A devastating flood in fall 1959 (likely 500-year high) began a river braiding process, causing significant land erosion, and has taken hundreds of old growth trees from around the Garland site, and on downstream past the Town of Index.
This river braiding appears to have severely degraded Salmon and Steelhead fish populations by stranding significant quantities of fish eggs that are unable to hatch. Hydrologists suggest that the river has probably reached its maximum intrusion and is likely to sweep back to the east where it ran prior to the 1959 flood.
Extensive recent research in river rehabilitation methods indicates that “engineered log jams” using “woody debris” (logs in the river) can keep the river in its original course, prevent soil erosion, and provide significant improvements in Salmon spawning. This “engineered log jam” process is now recognized as an inexpensive and effective method of land and “habitat restoration.”
“Engineered log jams,” using “woody debris” (logs) are a low-cost device used to manage water flow, protect land and return rivers to normal channels. These engineered log jams are stacked and sometimes tied together to prevent movement during major floods. The U.S.F.S. has expressed interest in cooperating with this effort to include road protection in the area.
Sport fishermen and Fisheries personnel have been very supportive of the “engineered log jam” process as it encourages Salmon, trout and Steelhead re-population. The process restores the river to a more healthy condition by reducing braiding, erosion and silting, while providing eddies and cover for fish to hover and spawn. A third benefit is that when the river reaches flood stage, water that filters through the “engineered log jams,” depositing silt to replenish topsoil.
One hydrologist estimated that the existing topsoil had been in place for at least 650-years, and likely longer. Some trees on site appear to have more than 1,000 rings. These facts indicate that the 1959 flood was possibly a 1,000 year high.