Dempsey Creek Family Forest Fish Passage Project

The Chehalis Basin, western Washington State, is Washington’s second largest river system, home to some of the state’s most important salmon rivers and one of the only major basins without any federally-listed endangered salmon. At the same time, salmon runs within the basin are returning at a fraction of their historical abundances, with fish passage barriers and other habitat loss representing one of many causes for this decline.

The project area included a section Dempsey Creek, a tributary to the Black River, where two culverts, one over-steep and one with an outfall drop, blocked coho, and cutthroat from accessing 0.7 miles vital stream and wetland habitat. By interrupting habitat connectivity, even a single barrier can have a disproportionately large impact on the abundance and resiliency of wild fish populations.

Man-made barriers to fish migration have significant impacts on wild fish; limiting distribution, reducing access to spawning and rearing habitats, and disrupting the spatial habitat complexity historically available to fish populations. Whether for resident species that spend their entire lives in one watershed, or migratory species that travel thousands of miles, instream barriers compromise a populations’ ability to weather environmental uncertainties. Evolutionary fitness of the entire population is weakened when barriers restrict gene flow, creating small, isolated sub-groups that can suffer from inbreeding.

The Family Forest Fish Passage Program (FFFPP) assists private forestland owners in removing culverts and other stream crossing structures that prevent ESA listed salmonids from migrating upstream. Through the management of the Department of Natural Resources Washington State Recreation and Conservation Office some 376 landowners have taken advantage of the program to remove 433 barriers since 2003.

Wild Fish Conservancy (WFC) staff replaced the first barrier was a culvert with a 3.27% slope (67% passible) and was replaced with a 5.5-foot high, 12-foot wide and 12-foot tall concrete box. The second barrier had a 1 meter outfall drop (0% passible) and was replaced with a 40-foot long steel bridge.