Urban 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.

Society 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.

AbstractWater-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, Chair

According 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.

Accurate 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.

There are significant problems in the management of coarse sediment (sand and gravels) in regulated rivers of California. Unfortunately, these have been generally treated (or ignored) on a case-by-case basis, however, the effects are pervasive and profound, with substantial costs and severe environmental impacts. Problems arise due to the human manipulation of coarse sediment through reservoir construction, which blocks the movement of coarse sediment down the river, and through instream gravel mining, which removes this material from the river system for use primarily in construction-related projects. Impacts identified include: bed material coarsening, channel incision, channel geometry changes, hydrologic regime alterations, and changes in transport of sediment. Many of these impacts result in damage to or destruction of anadromous fisheries habitat, and are partly responsible for the dramatic declines in anadromous fisheries resources in the last 50 years. other types of impacts include damage to instream structures, loss of riparian habitat, and increased risk of damaging channel changes.

We documented these types of impacts on a set of major river drainages on the western slope of the Sierra Nevada, along with several rivers in the Coast Ranges. We have reviewed the institutional and regulatory framework for both reservoir operation and instream mining, finding inconsistencies and lack of standard requirements for monitoring and mitigation of environmental impacts. various techniques that comprise the existing piecemeal approach to restoration and enhancement of coarse sediment resources were inventoried. We propose alternative strategies for management of coarse sediment that

Wide 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.

Large 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.