As October comes to a close, it has been twenty months since the February 28 2022 big flood devastated Lismore and the Northern Rivers.

There are signs of the rebuild in terms of businesses reopening, community infrastructure, like roads and the Lismore Baths, more deals are being done in the Resilient Homes Program with more and more houses wrapped in NRRC signage around North and South Lismore and the CBD. The Resilient Lands Program is one area that has shown no signs of life as the due diligence rolls on.

Arguably, the most important document throughout the flood recovery journey is that of the CSIRO. Their $11.4m Northern Rivers Resilience Initiative to help the Australian Government understand the drivers behind our unprecedented flood event and provide flood mitigation solutions to lower future flood levels, hopefully providing enough surety for insurance companies to start to offer flood insurance at an affordable price let alone investor confidence to help Lismore thrive and grow in the future.

Jai Vaze is the Senior Principal Research Scientist for the CSIRO. Jai has been in Lismore this week and agreed to sit down with the Lismore App to provide an update on the research project.

Jain explained that Phase One is now complete.

Phase One was ranking each local council's proposals for the $150 million Recovery and Resilience Program which was split into two announcements. $50m was announced in February 2023 where Lismore received the bulk of the funding and $100 million in July where Lismore received very little and Ballina the bulk of the funding ($48m).

NEMA (National Emergency Management Agency) is working with the NSW Government on the implementation of the announced funding.

Phase Two has the highest community expectations as it will deliver a world-class model of how floods behave in our region, not just Lismore but the whole Richmond catchment. Varying rainfall amounts can be fed into the model at different locations, even amounts greater than February 28 2022, which will show how the water travels through our waterways and out to sea.

Phase Two has two components, Part One is the data collection and Part Two is building the Hydrodynamic model.

Unfortunately, Jai started with the disappointing news that Part One has been delayed due to last year's very wet conditions.

"The digital elevation model for the whole Northern Rivers was delayed by nearly eight or nine months because of bad weather last year. It's collected through flights and when there is cloud you can't collect the data."

"We are hoping that we'll get the LiDAR (which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth) publicly released, after quality assurance, by June 2024. And the bathymetry, which is the cross sections of the rivers for Richmond and Tweed, they will get released with that as well."

Both sets of data should be collected by February 2024 before there are three to four months of quality assurance because it is a massive data set. Jai said that by June 2024 the data will be available for anyone to download and use, probably through Geoscience Australia. This is a federal government organisation that stores all high-quality data sets for Australia.

Part Two is building the hydrodynamic model for the full Richmond River catchment which is progressing well, but Jai will not see that data until June next year.

"That one will be fully calibrated to represent 2007, 2009, 2017 and 2022 flood events. Those results and the model will be available in June 2025.

To give you an indication of the size of the data sets, Jai said the CSIRO computers (some of the most powerful in the country) would be calibrating data for about a month.

"It's a pretty complex model, about eight to ten million grids. It's like triangular facets. So, the whole Richmond gets divided into these triangular facets."

"The important areas like Lismore CBD, will be a really fine grid so that you can pick everything right, and then as you go to the top of the hills, that never got flooded, we'll go coarser grids."

"We have really, really powerful computing systems at the CSIRO, but still, I will expect one run in calibration to take about a month, at least. As it gets wetter, it reduces the time step to like a second, it is running every second and then as it gets drier, it expands the time step, so it's a flexible mesh. It will be a full representation of the entire Richmond River catchment."

"We are trying to make the model reproduce the whole range of floods ('07, '09, '17), and then given these are observed floods, we do have Landsat images to see where the flooding was and we also have some on-ground measurements. Those will be used to validate whether the model is doing the job or not and then we will retune the model to get everything right."

At this point, Jai can then use theoretical rainfall data in the model and see how it behaves throughout the entire catchment including replicating the unique events of February 28 2022 when the low weather system stalled over the Northern Rivers for 24 hours dumping record rainfall and even increasing those numbers.

In contrast to the NRRC and NSWRA maps that indicate where the high-risk areas of Lismore are, (they are being peer-reviewed now and not by the CSIRO) the CSIRO will be releasing the results to the community. It is part of their mantra, to be truly open and transparent.

"I want to show and ask a lot of locals about their measurements. Quite a few from The Channon, a few from Lismore, a few from Woodburn, have their local measurements, like how high the water went. So, we can go into the model and see how accurately we are getting that in our model and if we are not getting accurate answers, what is the reason? We then re-tune the model to get all that right. But not just for Lismore but the entire catchment."

The modelling will also include upstream rain gauges and others inside the catchment. Jai explained it doesn't matter if they stopped working during the February 28 2022 event because there is a lot of other historical data that can be matched.

"When I bring the results and someone says it was the other way around, then there is surely some problem in my setup for that area. That actually helps me to re-tune the model because we must be getting something wrong."

"So, community (feedback), plus satellite imagery, plus all data. Once that's done we have confidence in the model, and once the community has confidence in the model, and we don't know in the future what will happen, if the future rainfall is 20% more or the distribution is slightly different, we can run it through the model and see what can happen."

When Jai and his team and the community have confidence in the model, then they can start introducing flood mitigation options to reduce the flood levels and estimate (it will be rough costings) how much each scenario will cost. This will occur between July 2025 to June 2026.

"Because it's a full model, any intervention we put upstream of Lismore, we can actually see the impact up to Ballina. This can occur only in the Richmond catchment, all 72.6km to be accurate."

The delayed timing is not ideal for any resident in Lismore and the Northern Rivers but as Jai said, it is better that he and his team get this model right so it can accurately reflect all past and even future floods in the Richmond River catchment as it can lead to the best flood mitigation options to be presented to the federal and state government.