On 7-8 April, Tropical Cyclone Seroja remained weak while interacting with a tropical low that later became the short-lived Tropical Cyclone Odette. The following day, the system was slow-moving and well west of the Pilbara but entered a more favourable environment and began to intensify. The system then accelerated towards the south-east and intensified into a Category 3 severe tropical cyclone on 11 April 2021.

Tropical Cyclone Seroja crossed the coast south of Kalbarri in the central west coast later that evening and tracked rapidly across northern and eastern parts of the South-West Land Division before moving into the Great Australian Bight as a low-pressure system. Maximum wind gusts of 170 km/h were recorded near Kalbarri and the strongest winds were experienced for 1-2 hours at all locations as it tracked inland. The impact area of the cyclone was estimated to be more than 133,000 km2 .

Significant damage occurred to critical infrastructure including roads, telecommunications and emergency services buildings. Several towns received damage with properties in Kalbarri, Northampton, Mullewa, Morawa and Mingenew sustaining considerable damage. The widespread damage prompted many calls to the State Emergency Service (SES) 132 500 emergency line requesting assistance. Department of Fire and Emergency Services (DFES) as the designated Hazard Management Agency for cyclone, received 1,659 requests for assistance and conducted 3,228 rapid damage assessments, with 317 residential properties assessed as being uninhabitable.

An emergency situation was declared at 3.50 pm on 11 April for 45 local government areas. To minimise the risk of fire impacting the state while emergency services were managing the cyclone, pre-emptive total fire bans were declared for the period to 12 April in 70 local government areas.

Observations

This is a rare event for people on the central west coast of Western Australia and many properties in the affected areas were not constructed to withstand a Category 3 cyclone impact. Many of the damaged properties contained asbestos building materials resulting in extensive contamination across much of the impacted area. DFES established a separate Asbestos Risk Management Division to develop an Asbestos Management Plan in consultation with the Department of Water and Environmental Regulation and Department of Health. Contractors were engaged in applying asbestos risk treatment through the application of sealant to prevent the release of asbestos fibres and making sites safe.

Approximately 30,000 homes and businesses were without power, and communication systems were extensively damaged. The damaged network covered an area more than 700 km long and 150 km wide which presented challenges to the community gaining emergency assistance, and for emergency teams operating in the affected areas. Generators, mobile satellite units and portable radio repeater towers were used extensively to re-establish communications with the Incident Management Team and emergency crews and to restore temporary power to affected communities.

In preparation for the impact of Tropical Cyclone Seroja, a Level 2 Incident Management Team and urban search and rescue resources were deployed to assist the Midwest–Gascoyne region on 8 April. Key stakeholders, pastoralists, remote communities (including the Abrolhos Islands) were engaged to ensure appropriate preparation action was taken and any emerging issues identified and mitigated. Extensive public consultation was initiated with public safety information and emergency warnings issued. The incident escalated to Level 3 on 12 April and subsequently a Level 3 Incident Management Team was established in Geraldton.

The DFES Geraldton Regional Operations Centre (ROC) transferred functions to the Kimberley ROC on 11 April until the red alert phase of the cyclone was lifted on 12 April. In addition, contingencies were established to transfer functions to the Metropolitan Operations Centre (MOC) in Perth should the Geraldton ROC redundancy plans become unachievable.

More than 600 DFES personnel and volunteers, over 200 personnel from Victoria, New South Wales, South Australia and 68 Australian Defence Force (ADF) personnel were deployed to the region to assist. Interstate SES teams were provided by Victoria, New South Wales and South Australia through coordination with the AFAC National Resource Sharing Centre. The first teams arrived from South Australia on 12 April. A request for Australian Government Physical Assistance for an airlift of personnel and equipment between Perth and the impacted tropical cyclone area was approved on 11 April. ADF personnel and aircraft were used extensively to move people, vehicles and equipment between Perth and Geraldton. Five Victorian SES vehicles were transported from Melbourne to Geraldton by an ADF aircraft.

Prior to the cyclone, the impacted areas had experienced a significant surge in temporary population due to the Easter long weekend and the commencement of school holidays. Aggregate numbers indicated a rise of the transient population to be in the vicinity of 20,000 to 30,000 people. As a result, extensive media coverage and public warnings were issued advising people to leave the area before the arrival of Tropical Cyclone Seroja. National parks in the forecasted path of Tropical Cyclone Seroja were also closed.

On 24 April, a COVID-19 lockdown by the Western Australian Government prompted enhanced Interim Operating Procedures. This included the introduction of face masks, daily briefings and the suspension of incoming interstate crews. All responders were offered testing, self-isolation in Geraldton for any positive test results and appropriate accommodation for self-isolating personnel was secured by the Incident Management Team. DFES monitored cases of personnel that may have visited exposure sites during the specified periods of concern. Replacements for the interstate teams were sourced from regions outside the Perth and Peel region affected by the COVID-19 lockdown. Transport arrangements were established to ensure the incoming teams bypassed or did not stop in the Perth and Peel region.

There were significant challenges with the provision of accommodation for personnel. The shortage of accommodation was caused by a number of factors:

• Many accommodation providers were unable to open because of the power outage.
• Many accommodation facilities were damaged and uninhabitable.
• Essential service network operators competing for accommodation for additional personnel.
• Tourist numbers for the area were high and lessened the availability.

DFES established temporary accommodation with the assistance of ADF personnel for 210 people.