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Water-Energy-Food Nexus: Decision-Support for Water Infrastructure Management
No full textAbstractWater-Energy-Food Nexus: Decision-Support for Water Infrastructure Management
By
Sooyeon Yi
Doctor of Philosophy in Landscape Architecture and Environmental Planning
University of California, Berkeley
Professor G. Mathias Kondolf, ChairAccording to the US Food and Agriculture Organization, the projections reveal that the water, energy, and food demands will increase significantly over the next decades due to population growth, economic development, technological changes, and climate change. The rapidly growing body of literature on the water-energy-food nexus discusses addressing complex resource systems, amplifying synergies, mitigating the tradeoffs, and developing cross-sectoral policies. The water-energy-food nexus offers a promising approach to simultaneously addressing the water, energy, and food sectors. Though, this approach has some limitations and challenges in understanding the interconnection of all three sectors in a single study. To address this limitation, we synthesize the water-centered nexus in dual-sector, including the water infrastructure-environment, water-energy, and groundwater-food nexus. The three main objectives of this dissertation are to evaluate the water-centered nexus approach incorporating the interdependencies between dual-sector in water infrastructure, assess the effectiveness of the broad-to-narrow scale approach in the water-centered nexus study, and examine the role of the water-centered nexus approach in decision-making for the water infrastructure. A water-centered nexus is a nexus study that stretches the focus of water by including at least one other resource (e.g., energy, carbon, land) that depends on water. Chapter I (water infrastructure-environment nexus) provides a comprehensive inventory of inter-basin water transfer projects (built, ongoing, proposed) and proposes directions for future inter-basin water transfer projects in the US. Chapter II (water-energy nexus) develops subsequent monthly energy use predictive models for the Mokelumne River Aqueduct in California. Chapter III (groundwater-food nexus) investigates the groundwater level changes before- and after- fully and partially opening the Baekjae Weir. The main methods are collecting and analyzing the secondary data (Chapter I) and applying machine learning algorithms to simulate energy use forecasting models for the inter-basin water transfer project (Chapter II) and groundwater level prediction model for the weir (Chapter III). Results showed that a nexus approach supported a better understanding of the complexity and dynamics of interlinkages between water, energy, and food resources. A broad-to-narrow scale approach was effective in analyzing the overall characteristics of water infrastructures and assessing their national, regional, and local specific problems. The water-energy-food nexus approach can support the decision-making for the proposed inter-basin water transfer project (Chapter I), ongoing inter-basin water transfer project (Chapter II), and currently operating weir (Chapter III). Thus, the water-energy-food nexus approach is effective in practical planning, management, and decision support framework for the water infrastructure
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Federal Flood Control Channels in San Francisco Bay Region - A Baseline Study to Inform Management Options for Aging Infrastructure
Full text linkThis dissertation focused on flood control channels in urban areas built by the USACE between the 1950s and 1970s. These uniform-shaped earth or concrete lined channels were designed to "control" flooding and to make possible expanded floodplain developments. As many of these channels have been in service for over 50 years, it may be instructive to reassess them to examine how they were planned, designed, and maintained, and to identify the current conditions and issues. The assessment provides the basis to develop management strategies for this aging infrastructure. In this dissertation, I examined the flood control channels in the Federal scale and the local scale. At the Federal scale, I reviewed the history and evolution of USACE policy, planning process, design criteria, and the 100-year flood standard. I also conducted a systematic evaluation of nine urban flood control channels built by USACE between the 1950s and 1970s in the San Francisco Bay Region. I found the commonality of problems in these flood control channels, driven by the USACE planning policies when these channels were built. The finding forms the justification to develop a channel safety program to manage all USACE flood control channels at the federal scale. The policy review found that the planning process for these projects singly focused on national economic benefits, while environmental consequences were largely excluded. The land enhancement benefit in the cost benefit analysis encouraged floodplain and tidal marsh developments. However, habitat elimination resulting from the developments was not considered as a cost. The land enhancement benefit had significant impact on project justification. The San Francisco Bay Area case study found that six of the nine projects included the land enhancement benefit in the cost benefit analysis. If the land enhancement benefit were subtracted from the total project benefit, three of the six projects would not have been authorized due to low cost benefit ratio. This implies that if habitat protection had equal footing as flood risk reduction, as a planning criterion for these projects, many of the projects would not have been authorized in the form they were constructed.The primary design criteria for these flood control channels were to maximize flow capacity within a minimal footprint. The hydraulic