Where is Natural Flood Management (NFM) occurring in eastern NSW? Detecting signals to guide strategic on-ground rehabilitation

Natural Flood Management (NFM) represents a paradigm shift in flood risk mitigation, emphasising the rehabilitation and enhancement of natural hydrological and morphological processes across catchments - to deliver slower and lower floods – and reduce flood risk. Interest in NFM has grown rapidly, particularly in regions facing increasingly intense and destructive flooding under climate change, such as eastern NSW (including the mid-coast and Northern Rivers) since 2021. NFM works with natural processes either through active implementation of nature-based solutions (NbS), or passive enhancement of river recovery. Delivering NFM also provides environmental co-benefits beyond just flood mitigation, including healthier river ecosystems, improved water quality, enhanced habitat and biodiversity, and increased climate resilience.

Despite the expanding number of NFM projects, clear proof-of-concept remains limited in NSW and Australia. Many researchers and practitioners agree that robust monitoring is essential for building the evidence base required to mainstream NFM as a reliable flood mitigation approach. Detecting NFM signals in hydrological records across a full range of flood magnitudes from minor, to moderate and major, is critical and a required first step in the process. However, such monitoring frameworks are not yet available.

This paper utilises the full capacity of available gauge records to detect NFM signals in two key flood prone catchments; the Richmond and Hunter (the remaining eastern NSW catchments are under review in Fryirs et al., subm). We use both at-a-station and upstream-to-downstream metrics as our analysis and monitoring tools. At-a-station analysis examines temporal changes in hydrograph shape using kurtosis, rate of rise and skewness metrics. Upstream-to-downstream metrics include peak-to-peak travel time, flood-wave celerity and peak attenuation. Detecting NFM signals helps identify where in the landscape NFM is already occurring, emerging, not yet evident, or just not feasible. With this understanding, practitioners can strategically enhance existing mitigation, initiate new rehabilitation, or redirect efforts.