Although flow deflectors are routinely placed in streams to create fish pool habitat, there is dissent in the literature as to what constitutes for them an appropriate design height to ensure their success. Our objectives were to (1) examine the temporal evolution of bed topography around submerged deflectors in a laboratory flume, for different deflector heights and discharge; and (2) quantify the flow dynamics in their vicinity. Results indicate that, all else being equal, higher deflectors (characterized by less overtopping) produce a greater volume of fish pools. In contrast, over a fixed deflector design, a higher discharge (synonymous with greater overtopping) results in larger pools, because flow velocities are then faster. We also observed differences in the temporal behaviour of scour: that next to high and medium height deflectors is self-similar, but not that for the shorter model. Our results challenge the notion that low deflectors are ineffective, provide information on the development of scour next to submerged structures, and reveal key differences between the geometry of the scour holes engendered by the different deflector height models.

A three-dimensional numerical model (PHOENICS) was used to investigate the role of stream deflector angle and length on the flow field in a rectangular laboratory flume. Subsequent bed topography surveys were performed to examine the role of obstruction angle on scour hole development over time. The model was capable of predicting laboratory velocity and turbulent kinetic energy measurements, performing better for flow over a flat stable bed than over a deformed sand bed. A new method of incorporating complex bed topography into a structured Cartesian mesh was developed in the process. Flow field properties such as dynamic pressure, velocity amplification, separation zone length and width, and downwelling extent and magnitude were found to be strongly dependent on deflector geometry. Equilibrium scour hole depths and geometry are also angle-dependent. A predictive equation was produced explaining the rate at which scour holes reach equilibrium, and compared well with existing literature. Finally, a method was developed whereby characteristics of the flow field over a flat, stable bed could be used to predict equilibrium scour hole geometry.

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [157]-174).

No description available.

No description available.

The goal of this research was to formulate new tools for instream-flow analyses, with emphasis on protecting fish assemblages in speciose, warmer-water streams. This included habitat and fish data sets for the upper Roanoke River (URR) in southwestern Virginia, collected during the warmer, low- f low seasons of 1989-1991. Physical data were collected in small, rectangular quadrats or crosssectional transacts, whereas fish were collected by seining and electroshocking in the quadrats. Statistical analyses included uni-, bi-, and multivariate analyses. The habitat analyses showed that mesohabitat types could be effectively defined with hydraulic, channel-roughness, and geomorphologic variables, and different habitat types showed characteristically different hydraulic dynamics across flows. The analyses also showed that physical habitat could be effectively described by 4 axes (sets of similar variables) at microhabitat scales, although greater covariation occurred at intermediate spatial scales (meso- and macrohabitat level). Habitat assessment for instream-flow analyses can thus be effectively simplified by undertaking visual assessment of several mesohabitat types and/or by measuring only a few physical variables for microhabitat analyses. The differences in hydraulic dynamics among mesohabitat types can simplify determination of changes in the availability of fish habitat across flows. The fish analyses showed that habitat-use guilds of fish species could be effectively defined with aggregated data, i.e., across mesohabitat types or by calculation of fishes' habitat-use means for physical variables. In contrast, unaggregated data (each quadrat considered separately) gave cruder habitat-use segregation of fish species, particularly because fish species were independent of each other at smaller spatial resolutions and larger spatial extents. The 7 guilds included 4 rheophilic (riffle-oriented) and 3 limnophilic groups (pooloriented). Habitat-suitability models developed for these guilds showed that fish selected habitat variables independently, such that simple models can be developed to predict fish abundance in response to differences in habitat availability. In sum, the analyses provided habitat-flow and fish-habitat data that can be interfaced (in future analyses) to predict changes in fish abundance and biodiversity to be expected from permanent changes in flow levels and thus habitat availability. / Ph. D.