design assumed a clear water condition, ignoring sediment effects. However, oversized thalwegs invite in-channel sediment deposition, and sediment transport increases channel roughness. Both effects reduce channel capacity. The clear water assumption led to questionable channel designs. The San Francisco Bay Area case study shows that six of the nine flood control channels have channel thalweg elevation at the outfall lower than the adjacent bay bed, created sediment sumps. The study also found that eight of the nine flood control channels had concrete channel reaches designed under supercritical flow. Such design demands the channel to function as designed under the clear water condition.The San Francisco Bay Area case study found that the maintenance guidelines were ambiguous, but sediment deposition created significant operation and maintenance burden to local sponsors. On average the current sediment maintenance cost is 5 times higher than the original design estimate. Due to sediment deposition and channel deterioration, the average channel capacity reduced by 31%, as compared to the original design capacity. None of the channels in the study have the capacity to convey the existing 100 year flow. Even under the original design condition, five of the nine channels cannot provide existing 100 year flow capacity, considering two of the five channels were designed for the Standard Project Flood. This result is a matter of concern, since even if the channels were maintained to the original design specification and under the clear water condition, these channels still cannot provide 100-year flood protection.The Federal scale analysis identified common issues among these flood control channels. These channels provide a false sense of flood protection security to the communities they serve, and the resultant floodplain developments further increase flood risk. At the Federal scale, the findings form the justification basis to develop a channel safety program to manage all USACE flood control channels. The proposed program would be similar to the existing dam and levee safety programs. The proposed program provides a management framework for the entire USACE flood control channel portfolio, for periodic inspection and risk assessment, condition review and classification, and critical improvement prioritization for flood risk reduction.At the local scale, I conducted a detail review on the planning process of the Corte Madera Creek flood control project, to validate the findings from the USACE planning policies review. I also developed a hydraulic analysis to evaluate how sediment management schemes affect channel capacity. The case study at Corte Madera Creek further illustrated the sediment management issue found in the Federal scale analysis. The local sponsor devised a more efficient sediment removal plan for 100 year flood protection, however it still costs 14 times more than the original maintenance budget estimate. Furthermore, the proposed flood protection projects in the upper watershed were designed based on the flood control channel providing 5,600 cfs capacity, about 2,000 cfs lower than the original design capacity. The analysis shows that even if the channel were maintained in accordance with the USACE operation and maintenance manual, the channel still would not provide the capacity needed. This finding validated the fundamental project design issues found at the Federal scale analysis.At the local scale, my analysis identified a need to update the USACE operation and maintenance manual, to specify sediment removal frequency and volume based on the required channel capacity. Local sponsors should develop a sediment deposition and channel capacity relationship, so the local sponsor can assess the need for sediment removal based on channel flow and stage monitoring data. The channel safety program provides the management tool to systematically prioritize and implement these updates to USACE projects.USACE should update the engineering manual for flood control channel project planning and design. The revision should include methods to estimate channel roughness coefficient under various sedimentation and sediment transport conditions. To provide the technical basis to update the engineering manuals and project assessment methods, additional research is needed to (1) investigate how bedload sediment transport on smooth surface with no deposition affects channel roughness, and (2) improve existing risk analysis tools to quantify the stage discharge uncertainty.In addition to managing the aging infrastructure to maintain its level of service, there is a need to develop intervention strategies to reinvent flood control channels to meet contemporary objectives in ecological restoration, floodplain management, recreation, and flood risk reduction. The intervention also needs to overcome the space limitation due to urban encroachments in the floodplain and often up to the channel banks
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The Downstream Geomorphic Effects of Dams: A Comprehensive and Comparative Approach
