Charts of the Past with Blair Trewin
BAMOS Autumn 2022
19
11 March 1974
The early months of 1974 were some of the wettest on record for Australia , as one of the strongest La Niña events on record brought heavy rain to most of the country . January 1974 brought major flooding to the Brisbane region , and widespread and long-lived flooding in many parts in northern and central Australia .
Coastal northern New South Wales , although it was significantly wetter than average , escaped the worst of the January flooding , but its turn was to come in the second week of March . A low , which became Tropical Cyclone Zoe , developed in the Coral Sea on the 6th , and moved slowly south towards southeast Queensland over the following week , strengthening to a peak intensity of category 3 on the 9th . A moist easterly flow developed between the cyclone and a high pressure ridge over southern Australia , reaching its peak on the 10th and 11th .
Following localised extreme rainfall on the 9th on the Mid- North Coast ( 386 mm at Macksville ), more general heavy falls occurred over the Northern Rivers and the Gold Coast on the 10th and 11th . Coolangatta received 461 mm on the 11th , and numerous other sites had more than 300 mm on either the 10th or 11th , with Woodburn recording 683 mm over the two days and numerous other sites on both sides of the border exceeding 500 mm . Further south , there was also 412 mm on the 11th at Crystal Creeks near Bellingen .
Major flooding occurred in the Northern Rivers , with the Wilsons and Richmond Rivers worst affected , as well as in the Bellinger River . At Lismore , the river reached 12.17 m on the 11th , the equal-highest flood on record before 2022 , and record heights were observed at numerous other points on the river . One death was reported and 1500 properties were evacuated , mostly in Lismore and Murwillumbah , with some evacuations taking place by boat . Brisbane received 265 mm over the two days ( and 420 mm over four ), only six weeks after the destructive January floods , but this time significant flooding was mostly confined to local creeks . In New South Wales , moderate flooding extended as far south as the Shoalhaven .
A second round of heavy rain occurred on the 12th and 13th as Zoe crossed the coast near Coolangatta , the southernmost east coast tropical cyclone landfall of the last 50 years . By then it had accelerated and weakened to a category 1 system , and there was no significant wind damage , but there was still enough moisture for daily rainfall totals above 300 mm in the Gold Coast hinterland ( 349 mm at Alpine Panorama on the Springbrook plateau ), and significant beach erosion . This produced a second flood peak at Lismore although it fell well short of that observed two days earlier . Zoe moved out to sea later on the 13th , bringing the heavy rain to a close . Weekly totals exceeded 800 mm at numerous sites , with the highest being 1045 mm at Doon Doon .
A monsoonal low over the Northern Territory brought a second area of heavy rain and flooding . By the 11th it was weakening , but earlier it had produced widespread multi-day totals above 200 mm , with 212 mm at Delamere on the 9th . Most major roads were flooded and the Katherine River reached its highest level since 1957 .
The story was not entirely one of rainfall . Away from the east coast , it was hot and humid in the east to northeasterly flow , with the 11th being the last of five consecutive days above 40 ° C at Moomba in outback South Australia . Heat also affected a Moomba of a different sort , with more than 400 festival attendees being treated by paramedics for heat-related conditions in Melbourne ( where it reached 33.1 ° C ). March nights were particularly warm in the southeast , with mean minimum temperatures the highest on record for both Victoria and Tasmania .
Synoptic chart for 0000 UTC , 11 March 1974