Channel morphology and habitat characteristics of stream segments draining unharvested old-growth forests were compared with those from streams within intensively and moderately logged basins. Sites covered a broad geographic range in western Washington State and were stratified by basin area and channel gradient. Although the number of pieces of large woody debris (LWD) within stream channels was unaffected by timber harvest, there was a clear reduction in LWD size in harvested basins. Timber harvest also resulted in a shift in location of LWD towards the channel margins, outside the low-flow wetted width of the channel. Intensive harvest simplified channel habitat by increasing riffle area and reducing pool area and depth, although the commonly used index of pool-to-riffle ratio appears inadequate to document these changes. Given the natural variation from stream to stream, we conclude that simple counts of instream LWD and channel units (habitat types) are not useful as management objectives. Instead, these attributes should be used collectively as indicators of the complexity and stability of in-stream habitat with respect to the specific channel and valley geomorphology.

Habitat unit classification can be a useful descriptive tool in hierarchical stream classification. However, a critical evaluation reveals that it is applied inappropriately when used to quantify aquatic habitat or channel morphology in an attempt to monitor the response of individual streams to human activities. First, due to the subjectivity of the measure, observer bias seriously compromises repeatability, precision, and transferability of the method. Second, important geomorphic and ecological changes in stream habitats are not always manifested as changes in habitat‐unit frequency or characteristics. Third, classification data are nominal, which can intrinsically limit their amenability to statistical analysis. Finally, using the frequency of specific habitat unit types (e.g., pool/riffle ratio or percent pool) as a response variable for stream monitoring commonly leads to the establishment of management thresholds or targets for habitat‐unit types. This, in turn, encourages managers to focus on direct manipulation or replacement of habitat structures while neglecting long‐term maintenance or re‐establishment of habitat‐forming biophysical processes. Stream habitat managers and scientists should only use habitat unit classification to descriptively stratify in‐stream conditions. They should not use habitat unit classification as a means of quantifying and monitoring aquatic habitat and channel morphology. Monitoring must instead focus on direct, repeatable, cost‐efficient, and quantitative measures of selected physical, chemical, and biological components and processes spanning several scales of resolution.

The loss of freshwater fluvial habitats is generally regarded as a key factor in the precipitous decline of native salmonids in the northwestern United States. State and federal water quality regulations, under the authority of the Clean Water Act (CWA), could be more relevant to recovery of Pacific salmon if physical habitat quality was explicitly integrated into water quality standards. We examine the concept of incorporating instream habitat measures into water quality regulations since these standards are the foundation of CWA programs. Commonly measured instream habitat variables for salmonids (flow regime, habitat space, channel structure, substrate quality, streambank stability) were evaluated in terms of their suitability as water quality criteria. The basis for this evaluation focused on these indicators in light of their: (1) relevance to ecological requirements of salmonid fishes, (2) applicability to landscape processes and the stream network in which they occur, (3) responsiveness to human‐caused stressors (linking cause v. effect), and (4) degree of measurement reliability and precision. Our evaluation suggests that most habitat indicators, as currently measured, do not meet these criteria due to the limitations in the state of the science as well as constraints imposed by the existing framework for water quality standards. There is general agreement on salmonid habitat requirements and the effects of land use on these habitats; there is less certainty on quantifying physical habitat quality and on the reliability of habitat assessment techniques. These obstacles can be overcome by applying the principles of landscape ecology and stream network classification to indicator development, identifying and quantifying reference area conditions at a regional scale, calibrating relevant indicators to specific locales, and developing systematic monitoring procedures that meet rigorous data quality objectives.

Two approaches to ecological restoration planning, limiting-factors analysis and process-based restoration, are employed in efforts to recover endangered salmonid species throughout the Pacific Northwest of North America. Limiting-factors analysis seeks to identify physical limitations to fish production that may be addressed by habitat restoration; it is known as the "Field of Dreams" hypothesis (i.e., if you build it, they will come). Process-based restoration, in contrast, assumes that protection and/or restoration of watershed-scale processes will best achieve self-sustaining habitat features that support salmon populations. Two case studies from the Columbia River basin (northwestern USA) display current efforts to integrate these two restoration approaches to improve salmonid populations. Although these examples both identify site-specific habitat features to construct, they also recognize the importance of supporting key watershed processes to achieve restoration goals. The challenge in advancing the practice of restoration planning is not in simply acknowledging the conceptual benefits of process-based restoration while maintaining a traditional focus on enumerating site-specific conditions and identifying habitat-construction projects, but rather in following process-based guidance during recovery planning and, ultimately, through implementation of on-the-ground actions. We encourage a realignment of the restoration community to truly embrace a process-based, multi-scalar view of the riverine landscape.