Full text linkLarge dams commonly alter the natural regimes of hydrologic and sediment processes that are critical for the maintenance of native instream and riparian communities, often affecting landscapes hundreds of kilometers from the dam. California has over 1,400 large dams, some of which have been in place for over 100 years. As a consequence, the legacy of large dam construction has greatly altered California's natural hydrologic and sediment processes. Previous attempts to estimate the effects of multiple large dams on sediment processes have ignored two key factors for large spatial and temporal modeling: sediment trapping due to multiple dams in the same watershed and decreasing sediment trapping as reservoirs fill. Here, I develop a spreadsheet-based model that incorporates both factors. Using California as a case study, measured sedimentation rates first were used to estimate sediment yields for distinct geomorphic regions and the rates then were applied to unmeasured reservoirs by region. The results of the model show that statewide reservoirs have likely filled with 2.1 billion m3 of sediment to date, decreasing total reservoir capacity by 4.5%. In addition, approximately 200 reservoirs have likely lost more than half their initial capacity to sedimentation.Fourteen of the fifteen major tributaries to the Sacramento-San Joaquin river system in California are dammed by "foothill" dams, very large dams situated at the base of the mountain fronts. Constructed primarily in the 1940s-1970s, the foothill dams include some of the largest dams in the United States. In addition to blocking access to migrating endangered salmonids, the dams have further altered downstream hydrologic and sediment processes by changing flow-duration and frequencies and releasing sediment-free flows. There has been no comprehensive effort to evaluate the long-term changes in magnitude and frequency of sediment transport downstream of these dams, despite hundreds of millions of dollars spent on restoration efforts. In this study, I evaluate the different effects of the foothill dams on downstream rivers using hydrologic analyses of pre- and post-dam flows, calculations of bedload transport from an extensive literature search and field data, and field observations using gravel tracer and monitored cross sections from water year 2006 (WY2006) to test the results of the bedload transport calculations. From the results of the hydrologic analysis, the average reduction in the 2-year return interval flow for the dams is 65%, however, there is a wide range in the results, with some post-dam flows remaining equal to pre-dam magnitudes, particularly at larger return intervals. Using topographic data and tracer gravel collected during water year 2006, extensive gravel movement was observed downstream of the dams, indicating that even after 50+ years of operation, the riverbeds below the dams are continuing to transport sediment and still are responding to the cessation in supply. From the calculation of bedload transport for each of the major tributaries, post-dam annual bedload transport has fallen by an average of 45%, with total bedload of particles greater than 8mm decreasing by 42%. Some rivers, while having reductions in flood flows, had increases in bedload transport downstream of the dam, primarily due to increases in medium-magnitude medium-frequency events. Bedload is still transported at high rates for most sites, with eleven of the fourteen rivers transporting more than 100,000 m3 / yr in the post-dam period. Effective discharge in these channels is difficult to determine due to confounding factors, however, the majority of the rivers have a high-percentage of total bedload transported at discharges larger than the 5-year return interval suggesting that higher discharge events tend to dominate the channel response. A sediment budget was constructed for both coarse and total sediment for each of the fourteen major tributaries to the Sacramento-San Joaquin river system downstream of the major "foothill" dams. The methods used to construct the sediment budget include a reservoir sedimentation model, bedload transport equations, and suspended and bedload measurements from gaging stations. The results of the sediment budget indicate a volume of approximately 244 million m3 of sediment is trapped behind dams in the upper watersheds, and 4.0 million m3 is trapped by the dams each year. With the exception of the mainstem Sacramento River, very little bedload material is supplied by smaller tributaries to the gravel-bed reaches downstream of the foothill dams. Ten of the fourteen rivers do not have enough supply from small tributaries to meet the calculated average annual bedload transport. Several of the rivers (Putah Creek, the Mokelumne River, and the San Joaquin River) may be strongly affected by small tributaries downstream of the dams because they have relatively large watersheds downstream of the dams and highly reduced post-dam transport ability. Approximately 267,000 m3 of gravel has been artificially augmented into Sacramento-San Joaquin tributaries downstream of the foothill dams through 2004. While gravel augmentation projects have been extensive on six of the rivers, they are minimal or absent on the other eight rivers. Overall, gravel is augmented at only 3.7% of the post-dam bedload transport capacity, however, some rivers with highly reduced flows have had gravel augmented at rates that approach the post-dam gravel transport rate, primarily due to the large post-dam reduction in bedload transport
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Multifunctional Riverscapes: Stream restoration, Capability Brown's water features, and artificial whitewater
Full text linkSociety is investing in river restoration and urban river revitalization as a solution for sustainable development. Many of these river projects adopt a multifunctional planning and design approach that strives to meld ecological, aesthetic, and recreational functions. However our understanding of how to accomplish multifunctionality and how the different functions work together is incomplete. Numerous ecologically justified river restoration projects may actually be driven by aesthetic and recreational preferences that are largely unexamined. At the same time river projects originally designed for aesthetics or recreation are now attempting to integrate habitat and environmental considerations to make the rivers more sustainable. Through in-depth study of a variety of constructed river landscapes - including dense historical river bend designs, artificial whitewater, and urban stream restoration this dissertation analyzes how