Heida L. Diefenderfer

Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: I. Along-channel Water Level Variations, Pacific Ocean to Bonneville Dam

This two-part paper provides comprehensive time and frequency domain analyses and models of along-channel water level variations in the 234-km-long Lower Columbia River and Estuary (LCRE) and documents the response of floodplain wetlands thereto. In Part I, power spectra, continuous wavelet transforms, and harmonic analyses are used to understand the influences of tides, river flow, upwelling and downwelling, and hydropower operations (“power-peaking”) on the water level regime. Estuarine water levels are influenced primarily by astronomical tides and coastal processes and secondarily by river flow. The importance of coastal and tidal influences decreases in the landward direction, and water levels are increasingly controlled by river flow variations at periods from ≤1xa0day to years. Water level records are only slightly nonstationary near the ocean, but become highly irregular upriver. Although astronomically forced tidal constituents decrease above the estuary, tidal fortnightly and overtide variations increase for 80–200xa0km landward, both relative to major tidal constituents and in absolute terms. Near the head of the tide at Bonneville Dam, strong diel and weekly fluctuations caused by power-peaking replace tidal daily (diurnal and semidiurnal) and fortnightly variations. Tides account for 60–70xa0%, river flow and seasonal processes 5–20xa0%, and weather 2–4xa0% of the total variance in the seaward 60xa0km of the system. In the landward 70xa0km of the LCRE, seasonal-fluvial variations account for 80–90xa0% of the variance, power-peaking 1–6xa0%, and tides <5xa0%. In Part II, regression models of water levels and inundation patterns are used to understand the distribution of floodplain wetlands, and a system zonation is defined based on bedrock geology, hydrology, and biota.

Multiscale Analysis of Restoration Priorities for Marine Shoreline Planning

Planners are being called on to prioritize marine shorelines for conservation status and restoration action. This study documents an approach to determining the management strategy most likely to succeed based on current conditions at local and landscape scales. The conceptual framework based in restoration ecology pairs appropriate restoration strategies with sites based on the likelihood of producing long-term resilience given the condition of ecosystem structures and processes at three scales: the shorezone unit (site), the drift cell reach (nearshore marine landscape), and the watershed (terrestrial landscape). The analysis is structured by a conceptual ecosystem model that identifies anthropogenic impacts on targeted ecosystem functions. A scoring system, weighted by geomorphic class, is applied to available spatial data for indicators of stress and function using geographic information systems. This planning tool augments other approaches to prioritizing restoration, including historical conditions and change analysis and ecosystem valuation.

Restoring Resiliency: Case Studies from Pacific Northwest Estuarine Eelgrass (Zostera marina L.) Ecosystems

An objective of many ecological restoration projects is to establish resilience to disturbances. Eelgrass (Zostera marina L.) represents a useful model to evaluate resilience because the plant community is dominated by one species and the estuarine environment is dynamic. Our studies of planted and reference plots used shoot density monitoring data from three projects spanning 3 to 12xa0years. Data show that eelgrass can recover from major shifts in pond position and shape on sandflats, as well as natural disturbances causing >20-fold change in density. However, cumulative effects of multiple stressors on unestablished plantings suggest algal blooms of unusual magnitude can tip normally marginal conditions to unfavorable. Thus, potential resilience appears to depend on landscape conditions. A dynamic equilibrium was evinced in even the deepest, lowest-density plantings, probably associated with light-mediated carrying capacity and vegetative belowground production characteristic of the Pacific Northwest. We recommend eight resilience-related planning elements to reduce uncertainties in eelgrass restoration.

Application of the diminishing returns concept in the hydroecologic restoration of riverscapes

Increasing our knowledge of unplanned anthropogenic synergies, which have affected ecosystems since prehistory, may facilitate ecological restoration. Predictive relationships between spatial pattern and ecosystem processes and functions in riverscapes have the potential to inform applied ecosystem restoration planning and design, where principles are needed for large-scale river reconnections. Although synergistic, additive, and antagonistic interactions affect ecosystems, the role of such interactions in restoration rarely has been evaluated. Using hydrodynamic modeling, we experimentally examine the aggregate effects of reestablishing hydrologic connections in a tidal freshwater tributary on the floodplain of the Columbia River, USA, which is currently undergoing dike breaching to restore juvenile salmon habitat. Sets of dike breaches yielded average wetted floodplain areas conforming to a two-parameter hyperbola (r2xa0=xa00.93). These findings demonstrate that the yield of inundated floodplain habitat area from dike breaching can conform to the well-established “law of the diminishing increment,” developed in the study of agriculture and economics. Furthermore, the influence of spatial configuration on yield was strong, with midstream breaches yielding 63% and upstream breaches 2% of the wetted area produced by downstream breaches, although conditions of extreme high river flow were not studied. Opening the dike at 26% of the historically present channel outlets provided the maximum return on investment for the study riverscape. Verification of this relationship elsewhere in tidal areas of the Columbia River and on other large river floodplains would contribute to cost-benefit analyses in ecological restoration program planning and have implications for effects on biota.

Research, Monitoring, and Evaluation for the Federal Columbia River Estuary Program.

