Background: "1997 New Year's Day Flood" caused considerable stream changes throughout areas of intense rainfall in southwest Oregon. Effects within the Applegate River watershed included major adjustments in stream channels, failure of culverts/bridges and landslides/debris flows that delivered large quantities of sediment and wood to streams. Within RRNF lands Little Applegate River, Beaver Creek, Palmer Creek, Elliott Creek, Squaw Creek, Steve Fork and Sturgis Fork of Carberry Creek appeared to be most altered by the flood. A Forest flood analysis team compared data before and after the flood and recommended restorative/repair projects on these streams. A recent in-depth report completed by the team entitled ``RRNF Stream and Riparian Flood Analysis Report, 1997 New Year's Day Flood Effects'' is on file at the Applegate Ranger District.
Findings: Streams with similar past management activities responded differently in the presence of large wood. Direct impacts from management activities include roads alongside the stream, past removal of trees within the channel and riparian zone, and the presence of road culverts that restrict flow of wood from tributaries into the main channel. Flood waters scoured streams devoid of trees in the channel and/or floodplain (Steve and Sturgis Forks, Squaw and Elliott Creeks and Little Applegate River).
Streams where wood was present, either naturally or from past habitat improvement projects (segments of Beaver and Palmer Creeks), generally formed and/or rearranged instream wood into jams or wood complexes resulting in higher quality niches for salmonids. Wood complexes had important "key" tree length pieces (large wood >35'' length and >24'' dbh) that provide the cornerstone for building and accumulating additional wood. The complexes contain a myriad of wood sizes that provide a home for small mammals, birds such as the winter wren and young trout and salmon rearing in the deep pools beneath the mass of wood. Streams in mature forests have the ability to accumulate complexes of wood pieces containing considerable biomass usually not found in the upslope forest. Streams in a mature forest where this legacy is still evident are rare today. Research papers depicting historical conditions described wood complexes in Oregon streams, but most of us have seen few of these complexes until the 1997 flood.
Previous attempts to improve fish habitat consisted of anchoring smaller wood pieces to channel features. The pools formed by these smaller pieces of wood created a moderate amount of habitat for young steelhead and salmon. Many of the wood jams formed by the 1997 flood incorporated pieces of wood from these earlier habitat improvement projects. In their new positions, the wood seems more effective.
Another benefit of the high profile complexes is the accumulation and sorting of many cubic yards of gravel, sand, and cobble upstream and downstream of the jam. For example, bedrock was previously the dominant substrate in Beaver Creek (pre-flood). Since the flood, gravel has started to accumulate providing important habitat for aquatic insects and spawning substrate for salmonids.
Attempts to create wood complexes during stream restoration may not compare to wood complexes created by flood events. However, they will provide immediate functional habitat between flood events, and "key pieces" (building blocks of complex habitat structure) during floods.
Applications: The flood instream design team plans on integrating wood complexes with "key" tree length pieces into project plans this summer. Instream project implementation is anticipated for next summer (2000).
Follow-up: Monitoring will be completed on upcoming instream/riparian flood restoration projects using similar pre/post flood surveys. Evaluating changes in fish abundance and stream habitat during winter and summer flows will be completed. This paper is a follow-up from a 1998 AMA learning paper "Comprehensive Restoration Strategy."
Submitted by: Su Maiyo, Siskiyou Zone Fish Biologist, RRNF, 482-3333
Date: April 8, 1999