aesthetic, ecological, and recreational functions intersect and potentially conflict. To explore how aesthetic and biophysical processes work together in riverscapes, I explored the relationship between one ideal of beauty, an s-curve illustrated by William Hogarth in the 18th century and two sets of river designs: 18th century river designs in England and late 20th century river restoration designs in North America. I used two quantifiable variables, sinuosity and symmetry, to compare the ideal curve of beauty to the designed river curves. Hogarth's s-curve and river restoration meanders had symmetrical curves. Symmetry in restoration designs represents a theoretical condition and is counter to how most natural rivers meander. A second aesthetic-ecological study examined whether 18th century English landscape design represents design with nature. By tracing the persistence of Capability Brown's river designs over the past two centuries, the results show Brown's designs required maintenance and are not self-perpetuating as expected of a design based on natural processes.To evaluate the intersection of recreation and ecological functions, I conducted a case study of three urban river projects, a historical study of artificial whitewater designs, and an observational study of summertime whitewater park use. By comparing the ecological and social impacts of three urban river projects (Cheonggyecheon in Seoul, South Korea, the South Platte Greenway in Denver, United States, and the Isar River in Munich, Germany), one emerged as moving towards multifunctional planning and design. The Isar River project was unique because the planners and designers used a dynamic guiding image, gave the river room to roam, and allowed some dynamic biophysical processes to occur. The selection of the guiding image for the Isar restoration was fortuitously a publicly valued stream reach for its aesthetics and existing recreational use. The South Platte Greenway, which contains a whitewater park, illustrates a riverscape made primarily for recreation. The history of artificial whitewater designs evolved since the 1970s to a point in 2000 when the Sydney Olympic Whitewater Course was disconnected from a stream to create a fair playing field for competitors where all of the whitewater variables could be controlled. Meanwhile, instream whitewater parks began to include habitat and fish passage considerations in the engineered wave structures. Observations of whitewater park use and surveys of park user's perceptions of the parks revealed that kayakers represent only a small fraction of park users and overall use evinced no clear relationship to streamflow but varied with air and water temperature. Summer streamflow provisions for whitewater parks potentially limits the diversity of instream users and the ecological function. While whitewater park users value clean water as the most important characteristic, all interviewed park users wanted the park to have a natural appearance, but they did not mind seeing concrete in the river. Understanding the patterns of recreation and perceptions of rivers in relation to biophysical processes such as streamflow or channel pattern is fundamental to achieving sustainability. The forms that people prefer--perhaps because they are beautiful--and a local-level understanding of recreational use need to be considered alongside the physical and ecological patterns and processes of rivers, the domain of landscape ecology and river science. Combining ground level research and perception studies with environmentally based landscape planning can create multifunctional landscapes. For previously impacted rivers in developed areas, multifunctional riverscape planning and design offers a sustainable development solution
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Metropolitan estuaries and sea-level rise: Adaptive environmental planning solutions at the regional scale
Full text linkWide estuaries are natural magnets for urban development. Several of the World’s major cities developed around estuaries, but at the same time encroached upon some of the most complex and vital ecosystems. Sea-level rise threatens to submerge both rare wetland habitat and essential urban areas and infrastructure. This prospect discloses the urgency of balancing urban development and environmental protection in Metropolitan Estuaries. The hard task of dealing with this threat may provide the opportunity to promote an integrated approach to regional planning, where the necessary adaptation of cities to sea-level rise could equally promote the preservation, or even the enhancement, of wetland habitat.The two case study metropolitan estuaries, San Francisco Bay (California, USA) and the Tagus Estuary (Lisbon, Portugal), share striking similarities in terms of morphology. They both host large metropolitan areas and important wetland ecosystems. Nevertheless, a finer analysis of development patterns reveals crucial differences in the extent of shoreline alteration and types of land use that now encroach upon natural estuarine habitat. The comparative study of both estuaries provides mutually beneficial insights on the shortcomings of each system, and helps identify opportunities to enhance coastal zone management, adaptive governance and environmental planning efforts.The evolution of both estuaries throughout the Holocene is reconstructed, with special emphasis on the process of anthropogenic alteration. While this impact has been significant and continuous in the Tagus Estuary for over two millennia, large scale disturbance of the San Francisco Bay was concentrated in the last two centuries. The legal frameworks that have guided, with varying degrees of effectiveness, the process of wetland reclamation and landfilling share a common ancestry in the Roman Law. These have evolved continuously in Lisbon and the State has upheld with relative