Tropical Cyclone Alfred: What did we learn?
- Briefing Note 514
Tropical Cyclone Alfred was a powerful slow-moving tropical cyclone that brought strong winds, extreme rainfall and large storm tide to Southeast Queensland and the New South Wales North Coast. It had an erratic path, stalling for several days off the coast increasing the duration of strong winds and rainfall. Alfred made landfall on Moreton Island as a Category 1 system at 11:30 pm on the 7th of March, and in the early hours on the 8th of March, at 6:45 am, Alfred was downgraded to a tropical low before crossing the mainland between Maroochydore and Bribie Island. It was the first cyclone to come within 200 km of Brisbane since 1974, and at one stage was projected to directly hit Brisbane as a Category 2 cyclone. The severity of such a potentially powerful system impacting such a largely populated area prompting several watches, warnings and evacuations. Fortunately, such a storm never materialised, but it did provide several learnings on Australia’s building stock, resilience, disaster preparedness and cyclone behaviour.
Tropical Cyclone Alfred
Alfred originated from a tropical low in the Coral Sea on the 20th of February. It traversed south-east before upgrading to a Category 1 system. It then headed south fluctuating in intensity, where it at one stage reached Category 4 status before undergoing an eyewall replacement cycle. It then travelled further south-east, moving further away from Australia, before doing a 180 and heading directly west towards Australia on the 4th of March as a Category 2 system. Alfred then fluctuated between a Category 1 and Category 2 as it headed towards the coast. As it headed towards the coast it stalled several times, performing small loops, delaying the expected arrival time by a couple of days. Eventually, on the 7th of March Alfred made landfall on Moreton Island as a Category 1 system at 11:30 pm. It then downgraded to a tropical low before in crossed the Australian mainland coast at 6:45 am on the 8th of March between Maroochydore and Bribie Island.
Disaster Preparedness
On the 2nd of March several predictive models were projecting Alfred to make landfall somewhere between the 6-8th in Southeast Queensland. Later that day Queensland entered a “precautionary and preparation phase”. On the 3rd the BOM indicated such a scenario was likely, and several government and disaster agencies had started preparing for a worst-case scenario. A Cyclone Watch was issued between Sandy Cape and Grafton, with locals informed to prepare and consider evacuating. Most at risk were residents of the islands and bay communities, and people in low-lying areas. In the following days several sandbagging stations were opened; five on the Gold Coast, nine in Noosa, and five on the Sunshine Coast. Over the following days almost a million sandbags would be made available to the public.
On the 3rd Brisbane’s CityCat and ferry services were suspended on to allow the vessels to be moved to safety.
On the 5th several evacuation centres were opened in the area. A ‘Red Alert’ was issued for all mariners, requiring vessels with permission only from the Brisbane Harbour Master to be on the water from Redcliffe to Coolangatta. The Gold Coast Airport also ceased operations. Several schools in the region were also closed. Later that day the Australian Prime Minister announced a ‘period of emergency’ had been enacted, with the Australian Defence Force being activated with immediate effect, including additional deployment of heavy-lift helicopters from the fleet.
On the 6th further public schools, public transport, major roads, and airports began to shut down, with Brisbane Airport ceasing operations.
Over this period several major sporting events were either cancelled, postponed or relocated, including NRL and AFL matches, similarly several concerts and events were cancelled, and schools and universities in the area closed to keep people out of harm’s way. Overall, 1,150 schools across Qld and NSW were closed during Alfred.
Overall, the disaster preparedness has been praised. The slow movement of Alfred provided ample time for residents, emergency services and Federal Government agencies including the ADF to prepare. Emergency Leaders for Climate Action (ELCA), a collection of 38 former Australian fire and emergency service chiefs, acknowledged the response helped save lives. ELCA also placed emphasis on the focus that the Prime Minister and dedicated public servants have placed on rebuilding agencies such as the National Emergency Management Agency (NEMA) which contributed to the response effort, working hand in hand with the Premiers of Queensland and New South Wales. Regular briefings and updates were provided by the SES, police and other combat agencies to local officials and the public through several mediums. Homes were prepped for high winds and potential flooding, with residents being well prepared moving furniture inside, covering windows, sandbagging entrances, tying down lose fixtures, and stocking up with the necessary provisions. Some also had generators ready. Businesses had time to move their stock and equipment, and truck drivers worked tirelessly to get supplies into towns with significant risk of isolation. Foodbank NSW & ACT also provided emergency hampers and pallets of bottled water to support impacted communities. Representatives of several towns, such as Balina, acknowledged they had never been better prepared for an event.
