A dynamic dendritic connectivity assessment tool for the planning and design of barrier mitigation strategies in river networks

Abstract

ContextIncreasing fragmentation of rivers caused by barriers continues to impact watersheds, especially disruption of fish migration patterns and loss of access to spawning and nursery habitats. Infrastructure expansion and ageing installations exacerbate the problem, reducing effectiveness of management in addressing barriers. Reduction in watershed connectivity requires effective tools capable of guiding river managers in remediation actions.ObjectivesOur objective was to develop a watershed dynamic connectivity assessment tool (D-CAT), a customizable geospatial tool capable of river analyses at varying watershed scales. The tool uses proven watershed connectivity modelling combined with an effective evaluation approach to provide measurable change model outcomes.MethodsThree different barrier encounter scenarios were examined using the D-CAT tool to study watershed connectivity. The tool was tested on a watershed area of the River Derwent, a major tributary of the River Trent system in the United Kingdom.ResultsFor each barrier scenario tested, the D-CAT tool indicated which barriers could be removed or modified to provide the greatest watershed connectivity improvement. The tool provided a prioritized list of barriers for each scenario under varying choices for the number of barriers to remove, demonstrating the utility of the D-CAT tool to planning and design.ConclusionsThe D-CAT tool is built to handle geographical data and variable user input, allowing in-depth watershed connectivity analysis. The tool forecasts the cumulative effects of alternative change scenarios for watershed connectivity, providing prioritization and optimization of removal strategies. The D-CAT tool offers significant support for landscape management towards better barrier removal/remediation decisions.