success the provision to keep estuarine lowlands in public control, even as they were steadily transformed to farmland. In San Francisco, a period of deep disturbances over the Sacramento River’s hydrology was coupled with extremely fast and under regulated development of lowlands. During a short period, the property of these lands, which would theoretically fall within the Public Trust, was transferred to local governments and private landowners, which led to their steady transformation onto salt ponds, industrial zones and even residential neighborhoods. As a consequence, the Bay Area now has extensive developed areas at very low elevations, vulnerable to low levels of sea-level rise, and remaining wetlands are now heavily encroached upon by urban development. Around the Tagus Estuary, while most original wetlands have long been drained for farmland, the remaining patches are adjacent to non-urban land uses, which could facilitate future efforts of restoration or allow wetland migration with rising seas.A comparative modelling of sea-level rise flooding over existing land uses reveals that, while around the Tagus Estuary most reclaimed lowlands are reserved for farmland and urban development over landfill is limited, the extent of developed urban areas at very low elevations is much greater around the SF Bay, which renders the region more vulnerable to early stages of SLR. Nonetheless, both cities have begun to incorporate climate adaptation onto their main environmental planning blueprints, for which they can be seen as early adopters of local sea-level rise adaptation strategies. Through interviews with stakeholders and document analysis, the planning and decision-making exercises that led to the recent elaboration of the first Tagus Estuary Management Plan, and the Bay Plan Climate Change Amendment, are analyzed and discussed.Lisbon benefits from a very simple, top-down, planning structure, with a handful of public entities directly communicating and articulating stakes and approaches along the planning process. A lack of transparency as to some specific interventions and a still somewhat incipient tradition of public participation have contributed to protract the Plan’s final approval.The Bay Area institutional framework is well-used to collaborative planning efforts, which are usually successful in articulating conflicting interests, but are prone to limitations derived from narrow, and often difficult to expand, mandates for environmental planning agencies, within an extremely complex, multi-level, governance structure involving three levels of government and very active interest groups. While broad mitigation/adaptation strategies are decided at the National or State levels, the actual implementation of SLR adaptation measures often require a great deal of involvement of local actors. Given that it is at this juncture that adaptation takes a concrete spatial expression, this is also the moment when land-use conflicts arise. Local governments are left with much of the burden of mediating competing interests, between urban development, environmental protection, and other social demands. In some instances, the prospect of shoreline development may be very attractive for both property owners/developers and local governments, given the potential land value and economic benefits, but these have to be weighed against the medium-/long-term costs of defending these assets from rising sea-levels.In San Francisco Bay, there is an increasing awareness of the challenges posed by SLR, but the institutional arrangements are complex, and communication between the different public agencies/departments is not always as streamlined as it could be. Some agencies and departments need to adapt their procedures in order to remove institutional barriers to adaptation, but path dependence is an obstacle. The several projects where different federal and state agencies are partnered with local governments highlight the benefits of a more frank and regular communication between public actors. It also emphasizes the benefits of a coordination of efforts and strategies, something that was eroded in the transition from government-led policies to a new paradigm of local-based adaptive governance.Whereas the articulation of public actors is often easy to address by increasing communication and coordination, conflicts involving private landowners and developers may be much complicated by the threat of litigation. The lack of a strong legal backing to public environmental protection mandates is a major obstacle to shoreline planning around the Bay and elsewhere, and this is highlighted by the extreme caution of some public agencies in upholding their jurisdictions over private property. Environmental NGOs have, in the case of California, a big role to play, as they are able to resort to the same legal and lobbying instruments as the developers, and may help even-out the field between public stakeholders with limited legal and economic resources, and powerful private developers with nothing to lose. There is seemingly a sense of urgency in pushing for the development of shoreline properties, as public opposition to development on locations exposed to SLR is most likely to increase in the coming decades. At the same time, NGOs and public agencies are aware of the stress wetlands will be under as the rates of SLR increase towards the end of the century.“Green”, or ecosystem-based, adaptation is already on the way around the Bay. Large scale wetland restoration projects have already been concluded, and further action now often requires articulation with the reinforcement of flood defense structures, given the level of urban encroachment. While levee setback, or removal, would provide greater environmental benefit, the need to protect urban areas and infrastructure has led to the trial of ingenious solutions for promoting wetland resilience while upgrading the level of protection granted by levees
