Fluvial adjustment to base level change has its roots in the fundamental concepts of geomorphology. This thesis explores the rate of erosion and sedimentation on the Colorado and Dirty Devil rivers and North Wash Creek under the current base level changes related to the drawdown conditions of Lake Powell. Through cross section and long profile resurveys, the current state of each system is captured and added to the historic record of sedimentation in Lake Powell. All three systems are generally forming narrow and deep incised channels driven by the rapid rate of base level fall. Cross sections that deviate from this are due to site-specific factors, such as channel armoring, the presence of local base levels, or bedrock canyon width in relation to active channel width. In all systems, sediment is being transported through the establishing fluvial regime and is deposited at or below the new base level. This has caused rapid downstream progradation of each delta front. The volume of sediment accumulation and erosion and rates through time are calculated for each system. Deposit volume is proportional to each systems drainage basin area, as are the rates and magnitudes of deposition and erosion. The percentage of sediment eroded versus deposited shows an inverse relationship, with North Wash eroding the greatest percentage of its delta. Field observations and repeat photography on the distribution, orientation, and activity of lateral slumping and mud cracks identify that thick beds of fine-grained and cohesive silts and clays are necessary for these features to form. These features act to destabilize sediment and, in the case of bank failure, deliver it directly to the channel.

Extensive research exists regarding invasive alien plant species including impacts to native ecosystems and efficacy of control methods on public lands and river corridors. Many studies have identified the need for more research regarding the social implications of invasive alien species management. More specifically, additional research is needed regarding the impacts of invasive alien plant management on the Colorado Plateau to river-based recreation experiences. It is important for public land management agencies like the National Park Service to understand recreation-based stakeholders’ knowledge, norms, and preferences toward managing prevalent alien plants like tamarisk. For this study, 330 river users were questioned about their knowledge of tamarisk and preferences for tamarisk management on the Green and Colorado River corridors of the Colorado Plateau. Results show that a majority of river users want tamarisk to be removed. The tamarisk control methods investigated in this thesis were also evaluated by respondents as acceptable. The methods evaluated to be the most acceptable were the cut-stump method and the use of tamarisk leaf beetle, while prescribed fire and the use of a machine to mulch tamarisk were found to be less acceptable. The use of chainsaws to perform the cut-stump method was found to be acceptable in both the Green and Colorado River corridors. This thesis concludes with a summary of findings and implications for land managers and future research.

Ecosystem services and goods are non-market values that are increasingly being accounted through contingent valuation methods and more specifically by studying people’s willingness-to-pay for them. Large ecosystem restoration is an area that benefits from economic valuation because placing a monetary value proves that restoration efforts are justified to preserve resources for future generations, wanted by a community, and even a profitable investment of public funds. However, what determines that a community supports and understands restoration efforts is linked to their social, economic, cultural, and geographic reality. In this study I adopted the idea of willingness-to-pay to examine people’s attitudes towards river flow restoration efforts in the Colorado River Delta. The Colorado River Delta is a resilient ecosystem that has endured severe river flow depravation for more than 70 years now; yet, this ecosystem still provides many environmental services and goods and its restoration is well justified for that. This research mainly reveals that the Colorado River Delta is still an undervalued ecosystem despite its resiliency and the many regional benefits it still provides. This study has two research questions. Fist, I determined what factors influence Mexicali’s willingness-to-pay. Second, I compared willingness-to-pay attitudes between the cities of Mexicali and San Luis Rio Colorado (SLRC); two neighboring Mexican cities of different size and economic structure but of similar social, ecologic and geographical conditions. The instrument to collect field data was a survey that posed a realistic river flow restoration scenario at a range of prices from 10 to 90 pesos in order to test people’s willingness-to-pay; a total of 564 surveys were delivered face to face in Mexicali. Subsequently, I compared Mexicali survey results with a previous SLRC survey. Descriptive statistics, non-parametric analysis, and qualitative analysis were the main instruments to arrive to my conclusions. Within Mexicali, I found that parenthood and the perception of received benefits from the river were the most significant factors that determined people’s willingness-to-pay. Migration was also a salient socio-demographic factor that probably has an influence on people’s attitudes towards river flow restoration. When making comparisons between cities I found that SLRC is more willing to pay than Mexicali, which confirmed my hypothesis that environmental awareness influences willingness-to-pay in each city given that SLRC is a true river city while Mexicali is 64 km away from the river. Pricing was also influential in both cities. People’s exposure to the river varied from one city to the other –SLRC people have more interactions with the river than people from Mexicali do, thus matching again the difference in willingness-to-pay attitudes of each city. Although income, education, frequency of visits, and awareness of dry river conditions were expected to have a clear connection to willingness-to-pay within Mexicali, I found only a marginal statistical relationship that was very close to be significant. This was due to the fact that I analyzed the dependency of those variables for all prices and not at a specific price range where the actual average willingness-to-pay resides. Finding that average and then analyzing the relationships again should clarify this issue. What motivates people to pay was related to resource conservation and the recognition of the river’s ecological importance. What motivates people to not pay relates to negative attitudes such as incredulity and lack of trust in Mexican institutions. My main recommendations are to raise local environmental awareness of river issues with environmental education, to address local negative attitudes towards river restoration, and to explore the analysis of these data with other approaches such as socio-psychological models.

