Rising tides: Tidal inundation in South east Australian estuaries
Global sea levels are rising and are likely to have an increasing impact on coastal communities over the coming decades and centuries. Within Australia, recent studies have identified that considerable development and infrastructure is at risk from sea level rise with low-lying areas adjacent to estuaries in New South Wales being subject to the greatest exposure. Increasing extent and frequency of tidal inundation is likely to be one of the more obvious impacts of sea level rise. In this study we examine the occurrence of tidal inundation at selected estuary sites in NSW. We identify sites experiencing tidal inundation now and examine recent changes to the frequency of inundation at two case study sites. We combine observations of local inundation and high-resolution digital elevation data with local tide gauge data to identify thresholds for tidal inundation. When these thresholds are exceeded, tidal water inundates streets and footpaths for a short period of time - so called 'nuisance inundation' or 'sunny day flooding'. We identify numerous sites along the NSW coast which are subject to tidal inundation. At two case study sites, Woy Woy and Botany, we show increasing frequency of inundation with nuisance events (5 year average) at Woy Woy more than doubling since the late 1980's. By examining current inundation exceedance, we show that even modest near-future increases in sea level are likely to lead to a significant increase in the number of days when inundation occurs in the lowest lying streets.