Responses of juvenile steelhead trout to changes in stream habitat resulting from an instream habitat rehabilitation project in Meadow Creek, Oregon were measured from 1991 through 1992 and compared to pre-treatment data from 1987 through 1990. Sixty nine pool-forming, and 59 channel-stabilizing log structures were constructed by the U.S. Forest Service in a 3.7 km reach in 1990. A 20-year flood caused extensive modifications to the instream structures in May 1991. Pool habitat and large wood volume increased in the treatment and the two reference reaches but pool development was greater in the treatment reach compared to the two reference reaches. Summer rearing densities of juvenile steelhead were similar for the treatment and the two reference reaches at the reach scale. Summer rearing densities were lower in the post-treatment period compared to the pre-treatment period for the treatment and two reference reaches. Mean density of juvenile steelhead was higher in complex pools compared to non-complex pools throughout the study area. Mean density of juvenile steelhead was higher in pools associated with large wood from washed-out structures compared to pools associated with intact structures in the treatment reach. Changes in smolt production from the treatment reach following the rehabilitation project could not be determined due to trapping difficulties. Only three percent of the smolts emigrating from the basin overwintered in the treatment reach in 1992. Four life history patterns of juvenile steelhead were identified. Only one of the four life history patterns rears in the Meadow Creek basin until smolting. From these findings I conclude that the instream habitat rehabilitation project did not increase the abundance of juvenile steelhead or smolt production during the first two years after treatment. An extended drought and a 20-year flood may have been the dominant factors controlling abundance of juvenile steelhead over the study period. The Meadow Creek rehabilitation project may have limited success at increasing smolt production because it influences only one of four life history patterns of juvenile steelhead during the entire freshwater rearing phase. / Graduation date: 1997

Thesis (Ph.D.)--Mississippi State University. Department of Wildlife and Fisheries. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--Mississippi State University. Department of Wildlife and Fisheries. / Title from title screen. Includes bibliographical references.

In 2000 the European Union introduced the Water Framework Directive, new legislation that regulates the use of surface waters within the European Community. The goal of this legislation is to protect, enhance and restore all surface waters within the Community to Good Surface Water Status. Good-Status is described as having low levels of anthropogenic distortion in its hydro-morphological and physiochemical components as well as possessing biota that would normally be associated with the type-specific aquatic ecosystem. The assessment of ecosystem status is to be defined by comparisons with intact representative reference sites, by using modelling techniques that define reference conditions, a combination of the two, or expert judgement. As undisturbed aquatic ecosystems are rare or non-existent in Europe the base-line data will have to be defined using the latter methodologies. The aim of this project is to help define reference conditions for lotic systems in Europe based on the physical instream habitat parameters of a resident species. Brown trout (Salmo trutta), a ubiquitous and well studies species endemic to Europe, was used as the target organism to develop the assessment protocol. The project focused on the requirements this species has of aspects of its physical habitat; specifically, its usage of depth, velocity, and substrate. An extensive survey of the scientific literature was used to define the requirements trout has for the three physical parameters at four life stages. These are the spawning, nursery, juvenile and adult-resident life stages. These requirements were expressed as tolerance profiles, which defined suitable, usable and not-suitable habitat. The methodology was demonstrated by evaluating the physical habitat available at six reaches in three small streams, March, Burnhouse and Bin Burns, which drain into the Carron Valley Reservoir in central Scotland. From the perspective of water depth, these streams seem best suited as nursery areas, are less well suited as juvenile habitat, and do not appear to be well matched for adult residents. The assessment of both velocity and substrate indicated that the portion of the study reaches available for use by resident brown trout increased with trout size. The assessment of all three physical habitat parameters at all study reaches found variable portions of the streams suitable for use by spawning trout. When the habitat variables are integrated all stream segments streams seem best suited as nursery and spawning areas. To a lesser extent juvenile trout can use these burns and very little habitat is available for use by adult resident trout. The tolerance profiles that were created in this study are standardized assessment criteria that when compared with stream survey data can produce an appraisal of habitat availability in any fluvial freshwater system that supports populations of brown trout (Salmo trutta). The assessment method can be combined to produce an integrated habitat assessment, using both an index and by the calculation of Froude number, which is a more realistic approach than the assessment of individual habitat parameters as salmonids choose their microhabitat based on multiple factors. This approach allows an investigator to determine the amount and relative portion of useable habitat and to determine the quality of that habitat. Finally, by examining the physical habitat variable that most strongly correlates with the final integrated habitat distribution the individual habitat parameter that is most important to the distribution of physical habitat at a site can be determined. While this technique would certainly benefit from further development it does show potential to aid in physical habitat assessment of trout streams.