Interactions Between Physical and Biological Processes in Riverine Landscapes VIII: Human Impacts and Salmonid Restoration
Presiding: J M Buffington, USDA Forest Service; C V Baxter, Colorado State University; A E Rosenberger, University of Idaho and USDA Forest Service
B53B-01 INVITED 13:30h
Geomorphology and the Restoration Ecology of Salmon
Natural and anthropogenic influences on watershed processes affect the distribution and abundance of salmon across a wide range of spatial and temporal scales, from differences in species use and density between individual pools and riffles to regional patterns of threatened, endangered, and extinct runs. The specific impacts of human activities (e.g., mining, logging, and urbanization) vary among regions and watersheds, as well as between different channel reaches in the same watershed. Understanding of both disturbance history and key biophysical processes are important for diagnosing the nature and causes of differences between historical and contemporary fluvial and watershed conditions based on evaluation of both historical and spatial contexts. In order to be most effective, the contribution of geomorphologic insight to salmon recovery efforts requires both assessment protocols commensurate with providing adequate knowledge of historical and spatial context, and experienced practitioners well versed in adapting general theory to local settings. The historical record of salmon management in Europe, New England and the Pacific Northwest indicates that there is substantial need to incorporate geomorphic insights on the effects of changes in watershed processes on salmon habitat and salmon abundance into salmon recovery efforts.
B53B-02 13:45h
Influences of fluctuating flows on spawning habitat and recruitment success
Over the 50 years of daily peak power generation, no ramping restrictions, and loss of gravel due to operations of Philpott Dam, on Smith River, has created a wider, rectangular-shaped channel, with steeper banks. The pattern caused by channel degradation, tributary headcutting, bank erosion, and downstream aggradation has limited the length of productive habitat to between 3 and 10 river kilometers from the dam. Here the channel appears to contain key habitats where we found the highest redd densities, abundance, and spawner biomass for brown trout (Salmo trutta). Recruitment of brown trout to the fishable size classes is constrained by the daily hydropower peaking operations. The number of young brown trout produced each year was strongly related to the average magnitude of the peak flow and the duration of generation flows. Magnitude of peak flows also depressed abundance of native fishes. Although, brown trout actively removed fine sediment via redd construction and spawning, thereby increasing gravel permeability, the fine sediments from tributaries and bank erosion rapidly intruded into the spawning gravel in downstream reaches of the river. We recommend mitigating the effects of fluctuating releases from Philpott Dam through a combination of flow management and habitat improvement.
B53B-03 14:00h
The effect of vegetation and beaver dams on geomorphic recovery rates of incised streams in the semi-arid regions of the Columbia River basin, USA.
Channel incision is a common occurrence in semi-arid regions of the Columbia River basin and throughout the world, where a fragile balance between climate, vegetation and geology makes channels susceptible to changes in hillslope erosion, stream discharge and sediment yield. Incision is defined as a rapid downcutting and lowering of the stream bed such that it reduces the frequency and duration of flooding onto the adjacent floodplain. We are studying the feasibility of restoring incised streams throughout the interior Columbia River basin. We hypothesize that under proper land use management, it is possible for them to aggrade such that they reconnect to their former floodplains within relatively short time frames. Theoretical and empirical evidence suggests that over decadal time scales, changes to land management that excludes grazing and allows riparian vegetation to become established can cause significant fill within the incised valleys. Preliminary modeling suggests that factors most affecting the length of time for an incised valley to completely aggrade and reconnect to its pre-incision floodplain are the depth of the incision, sediment production in the watershed, the amount and type of riparian vegetation, and the extent of beaver dam construction. While most natural resource and fisheries managers are aware of widespread incision throughout the Columbia River basin, the extent of incision within the range of the Pacific salmon is largely undocumented. However, we do know many incised streams that historically supported salmon no longer do so, and that habitat conditions are severely degraded in these incised streams. The historical record shows that numerous salmon-bearing streams in the semi-arid region of the interior Columbia River basin once contained narrow and deep, slowly meandering channels lined with cottonwoods, willows and/or sedges, contained numerous beaver dams, contained abundant and easily accessible off-channel habitat on the floodplain and had good flow and cool temperatures throughout most of the year. Today most of these streams are incised and contain little or no riparian vegetation or beaver dams. Stream temperatures are high and flow is ephemeral. Incision is thought to have lowered stream-adjacent water tables, causing both the loss of riparian vegetation and the increase in stream temperature. Many of these streams no longer support fish populations. We hypothesize that if incised streams were restored by creating conditions such that they could aggrade and reconnect to their former floodplains, that habitat conditions would be sufficient to again support salmon populations, and that this would greatly expand their range throughout much of the Columbia River basin.