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Analyzing Adaptation to Sea Level Rise and Stormwater Quality in Social-Ecological Systems
No full textThis dissertation adopts a social-ecological systems approach to examine two water-related problems resulting from global environmental change driven by urbanization and climate change. The first problem is the need to adapt coastal regions to rapidly rising seas; the second problem is the degradation of stormwater quality entering water bodies. In taking a social-ecological systems approach, this dissertation considers how human and biophysical processes are interconnected and interactive in shaping the outcomes of these problems. To do so, this dissertation combines methods, knowledge, and theory from environmental planning, ecology, and environmental engineering. On coastal adaptation to sea level rise, this dissertation develops an analytical framework to examine the interconnections between human and non-human adaptation. The analytical framework identifies positive and negative shifts in vulnerability between human and non-human actors across a number of dimensions. It is deployed in a literature review on the topic of wetland migration mainly focused on the US, showing multiple ways that humans and wetland ecosystem shift vulnerabilities between them across physical, economic, environmental, social, cultural, and institutional dimensions. But it also shows that synergies are possible between human and wetland adaptation to sea level rise. Whether positive or negative, these vulnerability shifts reflect particular biophysical, historical, and social contexts and can operate on multiple spatial and temporal scales.Next, the dissertation investigates in depth one kind of interconnection between human and non-human adaptation. Using an ecological model, it explores how the hydrodynamic effects of hardening or softening shorelines could 1) influence the ability of coastal wetlands to adapt to sea level rise and 2) change vegetative cover. Although focused on a case study in San Francisco Bay, California, US, the methods address multiple coastal contexts. It contributes an understanding of how human actions to adapt to sea level rise by hardening or softening shorelines could create both positive and negative ecological impacts to wetlands at a regional scale. It exposes tradeoffs that decision-makers may need to consider that span spatial and temporal scales.Finally, on stormwater quality, this dissertation analyzes the relationships between human and natural processes in producing stormwater pollution. The analysis centers on a large dataset of stormwater samples from 182 watersheds in 26 metropolitan areas in the US, combined with other ancillary datasets. It uses machine learning to identify patterns in the data that quantify how land use and land cover (human factors), along with climate and weather (natural factors), relate to stormwater pollution. These patterns are described as relationships between geography and stormwater “signatures,” defined as unique combinations of stormwater contaminants. This work advances an understanding of how contaminants in stormwater co-occur together as signatures, and how those signatures are then related to human and natural factors. It also contributes a comparative understanding of stormwater quality across the US. Overall, this dissertation demonstrates complex interconnections between human and biophysical systems that support the need for cross-sectoral, cross-scalar environmental planning
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The Role of Landscape Heterogeneity in Urban Runoff Generation, Modeling, and Management
Full text linkUrban areas -- often characterized by their impervious surfaces -- have a disproportionate impact on the hydrologic regimes of associated river systems and their water quality. Over the past century, enormous amounts of scientific research and funding has been allocated towards the effective management of urban runoff. Despite these investments, however, it continues to confound engineering solutions, causing pollution, flooding, and habitat destruction. These challenges are compounded by the need to plan for non-stationarity in climate, shifts in hydrologic regimes and land use, and inter-dependencies between ecological, hydrological, and human systems. The first chapter of the dissertation provides relevant background on the challenges associated with effectively managing the hydrologic impacts of urbanization. These challenges arise from some of the assumptions that have driven management decisions over the past century, namely: (1) that production of urban runoff is dominated by overland flow across impervious surfaces; and (2) that overland flow in urban areas is determined by the total quantity of impervious area, rather than their patterns with interspersed previous areas, and characteristics of these pervious areas.The second chapter of the dissertation explores the first of these assumptions, and asks: What are the implications of different hydrologic processes for the production of urban stormwater and its management? The assumption that runoff in urban areas is driven by impervious surfaces has dominated our understanding and management of urban catchments for decades. Through a literature review and theoretical framework, this chapter identifies the range and drivers of hydrologic processes in urban settings, characterizes their associated spatial and temporal scales, and shows how a mismatch in process and management scales can lead to unintended outcomes. It offers guidance for adaptation of the current `risk-based' approach for managing urban runoff across the different runoff processes and scales. The third chapter of the dissertation explores the second assumption, and asks: How does