontinuous Galerkin (DG) version of ADCIRC programme. We first vary the frequency on the on the ocean boundary of the model and examine at which frequency the model is mostly excited. Secondly we apply a wind disturbance to the model and analyse the frequency at which it resonates. We also examine the sensitivity of these results to the bed friction and changes in the tidal amplitude on the boundary or the sea water level. There are two main methods for estimating future changes in storm-surge heights: statistical analysis and dynamical modelling, and in this thesis we use both. Firstly the occurrence and severity of storm surge events in the Bristol Channel over the period 1961-2015 are examined by analysing field data derived from tide gauges at five key locations along the north and south coasts of the channel. then we explore the storm surges numerically on a large two-dimensional model using the continuous Galerkin (CG) version of ADCIRC. Different wind strengths and wind directions are considered, and the interactions between surge and tides are investigated. A reconstruction of the 30th January 1607 event in the Bristol Channel is also provided at the end of this study to further explore the physics of storm surges in the Channel.