B53B-04 14:15h
Incorporating Geomorphological and Biological Processes Into Recovery Planning Strategies for Listed Salmonids in the Pacific Northwest
A number of species of Pacific salmonids are listed under the U.S. Endangered Species Act due to a combination of habitat loss and degradation, hatchery programs, and harvest practices. Efforts are underway throughout the geographic ranges of the listed salmon to develop recovery plans describing the necessary conditions for delisting. Habitat restoration strategies in some watershed recovery plans address the functioning of landscape processes that create and sustain stream habitats, in addition to the traditional focus on instream habitat conditions and their effects on salmon populations. Including restoration approaches that aim to improve habitat-forming processes is a step forward in addressing the root causes of habitat problems for salmon. In this talk, we illustrate how GIS-based analyses indicating the degree of impairment to sediment supply, stream flows, and riparian functions were used to help identify restoration strategies for Chinook salmon populations in a watershed in Puget Sound, WA. We first developed empirical relationships between landscape attributes (i.e., land cover, geology and forest road density) and processes or conditions (stream flows, riparian zone condition, large wood recruitment, and sediment supply rates). Then we summarized those landscape attributes in all sub-basins within the watershed to indicate the likely current condition of peak flow hydrology, riparian function, and sediment supply. Finally, we quantified the degree of impairment in these 3 processes relative to their likely historical rates or conditions, and classified sub-basins into groupings of common restoration strategies. Specific habitat restoration actions aimed at redressing the riparian, sediment, and flow problems at their sources were identified separately for each sub-basin strategy group. We explored the potential effects of 3 alternative restoration approaches on the status of Chinook salmon populations at the watershed scale using a fish-habitat population dynamic model. Modeling results indicate that one of the restoration strategies would improve salmon population status enough to achieve viability goals adopted by the watershed planning group. The multi-stakeholder planning group in the watershed used our results as the basis for approving the habitat restoration strategy, which is now part of the recovery plan for Puget Sound Chinook.
B53B-05 14:30h
A Clustering Algorithm for Ecological Stream Segment Identification from Spatially Extensive Digital Databases
Remote sensing and geographic information systems have made it possible to attribute variables for streams at increasingly detailed resolutions (e.g., individual river reaches). Nevertheless, management decisions still must be made at large scales because land and stream managers typically lack sufficient resources to manage on an individual reach basis. Managers thus require a method for identifying stream management units that are ecologically similar and that can be expected to respond similarly to management decisions. We have developed a spatially-constrained clustering algorithm that can merge neighboring river reaches with similar ecological characteristics into larger management units. The clustering algorithm is based on the Cluster Affinity Search Technique (CAST), which was developed for clustering gene expression data. Inputs to the clustering algorithm are the neighbor relationships of the reaches that comprise the digital river network, the ecological attributes of the reaches, and an affinity value, which identifies the minimum similarity for merging river reaches. In this presentation, we describe the clustering algorithm in greater detail and contrast its use with other methods (expert opinion, classification approach, regular clustering) for identifying management units using several Michigan watersheds as a backdrop.
B53B-06 14:45h
Multi-scale Spatial Analysis Of Physical Habitat Of Pseudobagrus ichikawai (Siluriformes: Bagridae) In Third Order Stream Landscapes, Mie Prefecture, Japan
The bagrid catfish, Pseudobagrus ichikawai, is threatened with extinction, occurring only in the rivers flowing into Ise and Mikawa Bays. P. ichikawai is perceived to use the interstices of boulder clusters in backwaters. However, its ecology remains unclear owing to its nocturnal habits and unique habitat features. Recently, several river improvement works for controlling floods such as bank revetment, channel shortening and dam construction have decreased such environments in many rivers, and have also been considered to cause the reduction of catfish populations. The conservation of the remaining populations is fundamental not only for preserving species / genetic diversity, but also for sustaining the river landscape with its various environments. In other words, P. ichikawai can be utilized as an indicator species for this original river landscape. Therefore, in order to conserve a tiny population of the catfish, habitat restorations are planned in the 3rd order stream, a small branch of the Inabe River system in Mie Prefecture. The objectives of this study are to clarify the physical characteristics of P. ichikawai habitats and to help implementing habitat restoration in this small branch. This study consists of stratified analysis from the viewpoints of three kinds of spatial scale as follows: (1) landscape scale which includes physical land shape characteristics of the valley with each stream investigated before, (2) reach scale of the longitudinal 100 m length including the riparian zone with the multiple observed points of catfish and (3) micro-habitat scale of the quadrates (2m X 2m) where we observed the catfish individuals. At first, cluster analysis for scale (1) was conducted using variables such as sinuosity of channel, channel / valley width, and longitudinal / cross-sectional valley gradient. These parameters were obtained from general topographic maps and the 3rd order streams where local P. icihikawai populations survived in Mie Prefecture were covered in this analysis. The clustering determined one stream of the Miya River system as the reference stream. Thus, field investigations in scales (2) and (3) were conducted in both the target and reference streams. The inhabitation research for the P. ichikawai individuals with observation by snorkeling was carried out in the two streams at the beginning of the investigation. And then, the physical parameters (velocity, water depth, substrata and so on) were measured not only in the micro-habitat (3), but also in the reach scale (2). Furthermore, the topographic surveys in scale (2) were also exploited. According to these analyses, the individuals of P. ichikawai hided in the interstices of loose boulder clusters in backwaters during daytime. Particularly, this tendency became notable as they grew and gathered. In addition, the potential habitat area of catfish could be simulated in both streams, and thereby the difference of habitat conditions was quantitatively revealed. These results can be beneficial for rehabilitating the habitat of endangered bagrid catfish, P. ichikawai.