Nature-Based Solutions: Modelling NBS scenarios under Northern Rivers Resilience Initiative

The Northern Rivers Resilience Initiative (NRRI) is focused on understanding climate, catchment and hydrological drivers in the area. It also aims to find evidence-based ways to reduce flooding in the Richmond River catchment. National Emergency Management Agency (NEMA) and CSIRO are currently undertaking community consultation through face-to-face meetings as well as an online forum. They have provided 15 possible options for flood mitigations. They are calling these a conversation starter. However, they have not included any nature-based solutions options. Advice from CSIRO and NEMA is that NBS can be put forward as an alternative option but they need to have detail of what type of nature-based solutions are and where they are occurring in the catchment.

RLI is a volunteer managed Landcare network organisation supporting around 60 active Landcare groups within the Richmond River catchment and is delivering the pilot project Nature-based Solutions: Building Flood Resilience in the Lismore Catchment. The project is funded through the NEMA, and administered through Reconstruction Authority, under the federal Disaster Ready Fund initiative.

Given that NEMA is funding our project, we believe it is prudent that our project is included as a scenario in the next stage of the Northern Rivers Resilience Initiative, to compare the results with other scenarios being proposed. If you wish to make a formal submission that includes this nature-based solutions option, please visit a face to face meeting and add the following in the form they give you on the day (find this here: National Emergency Management Agency Events - 3 Upcoming Activities and Tickets | Eventbrite), or log in online submission form (CSIRO flood modelling community engagement), select “other” and add the following:

“Reforestation of riparian and floodplain areas in upper sub-catchment streams, as a nature-based solution, at a landscape scale using Richmond Landcare Inc. data”

Background:

This important project is focussing on reforestation of riparian and floodplain areas in upper sub-catchment streams using a diverse range of big scrub rainforest species. Reforestation of low gradient riparian and floodplain areas using deep rooted tree species will achieve this through:

• drawing water from the soil creating airspace for greater infiltration,

• adding organic matter to soil which increases its water holding capacity - 1% increase in soil organic matter in the topsoil across one hectare could hold up 30 000L of water

• root systems holding soil which prevents erosion,

• slowing down overbank flows and surface runoff and capture debris and sediment

The pilot is collecting evidence to demonstrate and quantify how reforestation can reduce the volume, intensity and frequency of flooding in the lower catchment, as well as reducing erosion and improving water quality. The project area is Tuntable and Terania creeks upstream of The Channon and, where possible, is revegetating neighbouring parcels of land. While individual parcels of land will have a negligible impact on flood flows, when aggregated up, the impact is much greater.

RLI is collaborating with three universities, Southern Cross University (SCU), Australian National University (ANU) and Macquarie University (MQ) to develop a fine scale hydrodynamic model to quantify the reduction in flow and flood peaks downstream of the pilot project area under a range of rainfall event scenarios.

The findings of the project will be essential to exploring what can be achieved through implementing nature-based solutions for protecting our community at a landscape scale. The primary output will be a prospectus that will include costings and will quantify the reduction in flood volume and flood peaks under a range of flood event scenarios in the Wilsons River and Leycester Creek catchments. The outcomes will also inform similar projects in other regions particularly as we increasingly deal with the consequences of climate change. Further, Reconstruction Authority has advised the intention of using the pilot project as a case-study in the State Disaster Mitigation Strategy Nature-based Measures knowledge hub.

For further information please contact Louissa Rogers, at nbs.project@richmondlandcare.org or 0461 554 591