This map presents the culvert conditions for the Tribal Lands across the lower 48 states of the U.S. based on the Database of Stream Crossings in the United States. In this Database, stream crossings were developed by intersecting the 2020 United States Census Bureau Topologically Integrated Geographic Encoding and Referencing (TIGER) U.S. road lines with the National Hydrography Dataset High Resolution flowlines. In addition, observations from the U.S. Department of Transportation, Federal Highway Administration’s 2019 National Bridge Inventory (NBI) were included to help identify crossing types of bridges and culverts.

The NBI ratings assess the structural condition and functional adequacy of culverts and bridges. For culverts, the NBI rating system evaluates factors such as alignment, settlement, joints, structural condition, and scour. The rating provides a comprehensive assessment of the culvert’s overall condition. Lower NBI ratings indicate more significant concerns and deficiencies, while higher ratings reflect fewer issues and better overall condition.

Below is a summary of all NBI ratings for culverts:

Users can explore the spatial distribution of culverts within each Tribal land area, categorized by National Bridge Inventory (NBI) ratings. This interactive tool offers a clear visualization of infrastructure and its relationship to Tribal lands, aiding both environmental analysis and decision-making.

To explore, simply click on a Tribal land area to view a pie chart displaying the distribution of NBI ratings for culverts within that area. Additionally, you can click on individual culverts to access detailed information about their condition from the most recent observation. The NBI observations are thorough assessments of the condition and performance of infrastructure throughout the United States.

Explore the map to gain insights into culvert conditions in your area of interest.