Across New South Wales more than 40,000 people were affected by evacuation orders, according to the NSW State Emergency Service. The damaging weather and flooding have caused several roads and schools to close across the state.

Entire communities were forced to evacuate their homes and businesses as the weather system slowly moved South. So far there have been three recorded fatalities.

The entire New South Wales coast was subject to a severe weather warning. Australia's Bureau of Meteorology stated that 10 million people across every state and territory except Western Australia were under weather warnings. Up to 38 places across NSW were classed as natural disaster areas and 19 evacuation orders where issued with more possible. Evacuation orders had been issued for 17 locations in eastern regions. NSW State Emergency Service reported 8 evacuation orders in Mid North Coast Region, 1 in the Hunter Region, 7 in the Sydney Western Region and 1 in the town of Kempsey. Almost 7,000 people were without power as of the morning of 24th March.

Days of torrential storms had caused rivers and dams to overflow around the state capital of Sydney and in south-east Queensland. In Sydney the rainfall total for the six-day event from Thursday to Wednesday was around 250mm to 350mm for most suburbs. The extreme conditions have set several new records, with Penrith receiving 400mm in a month, which is just under double the previous record of 230.2mm at that location. In 48 hours to 20the March the town of Nambucca Heads in Mid North Coast recorded over 560 mm of rain and Comboyne received 465 mm. 

Understanding the flood risk potential within New South Wales

A roughly 3.5 times the size of the UK the state of NSW covers a huge area. The large size of Australia provides challenges when forming an accurate view of flood risk for all locations. Since it was first launched in 2014 our Australia FloodMap has provided the most detailed and comprehensive view of risk across the entire continent of Australia. Our Urban model coverage is formed using high precision LiDAR terrain data for all mayor cities and around 85% of all properties nationwide. Further to this expansion in detailed coverage we have completely modelled the entire state of NSW a 5-meter grid resolution in our latest annual updates.

Our FloodMap, FloodScore and FloodCat products are used by insurance and reinsurance companies in Australia to understand their exposure to flood risk. Ambiental data is relied upon to assess risk, underwrite premiums, and to understand losses from catastrophic events. This helps them to accurately price risk and to avoid writing business in the most dangerous locations. During the current NSW flooding event our data is being used to identify the impacted exposure locations and to quantify expected losses.

The Insurance Council of Australia declared a catastrophe for large parts of New South Wales with more than 29,213 insurance claims already filed as of 29th March. The total expected losses are likely to be around AU $2 Billion.

Ensuring the predictive accuracy of our flood models

As part of our product validation process we routinely compare our FloodMap predictions to local council maps and historic events across Australia. This helps us to ensure that our modelling process has achieved a realistic outcome. A model which over predicts flooding will overstate risk to properties and lead to high insurance premiums and missed opportunities to write safe business. However, an under predicting model can lead to unexpected losses from flooding events. Finding the right balance here is crucial and flood events help us to calibrate our models and demonstrate the predictive accuracy of our models.

Through our analysis we have found good alignment between the Ambiental FloodMap predictions and the available sources of evidence. Our flood event report is available for download here and along with facts and figures relating to the floods it includes satellite and areal imagery validated alongside FloodMap data. We are confident in our predictions and we invite our prospective insurance customers to test their recent flood claims against our flood data.