The $11.4 million Northern Rivers Resilience Initiative aims to help the Australian Government understand the drivers behind the unprecedented flood events in February-March 2022 in this region of NSW and develop community-supported solutions for flood mitigation and resilience investment.
The National Emergency Management Agency (NEMA) has engaged Australia’s national science agency CSIRO to support the Initiative, which will consider climate, catchment and hydrological systems, and the broader influences of land-use practice and infrastructure.
This Initiative enabled us to assess existing project proposals and identify further long-term options for reducing flood risk in the Northern Rivers region. A core part of the first phase of the project was to undertake engagement with residents in flood-affected areas to seek their views regarding priorities for investment.
The project consists of two phases:
1. Rapid review and assessment phase – the first six months (July to November 2022). This phase identified and prioritised existing project proposals. It analysed the most effective intervention options for allocation of the Federal Government’s $150 million funding and characterised the catchment and climate conditions which led to the 2022 floods. This also involved considering the historical perspective of flooding in the NSW Northern Rivers region. Residents and councils, in each of the seven flood-affected Local Government Areas in the region (Ballina, Byron, Clarence Valley, Kyogle, Lismore, Richmond Valley and Tweed) were consulted to help identify and prioritise the most effective intervention options.
Outcome – CSIRO completed the rapid review and assessment phase and submitted two related reports to NEMA on 30 November 2022. These reports and a full list of project recommendations were then considered by the Federal and NSW governments.
On February 23 2023, the first 16 projects totalling $50 million were announced. These included combined upgrades to pumps and pump stations in Lismore, a new pump system to assist drainage in East Murwillumbah and installation of box culverts through a riverbank levee to improve local drainage in Grafton.
On July 28 2023, the second 20 projects totalling $100 million were announced. These included raising two low bridges at Tatham to improve access between Casino and Coraki during flood events and widening the Browns Creek flood channel at Lismore.
CSIRO and NEMA have now completed phase one of the Northern Rivers Resilience Initiative project with the allocation of the total $150 million Federal Government funds for flood mitigation and resilience projects in the Northern Rivers region.
2. Detailed modelling – July 2022 to June 2025. This work is generating Light Detection and Ranging (LiDAR) data (using planes) to inform spatial analysis for the entire Northern Rivers region. We are also collecting river bathymetry (using boats) for the Richmond and Tweed rivers. All this high-quality data will be used to underpin a detailed hydrodynamic model for the Richmond River catchment.
Outcome – CSIRO will generate high quality digital elevation data sets for the Northern Rivers region. This high-quality data will be used to underpin a detailed hydrodynamic model for the Richmond River catchment. It will be used to examine and evaluate possible events and scenarios that could take place in the future and predict possible outcomes, drawing on local knowledge and expertise on the catchment and flooding.
The report for this work and fully calibrated model is due by June 2025. Scenario testing will take place in 2025-2026.
Community and stakeholder engagement
CSIRO and NEMA provide regular updates on NRRI progress on our websites and through regular updates to project governance and advisory panels, the Northern Rivers Joint Organisation (NRJO), local councils, stakeholders and communities. For further details please email nrri@csiro.au or contact@nema.gov.au
Frequently asked questions
From your analysis so far, what led to the extreme 2022 flood event in the Northern Rivers region?
Between the February 23 and March 1, the highest daily rainfall totals were felt in most parts of the Richmond, Tweed and Brunswick areas. Conditions were already significantly wetter than average across the Northern Rivers region with rainfall totals, soil moisture and groundwater levels remaining above their 75th percentile during the two months preceding the flood. Extreme rainfalls translated into record high stream flows, volumes and water levels. Major flood levels were exceeded by more than 2 metres in several locations including in Lismore where the flood reached a record 14.37 metres.
Can you explain the two different methods researchers are using to collect data?
LiDAR flights – An aeroplane with LiDAR sensors attached, will be flying over the region. These sensors are a remote sensing method used to collect accurate digital elevation models for the region for hydrodynamic modelling. There will also be ground crews doing surveys to truth-test information collected by the LiDAR equipment attached to the plane.
River bathymetry – Locals may also see boats in the rivers with sonar equipment collecting accurate information on the cross sections of the river network (river bathymetry) to inform the hydrodynamic model. This may include small remote-controlled boats for smaller and steeper streams.
Will the LiDAR and bathymetry data sets for the modelling be made publicly available?
Yes, we will make the data sets available by mid 2024 once the collection and processing are done. This enables all seven LGAs to access and use the data for their own future flood-mitigation planning and model building purposes.
Has Phase 2 of the NRRI been delayed and if so, why ?
The LiDAR and bathymetry data collection commenced in July 2022 and is ongoing. The data will be publicly available in mid 2024. There were significant delays to the LiDAR collection due to unfavourable weather conditions across the region over the last year. This high resolution and high accuracy LiDAR data set is a critical input for the Richmond River catchment hydrodynamic model.
The detailed hydrodynamic model for the Richmond River catchment is currently being built. This will use the LiDAR and bathymetry data sets, and the model will be able to evaluate future changes in flooding due to climate and mitigation scenarios at the catchment scale. Although there are some existing flood models, these represent smaller areas or only sections within the catchment, and a catchment scale model has never been built before for the Richmond River catchment. Building this model is both a complex and time-consuming process, the model needs to be done at the highest precision to get reliable estimates to underpin any future flood mitigation options.
What is the model that CSIRO is building for the Richmond River catchment?
The model is a hydrodynamic model (HD), which is a representation of water flows across the Richmond River catchment (more than 7000km2). The model aims to represent the key hydrological (water flow) processes related to flooding across the catchment and will be able to reproduce the past flooding history in the catchment.
Once completed, the model can be used to investigate the changes in flooding associated with changed climate, and structural and non-structural infrastructure options designed to mitigate flooding.
The model design is based on detailed spatial representation of the catchment’s biophysical characteristics such as soils (infiltration rates, soil storage capacity, etc) and landscapes (roughness, flow paths, flow direction, structures, vegetation, etc.).
The hydrodynamic model will be validated (checked for accuracy) against:
- flood extents mapped through remote sensing (using satellite products from Landsat, Sentinel, etc.),
- measurements at internal flow gauges and
- on-ground observations.
This will provide confidence in the model to be used for any future climate change or flood mitigation scenario analysis.
Why are you only developing a detailed hydrodynamic model for the Richmond River Catchment?
To cover all the catchments in the Northern Rivers region, we would need to build 4 to 5 separate hydrodynamic models as these river basins drain through different points (and are independent of each other). Current resourcing restricts this. The focus on Richmond arises from the continual incidence of flooding and likely compounding impacts that come from a changed climate and hydrology. While we are constrained in terms of resources to do more models at this stage, lessons from the Richmond modelling will be applicable elsewhere and the approach could be duplicated. It is also worth noting that the LiDAR datasets at very high 1m resolution and accuracy are getting collected for the entire Northern Rivers region. The river bathymetry is also collected for both the Richmond and the Tweed rivers. All these data sets are available to councils and governments.
What are the long-term goals of the project?
We will continue to conduct our detailed modelling work until 2025 when we will start investigating different flood mitigation scenarios to recommend long term flood mitigation actions. Multiple flood mitigation/adaptation scenarios and the level of protection they can provide along with the associated costs can be investigated once we have a full catchment model calibrated for the Richmond River catchment. We are confident that we can reduce the impact of flooding and the associated damages to the region significantly through this project. We will also continue to communicate and work closely with the councils and the community.