Impacts
Although Alfred never materialised to the catastrophic event that was forecast, it still did significant damage to southeast Queensland, with PERILS estimating the insurance market loss to be
$2,568 million AUD. The Australian Reinsurance Pool Corporation estimated the cost from Alfred to be about $1.7 billion AUD.
Cyclone Alfred caused over 330,000 homes and businesses to be without power, caused minor damage to several homes, resulted in severe coastal erosion to the beaches on the Gold Coast and Sunshine Coast, there was one fatality and several injuries, major disruption to transport including the suspension of flights and closure of schools and businesses.
The Cyclone Testing Station (CTS) has noted that the slower than originally forecast winds had peak gusts measuring at 82% of the design serviceability wind speed and 55% of the design ultimate wind speed for importance level 2 buildings. These winds were not strong enough to pick debris off the ground to become wind-borne debris, which meant that few windows were broken, roof tiles remained in place, and external objects such as trampolines, garden sheds, rubbish bins and fallen branches were not picked up.
Though Alfred had relatively low wind speeds, some buildings in poorer condition were structurally damaged and wind-driven rain entered many buildings. The main cause of structural damage was trees falling on structures, and damage to roofs, such as metal sheeting being dislodged from garages and apartments, some tiles being dislodged, and damage to flashings, soffits and gutters. There were also some add-on structures, such as enclosed veranda, and fences.
Before Alfred made landfall, its strong winds in Ballina dislodged a big feeler from the Big Prawn tourist attraction. North Stradbroke Island was one of the first areas in Queensland to feel the effects of Alfred, with a lot of trees and powerlines being downed, and a bakery at Point Lookout had the shade sails smash through the glass frontage. At Redcliffe a two-storey fibro house that overlooks the beach had its corrugated iron roof completely torn off, being found a block over on top of power lines. Trees also fell on a retail precinct in the suburb of Everton Park in Brisbane. Another tree also fell onto an apartment building in Scarborough in Brisbane. On the Gold Coast a 30-metre Norfolk pine tree landed on top of a building, a giant gum tree fell through a house in Ashmore, and an apartment complex at Labrador had its roof torn off. A pole also fell and caused substantial damage to a putt-putt golf, and a Korean BBQ restaurant had it’s glass storefront shatter. Some schools in the area were also reported to have suffered significant damage. Fallen trees also impacted homes in Byron Bay.
The disruption from Alfred, such as power outages, had a significant impact on the region. It was the largest ever loss of power from a natural disaster in Queensland’s history, with over 330,000 homes and businesses being without power. There was a race against the clock to reconnect power to key infrastructure. The Gold Coast University Hospital and the John Flynn Hospital both lost mains power and were forced to run on generators. Two water treatment plants, one at Mount Cotton and another at Alexandra Hills, also lost power. Luckily power was restored before those reservoirs ran out of water. The Gold Coast Airport was also impacted, though power was restored before it resumed operations. Also, two of the city’s evacuation centres also lost power, hampering evacuation efforts. These widespread power outages also led to significant food spoilage and increased waste adding to the insured losses from homes and businesses. Alfred also caused a blood donation shortage, which can be in high demand during a natural catastrophe, as 22 blood centres were forced to close.
Storm surge greatly impacted the coastal communities. Main Beach on the Gold Coast had peak wave height of 12.34 m, the highest recorded in 38 years of measurements. Some beaches and dunes have been seriously eroded. Peregian Beach south of Noosa lost up to 30 m of width, and scarps up to 3 m high have appeared on the Gold Coast. The walkway at Main Beach Tourist Park on the Gold Coast was damaged. Coastal erosion experts have stated that it could take up to a decade for the beaches to recover to their sand volume before Alfred.
The flooding from Alfred was less than predicted, however several communities were millimetres from disaster. In total 644 properties were damaged by flooding, with 112 being labelled as severe damage. Complicating the matter, 97 of those damaged had been affected by the 2022 Northern NSW flooding in and had not been repaired. In total, 15 evacuation orders were issued for flooding in northern NSW for Lismore CBD, North Lismore, South Lismore, East Lismore, Richmond Terrace, Tumbulgum, Stotts Island and surrounds, Billinudgel and the Pocket, Kyogle and surrounds, Kyogle North, Uki and surrounds, Fingal Head, East Coraki, Coraki Caravan Park and foreshore, The Flat, Bungawalbin and surrounds. Not only were homes at risk of flooding, but their evacuation routes would have been flooded resulting in the communities being isolated if the flooding materialised as feared. Four locations exceeded the major flooding level, the Richmond River at Coraki, the Clarence River at Grafton, the Bellinger River at Thora, and Coutts Crossing. Lismore, which experienced catastrophic flooding in 2022 when the Wilsons River peaked at 14.4 m, was fortunate that it only peaked at 9.3 m. This was 0.4 m below the major flood level where water would then topple the levee and cause significant flooding to the township. In QLD, major riverine flooding occurred in the Lockyer, Laidley and Warrill Creeks, Bremer, Logan and Albert Rivers.
