The objective of a road-stream crossing prioritization is to help identify important sites for replacement or retrofit. Prioritization tools use the results of field assessments, modeling, and other criteria to help identify specific locations.
The following types of data are common inputs for prioritization tools:
- Aquatic organism passage field assessment results.
- Connectivity metrics including those that indicate how much stream habitat would be reconnected by removing a barrier or combination of barriers.
- Ecological criteria such as quality of habitat for particular species, presence of particular species, water quality, local land use, condition of the riparian zone, and importance of the stream for particular species.
Other criteria of importance that you may wish to include in your prioritization include:
- Structure condition: whether the crossing is likely to need replacement in the near future.
- Vulnerability: the likelihood of flooding and/or structure failure.
- Social criteria such as criticality: the importance of the road in the local transportation network.
- Economic criteria such as past flood damage or potential flood damage at the site.
Information about many of these criteria may be provided by local road managers and leaders.
Resources for Prioritization
A variety of tools can be used to help prioritize where to work to improve road-stream crossings; these tools serve different functions and are appropriate for use at different scales.
The Nature Conservancy’s Aquatic Connectivity Tools: The Nature Conservancy and partners have developed several related analyses to help identify aquatic connectivity restoration projects, based on the potential ecological benefit of conducting specific dam removals or other fish passage projects in the eastern U.S. The analyses share the same prioritization approach, wherein a suite of metrics to measure connectivity status and connectivity improvement (calculated by the BAT, described below), watershed condition, fish habitat presence, and stream size/habitat diversity are calculated for barriers using a GIS. The tools then implement a weighted ranking process, where users can determine the appropriate weights for each metric to best reflect their prioritization objectives (e.g. anadromous fish or brook trout). The tools allow for ranking of barriers at different spatial scales. These tools have been applied to expert-driven consensus prioritizations for dams in several different regions and basins in the eastern U.S., and for road-stream crossings in smaller basins:
Northeast Aquatic Connectivity Project (direct link to Aquatic Barriers prioritization Tool)
Southeast Aquatic Connectivity Assessment Project
Chesapeake Fish Passage Prioritization
Lake Champlain Basin Stream Crossing Prioritization
Barrier Assessment Tool (BAT): Developed by The Nature Conservancy, the Barrier Assessment Tool (BAT) is an ArcGIS add-in for analyzing the fragmenting effects of barriers, such as dams and culverts, on streams. Using data on barriers and streams as inputs, BAT allows users to calculate numerous metrics such as the potential mileage gains from removing any individual barrier as well as metrics of watershed connectivity such as the number of upstream and downstream barriers. Download the tool (8 MB zip folder), installation instructions, and quick-start guide.
Critical Linkages: The University of Massachusetts, in partnership with The Nature Conservancy and natural resource agencies in Massachusetts, developed Critical Linkages, an approach to assess the restoration potential of aquatic connectivity improvement actions (road stream crossing replacements and dam removals) and thus support the prioritization of these actions to improve aquatic connectivity across the Northeast. Data are available for the thirteen states of the North Atlantic Aquatic Connectivity Collaborative.Download data.
Aquatic Connectivity Optimization Tools
The Anadromous Fish Optimization Tool (APASS) is a barrier removal optimization-planning tool that can help determine how to maximize the total increase in connected stream habitat given a certain budget and considering the locations of other barriers in a stream network. The input data for APASS include passability of each culvert or other barrier, the distance to the next barrier downstream, and the cost to mitigate barriers. APASS was developed by Dr. Jesse O’Hanley of the University of Kent. Learn more and request the tool.
The Barrier Removal Optimization Tool is a GIS-based tool, grounded in the same methods that APASS uses, to support strategic removal of fish passage barriers to restore watershed-scale tributary connectivity at a watershed scale. The tool user supplies data to produce an optimal "portfolio" of barriers whose removal would reconnect the maximum amount of high-quality stream habitat while remaining within the limits of a specified budget. The tool was developed by Cadmus Group, Inc. , Ecointelligence LLC, and Matthew W. Diebel at the Wisconsin Department of Natural Resources. Learn more about the tool.
Fishworks is a web-based prioritization tool, based on the same methods that APASS uses, that can be run for any area in the Great Lakes Basin.
Fish Passage Extension for ArcGIS (FIPEX): Developed at Fisheries and Oceans Canada (Maritimes Region) by the Habitat Protection and Sustainable Division, the Fish Passage Extension for ArcGIS (FIPEX) is a GIS toolset for assessing the effects of watercourse obstacles on the ability of fish to travel within a watershed, and the connectivity of the watershed as a whole. Learn more and download the tool (note: need an account).
Photo: Bridget MacDonald, LLC