Australian Meteorological and Oceanographic Journal 64 (2014) 183–213

Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems

Jeff Callaghan1 and Scott B. Power2 1Bureau of Meteorology, Queensland Office, Brisbane (retired) 2Bureau of Meteorology, Melbourne, Australia.

(Manuscript received May 2014; revised September 2014)

A new historical database describing major floods and associated weather sys- tems 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 connect- ed 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 identi- fied 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 identi- fied 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.

Introduction from Brisbane (Queensland) in the north to Eden (New South Wales (NSW)) 1500 km further south. The study region is Major floods frequently isolate towns, and can cause death, depicted in Fig. 1. Over six million people live in this rapidly major disruptions to road and rail links, the evacuation of developing zone. many houses and business premises, and the widespread As we are specifically concerned with major flooding flooding of farmland. Major flooding can lead to high death near the coast, we consider a flood to be major if (i) it causes tolls. For example, there were at least 90 known deaths inundation of a river within approximately 50 km of the caused by floods in June 1852, and 25 deaths during the coast or (ii) if there is non-riverine flooding overland near Brisbane River catchment floods in January 2011. the coast, from the active part of a weather system, that Given these severe impacts, it is of interest to know extends at least 20 km along the coast. In (i) extreme rainfall how frequently major floods have occurred in the past and extends well into the hinterland and the upper reaches of the what weather systems were associated with such floods. river catchments, causing a flood that drains down the river We therefore examine a large number of historical records systems to coastal areas. In (ii) extreme rainfall is confined describing floods, and associated weather and impacts. to the coast and floods form directly over the coastal area We restrict attention to major floods that have occurred in rather than propagating down the river systems. At major coastal catchments in eastern Australia during 1860–2012, coastal centres there are official river height records that Corresponding author address: Dr Scott B. Power, Bureau of Meteorol- determine whether a flood meets the major level or not, and ogy, PO Box 1289, Melbourne, 3001, Victoria, Australia. Email: s.power@ we have used this data if available. bom.gov.au

183 184 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 1. The study region, between the coast and the white large dams in the study region in the Brisbane River System dotted white line. include Somerset Dam (opened in 1953) and Wivenhoe Dam (opened in 1985). In this investigation we determine whether or not a given weather system triggered major flooding. If major flooding was caused in more than one catchment we regard this as a single major flooding event. Major flooding has obviously been reduced in the above two major river systems. However, this is unlikely to have changed the number of major flood events in our study region. This is because adjacent river systems also experienced major flooding when the Hawkesbury and Brisbane River systems experienced major flooding, prior to the building of the dams. For example, all major floods in the Hawkesbury occurred in conjunction with major floods in the Georges River, and the situation in the Georges River is largely unchanged since the 19th century when the largest floods occurred there (Maddocks 2001). So any reduction in major flooding occurrences from the Warragamba Dam would not reduce the number of major flood events we identify. The situation in the Brisbane River is similar in that major floods there occurred simultaneously with major floods elsewhere. The historical and scientific information and the methods used to identify (a) major floods, (b) associated weather systems, and (c) death tolls are described in Section 2. An overview of the types of weather systems that triggered the major floods is provided in Section 3. Specific illustrative examples of the weather systems are provided in Sections 4 and 5. Monthly climatologies of the frequency of (a)–(c), and the number of deaths per flood and per weather system type, are given in Section 6. The results are summarised and discussed in Section 7.

Historical sources and method In some cases river floods and coastal flash flooding can Identifying major floods occur simultaneously, as was the case of the June 2007 storm Major floods are typically and most easily identified from in Newcastle and the Central Coast (known as the Pasha official river height records. Such records were available in Bulker storm as a result of a 40 000 tonne bulk carrier ship numerous reports from the Bureau of Meteorology, regional that was grounded during the event). This storm resulted councils and the NSW State government. See Appendix 1 in flash flooding in the urban area of Newcastle and as far for further details on these and other data sources. While south as the Central Coast, impacting 800 000 people, and this information provides an extremely valuable record of more general flooding on the Hunter River three days later major flooding, it does not provide a comprehensive list of (Verdon-Kidd et al. 2010; see also Section 4.1). flooding for our period of interest: 1860–2012. Gaps were River floods have been mitigated over the period of our most clearly evident for some of the less populated sections study by increasing discharge rates through dredging and of the NSW coast. In order to identify additional major floods removing rock outcrops etc., and by building dams to store we conducted a search and analysis of other information flood waters. This mitigation has been offset to some extent sources. We first noted the occurrence of severe weather by an increase in urban runoff, caused by growth in urban systems in the study region identified previously by Public areas, especially during the last 40 years. Dams have been Works Department (1985) and Callaghan and Helman (2008). constructed throughout the study region. For example, We then examined rainfall records, as well as newspaper the Warragamba Dam on the Nepean-Hawkesbury River reports archived in the Australian National Library. The System was opened in 1960. The Warragamba Dam slows latter included official reports from the Chief Astronomer the release of flood waters into downstream areas. In 1961 and Chief Meteorologist or official government observers flood waters coming from the Warragamba River were in remote areas at the time. This allowed us to ascertain reduced by a quarter and delayed by several hours. Other whether or not major flooding occurred in association with Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems185

these weather events, or if major floods might have occurred and the characteristics of the MSLP fields associated with in cases where corresponding river height information was them, are presented in later sections. incomplete or unavailable. This also revealed additional severe weather events not listed by Public Works Department (1985) or Callaghan and Helman (2008). It also revealed Weather systems associated with major flood events that did not correspond to known major major flooding flooding as indicated by official river height records. In East Coast Lows (ECLs) and Tropical Interactions (TIs) such cases the likelihood of major flooding was considered The records assembled for this investigation show that all of reasonably high because the available evidence pointed to the major floods were triggered by either (1) East Coast Lows extremely high rainfall over a broad area and/or widespread (ECLs) or (2) Tropical Interactions (TIs). ECLs are defined flood damage. These events were therefore included in our for the purposes of this study as (a) low pressure systems list of major floods. A full list of the major floods during the (either a closed low or trough) near or on the eastern coast period 1860–2012 is given in Table 1. Table 1 also indicates of Australia of non-tropical origin, which are located (b) east what sort of weather system triggered the flood, and it of a deep layered trough and (c) north of a high pressure provides the death tolls from freshwater flooding for each system, with (d) heavy rain in coastal areas generally south event. Further details on each of these events are available in or southwest of the low pressure centre. The importance of the supplementary appendix. ECLs to heavy rainfall over the eastern seaboard of Australia We identified a total of 253 major floods between 1860 has been noted previously (e.g. Hopkins and Holland 1997; and 2012 over eastern Australia. Of these 191 have river Pepler and Rakich 2010; Pepler et al. 2013). height records while the remaining 62 are based on the Three different types of TIs are identified: (i) Type one: complementary information discussed above. While care a tropical cyclone (TC) that moves into the study region has been taken, the partially subjective nature of the process retaining its TC characteristics (e.g. minimal vertical shear); means that there is no guarantee that all major floods have (ii) Type two: This occurs when a deep layered trough system been included or that all of the events included were actually extends well into the tropics and either interacts with a TC major floods. In fact we identified additional events in which or tropical low (TL), or forms an inland trough with strong major flood events might have occurred but as the evidence northeasterlies on the coast. (iii) Type three: a TC or TL that is was not as strong we did not include them in our analysis. re-organised or transformed into a more ECL-like structure All of these additional events are listed in Table 2. while interacting with a deep-layered trough as it moves into the study region. This particular TI is often referred to as an Determination and classification of weather system types Extratropical Transition or ET (e.g. Callaghan 2005). Weather systems associated with flooding were studied in detail using available upper wind data back to the 1950s. More details on the general features of the Prior to this we use NCEP/NCAR upper wind data back to weather systems linked to flooding 1948, when the scale of the flooding was sufficiently large All of the systems identified produced strong, large-scale, enough to be captured by the coarse resolution (2.5° by onshore winds. Our analysis of many systems also indicates 2.5°) of the reanalysis charts. From these analyses we were that thunderstorms are often embedded in this large- able to characterise the evolution and distortion of isobars scale wind structure, and the thunderstorms frequently during interactions with deep mid- to upper-level troughs contributed to major flooding. Such thunderstorms should for various kinds of synoptic systems. This then enabled us be contrasted with more typical thunderstorms that occur to infer upper level activity from the mean sea level pressure in winds with a westerly component above the atmospheric (MSLP) field alone. boundary layer (Callaghan and Davidson 1990; Callaghan Early MSLP analyses were obtained from Bureau of 1996). These more typical thunderstorms can also cause Meteorology charts published in various newspapers, the flooding. However, the associated flooding is almost always earliest being from 1910 in the Sydney Morning Herald. Prior much less extensive than flooding that occurs in association to this an excellent record of Australian charts and detailed with large-scale onshore winds identified in this study. newspaper description of significant weather was created TCs are characterised by moist inflow at lower levels, by the Meteorological pioneer Sir Charles Todd (Chief rising air particularly in the convective eye wall section Astronomer of South Australia). These charts extend back of the storms and then upper outflow at the top of their to 1879 and can be found at www.charlestodd.net/Todd_Hi- circulations generally in the 200 hPa to 150 hPa levels. This is Res/. Earlier charts were created using official meteorological often referred to as the in, up and out property of TCs. The observations published in the newspapers at the time. upper outflow in TCs can be inferred from cirrus cloud in In the period from 1948 we found that all major floods satellite imagery. A detailed description of the upper wind were associated with four distinct kinds of weather systems. pattern is described by e.g. Ventham and Wang (2007). By the As MSLP data are available for all major floods prior to 1948, time TCs reach the study region their structure has typically we were also able to infer which type of weather system changed to resemble an ECL. This change is referred to as triggered major flooding events. The four weather-types, Extratropical Transition (ET). 186 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Table 1. A list of the major floods identified in this study, together with the type of meteorological event that triggered the flood and the associated death tolls. East Coast Lows (ECLs) are sub-divided into two sub-classes depending on where the initial intensification occurred. ECL N refers to an ECL developing north of Yamba (29.4°S); ECL NC Yamba to Taree (31.9°S); ECL C Taree to Wollongong(34.5°S); ECL S Wollongong to Eden(37.0°S); ‘L’ added means the ECL made landfall from the sea and ‘SEC’ added means secondary low, an example of which is shown below. Tropical Interactions (TIs) are broken into three sub-classes as described in the text. An asterisk in the first column indicates that the event was identified in this study and was not recognized in official records previously. See Section 2 for further details.