In some areas flash flooding also impacted roads and homes from the torrential downpours. The Sunshine Coast saw many areas inundated, including Nambour which reported an annual highest daily rainfall record of 365 mm. Brisbane saw its wettest day since Tropical Cyclone Wanda in 1974 experiencing 260 mm, with flash flooding in low-lying suburbs such as Woolloongabba, Rocklea, Wavell Heights, Stones Corner and Windsor. This resulted in the rescues of seven people from flooded vehicles and nine people from inundated homes. Hervey Bay experienced 233 mm in six hours, and 108 mm in just one hour, causing flash flooding and inundation of homes and businesses. The Gold Coast, and several other communities in southeast Queensland and the Northern Rivers also experienced flash flooding.
Alfred caused one reported fatality, a 61-year-old man who went missing after his car was caught in floodwaters in Dorrigo in northern NSW. There were also several injuries reported. Notably, 32 Australian defence Force (ADF) personal were injured, with 13 hospitalised, after one vehicle rolled and the another collided into it south of Lismore whist assisting the community in the aftermath of Alfred. Four people were also rushed to hospital on the Gold Coast after they suffered carbon monoxide poisoning from a generator.
Emergency services and the State Emergency Service responded to over 150 water related incidents across Brisbane, Ipswich and the Sunshine Coast. In some areas residents had to climb on top of cars, roofs and even up trees to avoid flash flooding. One instance included a marine rescue of a sailor and his two dogs off Bribie Island as their boat drifted onto rocks. Police officers also rescued a woman who was trapped in her car which was stranded in fast-flowing floodwaters at Glenore Grove in the Lockyer Valley.
In total the NSW SES received 13,969 calls for assistance, and responded to 7,650 incidents over a fifteen-day period. There were also a large number of rescues, mostly from people driving through floodwaters. Though there are no reported totals for Qld, there had been more than 1300 requests for help in Queensland by Thursday noon before Alfred had made landfall. There were requests for people not to be ‘environmental tourists’, with locals and tourists putting their lives at risk to see the impacts of the rare southward tropical cyclone. There were multiple close calls as beachgoers and surfers got caught by sudden rising tides and eroding coastlines. Several people standing close to the shore were forced to flee from a rush of water sweeping in, and there were several instances of people standing near the sand cliff edges created by the erosion and the sand moving underneath their feet.
Cyclones Affecting SE Queensland
Southeast Queensland is vulnerable to tropical cyclones. They can traverse as far as the Qld/NSW border on the east coast, as the southern Coral Sea ocean temperatures can support category 1 or 2 tropical cyclones, and on rare occasions even up to category 4 systems. However, tropical cyclones that move so far south to such latitudes typically tend to move east, away from Australia. This is usually due to Southeast Queensland being prevalent to west-to-east winds, which act as a barrier and protect the coast. However, these winds aren’t always westerly, and particularly between January and early March, these wind patterns can shift. However, these winds aren’t always westerly, particularly between January and early March, where wind patterns are more likely to shift, allowing such rare southern cyclones to approach the coast.
Leading up to the formation of Alfred, in January and the first half of February, the steering flow in the Coral Sea remained a strongly westerly. These winds were also present as Alfred traversed south along the coast. However, Alfred repeatedly missed multiple passing upper troughs that could have captured it and pulled the system southeast, allowing it to travel so far south. Eventually, a mid-level ridge developed over eastern Australia and the Tasman Sea which shifted the steering winds and led Alfred towards the coastline.
During this time an upper ridge was also present over the northern Coral Sea, driving upper atmospheric flow. The interaction of these two competing phenomena is what is attributed to Alfred’s slow and erratic movement. However, as Alfred was not an overly tall system, the mid-level Tasman ridge ultimately had the stronger influence, leading to its westward direction.
Alfred is not the first tropical cyclone to impact Southeast Queensland. There have been several events which have had damaging winds, major flooding, and/or severe storm surge causing significant damage to the region.
