Major coastal flooding in southeastern Australia, associated deaths and weather systems

Abstract

A new historical database describing major floods and associated weather systems that occurred in coastal catchments, from Brisbane in southeastern Australia to Eden approximately 1500 km further south, is described. In order to produce a homogeneous record of major flood and weather-type frequency we restrict attention to the period 1860–2012, when the region (i) is extensively populated, (ii) has an extensive coverage of meteorological stations, (iii) is extensively connected by telecommunication, and (iv) when there is busy coastal shipping offshore. A total of 253 major floods over this period are identified. A flood is considered here to be ‘major’ if it causes inundation of a river within approximately 50 km of the coast or if there is non-riverine flooding over land near the coast, extending 20 km or more along the coast. All major floods are associated with either (a) East Coast Lows (ECLs) or (b) Tropical Interactions (TIs). Three types of TIs are identified and described. ECLs triggered more major floods than TIs (57 per cent versus 43 per cent), but TIs caused more deaths from freshwater flooding (62 per cent versus 38 per cent) and they tended to cause over twice as many deaths per event (3.6 versus 1.7 deaths/event on average). Some of the most extreme events identified occurred in the 19th century and early-to-mid 20th century. If such events were to occur today they would have catastrophic impacts due to the massive increase in urban development in the study region since that time.