Identifying corridors of river recovery in coastal NSW Australia, for use in river management decision support and prioritisation systems

Abstract

By connecting corridors of river recovery, resilience can be built into river systems to mitigate against future floods and droughts driven by anthropogenic disturbance or climate extremes. However, identifying where these corridors can be built is still lacking in river management practice. The Open Access NSW River Styles database contains comprehensive information on geomorphic river condition and recovery potential. The database can be used to systematically analyse where corridors of river recovery could be created via conservation or rehabilitation. Analysis was undertaken in ArcGIS using the recovery potential layer along 84,342 km of freshwater stream length, across 20 catchments of coastal NSW. We identified 4,905 km of reach connections, defined as an upstream to downstream section of river that is connected end-to-end, and 17,429 km of loci connections defined as more isolated sections of river from which recovery can be seeded and extended into adjacent reaches. There was significant spatial variability in the types and lengths of connections made across the catchments. Some catchments have significant potential to build corridors of recovery along large sections of river, whereas other catchments are more fragmented. These results provide practitioners with a user-friendly distillation of where river conservation and rehabilitation activities could be focussed when working with river recovery in practice. Combined with local on-ground knowledge, this information forms an important input to evidence-based prioritisation and decision making in river management.

A GIS workflow for the identification of corridors of geomorphic river recovery across landscapes

“…Agnew and Fryirs [ 22 ] uses the NSW River Styles database to identify and quantify where corridors of river recovery may be established as part of process- and nature-based approaches to river management. The NSW River Styles database contains extensive river characterisation information for over 216,000 km of stream length across the State of New South Wales (NSW) Australia, including a geomorphic recovery potential layer [ 23 , 24 ].…”

“…Recovery potential occurs along a continuum of classes starting with Conservation and Strategic, and followed by declining recovery potential from High Recovery Potential (HRP), to Moderate Recovery Potential (MRP) and Low Recovery Potential (LRP) [ 22 , 28 ]. The findings presented in Agnew and Fryirs [ 22 ] highlight the potential of using the state-wide NSW River Styles database in a new and novel way, in practice, to prioritise where corridors of river recovery can be created in catchments. The novelty of the GIS workflow developed is its analysis of patterns and sequences in polyline data.…”

“…The GIS workflow has been used to identify corridors of river recovery for all NSW coastal catchments as reported in Agnew and Fryirs [ 22 ]. In Agnew and Fryirs [ 22 ], 13 different combinations of reach and loci connections are identified using the protocol. The step-by-step GIS workflow is publicly available as an open access protocol with protocols.io.…”

“…Here, we analyse polylines based on their recovery potential class and their proximity to each other to identify ‘reach’ and ‘loci’ connections that create corridors of river recovery. In Agnew and Fryirs [ 22 ] reach connections are defined as an upstream to downstream section of a river that is connected end-to-end. Loci are isolated river sections, where more complex connections link trunk streams with their surrounding tributaries.…”

“…Recovery can be seeded from these reaches into adjacent reaches. In Agnew and Fryirs [ 22 ] loci connections are defined as upstream to downstream sections of a river that are connected both end-to-end within an individual stream, and directly linked to tributaries. Fig 1 shows a schematic representation of reach and loci connections.…”