The most recent event is tropical cyclone Debbie in 2017. Though it crossed Qld’s coast up north near Airlie Beach as a category 4 system, it then travelled south as a destructive tropical low storm. It delivered heavy rain and strong winds to southeast Queensland, causing flash floods throughout Brisbane, the Sunshine Coast, Ipswich and the Gold Coast. Debbie has a normalised loss of $1.8 billion AUD, though most of this loss occurred up north.
Tropical cyclone Oswald also impacted southeast Queensland. Similarly to Debbie, Oswald crossed the coast up north before travelling south as a tropical low storm. It delivered strong winds and persistent rain that isolated parts of Queensland and the northern rivers area of NSW. Oswald has a normalised loss of $1.1 billion AUD for Qld, and $140 million AUD for NSW.
In 1990 category 1 tropical cyclone Nancy came within 180 km of the Sunshine Coast. Whilst it didn’t make landfall between Bundaberg and Caloundra as forecast, it brought heavy rain and flash flooding to southeast Queensland. It has a normalised loss of $239 million AUD.
Meanwhile, in 1974, three tropical cyclones caused a severe impact on the southeastern corner of Queensland. Tropical cyclone Wanda, a weak category 1 system, crossed the coastline near Maryborough. It brought five days of torrential rain across southeast Queensland, with 642 mm of rain being recorded during a 36-hour period over Brisbane. It produced widespread flooding across Brisbane, as well as Ipswich, Beenleigh, and the Gold Coast. This event has a normalised loss of $3.2 billion AUD.
Tropical cyclone Pam only passed 500km east of the coast. However, it caused storm surge to batter beaches with huge waves, floods and gales on the Gold Coast. Palm Beach saw seawater drove over 6.2 m boulder walls and surge through residences.
Tropical cyclone Zoe was the last cyclone to make landfall in the region. It crossed the coast at Coolangatta before heading back out to sea. It caused flooding from Brisbane to Northern NSW, landslides, and severe coastal erosion. It has a normalised loss of $508 million AUD.
In 1972 tropical cyclone Daisy made landfall on Fraser Island as a category 3 system, before moving east out to sea. It was estimated 200 homes were damaged at Pialba, and more houses were impacted in widely scattered townships. It caused flooding throughout southeast Queensland, with major floods in Brisbane creeks, causing significant damage to commercial stock in Brisbane. Flooding on the Gold Coast also caused damage to commercial and domestic properties. There was also significant storm surge and coastal erosion reported.
In 1971 tropical cyclone Dora crossed the coast at Redcliffe, just north of Brisbane, as a category 1 system. It caused fairly widespread structural damage at Redcliffe.
In 1954, The Great Gold coast cyclone crossed over Coolangatta. It caused serious structural damage to buildings in Brisbane, Gold Coast and the Sunshine Coast. Storm surge was recorded in Moreton Bay, Beachmere and Kirra, where 3 m of water flowed onto the highway washing cars from the road. Heavy rainfall also caused severe flooding in Brisbane, Gold Coast and the Sunshine Coast. Severe flooding also occurred in areas of NSW including Cudgen, Casino, Lismore, Murwillumbah, Grafton, Maclean, Clarence, Yamba, Kyogle and Bryon Bay. The event caused several thousand people to be displaced, crop and stock losses, severe damage to residential and commercial premises, and roads and other infrastructure being destroyed.
There is also the 2001 hybrid low pressure system, unofficially referred to as Donald (or the Duck). It developed in the Tasman Sea under tropical–extratropical influence and made landfall near Byron Bay. The system displayed all the criteria of a tropical cyclone, except for forming in the tropics, having an eye with a short-lived warm core and reaching category 1 windspeeds.
Forecasting Australian Tropical Cyclone Losses in Real-Time
Over the past few years, Risk Frontiers has implemented and refined a capability to generate rapid loss estimates for specific live events such as tropical cyclones. This capability is embedded within the Multi-Peril Workbench – the loss modelling software through which all of Risk Frontiers’ natural catastrophe loss models are delivered to clients. It takes live forecast data from the Bureau of Meteorology and generates hazard data associated to wind field, storm tide and riverine flood. These hazards data are overlayed with the end-user’s portfolio to provide a tailored view of the forecast losses simulated through Risk Frontiers vulnerability modules for wind, water ingress, surge and riverine flood damage. The overall process takes from tens of minutes to a few hours depending on the portfolio size and analysis depth, meaning that, this capability provides Risk Frontiers (and by extension, their clients) with near real-time loss distribution estimates, given the current tracking and weather forecast.
