In 2018, shortly after the Bonasa Breaks Ranch dam breach, Rattlesnake Creek had very little shade from streamside plants. In 2025, the creek is fully shaded, showing a healthy riparian area.
On the morning of April 13, 2017, around 9.4 million gallons of water burst through an earthen dam on Bonasa Breaks Ranch in Asotin County, taking trees, shrubs, boulders, and critical steelhead habitat with it.
The flood and ensuing debris flow caused damage to a state highway, took out a bridge, and destroyed several acres of private property.
Engineering consultant and geomorphologist Rob Richardson and his firm Rio ASE were hired by the owner of Bonasa Breaks Ranch to restore damage created by the breach.
We joined Richardson on a recent site visit eight years later to monitor the recovery of Rattlesnake Creek.
What caused the dam to break?
Rattlesnake Creek is a small headwater stream feeding the Grand Ronde River near the town of Anatone. Aerial photos from Department of Ecology Dam Failure and Hydrology Report showing expansion of reservoir between 2006 (left) and 2009 (right).
The creek is home to federally threatened Snake River steelhead (native, ocean-going rainbow trout) that require cool, clean water to spawn and live before returning to the ocean.
The dam breach on Bonasa Breaks Ranch occurred upstream of steelhead habitat but caused severe damage downstream.
When the property owner of Bonasa Breaks Ranch purchased the property from the descendants of Ernest Hemingway, it included a pond estimated to hold around 3.26 million gallons of water, or less than 10-acre feet.
This size of a pond does not require a dam permit, according to the Bonasa Breaks Ranch Dam Failure and Hydrologic Report. However, investigation by Ecology after the flood using aerial photos revealed a much larger pond — close to three times the size — was created between 2006-2009. A pond of that size requires a permit.
The 2017 report concluded the modified dam would not have passed inspections based on several criteria.
After the flood
Steve Croskey and his company, Bonasa Breaks Ranch, were fined $15,000 for expanding the dam without a permit and $100,000 for violating Washington’s water quality laws. Croskey hired Rio ASE to restore the parts of Rattlesnake Creek damaged by the flood and debris flow. Top: Rattlesnake Creek and West Branch of Rattlesnake Creek with healthy riparian vegetation before the 2017 dam breach. Bottom: Rattlensnake Creek with no riparian vegetation after the flood, compared to the West branch of the Rattlesnake Creek that was not affected by the dam breach in 2017. Trees and shrubs along the main stem have made a substantial comeback since.
At first, nearby landowners were hesitant to allow access. Over time, Rio ASE was able to reach affected areas, assess the damage, and develop a restoration plan. The original restoration estimate was $2.5 million, but natural recovery has significantly lowered that cost.
After several years of studies, landowner agreements, and a civil lawsuit settlement, restoration work began in spring 2023. So far, Bonasa Breaks Ranch has:
- Planted trees near the dam breach
- Removed three fish passage barriers
- Repaired several stream channels
- Added woody debris to improve steelhead habitat
2025 will mark the third year of restoration. Rio ASE, with support from Ecology and the Washington Department of Fish and Wildlife, will continue to monitor the site for another seven years, through 2032.
Planned work for 2025, according to Rio ASE, includes:
- Stabilizing remaining head cuts and unstable banks
- Revegetating areas where natural recovery has been slow
- Permanently closing an access road to the upper reaches of the creek
Recovering naturally
Eight years after the flood, Rattlesnake Creek is recovering with help from Rio ASE, Bonasa Breaks Ranch, and partner agencies.
Tree roots stabilize stream banks by holding rocks and soil in place during high flows.
“Although the dam breach debris flow was unnatural, the stream has a long history of natural recovery from similar events and was therefore well-adapted to recover from a debris flow," Richardson said.
The site is a reminder of nature’s resilience — especially when given the chance to heal.
Nature moves back in
As we hiked through rocky streambeds, brushy hillsides, and forest edges, we saw signs of wildlife returning to Rattlesnake Creek.
Young of the year steelhead and caddisfly larvae were spotted in the lower creek — clear signs of a healthy stream. Elk tracks lined the banks. A black bear and her cub were flipping rocks on an old forest road, searching for food. Birdsong filled the air as kingfishers, yellow warblers, and lazuli buntings moved into the recovering streamside habitat, providing song and flashes of color on our journey downstream.
And of course, no visit to Rattlesnake Creek would be complete without seeing a rattlesnake.
A young rattlesnake slithers in the floodplain area along Rattlesnake Creek.