Christopher A. Frissell

A Hierarchical Framework for Stream Habitat Classification: Viewing Streams in a Watershed Context

Classification of streams and stream habitats is useful for research involving establishment of monitoring stations, determination of local impacts of land-use practices, generalization from site-specific data, and assessment of basin-wide, cumulative impacts of human activities on streams and their biota. This article presents a frame-work for a hierarchical classification system, entailing an organized view of spatial and temporal variation among and within stream systems. Stream habitat systems, defined and classified on several spatiotemporal scales, are associated with watershed geomorphic features and events. Variables selected for classification define relative long-term capacities of systems, not simply short-term states. Streams and their watershed environments are classified within the context of a regional biogeoclimatic landscape classification. The framework is a perspective that should allow more systematic interpretation and description of watershed-stream relationships.

A General Protocol for Restoration of Regulated Rivers

Large catchment basins may be viewed as ecosystems in which natural and cultural attributes interact. Contemporary river ecology emphasizes the four-dimensional nature of the river continuum and the propensity for riverine biodiversity and bioproduction to be largely controlled by habitat maintenance processes, such as cut and fill alluviation mediated by catchment water yield. Stream regulation reduces annual flow amplitude, increases baseflow variation and changes temperature, mass transport and other important biophysical patterns and attributes. As a result, ecological connectivity between upstream and downstream reaches and between channels, ground waters and floodplains may be severed. Native biodiversity and bioproduction usually are reduced or changed and non-native biota proliferate. Regulated rivers regain normative attributes as distance from the dam increases and in relation to the mode of dam operation. Therefore, dam operations can be used to restructure altered temperature and flow regimes which, coupled with pollution abatement and management of non-native biota, enables natural processes to restore damaged habitats along the river’s course. The expectation is recovery of depressed populations of native species. The protocol requires: restoring peak flows needed to reconnect and periodically reconfigure channel and floodplain habitats; stabilizing baseflows to revitalize food-webs in shallow water habitats; reconstituting seasonal temperature patterns (e.g. by construction of depth selective withdrawal systems on storage dams); maximizing dam passage to allow recovery of fish metapopulation structure; instituting a management belief system that relies upon natural habitat restoration and maintenance, as opposed to artificial propagation, installation of artificial instream structures (river engineering) and predator control; and, practising adaptive ecosystem management. Our restoration protocol should be viewed as an hypothesis derived from the principles of river ecology. Although restoration to aboriginal state is not expected, nor necessarily desired, recovering some large portion of the lost capacity to sustain native biodiversity and bioproduction is possible by management for processes that maintain normative habitat conditions. The cost may be less than expected because the river can do most of the work.

Incidence and Causes of Physical Failure of Artificial Habitat Structures in Streams of Western Oregon and Washington

Abstract In recent years an increasing share of fishery management resources has been committed to alteration offish habitat with artificial stream structures. We evaluated rates and causes of physical impairment or failure for 161 fish habitat structures in 15 streams in southwest Oregon and southwest Washington, following a flood of a magnitude that recurs every 2–10 years. The incidence of functional impairment and outright failure varied widely among streams; the median failure rate was 18.5% and the median damage rate (impairment plus failure) was 60%. Modes of failure were diverse and bore no simple relationship to structure design. Damage was frequent in low-gradient stream segments and widespread in streams with signs of recent watershed disturbance, high sediment loads, and unstable channels. Comparison of estimated 5–10-year damage rates from 46 projects throughout western Oregon and southwest Washington showed high but variable rates (median, 14%; range, 0–100%) in regions where peak discharge ...