Freshwater No. Location Date Type flooding fatalities

1 South Coast NSW 8–10 Feb 1860 ECL C L 36

2 Georges River and Shoalhaven River 28 April 1860 ECL C L 1

3 Georges River 17 Nov 1860 ECL C 1

4 Grafton 28 April 1861 ECL N

5 Grafton and Kempsey 13–17 Feb 1863 TI3 16

6 Brisbane 17 March 1863 TI2

7 Hunter and Macleay 8–12 Feb 1864 TI2 17

8 Brisbane 17–20 March 1864 TI1

9 Newcastle and Maitland 2–3 June 1864 ECL C

10 Georges and Shoalhaven Rivers 10–11 June 1864 ECL C

11 Macleay 14–15 July 1864 ECL NC 2

12 Grafton and Kempsey 7–9 August 1864 ECL N

13 Manning and Macleay River 12 July 1866 ECL NC

14 Kempsey, Grafton, Nowra and Moruya 26–27April 1867 TI2 7

15 Hawkesbury River and Hunter River 19–21 June 1867 ECL C L 36

16* Nepean River 8–9 May 1869 ECL C 2

17* Brisbane and all creeks 4–10 March 1870 TI1 2

18 Clarence, Richmond and Macleay 18–21 March 1870 ECL N 8

19 Hunter, Hawkesbury and Shoalhaven Rivers 25–26 April 1870 ECL S 7

20 Moruya and Hunter 11–13 May 1870 ECL C 1

21* Hunter to South Coast 24–26 Dec 1870 ECL C 1

22 Newcastle 18–19 March 1871 ECL C 2

23 Hawkesbury and Shoalhaven Rivers 25–26 Feb 1873 ECL NC

24 Maitland, Singleton and Morpeth 26 Jan 1874 TI2 2

25 Macleay and Kempsey 26–27 Feb 1875 TI2 1

26 Grafton 15–19 July 1876 ECL N 9

27 Sydney and Bega 6–9 Feb 1878 ECL NC 1

28 Grafton and Lismore 9–11 May 1879 ECL N 2

29 Macleay River 23–25 June 1879 ECL N 1 Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems187

Freshwater No. Location Date Type flooding fatalities

30* Wilson and Paterson Rivers 6–8 Aug 1879 ECL NC

31 Hawkesbury and Hunter Rivers 8–10 Sept 1879 ECL C 1

32 South Coast NSW 13–17 Sept 1879 ECL C 1

Brisbane, Logan, Upper Richmond and 33 20–24 Jan 1887 TI1 26 Clarence Rivers

34 Grafton, Port Macquarie 8–13 Feb 1887 TI1

35 Georges River 13–14 April 1887 TI2

36 Gold Coast 13–15 July 1887 TI3

37 Pine River Brisbane 12–13 Aug 1887 TI2 1

38* Port Macquarie 8–9 Nov 1887 ECL SEC NC

39* Yamba 8–11 Oct 1888 ECL N

40 Georges River 26 May 1889 TI3 4

41 Brisbane and Grafton 17–20 July 1889 TI3

42 Grafton, Coraki 24 Jan–4 Feb 1890 TI2 2

Brisbane, Lismore, Grafton, Macleay, Manning, 43 10–13 March 1890 TI1 17 Hasting and Hunter Rivers

44 Southeast Qld, Grafton 24–28 March 1890 TI2 9

45 Shoalhaven River 22–27 June 1891 ECL C

46* Port Macquarie 26–27 Feb 1892 ECL SEC NC

47 Georges River 18–20 Mar 1892 TI2

48 Grafton Lismore and Kempsey 1–4 April 1892 TI1 5

49 Brisbane and Ipswich 1–4 Feb 1893 TI3 29

50 Grafton 11 Feb 1893 TI1 1

Brisbane, Ipswich, Murwillumbah, Lismore 51 18 Feb 1893 TI1 6 and Grafton

52 Bega 4–6 March 1893 ECL S

53 Maitland, Kempsey 8–10 March 1893 ECL C 10

54 Brisbane, Ipswich, Grafton and Kempsey 10–11 June 1893 TI3 3

55 Taree, Macksville and Port Macquarie 5–6 March 1894 ECL NC 1

56 Tweed River 11–15 March 1894 TI3

57 Georges, Manning and Hunter Rivers 22–23 Jan 1895 ECL NC

58* Gold Coast Northern Rivers 29–31 Jan 1895 TI3

59 Brisbane 9–11 Jan 1898 TI2 3

60 Georges, Bega, Shoalhaven and Hunter Rivers 13 to 14 Feb 1898 TI3 3 188 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Freshwater No. Location Date Type flooding fatalities

61* Newcastle 5–7 May 1898 ECL C

62 Bega 23–29 May 1900 ECL S

Hawkesbury and Georges Rivers, Wagga and 63 4–6 July 1900 ECL C Goulburn

64 Belliinger and Nambucca Rivers 23 July 1900 ECL NC

65 Macleay 1–3 June 1903 ECL N

66 Hawkesbury and Hunter Rivers 8–11 July 1904 ECL C

67 Nambucca and Hunter Rivers 23–24 Feb 1908 ECL N

Brisbane River and Creeks Rosewood and 68 11–16 March 1908 TI3 9 Hunter River.

69* Illawarra area 18–19 July 1910 ECL C

70* SE Qld and Manly 12–13 Dec 1910 ECL NC 1

71* Shoalhaven River 11–13 Jan 1911 TI3

72* Sydney 8–9 March 1913 TI3 4

73 Macksville and Hunter at Morpeth and Dungog 13–15 May 1913 ECL NC 1

74 Bega 28–30 June 1913 ECL C

Georges River, Illawarra, Moruya and possibly 75 20–24 March 1914 TI2 Bega

76* Coffs Harbour to Sydney 17–19 June 1914 ECL N

77* Sydney Region 30–31 Dec 1914 TI3

78 Nowra 3–6 Oct 1916 TI3

79* Sydney 19 Sept 1917 ECL NC

80 Coffs Harbour LGA 8–10 Nov 1917 ECL N 7

81 Bega, Lake Illawarra 25–27 Feb 1919 ECL C 2

82 Newcastle 9–12 Dec 1920 ECL C 1

83 Grafton, Bellingen and Macksville 14–16 May 1921 ECL N 2

Murwillumbah Lismore, Casino, Kyogle, 84 22–24 July 1921 TI3 9 Grafton, Macksville and Kempsey

85* Southeast Qld and northern NSW 27–29 Dec 1921 TI2 5

86* Nowra 24–27 July 1922 ECL NC 1

87 Murwillumbah 4–12 March 1925 TI2 1

88 Shoalhaven River, Bega and Bulli 9–11 May 1925 ECL C 2

Moruya River, Nowra, Gundagai, Yass and 89 25–28 May 1925 ECL S 9 Wagga

90* Sydney Grafton Bellingen 18–23 June 1925 TI3 5 Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems189

Freshwater No. Location Date Type flooding fatalities

91 Hunter River 24 to 26 March 1926 TI3

92 Newcastle, Wyong, Hunter 15–18 April 1927 ECL NC 2

93 Grafton, Bellengen 14–20 Feb 1928 TI1 11

94 Macksville, Gloucester, Taree and Kempsey 7–9 Feb 1929 ECL NC 4

95* Brisbane, Gold Coast and northern NSW 29–30 June 1929 TI3 3

96 Illawarra, Nowra 1–2 June 1930 TI3 1

97 Hawkesbury near Gosford, Lake Macquarie 16–19 June 1930 ECL N 1

98 Brisbane suburbs, Murwillumbah and Lismore 3–8 Feb 1931 TI2 2

99 Hunter 21–23 April 1931 ECL NC 2

100 Gosford, Sydney 5–7 July 1931 ECL C 7

101* Sydney, Illawarra 21–23 Jan 1933 TI2 8

102 Bega 23–24 June 1933 ECL S

103 Moruya River and Clyde River (Batemans Bay) 5–8 Jan 1934 TI3 2

104 Nerang River and Brisbane Creeks 21–23 Feb 1934 TI3 3

Southeast Qld and just under major flood level 105* 15–16 March 1937 TI3 1 Grafton

Murwillumbah, Coffs Harbour LGA, Casino 106 17 to 20 Jan 1938 TI2 1 and Kyogle

107 Coffs Harbour Region 1 Feb 1938 TI2

Illawarra, Nepean, Hawkesbury and Georges 108* 22–25 Aug 1938 ECL C River

109* Sydney and suburbs 27–28 March 1942 ECL SEC C 6

110* Sydney, Illawarra 12–15 Oct 1942 ECL N 1

111 Georges River and Lake Illawarra 16–17 May 1943 ECL N

112 Nepean Georges and Hawkesbury Rivers 19–23 May 1943 ECL C

113 Moruya 7–9 April 1945 ECL N

Tweed, Richmond, Clarence and Bellinger 114 10–11 June 1945 TI3 5 Rivers

Grafton, Kempsey, Bellingen, Wauchope and 115 23–26 March 1946 TI3 5 Macksville

116 Lower Hunter, Lake Macquarie and Newcastle 16–18 April 1946 ECL NC 1

117 Logan and Nerang Rivers and Slacks Creek 23 Jan 1947 TI1 2

118 Macksville, Murwillumbah, Richmond River 1–2 May 1948 TI3 190 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Freshwater No. Location Date Type flooding fatalities

119 Lismore, Murwillumbah and Grafton 14–16 June 1948 TI3

Georges River, Lake Macquarie, Maitland, 120 19 June 1949 ECL NC 7 Wyong

121 Kempsey, Macksville 25–26 Aug 1949 ECL NC 6

122* Brisbane to Sydney 16–19 Jan 1950 TI3 7

123 Bega and Hunter River at Maitland 6–8 Feb 1950 ECL NC

124 Sydney, Hunter region 15–20 June 1950 ECL C 5

125 Macksville; Grafton, Kempsey and Maitland 21–26 June 1950 TI3 6

126* Newcastle, Sydney and Illawarra 10–12 Sept 1950 ECL NC 1

127 Maitland 17–19 Jan 1951 ECL NC 2

128* Northern Rivers 20–26 Jan 1951 TI3

129 Illawarra and Hawkesbury 14–16 June 1952 ECL C 3

130 Nepean River 24–28 July 1952 ECL C

131 Hunter River 4–7 Aug 1952 ECL C

Maitland; Bellingen, Mudgee, Singleton, 132 12 –15 Aug 1952 ECL N Walcha, Kempsey and Armidale

