Thesis (PhD) University of Montana, 2008. / Title from author supplied metadata. Contents viewed on May 19, 2010. Includes bibliographical references.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 61-65). Also available on the World Wide Web.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 146-153). Also available on the World Wide Web.

656 pages / Livestock grazing and beaver trapping alter streams hydrologically and geomorphically leading to declines in the quality and extent of stream-riparian ecosystems. The influence of reductions in grazing pressure and fluctuating levels of beaver activity (treatments) on channel capacity was studied at I 08 channel cross-sections, located on eight headwater streams in Montana and Arizona. Cross-sections were surveyed two or three times over a two-to-five year period to determine annual rates of change as a function of treatment. Most cross-sections in the cattle and elk exclosures and grazed areas showed minimal changes in area(< 10 percent). Large decreases in cross-section area were observed in reaches with intact beaver dams, especially near the dams. The beaver ponds reduced channel capacity between 50 to I 00% in most reaches, compared to< 25% in reaches without beaver ponds. The ponds effectively restored the hydrologic connection between the stream and valley floor in less than one year. Upon dam failure, channel capacity increased within a year by 40 percent or more as the ponds drained and sediment eroded. A conceptual model describing geomorphic and hydrologic response of a drainage basin to the entry of beavers and then their removal or abandonment was developed, based on a literature review and field data. The model suggests that the simultaneous existence of discontinuous arroyos and wetlands, observed by Euro-American expeditions to the Southwest prior to settlement, may in fact reflect landscapes transforming due to recent beaver trapping rather than a recent climate shift. Beaver-dam failures would trigger channelization and thus greater flood magnitudes as water was more rapidly routed from upper to lower watersheds. The study suggests that Euro-American trapping and grazing, though temporally and spatially separated, combined with two recent periods of above-average precipitation to transform drainage networks in the West and increase stream ecosystem sensitivity to climatic variability. This transformation pre-dates the installation of stream gages and the data collection that forms the current basis of our understanding hydraulic geometry and fluvial processes. Consequently, current hydraulic geometry relationships and our understanding of stream sensitivity to climatic variability reflect highly disturbed watersheds and ecosystems, not intact systems. / Version has slight corrections to the original by the author, as specified in separately attached file Corrections_to_Fouty_2003_PhD_20181810.pdf

The Skoenmakers River (located in the semi-arid Karoo region of the Eastern Cape) is being used as a transfer route for water transferred by the Orange-Fish-Sundays River Interbasin Transfer Scheme. The change in the hydrological regime of this once ephemeral stream to a much bigger perennial river led to dramatic changes to both the physical structure and riparian vegetation structure of the river system. These changes differ for each of the three river sections, the upper,middle and lower reaches. Qualitative, descriptive geomorphological data was gathered by means of field observations and this was then compared to the quantitative data collected by means of surveyed cross-sectional profiles at selected sites along the length of both the regulated Skoenmakers River and a nonregulated tributary of equivalent size, the Volkers River. Riparian vegetation data was gathered by means of plot sampling along belt transects at each site. A qualitative assessment of the vegetation conditions was also made at each site and then added to the quantitative data from the plot sampling. At each site the different morphological units were identified along the cross-section and changes in the vegetation and sediment composition were recorded. Aerial photographs were used as additional sources of data and observations made from these were compared to data gathered in the field. The pre-IBT channel in this river section was formed by low frequency flood flows but the hydrological regime has now been converted to base flows much higher than normal flood flows. Severe incision, erosion and degradation of both the channel bed and banks occurred. In the lower reaches, post-IBT base flows are lower than pre-IBT flood flows and, due to the increased catchment area, the impact of the IBT was better ‘absorbed’ by the river system. Aggradation and deposition increased for the regulated river in comparison to the non-regulated river due to more sediment introduced The IBT had the greatest impact in the upper reaches of the regulated river due to more sediment introduced at the top of the system.

A finite element numerical model is developed for the modeling of coupled surface-water flow and ground-water flow. The mathematical treatment of subsurface flows follows the confined aquifer theory or the classical Dupuit approximation for unconfined aquifers whereas surface-water flows are treated with the kinematic wave approximation for open channel flow. A detailed discussion of the standard approaches to represent the coupling term is provided. In this work, a mathematical expression similar to Ohm's law is used to simulate the interacting term between the two major hydrological components. Contrary to the standard approach, the coupling term is incorporated through a boundary flux integral that arises naturally in the weak form of the governing equations rather than through a source term. It is found that in some cases, a branch cut needs to be introduced along the internal boundary representing the stream in order to define a simply connected domain, which is an essential requirement in the derivation of the weak form of the ground-water flow equation. The fast time scale characteristic of surface-water flows and the slow time scale characteristic of ground-water flows are clearly established, leading to the definition of three dimensionless parameters, namely, a Peclet number that inherits the disparity between both time scales, a flow number that relates the pumping rate and the streamflow, and a Biot number that relates the conductance at the river-aquifer interface to the aquifer conductance. The model, implemented in the Bill Williams River Basin, reproduces the observed streamflow patterns and the ground-water flow patterns. Fairly good results are obtained using multiple time steps in the simulation process.