Multiscale geomorphic drivers of groundwater flow paths: subsurface hydrologic dynamics and hyporheic habitat diversity

Abstract Application of a hydrogeologic computer model underscored the importance of geomorphic controls on groundwater and surface-water flow dynamics in the Nyack Floodplain, a montane alluvial floodplain in Montana, USA. The model represented the floodplain as a hierarchy of geomorphic patches, which facilitated analysis of model results using independent (predictor) variables at multiple scales. The analyses revealed that geomorphic structures at various spatial scales interact with the flow regime to influence the direction, magnitude, and stability of hyporheic flow within individual floodplain patches. Specifically: 1) the hydrologic flow network within the hyporheic zone is more responsive to seasonal changes in river discharge if floodplain topography is complex and aquifer properties are heterogeneous, 2) simplification of internal patch structure across the floodplain eliminates the influence of fine-scale geomorphic structures on the stability of groundwater flow paths, although the influence of patch context remains, and 3) incremental changes in river discharge can abruptly and substantially restructure the relationship between river discharge and groundwater flow patterns when events such as inundation of previously dry flood channels occur on the floodplain. We believe that ecological theories of biodiversity can be used to understand interactions among geomorphic variation, hydrologic dynamics, and the maintenance of biodiversity in the hyporheic zone if abrupt reorganization and other variations in groundwater flow paths act as disturbances to hyporheic communities. From this perspective, we used model results to develop 4 hypotheses describing the potential for causal linkages among floodplain geomorphology, hyporheic flow-path variation, hyporheic habitat diversity/stability, and hyporheic community diversity.

Three-dimensional mapping of geomorphic controls on flood-plain hydrology and connectivity from aerial photos

Abstract The Nyack flood plain of the Middle Fork Flathead River, MT, USA is a 9-km anastomosed alluvial montane flood plain. Upstream from the flood plain, the river is unregulated and the catchment virtually pristine. A patchy mosaic of vegetation and channels exists on the flood-plain surface. The surface and subsurface geomorphic structures of the flood plain facilitate high hydrologic connectivity (water flux between the channel and flood plain) marked by complex seasonal patterns of flood-plain inundation, extensive penetration of channel water laterally into the alluvial aquifer, and springbrooks formed by ground water erupting onto the flood-plain surface. After delineating and classifying flood-plain “elements” (vegetation patches and channel reaches) on the flood plain, we analyzed field-based elevation survey data to identify expected relationships among flood-plain element type, surface scour frequency, and flood-plain elevation. Data analyses show that scour frequency was inversely proportional to the elevation of the flood plain above river stage, except when localized geomorphic controls such as natural levees prevent normal high flows from inundating and scouring relatively low flood-plain elements. Further, while different flood-plain element types occupy distinct elevation zones on the flood plain, the elevation of each zone above the river channel varies with localized channel entrenchment. We found that topographic variation among flood-plain elements is greater than the variation within elements, suggesting that coarse-scale flood-plain topography can be characterized by delineating flood-plain elements. Field data document strong associations between specific classes of flood-plain elements and preferential ground-water flow paths in the upper alluvial aquifer. Combined with preexisting ground penetrating RADAR (GPR) surveys, these data intimate a sinuous lattice of preferential ground-water flow paths (buried abandoned streambeds) in the upper alluvial aquifer at approximately the same elevation as the main channels streambed. Using aerial photo interpretation and the identified relationships among element-types, elevation, and preferential ground-water flow paths, we developed a quantitative, three-dimensional characterization of surface and subsurface geomorphology across the entire flood plain to support a heuristic modeling effort investigating the influence of flood-plain geomorphology on spatio-temporal patterns of surface and ground-water flow and exchange under dynamic hydrologic regimes.

