Date of creation: September 2015
Owner: Reef Catchments Ltd
Copyright: © Reef Catchments Ltd (2015)
Consultancy: Catchment Solutions
Contact Person: Matt Moore
What this project aims to address – the issue
The majority of freshwater fish species in coastal catchments of South East Queensland migrate at some stage during their life history. Some of these migrations are short and confined wholly to freshwater habitats, while some migrations occur across vast distances and between varying habitats, including between freshwater and near-shore marine environments. A portion of the fish community, including important commercial and recreational species such as sea mullet, long-finned eels and Australian bass require unimpeded access between freshwater and estuarine habitats to complete their life cycle or maintain sustainable populations.
Barriers such as culverts, pipes, road crossings, weirs, dams, flow gauging structures, bunds (or ponded pastures) and sand dams may prevent, delay or obstruct migration, impacting recruitment and reducing fish populations.
In many parts of the world remediation of barriers with appropriately designed fishways is one of the most successful management tools utilised by government agencies and natural resource management groups to help reduce the impacts of barriers. However, objectively choosing the ‘right’ barriers to remediate in order to obtain the greatest benefits requires a holistic prioritisation process. The following three-stage Greater Brisbane Urban Fish Barrier Prioritisation process achieves this by investigating the cumulative impacts barriers have on the environment, fishery, economy and local community.
Outcomes of this project
The final result of the prioritisation process after taking these considerations into account is a prioritised list of all actual and potential barriers and a further detailed priority ranked list of the top 40 ranked barriers showing remediation options and indicative cost.
Important geo-spatial characteristics fundamental to a potential barrier scoring high in the first stage (GIS) of the prioritisation include:
- Potential barriers located on large, low gradient high ordered waterways
- Potential barriers located in close proximity to the sea
- First barrier located laterally or longitudinally along the waterway
- Large amount of habitat upstream of the potential barrier
- Low proportion of intensive land use within the sub-catchment
To initially identify potential barriers raster data in the form of satellite imagery and aerial photography was used in ArcMap combined with high resolution satellite imagery in Google Earth Pro (GEP). Vector data in the form of stream and road network shape files were then acquired and imported into ArcMap and GEP to assist in identifying potential barriers.
Due to the extremely large project area and a high number of potential barriers encountered during the study (13,797) it was important to prioritise potential barriers so limited resources could be utilised in the most appropriate manner. To achieve this, a three-stage selection criteria process used by Moore and Marsden (2008) was refined and enhanced with the latest innovative river network analysis technology by Hornby (2015); RivEX. The three stages involved evaluating the biological, social and economic benefits of providing unimpeded fish passage past the barrier for the environment and local community. This is achieved by applying a multi-faceted approach, initially utilising the efficiency and unique decision-making capabilities of an automated GIS process.
The advantage of GIS during the first stage of prioritisation revolves around its capacity to assess wide-ranging temporal and spatial habitat characteristics associated with thousands of potential barriers over a large geographic area. Following the validation of high ranking potential barriers, further assessment and prioritisation of actual barriers are undertaken using optimisation and scoring-and-ranking methods in stage two and three. This efficient approach allows limited resources to be directed towards assessing the highest-ranking potential barriers after the initial GIS stage, rather than a ‘scattergun’ approach of visiting random and potentially less significant barriers.
Local, State and Federal Governments, Natural Resource Management Groups, Local Community Organisations, Not for Profit Environmental Organisations, General Public.
How this data can be used
The priority ranked fish barrier prioritisation can be utilised by natural resource managers, government agencies and decision-makers to assist in determining where best to allocate limited funding opportunities to ensure the greatest environmental and socio-economic outcomes for the Greater Brisbane Urban Area.