Ecology may be oonsidered as one of the vital parts of botany, since there are two ultimate facts in this science; namely, the plant and its habitat . The habitat is made up of the physical factors that control function. At Timpanogos there are so many different habitats, that the chief problem is not that of finding a problem to study, but rather that of selecting one from the many. The purpose of this paper is to point out some of the interesting features that are found in a study of Timpanogos Creek from Aspen Grove to Wildwood.

Riparian forests, which support rich biological diversity in the North American southwest, have experienced a sharp decline in the last century. The extent of this decline has been estimated to range from 70% to 95% across the southwest (Johnson and Haight, 1984). The principal components of riparian forests which sustain a broad spectrum of species and describe the overall health of a system are cottonwoods (sp. Populus) and willows (sp. Salix). The importance of cottonwoods is aptly described by Rood et al (1993): "....these trees provide the foundation of the riparian forest ecosystem in semi -arid areas of western North America. Unlike wetter areas to the east and west, a loss of cottonwoods in these riparian areas is not compensated through enrichment from other tree species. If the cottonwoods die, the entire forest ecosystem collapses." Cottonwood and willow species are adversely affected by anthropogenic influences ranging most prominently from the introduction of regulated flows via dams to agricultural clearing, water diversions, livestock grazing, and domestic settlement. These influences effectively alter the system hydrology that the forests rely upon. As the widespread destruction of these forests and the associated irreparable damage to endangered species habitat has come into clear view in the past decade, research efforts have focused upon identifying the ecological needs of riparian systems. The potential of modifying such systems to soften the human impact upon them, in effect presenting further alterations on a hydrologic system to return it to its natural regime, is another component of the research on riparian systems. The Bill Williams River riparian corridor, near Parker, Arizona (Figure 1.1), contains the last extensive native riparian habitat along the lower Colorado River (BWC Technical Committee, 1993). This unique resource was established as the Bill Williams River Management Unit, Havasu National Wildlife Refuge in 1941 and covers 6105 acres along the lower 12 miles of the Bill Williams River (Rivers West, 1990). The Bill Williams Unit is currently managed by the U.S. Fish and Wildlife Service of the U.S. Department of Interior. The U.S. Fish and Wildlife Service also funded this research effort. The lush vegetation corresponding to the wetland conditions along the valley floor sharply contrast with the Sonoran desert landscape of the upper valley walls creating a magnificent picture. The Management Unit terminates at Lake Havasu, which forms the confluence of the Bill Williams and Colorado Rivers. The system provides habitat for a wide variety of species, many of which are endangered or state- listed species, including habitat for neotropical migratory birds. This habitat has undergone serious degeneration during the past quarter century. The recruitment of cottonwood and willow trees has been fatally interrupted by anthropogenic encroachment in the form of the construction of Alamo Dam in 1969 at the head of the Bill Williams River and commercial development along the River.

Pacific salmon populations in Johnson Creek, Portland, Oregon have been adversely impacted by urbanization, and by residential and agricultural land development. f Ecological impacts include loss or depletion of riparian vegetation features which directly influence stream and associated salmonid ecology. This research examines the nearstream riparian zone's contribution to instream habitat complexity for anadromous salmonids in Johnson Creek. Visual surveys were conducted on over half the stream length. Five features were assessed to determine the extent of riparian influenced stream habitat including, overhead enclosure, overhanging vegetation, undercut banks, and large and small woody debris and root wads. The stream survey showed that areas of riparian-influenced habitat are spatially intermittent and present in areas of the least stream disturbance. Suitable riparian habitat is limited to locations where there is minimal riparian disturbance, property management, and channelization. I Although salmonid populations have been reduced, insufficient riparian influenced salmonid habitat features are not the primary limiting factor on salmon populations. Other factors such as pollution, sedimentation, hatchery fish introduction, low flows, inadequate food supplies, high stream temperatures, repress wild salmon populations.

This study conducts a dam-scale cost versus benefit analysis in order to explore the feasibility of each the 13 U.S. Army Corps of Engineers (USACE) commissioned dams in Oregon’s Willamette River network. Constructed between 1941 and 1969, these structures function in collaboration to comprise the Willamette River Basin Reservoir System (WRBRS). The motivation for this project derives from a growing awareness of the biophysical impacts that dam structures can have on riparian habitats. This project compares each of the 13 dams being assessed, to prioritize their level of utility within the system. The study takes the metrics from the top three services (flood regulation, hydropower generation and recreation) and disservices (fish mortality, structural risk and water temperature hazards) and creates a rubric that scores the feasibility of each dam within the system. Within a range between 0 to 3 for three dam services and 0 to -4.5 for two disservices, the overall calculated score elucidates for each structure whether its contribution to the WRBRS is positive or negative. Further analysis searches for spatiotemporal trends such as anomalous tributaries or magnified structural risk for structures exceeding a certain age. GIS data from the National Inventory of Dams (NID), U.S. Geologic Survey (USGS) water measurements, raw data from USACE, and peer-reviewed studies comprise the statistics that generate results for this analysis. The computed scores for each dam yield an average overall score of -1.31, and nine of the 13 structures have negative results, indicating that the WRBRS faces challenges going forward. The study seeks to contribute to the increasingly relevant examination of dam networks at the watershed scale.