Modelling the effects of climate change on urban coastal-fluvial flooding

Abstract

In coastal floodplains, high river flows and high coastal water levels can result in extensive flooding. Twenty-first century climate change is expected to alter these flood mechanisms. In this study, a coastal city of Cork, Ireland is used as a case study to investigate changes in flood mechanisms, dynamics and extents due to climate change. A hydrodynamic flood model MSN_Flood was used to compute potential future inundation patterns for a range of climate scenarios based on estimates of current, medium-range and high-end projections of extreme river flows and sea levels. Results illustrate that the flood mechanism is critical in controlling patterns and extent of inundation. Peak river discharges are the primary contributor to extreme flood events under the current climate scenario, however, high-end climate change could result in coastal inundation of comparable magnitude. The most extreme flood events affect the entire city centre – occurring as a result of a combination of fluvial and coastal drivers. The interaction of extreme fluvial discharges and coastal water levels is complex and characterised through comparison of multiple scenarios. This research establishes a best practice methodology for assessment of urban coastal-fluvial flood risk under a changing climate and can be used to determine climate-resilient flood management measures.