landscape variability impact the spatial production of urban runoff? This chapter uses a combination of hydrologic modeling, machine learning, and geospatial analysis to determine the extent to which different landscape factors moderate runoff contribution from impervious areas. Results show that impervious surface contribution to runoff (or, `hydrologic connectivity of impervious areas', HCIA), is controlled by spatial variability of pervious area characteristics and temporal variability in pervious area conditions and rainfall. To enable such analysis in practice and for urban planning purposes, this chapter presents a geospatial tool for estimation of HCIA at watershed scales.The fourth chapter of the dissertation explores the implications of the second assumption for the predictive accuracy of semi-distributed hydrologic models, and asks: How do land cover characteristics and climate variability impact calibration and predictive accuracy of semi-distributed runoff models? Semi-distributed models represent landscape heterogeneity, such as pervious and impervious patterns, with unobservable effective parameters. Through comparative `virtual experiments', this chapter demonstrates that the predictive accuracy of a widely used urban hydrological model (SWMM) can be affected by calibrated parameter dependence on soil, storm, and landcover characteristics. The inter-dependencies between the forcing parameters and calibration parameters can result in significant prediction error when a calibrated model is applied to predict runoff from novel climate and landcover conditions. The research presented in this dissertation will help municipalities and flood managers identify applicable policies, design standards, and planning mechanisms for urban runoff management. It also points to a need for a better understanding of the process (or processes) by which runoff is generated, the effects of human alteration and management on these processes, and the sensitivity of such processes to ongoing changes in climate, land use, and management
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Metrics and Approaches for Quantifying Ecosystem Impacts and Restoration Success
Full text linkAccurate quantification of ecosystem change is essential for effective environmental management. However, the selection of meaningful indicators of impacts to ecosystems and of benefits from restoration is not standardized. In this dissertation I investigate 1) the applicability of using sediment reduction as an indicator of the cumulative impacts of dams in the Mekong River basin; 2) review and evaluate the meaningfulness of common river restoration evaluation metrics such as macroinvertebrate diversity and richness in habitat heterogeneity projects, and 3) demonstrate the usefulness of prey availability as an indicator of restoration success in riparian restoration projects along the lower Colorado River. 1) The Mekong River, largely undeveloped prior to 1990, is undergoing rapid dam construction. Seven dams are under construction on the mainstem in China and 133 are proposed for the Lower Mekong River and tributaries. The question is what cumulative effect will these dams have on sediment movement in the watershed. There was a lack of data on sediment yields in some portions of the basin so we delineated nine distinct geomorphic regions, for which we estimated sediment yields based on geomorphic characteristics, tectonic history, and the limited sediment transport data available. We then applied the 3W model to calculate cumulative sediment trapping by these dams, accounting for changing trap efficiency over time and multiple dams on a single river system. Under a ‘‘definite future’’ scenario of 38 dams (built or under construction), cumulative sediment reduction to the Delta would be 51 percent. Under full build-out of all planned dams, cumulative sediment trapping will be 96 percent. That is, once in-channel stored sediment is exhausted, only 4% of the predam sediment load would be expected to reach the Delta. We then combined geomorphic assessments of the Mekong channel and delta with the 3W model’s results of sediment trapping to forecast geomorphic change. We expect the biggest changes to occur along alluvial reaches, though stripping of thin sediment deposits in bedrock reaches may also have significant consequences for benthic invertebrates, fishes, and other aquatic organisms dependent on the presence of alluvium in the channel. If all dams are built as proposed, the resulting 96% reduction in sediment supply would have profound consequences on productivity of the river and persistence of the delta landform itself and suggests that strategies to pass sediment through/around dams should be explored to reduce the magnitude and consequences of downstream sediment starvation. In this first case, we use sediment reduction as an indicator of watershed impairment. Though many complexities (e.g. oil, gas, and groundwater withdrawals, routing of sediment through deltas) influence coastal erosion, we found sediment reduction to be a meaningful worldwide indicator. We compiled sediment data from 24 worldwide deltas and results indicate a positive relationship of sediment reductions to deltas resulting in decreased rates of aggradation. In particular, sediment reductions of more than 80% are consistent in almost complete cessation in aggradation rates. The full-build scenario of Mekong dam building would result in 96% reduction in sediment delivery and we would then expect an almost complete cessation in sediment deposition in the delta.2) In a search for accountability, the effectiveness of many large restoration programs has been evaluated using standard such as acres or length of stream restored per dollar, but this was recognized to be inadequate. Another common restoration metric is based on the common goal of enhancing ecosystems by creating