The purpose of this document is to describe research, monitoring, and evaluation (RME) for the Federal Columbia River Estuary Program, hereafter called the Estuary Program. The intent of this RME effort is to provide data and information to evaluate progress toward meeting program goals and objectives and support decision making in the Estuary Program. The goal of the Estuary Program is to understand, conserve, and restore the estuary ecosystem to improve the performance of listed salmonid populations. The Estuary Program has five general objectives, designed to fulfill the program goal, as follows: (1) Understand the primary stressors affecting ecosystem controlling factors, such as ocean conditions and invasive species. (2) Conserve and restore factors controlling ecosystem structures and processes, such as hydrodynamics and water quality. (3) Increase the quantity and quality of ecosystem structures, i.e., habitats, juvenile salmonids use during migration through the estuary. (4) Maintain the food web to benefit salmonid performance. (5) Improve salmonid performance in terms of life history diversity, foraging success, growth, and survival. The goal of estuary RME is to provide pertinent and timely research and monitoring information to planners, implementers, and managers of the Estuary Program. The goal leads to three primary management questions pertainingmorexa0» to the main focus of the Estuary Program: estuary habitat conservation and restoration. (1) Are the estuary habitat actions achieving the expected biological and environmental performance targets? (2) Are the offsite habitat actions in the estuary improving juvenile salmonid performance and which actions are most effective at addressing the limiting factors preventing achievement of habitat, fish, or wildlife performance objectives? (3) What are the limiting factors or threats in the estuary/ocean preventing the achievement of desired habitat or fish performance objectives? Performance measures for the estuary are monitored indicators that reflect the status of habitat conditions and fish performance, e.g., habitat connectivity, survival, and life history diversity. Performance measures also pertain to implementation and compliance. Such measures are part of the monitoring, research, and action plans in this estuary RME document. Performance targets specific to the estuary were not included in the 2007 draft Biological Opinion.«xa0less

Storm‐driven particulate organic matter flux connects a tidal tributary floodplain wetland, mainstem river, and estuary

The transport of terrestrial plant matter into coastal waters is important to regional and global biogeochemical cycles, and methods for assessing and predicting fluxes in such dynamic environments are needed. We investigated the hypothesis that upon reconnection of a floodplain wetland to its mainstem river, organic matter produced in the wetland would reach other parts of the ecosystem. If so, we can infer that the organic matter would ultimately become a source for the food web in the mainstem river and estuary. To accomplish this, we adapted numerical hydrodynamic and transport modeling methods to estimate the mass of particulate organic matter (POM) derived from the annually senescent aboveground parts of herbaceous marsh plants (H-POM). The Finite-Volume Community Ocean Model (FVCOM), parameterized with flow, tide, and aboveground biomass data, simulated H-POM mobilization from fluid shear stress during tidal exchange, flooding, and variable river flow; entrainment into the water column; transport via channel and overland flow; and entrapment when wetted surfaces dry. We examined export from a recently reconnected, restoring tidal emergent marsh on the Grays River, a tributary to the Columbia River estuary. Modeling indicated that hydrologically reconnecting 65xa0ha at the site resulted in export of about 96xa0×xa0103 xa0kg of H-POM, primarily during pulsed storm flooding events in autumn and early winter. This exported mass amounted to about 19% of the summer peak aboveground biomass measured at the site. Of that 19%, about 48% (47xa0×xa0103 xa0kg) was deposited downstream in the Grays River and floodplain wetlands, and the remaining 52% (50xa0×xa0103 xa0kg) passed the confluence of the Grays River and the mainstem estuary located about 7xa0km from the study site. The colonization of the restoring study site largely by nonnative Phalaris arundinacea (reed canarygrass) may have resulted in 18-28% lower H-POM mobilization than typical marsh plant communities on this floodplain, based on estimates from regional studies of marshes dominated by less recalcitrant species. We concluded that restored floodplain wetlands can contribute significant amounts of organic matter to the estuarine ecosystem and thereby contribute to the restoration of historical trophic structure.

Facilitation of the Estuary/Ocean Subgroup for Research, Monitoring and Evaluation - FY07 Annual Report.

This annual report is a deliverable for fiscal year 2007 (FY07) for Project 2002-077-00, Facilitation of the Estuary/Ocean Subgroup (EOS). The EOS is part of the research, monitoring, and evaluation (RME) effort of the Action Agencies (Bonneville Power Administration, U.S. Army Corps of Engineers, U.S. Bureau of Reclamation) developed in response to responsibilities arising from the Endangered Species Act as a result of operation of the Federal Columbia River Power System (FCRPS). The goal of the EOS project is to facilitate activities of the estuary/ocean RME subgroup as it coordinates design and implementation of federal RME in the lower Columbia River and estuary. In FY07, EOS project accomplishments included (1) subgroup meetings; (2) participation in the estuary work group of the Pacific Northwest Aquatic Monitoring Partnership; (3) project management via the project tracking system, PISCES; (4) quarterly project status reports; and (5) a major revision to the Estuary RME Plan (new version September 2007) based on comments by EOS members and invited reviewers.