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February 7, 2024

USGS is working with federal land management agencies to develop a series of structured science syntheses to support analyses that agencies conduct to comply with the National Environmental Policy Act (NEPA). This synthesis provides information to facilitate the use of science information in agency decisions regarding the installation or modification of culverts on public lands.

photo of a culvert in the middle of a forest, water flowing
A sub-alpine stream flowing through a perched culvert. Zachary Lafaver (Battelle Memorial Institute).


Federal land management agencies complete thousands of environmental effects analyses every year to support decisions in diverse ecosystems across the United States. These NEPA analyses can involve complex issues that require consideration of wide-ranging bodies of scientific information. Staff from the Bureau of Land Management, U.S. Fish and Wildlife Survey, and U.S. Geological Survey are working together to develop NEPA-focused science syntheses that provide agency staff with science information that can directly and efficiently inform NEPA analyses. 

The second report in this series of structured science syntheses, “Effects of culverts on habitat connectivity in streams—A science synthesis to inform National Environmental Policy Act analyses,” synthesizes information about data, scientific studies, and analysis methods to inform analyses about the potential effects of culverts on stream connectivity and the associated effects on freshwater fishes. The synthesis describes habitat connectivity in streams and the characteristics of culverts that may affect it, tools for quantifying habitat connectivity, and the potential effects of decreased connectivity on fishes. The synthesis is organized according to the major sections of a NEPA analysis to facilitate incorporation of science into agency decision making on public lands. 

The publication was authored by Richard Lehrter, a contractor with the Bureau of Land Management National Operations Center; Tait Rutherford and Sarah Carter with the Fort Collins Science Center; Jason Dunham with the Forest and Rangeland Ecosystem Science Center; Aaron Johnston with the Northern Rocky Mountain Science Center; and David Wood and Travis Haby with the Bureau of Land Management National Operations Center. This synthesis was published as a U.S. Geological Survey Scientific Investigations Report and is available online at

The first synthesis, regarding the effects of noise from oil and gas development on ungulates and small mammals, and additional information about the structured science syntheses project are available on the project webpage.

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