133 Macksville 23–25 March 1953 TI3 2

134 Gold Coast to Kempsey 19–22 Feb 1954 TI1 30

135 Grafton 11–13 July 1954 TI3

136 Maitland, Dubbo, Gilgandra 22–26 Feb 1955 TI2 25

137 Murwillumbah, Lismore and Grafton 26–29 March 1955 TI2 1

138* Sydney, Illawarra southern suburbs 30 April–1 May 1955 ECL C 1

139 Georges, Hawkesbury and Shoalhaven Rivers 9–11 Feb 1956 ECL C 7

140 Murwillumbah, Lismore and Grafton 17–19 Feb 1956 TI3 2

141 Grafton, Coffs Harbour LGA 21–22 Jan 1959 TI3

142 Major floods Grafton and Lake Illawarra 16–19 Feb 1959 TI3

143* Sydney 21 July 1959 ECL C

144 Widespread very severe floods Illawarra 20–22 Oct 1959 ECL C

145 Nowra 29–30 Oct 1959 TI2

146 Macksville, Kempsey 11–14 Nov 1959 ECL N L

147* Bega 3–5 March 1961 ECL C

148* Nowra 24–26 March 1961 TI2

149 Hawkesbury and Georges Rivers.,Illawarra 17–22 Nov 1961 ECL N Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems191

Freshwater No. Location Date Type flooding fatalities

150* Port Macquarie 7–12 Jan 1962 ECL SEC NC

151 Grafton, Coffs Harbour LGA, Macksville 6–9 April 1962 TI3

152 Hunter River 9–14 May 1962 ECL NC

153 Lismore, Bellingen and Grafton. 9–12 July 1962 ECL N 3

154 Grafton 1 Jan 1963 TI3

155* Port Macquarie 28–29 March 1963 ECL NC

Hastings, Macleay, Bellinger, Nambucca Rivers 156 24–29 April 1963 TI3 and Coffs Harbour LGA

Murwillumbah, Lismore, Grafton, Kempsey, 157 7–9 May 1963 ECL N Coffs Harbour LGA and Macksville

158 Georges River. 29–30 August 1963 ECL SEC C

159 Macksville 6–9 March 1964 ECL N

Illawarra and Hawkesbury, Georges and 160 9–12 June 1964 ECL C Hunter Rivers

161 Lismore 18–21 July 1965 ECL N

162 Coffs Harbour LGA 28–31 Jan 1967 TI1

163 Lismore 18–19 March 1967 TI1

Gold Coast, Lismore, Murwillumbah, Grafton 164 10 to 14 June 1967 TI3 3 and Macksville

165 Clarence, Macleay and Nambucca Rivers 9–13 Jan 1968 TI2 1

166* Severe floods Illawarra 15–16 April 1969 ECL S

167* Severe flooding Illawarra 13–14 Nov 1969 ECL C

168 Hunter Jan/Feb 1971 TI2 5

169 Bega 6–7 Feb 1971 TI2 2

170 Tweed River 11–13 Feb 1972 TI1

171 Tweed River 2–3 April 1972 TI3

172 Macksville, Murwillumbah and Lismore 27–29 October 1972 TI2

173 Brisbane Coffs Harbour LGA 6–8 July 1973 TI3 4

Brisbane, Ipswich, Gold Coast, Murwillumbah, 174 25–29 Jan 1974 TI3 10 Grafton and Lismore

Murwillumbah, Lismore, Grafton and 175 11–13 March 1974 TI2 Macksville

176 Coffs Harbour LGA 19–23 April 1974 TI2 1

177 Shoalhaven and Moruya Rivers. Illawarra 26–28 August 1974 ECL C Unknown

178* Mid North Coast NSW 24–25 Feb 1975 ECL NC

179 Lismore 2–3 March 1975 ECL N 192 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Freshwater No. Location Date Type flooding fatalities

180 Moruya, Illawarra 9–12 March 1975 ECL S

181 Illawarra, Shoalhaven River 21 June 1975 ECL NC Unknown

182* Coffs Harbour , Macleay 11–13 Nov 1975 ECL N

183* Bowraville 18–22 Dec 1975 TI2

184 Tweed and Clarence Rivers 1–12 Feb 1976 TI3

185 Kempsey , Lismore region 28 Feb–5 Mar 1976 TI2

186 Nowra, Moruya 14–19 Oct 1976 ECL C

187* Illawarra, Nowra 22–24 Feb 1977 ECL C

188 Hunter River and Lake Illawarra 3–4 March 1977 ECL C

189 Coffs Harbour LGA and Macksville 15–18 May 1977 ECL NC

190* Newcastle and Sydney 28–29 Jan 1978 ECL C

Richmond, Tweed, Hastings, Manning, 191 Hawkesbury, Georges, Shoalhaven, Moruya 17–21 March 1978 TI3 6 Rivers and Lake Illawarra

192* South Coast NSW 1–3 June 1978 ECL C

193 Gold Coast, Grafton and Macksville 6–10 May 1980 ECL N

194 Georges River 20–22 March 1983 TI2

195 Illawarra 18 Feb 1984 TI2

196 Lismore 7–9 April 1984 TI3

197* South Coast NSW 28 July 1984 ECL C

198* Sydney 5–9 Nov 1984 ECL NC

199 Macksville 8–10 July 1985 TI3

200 Nepean, Hawkesbury and Georges Rivers 5–8 Aug 1986 ECL C 6

201 Lismore 4–5 March 1987 ECL N

202 Murwillumbah and Lismore 9–10 May 1987 ECL N 4

203 Georges River. 24–26 Oct 1987 ECL NC

204* Sydney, Newcastle 11–13 Nov 1987 ECL NC

205 Grafton 4–7 April 1988 TI3

206 Southeast Qld 10–11 April 1988 TI3

207 Hawkesbury, Georges and Shoalhaven Rivers 29–30 April 1988 ECL NC

208 Sydney beach suburbs, Bega and Nowra 5–7 July 1988 ECL SEC N

209 Murwillumbah, Lismore and Grafton 1–2 April 1989 TI2 7

Major floods Kempsey, Murwillumbah and 210 23–25 April 1989 TI3 3 Grafton Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems193

Freshwater No. Location Date Type flooding fatalities

211 Georges River 2–3 Feb 1990 TI3 6

212* Illawarra 23–24 May 1990 ECL S

213 Shoalhaven, Nepean River and Lake Illawarra 1–3 Aug 1990 ECL C

214 Georges River 8–12 June 1991 ECL NC

215 Coffs Harbour LGA, Pine River and Ipswich 11–15 Dec 1991 TI2 2

216 Illawarra, Moruya River 9–10 Feb 1992 ECL NC

217* Narooma 25 Sept 1992 ECL S

218* Brisbane 19–20 Jan 1994 TI 2 4

219* North Coast NSW 1–7 March 1995 TI3

220* Newcastle to Illawarra 25 Sept 1995 ECL C

Grafton, Logan River, Brisbane Creeks, Ipswich 221 1–6 May 1996 TI3 5 and Laidley region

222 Illawarra, Georges River 30 Aug–1 Sept 1996 ECL C 3

223 Coffs Harbour 23–24 Nov 1996 ECL N 1

224* Bega 1–2 March 1997 ECL S

225* Sydney 08–11 April 1998 ECL NC 1

226* Sydney 7–8 Aug 1998 ECL C 4

227 Illawarra 17 Aug 1998 ECL SEC C 1

Major flood Brisbane River above Wivenhoe 228 8–10 Feb 1999 TI3 7 and Pine River

229* Northern Rivers 1–3 March 1999 TI2

230 Macksville 14–16 July 1999 ECL NC

231* Illawarra Flood Nowra 3.5m 23–25 Oct 1999 ECL S

232* Mid North Coast NSW 7–9 March 2000 ECL S

233 Lismore, Murwillumbah and Grafton 30 Jan–2 Feb 2001 TI3 1

Grafton, Coffs Harbour region, Brisbane and 234 8–9 March 2001 ECL N 2 Gold Coast

235* Southeast Qld. Northern Rivers 4–6 March 2004 TI3 3

236 Bellinger River 18–20 Oct 2004 ECL N

237 Gold Coast and Tweed Heads. Lismore 30 June 2005 ECL N 3

238 Hunter River 8 June 2007 ECL C L 9

239* Mid North Coast NSW 20–25 Aug 2007 ECL N

240 QLD/NSW border areas 27 Dec 2007–5 Jan 2008 TI3 194 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Freshwater No. Location Date Type flooding fatalities

241* Mid North Coast to Illawarra 2–6 Feb 2008 TI2

242 Bellinger River 13–17 Feb 2009 ECL N

243 Bellinger and Nambucca Rivers 30 Mar–2 Apr 2009 ECL N 1

Lismore, Grafton and Kempsey. Brisbane and 244 19–24 May 2009 ECL N 1 Ipswich Creeks

245 Bellinger, Orara, Nambucca and Kalang Rivers 26–28 Oct 2009 TI2

246* Coffs Harbour Severe flash flooding 5–7 Nov 2009 ECL NC

247 Albert River, South Coast NSW 5–7 Feb 2010 TI3

248* South Coast NSW 14–16 Feb 2010 ECL S

249* Lennox Head 2–3 June 2010 ECL N

Brisbane and Bremer Rivers, Lockyer Creek 250 6–11 Jan 2011 TI2 25 and Clarence River

251 Bega and Moruya Rivers. 19 to 24 March 2011 ECL SEC S 1

Kempsey, Taree, Wauchope, Wingham and 252 13 –15 June 2011 ECL N Coffs Harbour LGA

Tweed, Clarence and Bellinger Rivers, 253 22–27 Jan 2012 TI2 Gold Coast

Table 2. Additional high rainfall events not considered major floods after assessment of all available historical evidence of associ- ated impacts. Fatalities from all causes listed in text. Fatalities from freshwater drowning are singled out in column three.

Fresh- Fresh- water water No. Event No. Event flooding flooding fatalities fatalities

1 2–25 July 1860 Low passed east of Sydney 1 4 Tropical low 3–6 Aug 1889, Yamba 231.1 on a southward track. One fatality. Huge mm record Aug daily rainfall flooded the waves came through the Heads bursting lower town and caused a huge damaging on the rocky headland of Middle Head and landslide. adjacent points, the foam was carried high above the cliffs and swept far inland. Three vessels wrecked. Near Major floods. 5 The East Coast Low 23–24 September 1892. Ten fatalities. Heavy rain. Maximum mea- sured gust 104 knots Sydney with many 2 February 1867 Tropical Low near Brisbane. 1 buildings damaged or unroofed. Robert- One fatality. Flooding in Brisbane City son PO 196.9 mm 24 Sept record. Schooner basements. Severe flash flooding. Prob- disappeared. ably record rain SEQ—200 mm in 13.5 h Brisbane. Flooding Brisbane, Ipswich and 6 East Coast Low 8–13 July 1899. Bilambil Lockyer. (Tweed) 24 h rainfall 323.1 mm July record and just below major flood level at Lismore 3 East Coast Low Near Port Macquarie 22–24 and Coraki Sept 1881 (-11.4 -13.6 -23.9)/3=-16.3 Port Macquarie record September daily rainfall. Three vessels wrecked. 7 East Coast Low 27 Sept 1903. Flooding in Newcastle. Ship ashore Port Stephens. 24 h rain to 262.1 mm Raymond Terrace 24 h record Nobbys 157.5 mm. Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems195

Fresh- Fresh- water water No. Event No. Event flooding flooding fatalities fatalities

8 Coast Low 27–29 April 1904. Two fatalities. 16 4–8 June 1933 Low formed off Northern Two men drowned in fishing boat at Bondi Rivers Coast and then moved NE. Record as heavy seas suddenly came up. 24 h re- June rain Mid North Coast and Floods. cord April rain Mount Kembla 209.6 mm

9 East Coast Low 30–31 August 1906. Seven 17 9–10 July 1950 Easterly gales north of fatalities at sea. Record Rainfall Coffs large high 24 h July record rain Mid North Harbour 269.2 mm. Schooner Broke up in Coast—Raleigh 177.8 mm big seas.

