The Insurance Council of Australia (ICA) has declared a catastrophe for the NSW emergency as widespread sustained rainfall and flooding causes a once-in-a-century event in some parts of the state.

“It’s too early to understand the extent of the damage to property in affected areas and to estimate the insurance damage bill, however insurers have received over 5000 claims in the past few days,” ICA CEO Andrew Hall said today.

“As many areas are currently inaccessible due to floodwater, insurers are expecting further claims in coming days as emergency services allow residents to return to their properties to examine the extent of their damage and losses.”

Premier Gladys Berejiklian says the disaster is a 1-in-100-year event for parts of the Mid North Coast and a 1-in-50-year event in the Hawkesbury Nepean valley area.

The wild weather hit southeast Queensland and northern NSW early last week before moving southward and intensifying in the Sydney region on Saturday as the system stalled and brought sustained rainfall.

The Warragamba Dam is also still spilling today after water began flowing on Saturday afternoon. The flooding comes as debate continues over proposals to raise the height of the concrete barrier and over the mitigation role of the dam.

“Flooding in Western Sydney has been described as the worst in 60 years, and major flooding is occurring at North Richmond and Windsor along the Hawkesbury River,” the Bureau of Meteorology said today.

“As we head into Tuesday, the merging of two weather systems along the east coast may exacerbate conditions, with further heavy falls possible.”

The bureau says almost 900mm has fallen in some locations around Port Macquarie in the six days to 3am today, while Warragamba received 120mm between 9am Saturday and 4am yesterday. NSW flood warnings have been issued for coastal rivers from the Queensland border to Victoria.

IAG says more than 2100 claims had been lodged by 8pm last night covering mainly property damage.

“We now have additional resources in place to help our customers get back on their feet and we encourage customers to contact us to lodge their claim as soon as possible so we can organise immediate assistance,” CEO Nick Hawkins said.

The NSW and Federal Governments have issued more than 30 natural disaster declarations for local government areas in the past couple of days, triggering access to assistance funding. The areas include the Blue Mountains, Campbelltown, Bankstown, Hawkesbury, Hornsby, Inner West, Sutherland, Parramatta, Newcastle City, Kempsey, Port Macquarie-Hastings and Central Coast.

Police and Emergency Services Minister David Elliott yesterday warned insurance companies about their policy obligations.

“After every disaster, we see insurance companies trying to reduce their payouts by being tricky with their wording, and my strong advice to them is don’t do it because we have very strong laws in this country to protect those policyholders,” he said.

The torrential rain comes as a La Nina weather system, typically associated with wet conditions in the country’s east, begins to fade. The bureau says above average rainfall is still forecast for parts of eastern and northern Australia during April.