Southeast Aquatic Barrier Prioritization Tool
Southeast Aquatic Barrier Tool

Southeast Aquatic Barrier Prioritization Tool

Improve aquatic connectivity by prioritizing aquatic barriers for removal using the best available data.

Aquatic connectivity is essential. Fish and other aquatic organisms depend on high quality, connected river networks. A legacy of human use of river networks have left them fragmented by barriers such as dams and culverts. Fragmentation prevents species from dispersing and accessing habitats required for their persistence through changing conditions.

Recently improved inventories of aquatic barriers enable us to describe, understand, and prioritize them for removal, restoration, and mitigation. Through this tool and others, we empower you by providing information on documented barriers and standardized methods by which to prioritize barriers of interest for restoration efforts.

Enhancing aquatic connectivity by empowering people with actionable data:


The aquatic barrier inventory is the foundation for identifying and prioritizing aquatic connectivity projects with partners. It provides essential information about the location, status, and characteristics of potential aquatic barriers.

Scroll down for more information.


In order to maximize partner effort and return on investment, aquatic barriers are prioritized based on their contribution to the aquatic network if removed. Quantitative metrics provide actionable information to assist barrier removal projects.



Aquatic connectivity teams make barrier removal projects a reality. By combining effort across organizations and jurisdictions, partners work together to identify, prioritize, and implement barrier removal projects.


The Southeast Aquatic Barrier Inventory:

This inventory is a growing and living database of dams, culverts, and other road crossings compiled by the Southeast Aquatic Resources Partnership with the generous support from many partners and funders. The Inventory is the foundation of SARP's Connectivity Program because it empowers Aquatic Connectivity Teams and other collaborators with the best available information on aquatic barriers. The inventory directly supports prioritization of barriers by including metrics that describe network connectivity, landscape condition, and presence of threatened and endangered aquatic organisms.

This inventory consists of datasets from local, state, and federal partners. It is supplemented with input from partners with on the ground knowledge of specific structures. See an example of how the inventory can assist local partners to identify and prioritize barriers for removal.

The information on barriers is not complete or comprehensive across the region, and depends on the availability and completeness of existing data and level of partner feedback. Some areas of the region are more complete than others but none should be considered 100% complete.

At a Glance

  • 14 states and Puerto Rico
  • 146,244 dams
  • 30,206 road-related barriers assessed for impact to aquatic organisms
  • 8.8 miles of connected aquatic network length, on average
Data version: 2.3.1 (3/10/2021)

The Southeast Aquatic Barrier Prioritization Tool empowers you with the latest inventory data:

Summarize the inventory across the region

Explore summaries of the inventory across the region by state, county, or different levels of watersheds and ecoregions.

These summaries are a good way to become familiar with the level of aquatic fragmentation across the Southeast. Find out how many aquatic barriers have already been inventoried in your area! Just remember, the inventory is a living database, and is not yet comprehensive across the region.

Prioritize aquatic barriers for removal

Identify barriers for further investigation based on the criteria that matter to you.

You can select specific geographic areas for prioritization, including counties, states, watersheds, and ecoregions. You can filter the available barriers based on criteria such as likely feasibility for removal, height, and more. Once you have prioritized aquatic barriers, you can download a CSV file for further analysis.

How are barriers prioritized for removal?

Aquatic barriers are identified and measured for their potential impact on aquatic organisms:

Aquatic barriers are natural and human-made structures that impede the passage of aquatic organisms through the river network.

They include:

  • Waterfalls
  • Dams
  • Road-related barriers

Where possible, human-made barriers have been assessed using field reconnaissance to determine their likely impact on aquatic organisms as well as their feasibility of removal. You can leverage these characteristics to select a smaller number of barriers to prioritize.

Aquatic barriers are measured for their impact on the aquatic network:

Functional aquatic networks are the stream and river reaches that extend upstream from a barrier or river mouth to either the origin of that stream or the next upstream barrier. They form the basis for the aquatic network metrics used in this tool.

To calculate functional networks, all barriers were snapped to the USGS High Resolution National Hydrography Dataset (NHDPlus), except in Puerto Rico, where they were snapped to the USGS Medium Resolution version. Where possible, their locations were manually inspected to verify their correct position on the aquatic network.

Read more about network analysis methods.

Note: due to limitations of existing data sources for aquatic networks, not all aquatic barriers can be correctly located on the aquatic networks. These barriers are not included in the network connectivity analysis and cannot be prioritized using this tool. However, these data can still be downloaded from this tool and used for offline analysis.
Barriers are characterized using metrics that describe the quality and status of their functional networks:

Network Length

Network length measures the amount of connected aquatic network length that would be added to the network by removing the barrier. Longer connected networks may provide more overall aquatic habitat for a wider variety of organisms and better support dispersal and migration.


Network Complexity

Network complexity measures the number of unique upstream size classes that would be added to the network by removing the barrier. A barrier that has upstream tributaries of different size classes, such as small streams, small rivers, and large rivers, would contribute a more complex connected aquatic network if it was removed.

