The purpose of this research is to adapt and improve existing two-dimensional numerical tidal models so that they can cope with regions where the tide falls and rises to uncover and cover inter-tidal banks without incurring numerical shocks which may be caused by the discretization of time and space. This thesis presents a review of current practices in the numerical modelling of flooding and drying banks in two dimensions. A two-dimensional depth-averaged numerical model has been written and is presented. It is used as a tool with which to investigate various existing algorithms which represent the physical process of the wetting and drying of intertidal zones. An alternative method with which to represent the moving boundary has been developed. This method is free from disturbances usually caused by the implementation of a moving boundary in such a numerical scheme. A 2NM numerical model of the Wash, U.K., is run to provide hind-cast tidal data pertaining to a particular site and period. A field programme is established to provide validation data for the model. Finally, conclusions from the programme of research are drawn.

Millions of people in low-lying areas are already affected by flooding, and the number will increase substantially in the future. Tidal flooding, the form of flooding caused by a combination of high tides and sea level rise to overcome protection levels, can cause damage and inconveniences such as road closures, overwhelmed drainage systems, and infrastructure deterioration from water damage. Tidal flooding already occurs annually in cities along the U.S. east coast, most notably Miami. However, the time it will take for other regions globally to begin to experience tidal flooding has not yet been assessed. Therefore, there is a limited understanding of how and when human populations will be exposed to this type of flooding. Tide gauge data from the GESLA-2 data base are used to obtain information about the highest astronomical tide (HAT) and extreme value statistics for 571 locations globally. For a complete spatial analysis, modelled water levels from the Global Tide and Surge Reanalysis (GTSR) are also used. Estimated protection levels are extracted from the DIVA database and translated to absolute heights based on the extreme value statistics of high water levels. This analysis is based on calculating the difference between the existing protection level and HAT, which indicates how much sea levels can rise before tidal flooding occurs, and evaluating in what decade this is expected to happen under different sea-level rise (SLR) scenarios. Tidal trends from the nodal and perigean are also taken account and used to modify 1000 different sea level rise scenarios to provide a more comprehensive analysis of possible tidal flooding years. Our results indicate that tidal flooding may occur within a few decades in many locations (under the assumption that no adaptation will take place), and therefore awareness should be heightened so that actions can be taken to minimize the impacts.