10 1–2 Feb 1908 Low rapidly developed 18 28–30 July 1950 Low developed near Newcastle/Sydney. Floods Illawarra 24 h Brisbane. 24 h July record rain Northern rainfall to 238.3 mm. Cruise ship damaged Rivers Mullumbimby 271.8 mm off Sydney Heads and Ferries damaged in Harbour. Wind damage in Watsons Bay.

19 16–17 November 1950 Low Brisbane. One 11 East Coast Low 9–11 June 1909. Flash fatality. Structural wind damage; 24 h Nov flooding South Coast NSW with heavy record rainfall Mid North Coast Telegraph 24 hour rainfall totals 228.9 mm Brogers Point 222.3 mm Creek.

20 Tropical Cyclone 19 March 1951 24 h rain 12 1–2 June 1910 Tropical low. Record southeast Qld to 309.9 mm March record 24 h June rainfall Cleveland (Brisbane) Point Lookout 243.8 mm. 285.4 mm; Other totals St Helena Island 246.4 mm; Northern Rivers Mullumbimby 231.1 mm. 21 24–26 Sept 1951 East Coast low Record Sept rainfall Illawarra Kangaroo Valley 13 Small intense East Coast Low 18–20 348.0 mm 25th where farmer drowned; October 1914. Rozelle schooner 98 tons Large storm surge Jerry Bailey (Shoal- wrecked near Cape Three Points. Sudden haven River). storm destroyed all six fishing boats Coffs Harbour. Port Macquarie 151 mm record 22 East Coast Low 14–16 April 1952. One 1 Oct daily rainfall. fatality. Heavy rain washed sections of the South Coast railway line away. 24 h rainfall April record NSW South Coast Tilba Tilba 207.0 mm. 14 Tropical cyclone extra tropical transition 6–8 April 1921. Heavy rainfall. Steamer in 23 East coast low 3–8 May 1953. One fatality. 1 distress in heavy seas off Jervis Bay (Navy 24 h rainfall record NSW South Coast to aid); Launch driven ashore Gunnamatta Benandra 358.1 mm Bay. Severe wind damage Cronulla. 24 h rainfall to Illawarra 265.4 mm 24 1–23 January 1955 Monsoon Low near Ten- nant Creek with NE tropical flow into NSW Record January 24 h rainfall Northern Riv- 15 9–12 September 1929. One fatality. Heavy ers to 309.9 mm at Mullumbimby. 75 mm in rainfall. Long fetch of gales generated one hour Sydney flooded homes. big seas and launch was wrecked on Seal Rocks; Wauchope was cut off by floods; Floods in the Hunter and Paterson Rivers; 25 26–27 November 1955. East Coast Low. 24 Wind damage in Newcastle. Very heavy h rainfall record in Sydney at Sans Souci 24 h rainfall in Hunter Gresford 199.4 mm 191.8 mm 11th all time 24 h record rainfall. 196 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fresh- Fresh- water water No. Event No. Event flooding flooding fatalities fatalities

26 ECL South Coast NSW 11–13 May 1956 36 5 March 1959 Low near Melbourne. 24 h 24 h May rainfall record Bermagui South rainfall South Coast NSW Bermagui South 170.9 mm 203.2 mm March record.

27 East Coast Low 24–26 June 1956 Eight 37 19–21 January 1960 Low Coffs Harbour; fatalities. Mountainous seas South Coast Record 24 h Jan rain Macksville 186.2 mm and Bass Strait and ship sunk near Wilsons (116.1 mm day before). Promontory. Heaviest 24 h rainfall South Coast. Wapengo Lake 166.1 mm, Record for June. 38 East Coast Low 24–26 May 1960; Extensive sea damage to Gold Coast Beaches and 28 Tropical cyclone. 21–23 Dec 1956. One 1 interruptions to shipping. fatality. Record Dec 24 h rain Brisbane Airport 152.7 mm Rapid flooding southeast Qld. 39 15–16 Sept 1962 East Coast Low. 24 h totals to 219 mm South Coast and Bega 129.5 mm 29 8–11 July 1957 East Coast Low Sydney 16th (Sept record). Airport 132.6 mm 10th (record for July)— Moruya Heads 165.6 mm 11th (record for July) 40 6–20 March 1963 East Coast Low; 24 h rain to 250.7 mm NSW South Coast March 30 2–24 August 1957 East Coast Low. Damage record at Bundanoon 200.2 mm; 208.3 mm to ships in harbour. Bega 162 mm 23rd Mid North Coast; 242.6 mm Gold Coast record August daily rainfall.

41 East Coast Low June 9–13 1966 Qld/ NSW; Storm surge at Sydney of 0.51 m. 31 9–30 January 1958 ECL near Nowra NSW Maximum 24 h rainfall at Nimbin 253.5 mm South Coast—Tilba Tilba 254.0 mm all time 11th. Record June rainfall since 1903 record 1901 to 1962.

42 7–10 November 1966 1000 hPa ECL Nowra. Robertson 330.2 mm 9th. Record daily 32 11 March 1958 East Coast Low Heavy rainfall for November 1890 to present. seas and erosion Central Coast NSW; 24 h rainfall Central Coast, Avoca Beach 323.9 mm—all time record; Landslides, floods, shipping delayed. Sydney Airport gusts to 43 4–6 Sept 1967 East Coast Low near Smoky 48 knots. Cape; South Coast daily rainfall records for Sept Nowra 134.4 mm and Yalwal 147.3 33 29 June–1 July 1958 Intense low formed mm off Newcastle, July record 24 h rainfall 232.9 mm Benandra South Coast; shipping delayed, Coastal damage. 44 19–23 Oct 1967 East Coast Low; Mid North Coast Wingham 256.5 mm 21st record for Oct 1888 to present 34 Small East Coast Low 5–6 Aug 1958. Record 24 h rain Northern Rivers NSW Rosebank 249.7 mm. 45 Low SW Qld to east of S NSW Coast 4–6 January 1968 Hunter River daily rainfall records-Owens gap 160.8 mm 5th all time 35 East Coast Low 3–5 Jan 1959; January daily record—Aberdeen 140.0 mm 5th Jan Record 24 h rain Lake Cathie (Mid North daily record Coast) 255.4 mm. Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems197

Fresh- Fresh- water water No. Event No. Event flooding flooding fatalities fatalities

46 12–14 August 1968 Low moved to Byron 56 Major low over Eastern Australia 21–25 2 Bay and Lord Howe. Record daily rainfall May 1981 with secondary ECL. At least Mid North Coast Megan and Meldrum two fatalities. Record May 24 h rainfall Mid 251.5 mm and 229.9 mm North Coast Eungai 246.4 mm

47 30–31 October 1969 Low moved west over 57 2–4 Nov 1981 East Coast Low Fraser Is- Nowra; Oct daily rainfall record Illawarra land. Flooding Brisbane City metropolitan Yalwal 174.0 mm. creeks Nov Record 24 h rainfall Brisbane Show Grounds 218.0 mm.

48 Sept 1–2 1970 Lord Howe Low, Roseville 58 9–11 Oct 1982 East Coast Low 24 h rainfall (Sydney), 149.1 mm Sept daily record record Mid North Coast Comboyne South 307.0 mm.

49 Bass Strait and Tasmanian East Coast low 60 3–14 Oct 1985 East Coast Low. Hunter 24 h 8–10 Dec 1970, 9–10 m swells Bass St Oil rainfall records to 205.2 mm Wamberal. rigs large seas NSW south coast -24 h rainfall totals NSW Illawarra to 308.4 mm Maddens Creek

50 ECL 18–21 Jan 1971 daily rain in Hunter to 61 16–17 East Coast Low January 1988 Sydney 263.7 mm Hilldale all time record City 191 mm wettest Jan day on record- Highest 24 h registration Cromer Golf Club 250.4 mm.

51 15–17 Dec 1971 East Coast Low, Mid North 62 The East Coast Low of 29–30 April 1988. 24 Coast Laurieton 215.1 mm 16th December h rainfall April record at Towamba (NSW record 1885 to present South Coast) 206.4 mm.

52 4–5 Nov 1973 East Coast Low. Heavy rain 63 East Coast Low 14–16 Sep 1988. Large South Coast NSW 24 h totals to 228.9 mm swells hit the Gold Coast and N NSW By- Nov records broken ron Bay buoy significant wave height 6.0 m from SE. Lismore 171 mm and Coffs Har- bour 161 mm—record Sept Daily rainfall.

53 980hPa low South Coast NSW 27–28 Nov 1974. Williamtown 100.0 mm 28th wettest 64 9–23 June 1989 East Coast Low. Record Nov day on record. June 24 h rain Mid North Coast Leigh 231.4 mm. Record wave heights Coffs Harbour Buoy.

54 ECL near Coffs Harbour 3–5 July 1975. Wollongong 198.8 mm record July daily 65 5–7 Dec 1989 East Coast Low. 24 h rain rainfall (4th highest). Heavy 24 h rainfall to record Wyong 266.4 mm 253.4 mm.

55 2–3 April 1981 East Coast Low Heavy 24 h 66 4–6 April 1990 East Coast Low conditions. rainfall Mid North Coast Thora 278.2 mm 24 h rainfall record Little Nerang Dam April record Gold Coast 270.0 mm. 198 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fresh- Fresh- water water No. Event No. Event flooding flooding fatalities fatalities

67 East Coast low 5–8 December 1992 Mer- 77 24 Feb 2003 Coral Sea Low. Heavy 24 h imbula 252 mm 6th highest daily rainfall. rain near Grafton 260.6 mm South Grafton Bega 235 mm 6th highest daily December February record rainfall.

68 9–10 March 1993 Tasman Low. Narooma, 78 8 Dec 2004 Developing 999 hPa low NW 195.0 mm 10th March record 1910 to pres- NSW. Heavy 24 h rainfall 208.6 mm Tweed ent. Heads Dec record 1886 to present.