Ecosystem services and goods are non-market values that are increasingly being accounted through contingent valuation methods and more specifically by studying people’s willingness-to-pay for them. Large ecosystem restoration is an area that benefits from economic valuation because placing a monetary value proves that restoration efforts are justified to preserve resources for future generations, wanted by a community, and even a profitable investment of public funds. However, what determines that a community supports and understands restoration efforts is linked to their social, economic, cultural, and geographic reality. In this study I adopted the idea of willingness-to-pay to examine people’s attitudes towards river flow restoration efforts in the Colorado River Delta. The Colorado River Delta is a resilient ecosystem that has endured severe river flow depravation for more than 70 years now; yet, this ecosystem still provides many environmental services and goods and its restoration is well justified for that. This research mainly reveals that the Colorado River Delta is still an undervalued ecosystem despite its resiliency and the many regional benefits it still provides. This study has two research questions. Fist, I determined what factors influence Mexicali’s willingness-to-pay. Second, I compared willingness-to-pay attitudes between the cities of Mexicali and San Luis Rio Colorado (SLRC); two neighboring Mexican cities of different size and economic structure but of similar social, ecologic and geographical conditions. The instrument to collect field data was a survey that posed a realistic river flow restoration scenario at a range of prices from 10 to 90 pesos in order to test people’s willingness-to-pay; a total of 564 surveys were delivered face to face in Mexicali. Subsequently, I compared Mexicali survey results with a previous SLRC survey. Descriptive statistics, non-parametric analysis, and qualitative analysis were the main instruments to arrive to my conclusions. Within Mexicali, I found that parenthood and the perception of received benefits from the river were the most significant factors that determined people’s willingness-to-pay. Migration was also a salient socio-demographic factor that probably has an influence on people’s attitudes towards river flow restoration. When making comparisons between cities I found that SLRC is more willing to pay than Mexicali, which confirmed my hypothesis that environmental awareness influences willingness-to-pay in each city given that SLRC is a true river city while Mexicali is 64 km away from the river. Pricing was also influential in both cities. People’s exposure to the river varied from one city to the other –SLRC people have more interactions with the river than people from Mexicali do, thus matching again the difference in willingness-to-pay attitudes of each city. Although income, education, frequency of visits, and awareness of dry river conditions were expected to have a clear connection to willingness-to-pay within Mexicali, I found only a marginal statistical relationship that was very close to be significant. This was due to the fact that I analyzed the dependency of those variables for all prices and not at a specific price range where the actual average willingness-to-pay resides. Finding that average and then analyzing the relationships again should clarify this issue. What motivates people to pay was related to resource conservation and the recognition of the river’s ecological importance. What motivates people to not pay relates to negative attitudes such as incredulity and lack of trust in Mexican institutions. My main recommendations are to raise local environmental awareness of river issues with environmental education, to address local negative attitudes towards river restoration, and to explore the analysis of these data with other approaches such as socio-psychological models.

Thesis (M.S.)--University of Waterloo. / Includes bibliographical references.

Debris flows in at least 529 Grand Canyon tributaries transport poorly-sorted clayto boulder-sized sediment into the Colorado River, and are initiated by failures in weathered bedrock, the "fire-hose effect," and classic soil-slips often following periods of intense rainfall coincident with multi-day storms. Recent debris flows had peak-discharges from about 100-300 m3/s. Twentieth-century debris flows occurred from once every 10-15 years in eastern tributaries, to once in over a century in western drainage areas. Systemwide, debris flows likely recur about every 30-50 years, and the largest recent flows were initiated during Pacific-Ocean storms in autumn and winter. Three idealized hydrographs are inferred for recent debris flows based on deposits and flow evidence: Type I, has a single debris-flow peak followed by a decayed recessional streamflow; Type II, has multiple, decreasing debris-flow peaks with intervening flow transformations between debris flow and non-debris flow phases; and Type III, may have either a simple or complex debris-flow phase (begin as either Type I or II), followed by a larger streamflow peak that reworks or buries debris-flow deposits under streamflow gravel deposits. From 1987 through 1995, at least 25 debris flows constricted the Colorado River, creating 2 rapids and enlarging at least 9 riffles or rapids. In March-April, 1996, reworking effects of a 7-day controlled flood release (peak = 1,300 m³/s) on 18 aggraded debris fans in Grand Canyon were studied. Large changes occurred at the most-recent deposits (1994-1995), but several other older deposits (1987-1993) changed little. On the most-recent fan deposits, distal margins became armored with cobbles and boulders, while river constriction, flow velocity, and streampower were decreased. Partial armoring of fan margins by relatively-low mainstem flows since the debris flows occurred, was an important factor limiting fan reworking because particles became interlocked and imbricated, allowing them to resist transport during the flood. Similar future floods will accomplish variable degrees of fan reworking, depending on the extent that matrix-supported sediments are winnowed by preceding mainstem flows.

