High-resolution multi-scale modelling of coastal flooding due to tides, storm surges and rivers inflows. A Cork City example

Abstract

This paper demonstrates the capability of a new state-of-the-art flood modelling system consisting of multiple nested models to simulate urban coastal flood inundation. A flood event in Cork City, Ireland which occurred in November 2009 is analysed in detail. The new flood modelling system comprises of two dynamically linked models: an ocean model (POM) of the northeast Atlantic (ca. 5 km grid) and a coastal flood model, MSN_Flood, which resolves the hydrodynamics of Cork Harbour and its sub region at four spatial scales 90 m, 30 m, 6 m and 2 m through a cascade of four nested grids. Flood water propagation through Cork City floodplains is simulated by the 2 m grid model. The POM-MSN_Flood modelling system, presented for the first time in this paper, was used to investigate the dynamics of coastal flooding resulting from a complex set of tides, storm surges, rivers inflows and the interactions between them. Unlike many flood models, the modelling system used in this research provides a full description of water levels and flow regimes, both in coastal waters and urban floodplains. Validation results clearly demonstrate that the model is capable of resolving hydrodynamics at scales commensurate with flow features including the large scale processes of the NE Atlantic Ocean and the fine resolution circulation of coastal waters. With regards to urban flooding, the model was found to accurately determine flood wave propagation patterns, flood wave heights, speeds and inundation extents. Ultimately, the model was used to investigate mechanisms of flooding resulting from multiple process drivers and to assess flood risk to human safety. Such an analysis facilitates better understating of the mechanics and dynamics of complex coastal urban flooding and would therefore be of interest in the field of coastal management.