69 10–13 April 1994 East Coast Low. All time 79 9–11 July 2005 Tasman Low. 24 h rainfall to daily rainfall records Illawarra—Culburra 155.0 mm Eden (Timbillica) July record. 229.0 mm and Greenwell Point 225.6 mm

70 1–3 Dec 1994 East Coast Low conditions. 80 30–31 Oct 2005 Low southern inland NSW. Dec record Northern Rivers at Federal 24 h rainfall to 187.4 mm Batemans Bay 196.0 mm. (Buckenbowra) Oct record.

71 2–4 January 1995 Inland low strong NE 81 20 Jan 2006 Tropical Low. 24 h rainfall to winds on coast. All time record daily rain 268.0 mm Tweed Heads Jan record. Local Lorne (near Taree) 269 mm and Flash flooding Northern Rivers.

72 17–19 May 1995 Tasman Low. May 24 h 82 9–30 August 2006 trough Coral Sea. record Illawarra Beaumont 255.0 mm August 24 h record Maclean Northern Riv- ers 159.4 mm.

73 23– 24 Dec 1998 Tropical Low. Record Dec 83 10–12 February 2007 Low Central Inland 24 h rain Gold Coast Hinterland Numinbah Qld. Illawarra 24 h record rainfall for Feb- 308.0 mm. ruary to 247.0 mm Beaumont.

74 4–29 January 1999 Tropical Dip. 24 h totals 84 8–9 April 2008 Coastal Trough. 24 h April to 275.6 mm Narooma 242.4 mm 29th 24 h record 153.2 mm Evans Head record for Jan.

75 1–2 April 1999 East coast low type condi- 85 East Coast Low 3–6 September 2008. Sept tions. Heavy 24h totals Mid N Coast Dia- 24 h record Gold Coast Hinterland 191.0 mond Head 249.0mm all time record. mm at Numinbah and Mid North Coast Upper Orara 161.2 mm.

76 1008hPa low east of Brisbane 5–6 Febru- 86 East Coast Low conditions 9–12 October ary 2002. Heavy rain Mid North Coast Port 2010. 24 h Oct records Brisbane suburbs Macquarie 6th 212.2 mm wettest February Boondall 185.8 mm; Alderley 161.2 mm; day on record. Large waves hit southeast Qld and N NSW beaches. The Brisbane Buoy significant wave height reached 5.0 m. Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems199

We have examined the vertical structure of many ETs and Examples of East Coast Lows (ECLs) ECLs over the last 40 years (Callaghan 2005; 2008). Based In this section we provide examples of East Coast Lows on this extensive analysis, we know that the most common (ECLs) linked to major flooding. We also describe the pattern preceding the development of intense systems, features in MSLP and their development. This development is one in which a tropopause undulation approached the is in many ways characteristic of development in all ECLs. TC from the west. This is similar to the development of an ECLs are sub-divided into four groups, depending on ECL. The tropopause undulation is one of the most obvious where the initial intensification occurred. ECL North (ECL features on a weather chart and is readily identified as a N) refers to an ECL developing north of Yamba (29.4°S); warm anomaly in the 200 hPa isotherm analysis. The low ECL North-Central) (ECL NC) Yamba to Taree (31.9°S); ECL level cyclonic circulation lies mostly to the east or south Central (ECL C), Taree to Wollongong (34.5°S); ECL South east of the undulation and warm air advection at the 200 (ECL S) Wollongong to Eden (37.0°S). While only a minority hPa level over the heavy rain areas of the cyclone leads to of ECLs make landfall, this can cause major disasters. We MSLP falls (Hirschberg and Fritsch 1993). This is consistent identify land-falling ECLs in Table 1 by adding the letter L. with the potential vorticity (PV) arguments of Hoskins et al Sometimes small, intense, generally short-lived ECLs form (1985). There have been numerous papers describing how within a much larger low pressure circulation. We identify the upper warm air advection leads to such pressure falls these ECLs by adding the letters SEC , which refers to the (e.g. and in particular see; Holland 1997; Chen et al. 2013; broader secondary low. Zonghui et al. 1995; Miho et al 2009; Rolfson and Smith 1996; Three examples are given below. The first (in Section 4.1) Sinclair and Revell 2000; and Strahl and Smith 2001). is an ECL C, the second (in Section 4.2) is an ECL S SEC. The This process triggered some extreme flooding in the study third is a very early (1867) example of an ECL (actually an ECL region, from lows travelling south from deep in the tropics. C), which occurred prior to the availability of any synoptic This happened most often in winter, though sometimes in charts. It is included (in Section 4.3) to demonstrate how summer. As an example of their power Farrington (1995) the synoptic type triggering the major flood can be inferred described the infamous June 1994 storm which rapidly from official data (e.g. Harbourmaster and Postmaster data developed east of New Caledonia east of a tropopause etc.) presented in newspapers at the time. undulation. This ferocious system caused seven yachts to be abandoned and three people tragically lost their lives in a The Pasha Bulker storm, June 2007 fleet sailing from Auckland to Tonga. A huge southerly swell As described in the supplementary appendix, this ECL was generated by the storm causing substantial damage at occurred over Friday 8 and Saturday 9 June, 2007. The Majuro (7° 09’ N, 171° 12’ E) in the Marshall Islands. event caused widespread damage in the coastal parts of We examined in detail all major floods over the last 40 the Hunter, Central Coast and Sydney Metropolitan areas, years and almost all develop east of a tropopause undulation. resulting from sustained heavy rain, strong winds and large A recent paper (Browning and Goodwin 2013) investigated ocean waves and swell. There were nine fatalities associated the structure and climatology of what they termed East Coast with the storm and nearly 20 000 calls for assistance made to Cyclones in the Tasman Sea. Their dominant system, which the State Emergency Service. Ferry services were cancelled they referred to as Easterly Trough Lows (ETL) includes on Sydney Harbour. Severe beach erosion occurred at many some of our major systems i.e ECLs and TI 3 with a TL. Sydney beaches due to huge swells up to 14 m high. High In particular these systems sloped with height to the winds blew beach sand hundreds of metres inland. Over 300 west during the early part of their evolution. This structure 000 homes lost power in the Sydney–Newcastle area due to coincides with the extreme rainfall we observed in our flooding and high winds. Many thousands more lost phone flood study and we have developed a diagnostic of extreme lines when telephone exchanges were flooded. Insurance rainfall based on this sloping characteristic (Callaghan costs were approximately AUD$1.7 billion (Insurance and Tory 2014). This will be described in more detail in a Council of Australia 2014; in 2011 dollars). See Verdon-Kidd future paper. We have classified these major flood systems et al. (2010) for more details on the meteorological event and primarily based on how the strong onshore flow interacts associated impacts. with troughs clearly evident at the 500 hPa level. In the TI2 At 9 am AEST 7 June 2007 (2300 UTC 6 June, left frame cases this onshore flow is either well south of the TC or TL Fig. 2) a low was forming east of Port Macquarie and by the located in the deep tropics, or else the interaction produced night of 7 June, the low deepened to 1009 hPa just north of an overland surface trough with strong onshore flow (mostly Newcastle. At 9 am 8 June it was located east of Seal Rocks from the northeast) east of this surface trough. with gale to storm force winds southwest of the centre Note that others may wish to use alternative classification (centre frame Fig. 2). Southeasterly gales started early on 8 schemes for particular purposes. The Supplementary June and continued for 12 hours. It was during this period Material provided should prove useful in this regard. that the ship Pasha Bulker ran aground at Nobbys Beach, giving the event its name. 200 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 2. Example of an East Coast Low (ECL): The Pasha Bulker Storm, June 2007. Mean Sea Level Pressure (MSLP) sequence from 2300 UTC 6 June 2007 (9 am AEST 7th), 2300UTC 7 June 2007 (9 am AEST 8th) and 1100 UTC 8 June 2007 (9 pm AEST 8th). Contours: MSLP (hPa), with surface wind vectors also shown. Conventional wind-plotting is used, where Flag represents 25m/s (50 knots), one barb represents 5m/s (10 knots) and a half barb 2.5 m/s (5 knots).

The ECL core intensified late on Friday evening (Fig. 2 with 273.0 mm and Verona with 262.8 mm. This produced right frame) and crossed the coast over Newcastle in the major flooding in the Bega and Moruya Rivers. The ECL early hours of Saturday morning bringing gale to storm subsequently moved offshore and easterly winds averaging force winds and the strongest observed wind gusts (135 39 knots were reported near Bega at Montague Island. Soon km/h at Norah Head and 124 km/h at Newcastle). The lowest after this the main low continued to develop and moved into pressure officially recorded was 994 hPa at Williamtown Bass Strait and dragged the ECL back overland. 370 mm fell in and the minimum central pressure of the low was estimated 24 h at Tidal River (near Wilsons Promontory) while this was to be 990 hPa. The record wave height recorded at Sydney going on. Before the ECL developed, record rain fell in the Wave rider Buoy of 14.13 m at 2 am Saturday was the highest Wollongong area and the pattern would be better described recorded since records began in 1992. by a TI 2 seeing the high dew point air moving down the The MSLP fields in Fig. 2 shows rapidly deepening NSW coast. This illustrates the difficulty in classifying some low pressure near the east coast, and a rapidly increasing systems, as many ECLs have tropical influence (which is pressure gradient to the south, especially between the first why the southern NSW coast can experience such extreme two panels. In our classification scheme all weather systems rainfall from ECLs). with these features—whether the isobars are closed or To gain some appreciation of the scale of the heavy unclosed­—are referred to as ECLs. Note that similar features rainfall, Fig. 4 shows the radar reflectivity over the Bega may also occur in TI Type 3 events. TI Type 3 events can be catchment (which lies between Bega, Bemboka, Bombala and distinguished from ECLs via inspection of the MSLP field Merimbula) evident on the radar images. For scale the radar prior to the intensification. This is described in more detail range rings over this region are between 100 km and 200 km below. from the radar at Captain Flat near Canberra. The light to moderate radar reflectivity on face value is a poor guide to The record Bega flood, March 2011 rainfall intensity in these images. Here the lowest reflectivity Figure 3 provides an example of an ECL S SEC which is white with increasing reflectivity through to dark blue with triggered a record flood in the Bega River on the NSW the strongest reflectivity the bright blue colour. The rainfall South Coast. At Bega the river reached 4.9 m at 0955 UTC distribution is typical of these events with general heavy 21 March 2011; 7.0 m at 1140 UTC 21 March: and it was over rain with very intense convective rainfall embedded within 8.0 m (major flood height) 1600 UTC 21 March. This was a the rain areas. Radar reflectivity is strongly dependent on historical event for the region. It reached 8.7 m greater than rain drop size (to a sixth power) and this maritime rainfall is the 1971 flood, was similar to the 1893 flood, and caused composed of numerous raindrops of small diameter. much damage and threat to life, with 43 rescues. The main development at 0000 UTC 21 March 2011 (upper The Catherine Hill Gale, June 1867 frame) is a low over inland southern NSW with warm moist As mentioned above, MSLP analyses from the Bureau of air advecting down the NSW coast (dewpoints greater than Meteorology are available back to 1879 from various sources 20 °C). A low then began developing near Merimbula (lower though with nothing like the amount of observational frame). Extreme rainfall occurred in the 24 hours covered data shown for the events which steadily increased after by this figure along the NSW South Coast—Cathcart (Mount 1878. Modern events, one in 2007, the other in 2011, were Darragh TM) with 397.8 mm, followed by Brogo Dam described above in Sections 4.1 and 4.2 respectively. In this Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems201