The Bureau of Reclamation (BOR) is interested in understanding the human and environmental consequences of past Glen Canyon Dam water release policies and using these data to inform future water release and land management policies. One step in this direction is to understand how American Indian people have used the Colorado River and adjoining lands in Glen Canyon and Grand Canyon. The BOR, through its Glen Canyon Environmental Studies (GCES) office, has provided funds for various American Indian groups to identify places and things of cultural significance in the 300 mile long river and canyon ecosystem that has come to be called the Colorado River Corridor. This study is the second to report on the cultural resources of the Southern Paiute people found in this riverine ecosystem. The rock art study funded by the BOR and managed by the Glen Canyon Environmental Studies (GCES) office is the basis of this report. This study is unique in the history of rock art studies and is unusual when compared with other American Indian cultural resource assessments. There are five unique features of this study. First, all funds for conducting the research were contracted to the Southern Paiute Consortium. Second, the Southern Paiute people decided during the previous studies that their next study would be about rock art. Third, the GCES /BOR permitted research to be conducted in terms of Paiute perceptions of the study area rather than specifically in terms of the scientifically established study area for the project. Thus, it was possible to conduct the Kanab Creek side canyon study. Fourth, all interviews were guided by a ten -page survey instrument, so Southern Paiute responses could be systematically compared. Fifth, both all-male and all- female research trips were conducted, thus producing the first gender - specific interviews of rock art sites. The resulting study is both interdisciplinary and multivocal.

This study is an investigation of land transformations along the Colorado River in Bastrop County, Texas, and a presentation of planning suggestions to protect and improve the ecology of the river corridor. The rapid population growth experienced in central Texas over the last few decades has manifested itself in extensive land use changes. The Colorado River Valley in Bastrop County has experienced this development in some areas, although, as a whole, it has remained largely agricultural in nature, with more extensive changes occurring in adjacent Travis, Hays, and Williamson Counties to the west. As land values increase and the stock of undeveloped land dwindles, developers are turning their attention east to Bastrop County. This study primarily utilizes historic aerial maps to identify changes along the Colorado River corridor in Bastrop County. The choice of the river corridor as the extent of the study area was made because of the disproportionate importance of this land area for environmental systems services, the myriad contributions that the ecological community provides to humanity and agriculture. This study’s primary purpose is to create a baseline documentation of the corridor’s existing condition and a menu of recommendations to promote intelligent growth. The study pays special attention to the present and historic extent of the riparian forest (the forest that brackets the river), as this is the “natural” land use that existed prior to Anglo settlement. The study identifies specific instances and trends in land use, which, due to their degree and extent, are having adverse ecological and hydrological impacts. These include industrial, commercial, and residential development, as well as gravel mining and large infrastructure projects. / text

This report concludes the first four years (1992 -1995) of Southern Paiute involvement in the Glen Canyon Environmental Studies (GCES), a program initiated by the Bureau of Reclamation (BOR) in 1982. Southern Paiutes have conducted ethnographic research and participated in the Congressionally mandated Environmental Impact Study (EIS) of Glen Canyon Dam water release policies on natural and human-made resources found in the Colorado River Corridor. These ethnographic studies have taken place in what is called the Colorado River Corridor which extends 255 miles down stream from Glen Canyon Dam to the end of the free flowing river at Separation Canyon within the Grand Canyon National Park. They have concentrated on investigating the impacts of the Dam's water releases to Southern Paiute cultural resources. Since the Final EIS was published in March 1995, emphasis has been placed on what is called the Adaptive Management Program of the GCES and attention has shifted to monitoring the water release impacts.

Invasive species such as quagga mussel (Dreisseina bugensis) alter native ecosystems around the world. This study uses genetic markers to examine historical lineages for quagga mussels in lakes (reservoirs) of the Colorado River System. Specimens were collected from Lake Mead, Lake Mohave, Lake Pleasant, Lake Havasu, Lower Otay Reservoir, Yuma Area, and two Central Arizona Project pumping stations. Objectives of this project were to perform analyses of genetic variability within populations and determine if relatedness among individuals could resolve whether they originate from a single, or multiple, invasion events and genetically distinguish the populations at each water body. Analyses examined the mitochondrial DNA COI region and eight microsatellite DNA markers. Three populations were characterized in the study area and compelling information gathered about gene flow between them. Results indicate that microsatellite markers are useful to track quagga mussel invasions and provide insights into migration patterns that would otherwise be missed.