more complex and varied habitats. Although widely implemented, there is little understanding of the success to date of such projects. There is also little agreement on the best approaches and metrics for quantifying success. We reviewed the methods of 26 peer-reviewed evaluation studies and investigated the influence of study design on evaluation results. Of the 26 studies, many did not implement rigorous study designs. For example, only 46% of the studies used quantitative measures of habitat, 62% included only one year of post-project monitoring, 46% used zero or one control (unrestored) sites, and 62% did not include reference (best potential ecological condition) sites. Studies that used more rigorous designs (e.g. sampled more years, measured habitat quantitatively) were more likely to find increased ecosystem diversity and richness in response to heterogeneity enhancement. More fundamentally, all studies used macroinvertebrate diversity and/or richness as the measure of ecological success. We question the logic of assuming that reach-scale diversity or richness is useful as a universal measure of ecosystem integrity. Monitoring and evaluation should first establish hypotheses and conceptual models based on watershed perturbations and set specific milestones towards a sustainable, dynamic, and healthy ecosystem. Restoration targets should be defined based on regional, historical, and analytical reference conditions and by conducting manipulative experiments that can help predict ecosystem responses to restoration actions. It is important to understand if habitat heterogeneity projects are succeeding, but it is not yet possible to draw general conclusions. Metrics to evaluate performance of stream restoration projects need more rigor and should be tied to project specific goals. Generic metrics may yield misleading results. 3) Below Hoover Dam, riparian vegetation along the Colorado River was extensively cleared for agriculture. Thus, large areas of habitat were lost to clearing. Moreover, the functions of the ecosystem were compromised as the connections of the river to its floodplain were severed by levees, flow reduction by dams and diversions, channel incision, and groundwater pumping. Subsequently, native species declined, including the southwestern willow flycatcher (Empidonax traillii extimus) that nests along rivers in dense riparian thickets. The Lower Colorado River Multi Species Conservation Program (MSCP) was established in 2005 to re-create habitat for 26 species including the flycatcher, but the benefits of these restoration sites for target species have not been quantified. Many MSCP projects have involved extensive plantings of willow (Salix exigua, S. gooddingii] and cottonwood [Populus fremontii) on high terraces disconnected from the river by levees. MSCP projects goals are specified as acres of habitat, but to support functioning food webs, riparian ecosystems in arid regions require a subsidy of aquatic insects. We documented prey availability for the southwestern willow flycatcher in constructed habitats as an indicator of their potential to support the species. The number of aquatic insects, proportion of aquatic insects, total number of insects, and number of insect orders all decreased with distance from the river, and the decrease occurred within the first 100 meters from the river. The MSCP cottonwood-willow plantation (more than 500 m from the river) at Cibola National Wildlife Refuge had 86% fewer total insects (p=0.055), 97% fewer aquatic insects (p=.032), and only half as many insect orders (p=0.015) as sites adjacent to the river. In the plantation, only 16% of the insects were aquatic vs. 59% aquatic at the river’s edge (p=.063). Our results suggest that restoration success (and the recovery of southwestern willow flycatcher) may be limited by prey availability and that future riparian plantings should be concentrated along the river or tributary channels. Southwestern willow flycatchers have not been nesting in MSCP plantations. Thus the metric of “acres restored” is inadequate to capture ecosystem function. More meaningful metrics would identify potential limitations in ecosystems (such as prey availability) so that habitat suitability and functionality can be assessed and adaptively managed. Together, the chapters of this dissertation highlight different approaches and considerations for the quantification of ecosystem impacts and restoration success. The field of ecosystem quantification is still far from adopting universally appropriate indicators of change, but this dissertation seeks to highlight problems in current approaches, and to demonstrate useful models and approaches
Using environmental radionuclides, mineral magnetism and sediment geochemistry for tracing and dating fine fluvial sediments
No full textThis chapter focuses on the measurements (the tools), namely gamma‐emitting radionuclides, environmental magnetism and sediment geochemistry. By studying the post‐fallout redistribution and fate of these fallout radionuclides, it is possible to obtain essentially unique information on soil and sediment redistribution and, therefore, on erosion and deposition rates. The chapter reviews the various approaches that can be used to obtain information on sediment source. The set of sediment properties to be included in a composite fingerprint is frequently selected empirically. The chapter presents a case study illustrating combining fallout radionuclide measurements and sediment source fingerprinting for sediment budgeting: Pang and Lambourn Catchments, United Kingdom. The tools are often used by geomorphologists to date recent sedimentary deposits, document rates of soil and sediment redistribution, establish sediment sources, generate sediment budgets and reconstruct the functioning of past sediment systems
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