Fig. 3. Example of a Secondary ECL on the NSW South Coast: Record Bega Floods March 2011. MSLP analyses overlaid on scat- terometer images upper frame: 0000 UTC 21 March 2011 (10 am AEST 21st), lower frame: 0000 UTC 22 March 2011 (10 am AEST 22nd) Contours: MSLP (hPa), with surface wind vectors also shown and selected dew points (degrees Celsius) shown (blue numbers).

sub-section we describe a very early event to illustrate that modern events when substantially more data is available. the meteorological system triggering a major flood can be The Catherine Hill Gale (Fig. 5) was one of the most inferred despite the relatively sparse data available at that severe ECLs ever recorded. This storm was named after the time. This is done by first constructing MSLP charts on the schooner Catherine Hill, which was deliberately beached basis of official observations published in newspapers at the during the storm, approximately five miles from Lake time and then by making use of the relationship between Macquarie. Extracts from the Catherine Hill’s official log- MSLP patterns and the tropospheric synoptic structures book, reproduced in the Sydney Morning Herald on 4 July established from the robust relationships identified for the 1867 make for fascinating reading: 202 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 4. Radar images from Captain Flat radar (near Canberra) with reflectivity intensity grading from light (white) through to mod- erate (dark blue) and maximum reflectivity (bright blue colours) for scale radar rings are 100 km apart covering period of heaviest rainfall in the Bega River catchment from 0700 UTC 21 March 2011 (5 pm AEST 21st) to 1300 UTC 21 March 2011 (11 pm 21st).

Fri June 21 1867 commenced with terrific gale blowing, Bridge reached 19.26 m on June 23—the highest flood level attended by tremendous heavy squalls at intervals, a ever recorded (Nichols 2001)—a record which still stands continuance of lightning and rain falling in torrents ... at today. Bringelly, in the foothills of the Blue Mountains, 5.30 p.m., the wind shifted suddenly to the east, and a received over 100mm per day of rainfall for three days in heavy squall commenced blowing with great fury. ... At a row, which is well above the monthly June average of 64 8 o’clock p.m., it was blowing a perfect hurricane ... At mm. It is likely that rainfall over the Blue Mountains was midnight, a continuation of the same weather, with torrents much higher. This heavy rainfall occurred in a catchment of rain ... the sea at this time running mountains high ... that was probably already saturated from very heavy prior At daylight, the weather was fearful, and sea terrific. … rainfall: Bringelly received five times the average monthly we kept her head to the beach in order to save life, but, rainfall during April. This highlights two important factors … a heavy sea broke all over her, and washed overboard associated with some of the major floods: rain-bearing Thomas Haywood (mate), and John Doring (cook) ... it was weather systems that remain stationary or move very slowly, truly a miracle how any one on board the vessel escaped. and wet prior conditions. Further details are available in the The MSLP fields in Fig. 5 show features that characterise supplementary appendix. ECLs i.e. rapidly deepening low pressure near the east coast, and a rapidly increasing pressure gradient to the south. This ECL became stationary over the Blue Mountains west of Sydney for approximately 48 hours. From newspaper reports it killed 41 people. The Hawkesbury River at Windsor Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems203

Fig. 5. Second example of an ECL: Catherine Hill Gale, which caused the record Hawkesbury River Flood of June 1867. Schematic representation. Note the lack of Meteorological reports on the 21 and 22 June (lower frames) due to Telegraphic disruptions.

Examples of Tropical Interactions (TIs) Fig. 6. The close spacing of the isobars indicates the very destructive wind zone near the centre of the cyclone, which In this section we provide examples of each type of TI, and led to very damaging waves and storm surges. Record again describe the MSLP fields associated with such events. rainfall accompanied the cyclone. For example, 900 mm was recorded at Springbrook in the Gold Coast Hinterland in the Example of a TI Type 1 TC : The Great Cyclone of 1954 24 hour period up to landfall. Floods combined with storm A Type 1 TI is a TC that moves into the study region retaining surge and cyclonic winds resulting in approximately 26 to 30 its tropical cyclone characteristics (e.g. minimal vertical deaths. The outer section of the Byron Bay jetty was swept shear). Such an event occurred in 1954 (Callaghan and Power away, taking with it all 22 vessels comprising the fishing 2011). Around 10 pm on 20 February 1954 a severe TC crossed fleet. The lowest pressure recorded over land was 973 hPa at the coast at the border twin towns of Coolangatta and Tweed Coolangatta and Condong sugar mill near Murwillumbah. Heads. The large circulation of the cyclone is illustrated in 204 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 6. Example of a Tropical Interaction, Type 1: The Great Cyclone of 1954. The MSLP distribution (hPa), with some wind observa- tions at 2000 UTC 19 February 1954 (left) and 0800 UTC 20 February 1954 (right). Normal wind plotting convention as in Fig. 2.

Fig. 7. Example of a TI Type 2: Brisbane River Catchment devastated by wind and rain. Houses were unroofed, fences Flood, 10 January 2011 at 0000 UTC a few hours be- flattened, trees uprooted, and communications were cut. fore disastrous flash-flooding in Toowoomba and the Scarcely a house escaped damage. Lockyer Valley. Shows isoabars and normal wind plot- ting convention as in Fig. 2. The MSLP pattern (Fig. 6) shows intense closed isobars, characterising tropical cyclones. See the online supplementary appendix for further details.

Examples of TI Type 2: TC/TL-tropical/trough interaction These occur when a deep layered trough system extends well into the tropics and either interacts with a TC or TL; or it forms an inland trough with strong northeasterlies on the coast.

The Brisbane, Toowoomba, and Lockyer Valley Floods, January 2011 A TL interacting with a deep layered trough occurred in the Brisbane River Catchment Floods in January 2011, when an active monsoon trough had an embedded tropical low northeast of Rockhampton (on the Tropic of Capricorn) with a developing TC further east near New Caledonia (Fig. 7). An intense pressure gradient between the low and the subtropical ridge further south drove strong to gale force winds over the Queensland south coast. The most disastrous period of this event occurred when intense flash flooding occurred in Toowoomba and the Lockyer Valley and 25 In the early hours of Sunday 21 February 1954 the Richmond people died. This was linked to a thunderstorm complex River at Kyogle peaked, recording an unprecedented height embedded into the larger-scale onshore flow (Fig. 8), which of 19.1 m, and ten people drowned. fed very moist air (with dewpoints of 23 °C to 24 °C) into A record flood occurred in the Coffs Harbour region the storm system. The occurrence of intense thunderstorm where some of the heaviest rainfall was recorded. Dorrigo, activity during TI events is very common. 39 km west of Coffs Harbour, received 809 mm in 24 The MSLP field (Fig. 7) shows a monsoon trough to the hours. This still stands as a record for NSW. Kempsey was north, a strong pressure gradient south of the low, and an Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems205

Fig. 8. Radar echoes and MSL analyses for 0200UTC 10 January 2011 (left) and 0300 UTC 10 January 2011 (right). Mean wind speed in knots in normal plotting convention and dew points (black numbers).

east by northeast orientation of the isobars. Our analysis of Examples of a Type 3 TI: Extratropical Transitions (ETs) weather events since 1948 reveals that these features only As noted above, a Type 3 TI occurs when either a TC or a occur in association with an upper trough to the west of TL that is reorganised or transformed into a more ECL- the surface low. Collectively, these features in the MSLP like structure while interacting with a deep-layered trough characterise TI Type 2 events. as it moves into the study region. In Section 5.3.1 we will describe a transitioning TL, while in 5.3.2 we will describe A Tropical Dip a transitioning TC. A trough system extending over land from the tropics into the study region has been referred to as a Tropical Extratropical transition of a Tropical Low (TL) Dip by forecasters in the Queensland office of the Some of the most damaging systems in our study occurred Bureau of Meteorology for many decades. An example is when upper troughs interacted with a TL or a TC. Below we shown in Fig. 9 indicating generally strong to gale force examine an event which produced a disastrous flood in the northeasterly winds across the northern part of the study Nepean/Hawkesbury River system in March 1978. It, like the area. The figure shows its detailed structure during a heavy Catherine Hill Gale, involved a low pressure system which rain period, with a small-scale coastal trough forming in crossed the NSW coast. the general northeasterly flow. On 15 and 16 March 1978 a low in the Monsoon trough There was very heavy rain reported between Brisbane north of Vanuatu moved south. By 2300 UTC 16 March 1978 and Coffs Harbour. Mt Glorious (western Brisbane suburb) (top left frame Fig. 10) a TL can be seen passing to the east recorded 500 mm in 24 hours and 211 mm fell in six hours of Fraser Island on its way south. The low then intensified to 2200 UTC 11 December 1991 (9 am local daylight saving before making landfall near Cape Byron, and then moved time 12th). Official 24 h totals to 9 am were 319.2 mm on the inland much like the Catherine Hill Gale above. It brought 12th and 269.0 mm on the 13th. There was severe flooding gales to storm force winds onto the New South Wales coast. at Samford (just east of Mt Glorious) with dams and For example the Newcastle Nobbys Pilot Station recorded a roads washed away. In Ipswich (a southwestern suburb gust of 131 km/h (71 knots) at 0350 UTC 19 March. Sydney of Brisbane) there was major flooding along the Bremer Airport recorded gusts to 95 km/h (56 knots). River, Bundamba and Warrill Creeks causing significant Record rain fell along the NSW South Coast and about the property loss and damage. In the Bundamba Creek area, Blue Mountains where many long term all time daily rainfall 42 people were rescued from flooded homes. Further south records were broken in the 24 hours to 2300 UTC 18 March Coffs Harbour recorded 230 mm in the 24 hours to 9 am on 1978. For example, Bilpin (27 km NE of Katoomba) received the 13th, which was a record for a daily December total. 237.6 mm and Bullaburra (9 km ESE of Katoomba) received 284.6 mm. Major floods occurred on the Richmond/Wilsons 206 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 9. MSLP analyses during the heavy rain with wind observations for 2200 UTC 11 December 1991 (left) and 0400 UTC 12 December 1991 (lower right). Wind observations are plotted using normal convention.

