Variability in Severe Coastal Flooding, Associated Storms, and Death Tolls in Southeastern Australia since the Mid–Nineteenth Century

Abstract

The variability in the number of severe floods that occurred in coastal catchments in southeastern Australia since the mid–nineteenth century, along with the variability in both the frequency of the weather types that triggered the floods and the associated death tolls, is analyzed. Previous research has shown that all of the severe floods identified were associated with one of two major weather types: east coast lows (ECLs) and tropical interactions (TIs). El Niño–Southern Oscillation (ENSO) is shown to strongly modulate the frequency of severe coastal flooding, weather types, and the number of associated deaths. The analysis presented herein, which examines links over more than a century, provides one of very few known statistically significant links between ENSO and death tolls anywhere in the world. Over the period 1876/77–2013/14 the average numbers of coastal floods, ECLs, TIs, and deaths associated with freshwater drowning in La Niña years are 92%, 55%, 150%, and 220% higher than the corresponding averages in El Niño years. The average number of deaths per flood in La Niña years is 3.2, which is 66% higher than the average in El Niño years. Death tolls of 10 or more occurred in only 5% of El Niño years, but in 27% of La Niña years. The interdecadal Pacific oscillation also modulates the frequency of severe floods, weather types, and death tolls. The results of this study are consistent with earlier research over shorter periods and broader regions, using less-complete datasets.

Links between East Coast Lows and the spatial and temporal variability of rainfall along the eastern seaboard of Australia

“…have been suggested and this is the topic of recent and ongoing research (e.g. Gallant et al 2012, Pepler et al 2014a, 2014b, Twomey and Kiem 2015, 2016a, Power and Callaghan 2016, Tozer et al 2016). …”

“…frequency, timing) is related to large-scale processes known to be associated with interannual to multidecadal hydroclimatic variability in Australia (e.g. Gallant et al 2012, Pepler et al 2014a, 2014b, Twomey and Kiem 2015, 2016a, Power and Callaghan 2016, Tozer et al 2016. Figure 5 shows the spatial variation in the location of ECLs, categorised by ECL sub-type as per Section 2.1, that have occurred from 1979-2011 during four different phases of the ECL event.…”

The Defining Characteristics of ENSO Extremes and the Strong 2015/2016 El Niño

“…Generated in the equatorial Pacific, ENSO vacillates irregularly between its warm phase, El Niño, and its cold phase, La Niña, peaking in boreal winter and recurring every 2 to 7 years. The central‐to‐eastern tropical Pacific Ocean warms during an El Niño and cools in a La Niña, causing large‐scale changes in ocean and atmospheric circulations within and outside the tropical Pacific, elevating likelihood of extreme weather events around the globe, such as cyclones (e.g., Bell & Chelliah, ; Jin et al, ) and extreme rainfall (e.g., Power & Callaghan, ). The impacts tend to be more dramatic overall during extreme El Niño events, such as the 1982/1983 (Philander, ) and 1997/1998 (McPhaden, ) events, which can translate to significant fatalities, economic losses, and large‐scale environmental degradation (Changnon, ; Glynn, ; Merlen, ; Valle et al, ).…”

The frequency of major flooding in coastal southeast Australia has significantly increased since the late 19th century

“…Previous research indicates that there is a great deal of variability in eastern Australian streamflow, flooding and flood risk on interannual (Chiew et al 1998, Power et al 1999, Kiem et al 2003, Verdon et al 2004, Power and Callaghan 2016, and decadal/multidecadal timescales (Power et al 1999, Franks 2002Kiem et al 2003, Power andCallaghan 2016). Much of the interannual variability is due to the El Niño-Southern Oscillation (Chiew et al 1998, Power et al 1999, Kiem et al 2003, Verdon et al 2004, Kiem et al 2001, 2003, Pui et al 2011, Power and Callaghan 2015.…”

“…Much of the interannual variability is due to the El Niño-Southern Oscillation (Chiew et al 1998, Power et al 1999, Kiem et al 2003, Verdon et al 2004, Kiem et al 2001, 2003, Pui et al 2011, Power and Callaghan 2015. Much of the decadal/multidecadal variability is due to the Interdecadal Pacific Oscillation (IPO; Chiew et al 1998, Power et al 1999, Franks 2002, Kiem et al 2003, Verdon et al 2004, Franks and Kuczera 2002, Henley et al 2015, Micevski et al 2006, Christensen et al 2013, Kiem and Verdon-Kidd 2013, Power and Callaghan 2016.…”