Geography of Invasion in Mountain Streams: Consequences of Headwater Lake Fish Introductions

The introduction of fish into high-elevation lakes can provide a geographic and demographic boost to their invasion of stream networks, thereby further endangering the native stream fauna. Increasingly, remaining populations of native salmonids are concentrated in fragmented headwater refugia that are protected by physical or biological barriers from introduced fishes that originate in the pervasive source populations established at lower elevations. Although fish introduced near mainstem rivers frequently encounter obstacles to upstream dispersal, such as steep slopes or falls, we found that brook trout (Salvelinus fontinalis) dispersed downstream through channel slopes of 80% and 18-m-high falls. Thus, headwater lake stocking provides source populations that may be capable of invading most downstream habitats, including headwater refugia of native fishes. The extent of additional area invasible from lakes, beyond that invasible from downstream, depends on the geography of the stream network, particularly the density and distribution of headwater lakes and their location relative to barriers inhibiting upstream dispersal. In the thermal and trophic environments downstream of lakes, fish commonly grow faster and thus mature earlier and have higher fecundity-at-age than their counterparts in other high-elevation streams. The resulting higher rates of population growth facilitate invasion. Larger body sizes also potentially aid the fish in overcoming barriers to invasion. Trout introductions to high-elevation headwater lakes thus pose disproportionately large risks to native fishes—even when the place of introduction may appear to be spatially dissociated from populations of the native species. Mapping the potential invasible area can help to establish priorities in stocking and eradication efforts.

Movements of Nonnative Brook Trout in Relation to Stream Channel Slope

Abstract We provide new insights on the ability of naturalized brook trout Salvelinus fontinalis to ascend steep, headwater streams in the western USA. We tested hypotheses that upstream movements by brook trout are limited or absent in reaches of steep streams and are more prevalent and longer in gradually sloping streams. We compared brook trout movements in headwater streams in Idaho at sites with varied channel slopes (averages of <1–12%). After eradicating fish from 200-m stream sections, we assessed immigration of marked fish into these sections. Contrary to our hypothesis, upstream movements were more prevalent than downstream movements during the summer, even in steep streams. Marked brook trout ascended stream channels with slopes of 13% that extended for more than 67 m and 22% for more than 14 m; they also ascended a 1.2-m-high falls. Nearly vertical falls, rather than steep slopes per se, apparently inhibited upstream movements. Our hypothesis that upstream movements would decrease with increas...

Geomorphology, Logging Roads, and the Distribution of Bull Trout Spawning in a Forested River Basin: Implications for Management and Conservation

Abstract The Swan Basin in Montana is considered a stronghold of regional significance for the bull trout Salvelinus confluentus, a native char whose populations are fragmented and declining throughout its range. We used correlation analysis to examine spatial and temporal variation of bull trout redd count data (1982–1995) relative to geomorphic and land-use factors among nine principal spawning tributaries of the Swan River. Bull trout redd numbers were positively correlated with the extent of alluvial valley segments bounded by knickpoints and negatively correlated with the density of logging roads in spawning tributary catchments. The density of logging roads in spawning tributary catchments was not significantly correlated with geomorphic factors. Temporal trends among the principal spawning streams were variable. In four of the nine principal spawning streams, redd numbers increased significantly during the survey period, and in the remaining streams, redd numbers showed no significant change. Chang...

The Effects of Postfire Salvage Logging on Aquatic Ecosystems in the American West

Abstract Recent changes in the forest policies, regulations, and laws affecting public lands encourage postfire salvage logging, an activity that all too often delays or prevents recovery. In contrast, the 10 recommendations proposed here can improve the condition of watersheds and aquatic ecosystems.

Return to the River: Scientific Issues in the Restoration of Salmonid Fishes in the Columbia River

Abstract The Columbia River once was one of the most productive river basins for anadromous salmonids on the West Coast of North America; however, its current runs total less than 10% of historic levels. The Independent Scientific Group (ISG) of the Northwest Power Planning Council reviewed regional salmon management actions described in the Columbia River Basin Fish and Wildlife Program and concluded that the current program is unlikely to recover declining salmon and steelhead stocks. Adoption of a salmon life history ecosystem concept as a guiding foundation is needed to recover depressed stocks. Increasing natural ecosystem processes and functions should rebuild salmon populations to more abundant, productive, and stable levels. Elements of a salmon recovery program that increase these normative conditions include restoration of habitat for all life history stages (including migrations), reduction of mortality sources (including harvesters), planning of hydropower mitigation measures in the context of...