River, the Tweed River, the Hastings River, the Manning Sometimes the TC centre itself can move into the River, Nepean/Hawkesbury Rivers and the Georges River. study region, taking on ECL-like characteristics. On other occasions a new centre develops (as in this 1893 case). Second example of a TI Type 3: a transitioning TC Internationally this particular TI is often referred to as an Extratropical Transition (e.g. Callaghan 2005). Such an Statistics of and relationships between major event occurred during February 1893 in the Brisbane River floods, ECLs, TIs and death tolls catchment. In this case a new low pressure system developed Basic statistics poleward of the cyclone though in other cases the cyclone We identified a total of 253 major floods between January centre can remain the dominant feature. 1860–December 2012. Of these 57 per cent were associated A severe TC crossed the coast near Yeppoon early on with ECLs and 43 per cent were associated with TIs. TI Types 1 February 1893 (Callaghan and Power 2011) and began to 1, 2, and 3 accounted for approximately six per cent, 16 per interact with an upper trough the result which produced cent, and 22 per cent of the major floods respectively. an 998 hPa east coast low east of the Sunshine Coast on A total of 75, 107, 92 and 71 major floods occurred in region 2 February (see Fig. 11). The low remained slow moving N, NC, C and S, respectively, which corresponds to flooding and made landfall on the Sunshine Coast at 9 am in 49 per cent, 70 per cent, 60 per cent and 46 per cent of 4 February. Crohamhurst (on Stanley River) recorded 907 years on average in the four sub-regions respectively. Note mm of rain in 24 hours to 9 am 3 February 1893 which was that the total exceeds 253 because major flooding sometimes an Australian record from 1893 to 1979. A 15.2 m high wall occurred in more than one sub-region at the same time. of water was observed to roar down a Stanley River gorge. As noted in Section 4, ECLs are sub-divided into four More than 150 houses were washed down the Brisbane groups, depending on where the initial intensification River. The Indooroopilly Railway Bridge and the Victoria occurred: north of Yamba (29.4°S); north–central, from Yamba Bridge were both washed away. Around 29 lives were lost to Taree (31.9°S); central from Taree to Wollongong (34.5°S); in the Brisbane region. and in the south, from Wollongong to Eden (37.0°S). The The MSLP field in Fig. 11 showed a portion of the percentage of ECLs with initial intensification in the north, circulation of a TC in the northwest in the first panel (upper north–central, central and south is 27 per cent, 27 per cent, left), and the development of a closed low near the east coast 36 per cent, ten per cent respectively (and approximately). Of to the southeast of the cyclonic circulation. The 24 hour these only 3.5 per cent made landfall, and only 5.6 per cent of rainfall totals are shown in these figures and note the 907 the ECLs were embedded in a secondary low (see Section 4). mm total near the low. The monthly climatology of (1) major floods, (2) ECLs Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems207

Fig. 10. MSLP Analyses (NCEP/NCAR reanalyses for 2300 UTC 16 March 1978, and from Bureau of Meteorology charts for 2300 UTC 17 March 1978, 2300 UTC 18 March 1978, and 2300 UTC 19 March 1978. Some surface wind observations are plotted using arrows for wind directions with the mean wind speed in knots marked on the tail.

and (3) TIs are given in Fig. 12. Major floods occurred most winter, and least common during spring and summer. TIs frequently during January through July, with most floods in were most frequent during January–April. No TIs associated February and March. ECLs linked to major floods occurred in with major floods occurred during September or November. all months. ECLs tended to be most common in autumn and The seasonal climatologies of the number of major flooding 208 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 11. Example of a TI, Type 3: Extratropical Transion (ET): 1893 Brisbane floods. MSLP (hPa) distribution and wind observations constructed from charts held in Commonwealth Archives. The rainfall (mm) over the previous 24 hours is shown in red, for 2300 UTC 31 January (9 am 1 February 1893 local (top left), 2300 UTC 1 February (9 am 2 February 1893 local top right), 2300 UTC 2 February (9 am 3 February 1893 local lower left) and 2300 UTC 3 February (9 am 4 February 1893 local lower right). Isobars, wind-vectors (conventional plotting as in Fig. 2) and 24 hour rainfall totals (mm) shown.

in the four subregions are given in Fig. 13. Most major floods Associated deaths due to freshwater flooding occurred in MAM, and fewest occurred in SON, in all four There were a total of 644 reported deaths due to freshwater sub-regions. The north-central sub-region (from Yamba to flooding over the period 1860–2012, which represents an Taree) experienced the most floods (0.7 major floods/year), average of 2.5 deaths per major flood. The vast majority of while the southern sub-region (from Wollongong to Eden) deaths (88 per cent) occurred in the first six months of the experienced the fewest (0.46 major floods/year). calendar year, while 61 per cent of all freshwater deaths occurred during the first three months. TIs were linked to 62 per cent of the deaths, while only 38 per cent were linked to ECLs. The number of deaths per Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems209

Fig. 12. Average number of major floods, ECLs and TIs, Fig. 13. The number of major floods that occurred in each sea- 1860–2012. son in the four subregions: north of Yamba (29.4°S); north–central, from Yamba to Taree (31.9°S); central from Taree to Wollongong (34.5°S); and in the south, from Wollongong to Eden (37.0°S).

event was 3.6/TI and 1.7/ECL. So while ECLs occurred more frequently than TIs, most reported deaths during 1860–2012 were caused by TIs, because individual TIs tended to be much deadlier than individual ECLs. Type 1 TIs were the rainfall is confined to the coast and floods form directly over deadliest, with an average of 7.1 deaths per event. the coastal area rather than propagating down the river The largest death tolls from freshwater flooding occurred systems. The database shows that major floods frequently in February 1860 (36), June 1867 (36), January 1887 (26), isolate towns, and cause death, major disruptions to road February 1893 (29), February 1954 (30), February 1955 (25) and rail links, the evacuation of many houses and business and January 2011 (25). There were 13 major floods causing premises, and the widespread flooding of farmland. ten or more deaths. Ten of these major floods were triggered In order to produce homogeneous records of the by TIs and only three were triggered by ECLs. All three frequency of flooding and weather types we restricted of these ECLs occurred in the 19th century. Two of these attention to the period from 1860, when the region (i) is occurred in the 1860s, when farming communities were extensively populated, (ii) has an extensive coverage of located on the lower reaches of flood plains (attracted by meteorological stations, (iii) is extensively connected by fertile alluvial soil). telecommunication, and (iv) when there is a busy coastal The higher death tolls linked to TIs is primarily due to shipping offshore. the tendency for rainfall to be higher during TIs than during We identified a total of 253 major floods during 1860– ECLs. This is illustrated in Appendix 2, which lists the 2012. Without exception, these large-scale coastal and weather events associated with the 12 highest recorded 24 riverine floods were linked to either an (a) East Coast Low h rainfall totals in our study region. Of these 12 events ten (ECL) or (b) a Tropical Interaction (TI). ECLs were defined are associated with TIs, while only two are associated with for the purposes of this study as (a) low pressure systems ECLs. (either a closed low or trough) near or on the eastern coast The average number of deaths in each month due to of Australia of non-tropical origin, which are located (b) east freshwater flooding associated with major floods is presented of a deep layered trough and (c) north of a high pressure in Fig. 14. Virtually all deaths (96 per cent) occurred January– system, with (d) heavy rain in coastal areas generally south August, with very few deaths at other times of the year. or southwest of the low pressure centre. Three types of TIs were identified: Summary and discussion (i) a tropical cyclone (TC) that moves into the study region retaining its TC characteristics; We described and used a new historical database describing (ii) a deep layered trough system extends well into the tropics major floods that occurred in coastal catchments in eastern and either interacts with a TC or tropical Low (TL) or Australia from Brisbane in Queensland to Eden in NSW forms an inland trough with strong northeasterlies on approximately 1500 km further south from January 1860 to the coast. December 2012. We considered a flood to be major if it (i) (iii) an Extratropical Transition (ET) whereby a TC or TL caused inundation of a river within approximately 50 km is reorganised or transformed into a more ECL-like of the coast or (ii) caused non-riverine flooding over land structure (while interacting with a deep layered trough) near the coast, extending at least 20 km along the coast. In as it moves into the study region. (i) extreme rainfall extends well into the hinterland and the All of the case studies examined were associated with upper reaches of the river catchments, causing a flood that winds with an onshore (easterly) component up to at least drains down the river systems to coastal areas. In (ii) extreme 210 Australian Meteorological and Oceanographic Journal 64:3 September 2014

Fig. 14. The total number of deaths in each calendar month calendar year, while 61 per cent of all freshwater deaths from freshwater flooding, 1860–2012. occurred during the first three months. Some of the most extreme events identified in this study occurred in the 19th century and the early-to-mid 20th century. This includes The Great Cyclone of 1954 and the Catherine Hill Gale in 1867. If these and other extreme events were to occur nowadays they would have catastrophic impacts, given the massive increase in population and infrastructure now present in those regions, and despite major improvements in warning and emergency services. For example, in the Gold Coast in 1954 there were just over 18 000 residents, whereas today there are approximately 0.5 million residents, and the population of the adjacent Northern Rivers of NSW is over 0.25 million. The population of these two regions continues to grow rapidly. It is therefore crucial that the risk of such events is clearly reflected in planning. This is especially important given that there is no 700 hPa. Thunderstorms are often embedded in such large- guarantee that we have actually witnessed the full severity scale winds and frequently contributed to major flooding. of weather systems that could have actually occurred during Such thunderstorms should be contrasted with more the historical period. For example, if a system like the Great typical thunderstorms that occur in winds with a westerly Cyclone had stalled in a similar manner to the Catherine component above the atmospheric boundary layer. These Hill Gale, or ex-tropical cyclone Oswald in the central more typical thunderstorms can cause flooding, however, Queensland area in January 2013, the impacts would have the associated flooding is almost always much less extensive been even greater. than flooding that occurs in association with large-scale This risk is further increased because extreme precipitation onshore winds and, consequently, in the events this study is projected to become more extreme for a given synoptic focuses on. situation in response to human-forced global warming (IPCC We found that ECLs triggered more major floods (57 2013; Braganza et al. 2011; Whetton et al. 2011). per cent) than TIs (43 per cent), but death tolls linked to TIs tended to be much higher (3.6 deaths/TI cf. 1.7 deaths/ ECL). All TI Types tended to be deadlier than ECLs. Future work The higher death tolls that tend to occur during TIs are The focus in this paper is on major floods and the weather primarily due to the tendency for rainfall to be higher events that triggered them. We intend to provide more during TIs than during ECLs (see Section 6). It is important information on the vertical wind structure associated with to note, however, that while TIs tended to be deadlier than the major floods, and temporal variability in floods, weather ECLs, ECLs still killed many people. systems and death tolls on interannual and longer time- The ECLs were then sub-divided into four groups, scales in future reports. The latter will complement several depending on where the initial intensification occurred: previous studies (e.g. Hopkins and Holland 1997; Franks and north of Yamba (29.4°S); north-central, from Yamba to Kuczera 2002; Kiem et al. 2003; Verdon et al. 2004; Speer et Taree (31.9°S); central from Taree to Wollongong (34.5°S); al. 2008; 2009) by focusing on major flooding in the coastal and in the south, from Wollongong to Eden (37.0°S). The zone over a longer period than has been studied previously. percentage of ECLs with initial intensification in the north, north–central, central and south were 27 per cent, 27 per cent, 36 per cent, ten per cent approximately. Most major Acknowledgments floods occur in MAM, and fewest occur in SON, in all four We acknowledge our use of and express our gratitude for the sub-regions. Only 3.5 per cent of the ECLs made landfall and availability of earlier analyses described by Blain, Bremer, only 5.6 per cent of all ECLs were embedded in a secondary and Williams (Public Works Department (1985)), P. Helman, low (see Section 4). M. Speer and B. Trewin, and archives of (a) weather data The north–central sub-region (from Yamba to Taree) by Laurier Williams, (b) radiosonde data at the University experienced the most floods (0.7 major floods/year), while of Wyoming, and (c) newspapers at the National Library of the southern sub-region (from Wollongong to Eden) Australia web-site. We thank NCAR and NCEP for making experienced the fewest (0.46 major floods/year). available their joint reanalysis of past weather, Google for There were a total of 644 reported deaths due to freshwater Fig. 1, and G. Holland, K. Tory, A. Pepler, D. Verdon-Kidd, M. flooding over the period 1860–2012, which represents an Speer, C. Lucas and an anonymous reviewer for very helpful average of 2.5 deaths per major flood. The vast majority of comments on earlier drafts. deaths (88 per cent) occurred in the first six months of the Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems211