Network Sinuosity

Network sinuosity measures the amount that the path of the river or stream deviates from a straight line. In general, rivers and streams that are more sinuous generally indicate those that have lower alteration from human disturbance such as channelization and diking.

Natural Landcover

Natural landcover measures the amount of area within the floodplain of the upstream aquatic network that is in natural landcover. Rivers and streams that have a greater amount of natural landcover in their floodplain are more likely to have higher quality aquatic habitat.

Metrics are combined and ranked to create three scenarios for prioritizing barriers for removal:

Network Connectivity

Aquatic barriers prioritized according to network connectivity are driven exclusively on the total amount of functional aquatic network that would be reconnected if a given dam was removed. This is driven by the network length metric. No consideration is given to other characteristics that measure the quality and condition of those networks.

Watershed Condition

Aquatic barriers prioritized according to watershed condition are driven by metrics related to the overall quality of the aquatic network that would be reconnected if a given dam was removed. It is based on a combination of network complexitynetwork sinuosity, and floodplain natural landcover. Each of these metrics is weighted equally.

Network Connectivity + Watershed Condition

Aquatic barriers prioritized according to combined network connectivity and watershed condition are driven by both the length and quality of the aquatic networks that would be reconnected if these barriers are removed. Network connectivity and watershed condition are weighted equally.

To reduce the impact of outliers, such as very long functional networks, barriers are scored based on their relative rank within the overall range of unique values for a given metric. Many barriers have the same value for a given metric and are given the same relative score; this causes the distribution of values among scores to be highly uneven in certain areas.

Once barriers have been scored for each of the above scenarios, they are binned into 20 tiers to simplify interpretation and use. To do this, barriers that fall in the best 5% of the range of scores for that metric are assigned to Tier 1 (top tier), whereas barriers that fall in the worst 5% of the range of scores for that metric are assigned Tier 20 (bottom tier).

Note: tiers are based on position within the range of observed scores for a given area. They are not based on the frequency of scores, such as percentiles, and therefore may have a highly uneven number of barriers per tier depending on the area. In general, there are fewer barriers in the top tiers than there are in the bottom tiers. This is largely because many barriers share the same value for a given metric.

Example: prioritizing a failing dam for removal

The Southeast Aquatic Barrier Inventory and this tool will enable partners to identify and prioritize aging dams for removal, such as the Roaring River Dam in Tennessee removed in 2017. At 220 feet wide and 15 tall, this dam is the largest removed in Tennessee for river and stream restoration.

Built in 1976 by the U.S. Army Corps of Engineers to keep reservoir fish species from migrating upstream, partners determined that this deteriorating dam no longer met its original purpose. Instead of repairing the dam, partners decided that it would be better to remove the dam altogether in order to restore aquatic connectivity. Partners working on this project included the Tennessee Wildlife Resources Agency, the U.S. Army Corps of Engineers, The Nature Conservancy, the U.S. Fish and Wildlife Service, and the Southeast Aquatic Resources Partnership.

How to get involved?

The Southeast Aquatic Resources Partnership  (SARP) was formed by the Southeastern Association of Fish and Wildlife Agencies (SEAFWA) to protect aquatic resources across political boundaries as many of our river systems cross multiple jurisdictional boundaries.

SARP works with partners to protect, conserve, and restore aquatic resources including habitats throughout the Southeast for the continuing benefit, use, and enjoyment of the American people. SARP is also one of the first Fish Habitat Partnerships under the the National Fish Habitat Partnership umbrella that works to conserve and protect the nation’s fisheries and aquatic systems through a network of 20 Fish Habitat Partnerships.

SARP and partners have been working to build a community of practice surrounding barrier removal through the development of state-based Aquatic Connectivity Teams (ACTs). These teams create a forum that allows resource managers from all sectors to work together and share resources, disseminate information, and examine regulatory streamlining processes as well as project management tips and techniques. These teams are active in Arkansas, Florida, Georgia, North Carolina, and Tennessee.

Learn more about aquatic connectivity teams.

Get involved!

You can help improve the inventory by sharing data, assisting with field reconnaissance to evaluate the impact of aquatic barriers, joining an Aquatic Connectivity Team, or even by reporting issues with the inventory data in this tool.

Contact us to learn more about how you can help improve aquatic connectivity in the Southeast.

Need Help?

If you are not able to get what you need from this tool or if you need to report an issue, please let us know!

This application was created by Brendan C. Ward at the Conservation Biology Institute (CBI), now with Astute Spruce, LLC, in partnership with Jessica Graham and Kat Hoenke at the Southeast Aquatic Resources Partnership. CBI provides science and software development to support the conservation of biodiversity.

This project was supported in part by grants from the U.S. Fish and Wildlife Service Fish Passage Program, the Gulf Coastal Plains and Ozarks Landscape Conservation Cooperative, and the Florida State Wildlife Grants Program.