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NSW major flood events were listed on the following Speer M. S., 2008. On the late twentieth century decrease in Australian websites: east coast rainfall extremes. Atmos. Sci. Lett., 9, 160–70. Speer, M.S., Phillips, J. and Hanstrum, B.N. 2011. Meteorological aspects of the 31 March 2009 Coffs Harbour flash flood. Aust. J. Meteorol. Historical flood heights on web: Oceanogr., 61, 201–10. Georges River: Strahl, J.L.S. and Smith, P.J. 2001. Diagnostic Study of an Explosively www.georgesriver.org.au/IgnitionSuite/uploads/docs/ Developing Extratropical Cyclone and an Associated 500-hPa Trough Merger, Mon. Wea. Rev., 129, 2310– 28 Have%20We%20Forgotten%20About%20Flooding%20 Ventham, J.D. and Wang, B. 2007. Large-Scale Flow Patterns and Their on%20the%20Georges%20River.pdf Influence on the Intensification Rates of Western North Pacific Tropi- cal Storms. Mon. Wea. Rev., 135, 1110– 37. Tweed River: Verdon, D.C., Wyatt, A.M., Kiem, A.S., and Franks, S.W. 2004. Multi- www.google.com.au/webhp?sourceid=navclient&ie=UTF- decadal variability of rainfall and streamflow: Eastern Australia. Water 8#hl=en&site=webhp&q=Tweed+river+flood+report&rlz= Resources Research, 40, doi:10.1029/2004WR003234. 1W1SUNC_enAU373&oq=Tweed+river+flood+report&aq Verdon-Kidd, D.C., Kiem, A.S., Willgoose, G., and Haines, P. 2010. East Coast Lows and the Newcastle/Central Coast Pasha Bulker Storm, =f&aqi=g1&aql=&gs_sm=13&gs_upl=3794l11951l0l14077l National Climate Change Adaptation Research Facility, Gold Coast, 26l26l1l11l11l0l276l2733l1.2.10l13l0&fp=1&biw=1248&bih= 55pp. ISBN: 978-1-921609-14-5. 602&tch=3&ech=1&psi=P8Q0T4vuH8jZmAWhl6D_AQ.13 Visher, S.S. and Hodge, D. 1925. Australian Hurricanes and Related Storms with an Appendix on Hurricanes in The South Pacific, Published by the 28858178668.5&wrapid=tlif132885821840121&bav=on.2,or Bureau of Meteorology, 54 pp. .r_gc.r_pw.,cf.osb&cad=b Watt, W.S., Commonwealth Meteorologist 1940. Results of Rainfall Obser- vations in Queensland, 79 pp. Lismore: Whetton, P., Moise, A. and Abbs, D. 2011. Projections. In: Climate Sci- australiasevereweather.com/storm_news/2008/docs/ ence Update: A Report to the 2011 Garnaut Review, Keenan, T.D. and lismore_flood_pictures_reports.htm Cleugh, H.A. (Eds), CAWCR Technical Report No. 36. Wilson, L., Manton, M.J., and Siems,S.T. 2013. Relationship between Clarence River: rainfall and weather regimes in south-eastern Queensland, Australia. www.clarence.nsw.gov.au/cp_content/resources/Historic_ Int. J. Climatol., 33, 979–991, DOI: 10.1002/joc.3484. Zonghui, H., Zhang, D.-L. and Gyakum, J. 1995. A Diagnostic Analysis of Flood_peak_heights.pdf the Superstorm of March 1993. Mon. Wea. Rev., 123, 1740– 61. Hawkesbury River: www.hawkesburyhistory.org.au/articles/floods.html Appendix 1. Information sources used to City of Wollongong: identify events and impacts www.conferenceworld.com.au/resources/other/Pas%20 Silveri%20paper%201.pdf Many newspapers along the eastern seaboard have archives on the National Library site trove.nla.gov.au/newspaper Moruya: These early newspaper descriptions of severe weather www.esc.nsw.gov.au/media/383419/moruyafscc_part1.pdf events were extensive. Severe floods can be identified by Nowra: using the search engine on the National Library of Australia doc.shoalhaven.nsw.gov.au/displaydoc. site. To illustrate the detail of the articles below is an example aspx?record=D11/115643 from page 5 of the Sydney Morning Herald of 12 September 1876 giving an account of the effects of the Dandenong Gale Kempsey Shire: in Sydney: trove.nla.gov.au/ndp/del/printArticlePdf/13379832/3 mhl.nsw.gov.au/www/NatureofFloodinginKempseyShire.pdf ?print=n Queensland floods: To help identify extreme rainfall events not listed as www.bom.gov.au/hydro/flood/qld/fld_history/index.shtml major floods we used historical rainfall data obtained from the site: www.australianweathernews.com/recent_AWN_ Lake Illawarra floods: daydataArchive_element.html www.wollongong.nsw.gov.au/services/sustainability/ floodplainmanagement/Documents/Lake%20Illawarra%20 Floodplain%20Risk%20Management%20Study%20 part%201.pdf Callaghan and Power: Major coastal flooding in southeastern Australia 1860–2012, associated deaths and weather systems213

Illawarra Floods: Appendix 2. Twelve highest 24 h rainfall www.wollongong.nsw.gov.au/services/sustainability/ events (to 9 am unless stated otherwise) floodplainmanagement/Documents/Fairy%20and%20 recorded in the study area. Cabbage%20Tree%20Creeks%20Floodplain%20Risk%20 1. 907 mm, Crohamhurst (Brisbane River catchment), Management%20Study%20and%20Plan%20-%20 3 February 1893 (TI3). Part%204.pdf 2. 900 mm, Springbrook (Gold Coast Hinterland), to 10 pm, Nambucca Shire: 20 February 1954 (TI1). www.google.com.au/webhp?sourceid=navclient&ie=UTF- 3. 809.0 mm, Dorrigo (Coffs Harbour Hinterland), 8#q=nambucca+River+historical+floods&hl=en&rlz=1R2SU 21 February 1954 (TI1). NC_enAU373&site=webhp&prmd=imvns&ei=YtZST5iKG4a 4. 796.5 mm, Wongawilli (Illawarra Escarpment), eiAfzk7XMCw&start=10&sa=N&bav=on.2,or.r_gc.r_pw.,cf. 18 February 1984 (TI2). osb&fp=2e4f11321d9dd194&biw=1236&bih=601 5. 744 mm, Springbrook (Gold Coast Hinterland), Nambucca Shire local flood plan, a sub-plan of the 28 January 2013, TC Oswald (TI3). Nambucca Shire local disaster plan, July 2007. 6. 709 mm, Mt Castle (Brisbane River Catchment), 28 January 2013, TC Oswald (TI3). To augment this we used a study using shipwreck and 7. 653 mm, Numinbah (Gold Coast Hinterland), other data going back to the eighteenth century (Callaghan 28 January 2013, TC Oswald (TI3). and Helman 2008) and reports by the Public Works 8. 636 mm, Dorrigo (Coffs Harbour Hinterland), Department (1985, 1986). 24 June 1950 (TI3). We identified coastal impact events between Brisbane 9. 630 mm, Springbrook (Gold Coast Hinterland), and Eden that produced very heavy rain. In doing this we 12 June 1967 (TI3). include events where the cyclogenesis occurs close to the 10. 510 mm, Springbrook (Gold Coast Hinterland), coast to produce other types of severe weather e.g. large 20 July 1965 (ECL). waves, storm surge and wind damage. 11. 509 mm, Mount Cotton West (Redland Shire), For events prior to 1957 the impact of each possible event 6 February 1931 (TI1). was then sought from archived newspaper reports on the 12. 503 mm, Bulahdelah (near Newcastle), National Library of Australia website: trove.nla.gov.au/ 16 April 1927 (ECL). newspaper. Additional historical sources used in this investigation are Bond and Wiesener (1955), Bridgeman (1986), Brunt Supplementary appendix (1956ab, 1958), Bureau of Meteorology (1974), Callaghan A supplementary appendix, ‘Details on severe weather (1986, 2004), Callaghan and Bonell (2005), Callaghan and systems over south-east Australia, 1799–2013’ is available on Davidson (1985), Carr (1965) Foster et al. (1975), Gourlay the Journal website. (1971), Higgs and Nittim (1988), Holland et al. (1987), Hunt (1914), Joubert (2005), Kalnay et al. (1996), Leslie and Speer (1998), Lynch (1987), Malone and Muller (2004), McInnes and Hubbert (2001), Sanders and Guyakum (1980), Shepherd and Coloquhoun (1985), Speer et al. (2009, 2011), Speer (2008), Visher, and D. Hodge (1925), Watt (1940), Whetton, et al. (2011), and Wilson et al. (2013). Additional historical references used, that are cited in the text, are given in the reference list at the end of the paper. 214 Australian Meteorological and Oceanographic Journal 64:3 September 2014