New River Inlet DRI: Observations and Modeling of Flow and Material Exchange & Field and Numerical Study of the Columbia River Mouth

LONG-TERM GOALS: The goal of our effort is to understand river and inlet fluid dynamics through in situ field observations and model validation.N0001411WX20962; N0001412WX20498; N0001413WX20480; N000141110376, N000141010379, N00014131018

Historical evolution of the Columbia River littoral cell

This paper details the historical coastal evolution of the Columbia River littoral cell in the Pacific Northwest of the United States. Geological data from A.D. 1700 and records leading up to the late 1800s provide insights to the natural system dynamics prior to significant human intervention, most notably jetty construction between 1885 and 1917. All reliable surveys, charts, and aerial photos are used to quantify decadal-scale changes at the three estuary entrances and four sub-cells of the littoral cell. Shoreline, bathymetric, and topographic change over three historical intervals—1870s–1920s, 1920s–1950s, and 1950s–1990s—are integrated to provide an understanding of sediment-sharing relationships among the littoral cell components. Regional morphological change data are developed for alongshore segments of approximately 5 km, enabling comparisons of shoreline change to upper-shoreface and barrier volume change within common compartments. The construction of entrance jetties at the Columbia River (1885–1917) and Grays Harbor (1898–1916) has profoundly affected the evolution of the littoral cell, and has accentuated the morphological coupling between the inlets, ebb-tidal deltas, shorefaces, and barriers. The jetties induced erosion of the inlets and offshore migration of ebb-tidal deltas. The change in boundary conditions at the entrances enabled waves to rework the flanks of ebb-tidal deltas and supply enormous quantities of sand to the adjacent coasts. Over several decades the initial sand pulses have been dispersed alongshore up to tens of kilometers from the estuary entrances. Winter waves and coastal currents produce net northward sediment transport across the shoreface while summer conditions tend to induce onshore sediment transport and accumulation of the upper shoreface and barriers at relatively high rates. Historical shoreline progradation rates since jetty construction are approximately double the late prehistoric rates between Kaminsky et al., MGSI 3 of 107 9/15/2009 1700 and the 1870s. Erosion rates of the mid- to lower shoreface to the south of the jettied estuary entrances have typically been greater than the accumulation rates of the upper shoreface and barrier, suggesting that the lower shoreface has been an important source of littoral sediments over decadal and longer time scales. Until recent decades, sediment supply from the ebb-tidal delta flanks and lower shoreface has largely masked the decline in Columbia River sediment supply due to flow regulation and dredging disposal practices. With the contemporary onset and expansion of coastal erosion adjacent to the jettied estuary entrances, proper management of dredged sediment is imperative to mitigate the effects of a declining sediment budget.Keywords: Washington State, Columbia River littoral cell, coastal evolution, sediment budget, shoreline change, large-scale coastal behavior, Oregon Stat

Integrated modeling framework to quantify the coastal protection services supplied by vegetation

Vegetation can protect communities by reducing nearshore wave height and altering sediment transport processes. However, quantitative approaches for evaluating the coastal protection services, or benefits, supplied by vegetation to people in a wide range of coastal environments are lacking. To begin to fill this knowledge gap, we propose an integrated modeling approach for quantifying how vegetation modifies nearshore processes—including the attenuation of wave height, mean and total water level—and reduces shoreline erosion during storms. We apply the model to idealized seagrass-sand and mangrove-mud cases, and illustrate its potential by quantifying how those habitats reduce water levels and sediment loss beyond what would be observed in the absence of vegetation. The integrated modeling approach provides an efficient way to quantify the coastal protection services supplied by vegetation and highlights specific research needs for improved representations of the ways in which vegetation modifies wave-induced processes.Keywords: coastal vegetation, wave setup and runup, coastal erosion, mud bed scou

Nearshore subtidal community response during and after sediment disturbance associated with dam removal

Dam removal is used increasingly to restore aquatic ecosystems and remove unnecessary or high-risk infrastructure. As the number of removals increases, there is a growing understanding about the hydrologic, geomorphic, and ecological responses to these removals. Most dam removal studies, however, focus on river and watershed responses to dam removal. The removal of two dams on the Elwha River provided a unique opportunity to characterize the response of nearshore (coastal) ecosystems. We conducted SCUBA surveys between 2011 and 2022 to quantify trajectories of change in a nearshore ecosystem during and after dam removal. We focused on the degree to which the abundances of kelp, benthic invertebrates, and fish changed in response to patterns of sediment fluxes during and after dam removal. Our findings point to two pathways of response depending on the disturbance mechanism and species type. Sites with persistent sediment deposition were characterized by wholesale community changes that did not recover to a before dam removal condition. Instead, the sites were colonized by new species that were largely absent prior to dam removal. Sites that experienced high turbidity but lacked persistent seafloor deposition were primarily characterized by a reduction in the abundance of kelp and other algae during dam removal and a rapid recovery after sediment flux to the nearshore declined. Dam removal influences on invertebrates and fish at these sites were more variable, benefiting some species and disadvantaging others. In addition to dam removal, sea star wasting syndrome and a marine heatwave exerted distinct controls on subtidal communities during the same period. The loss of the predatory sea star Pycnopodia helianthoides was associated with gains in some of its prey species, and kelp community changes reflected regional trends in ocean temperature and kelp abundance. The results presented here have important implications for understanding the response of marine ecosystems to future dam removals and similar sediment perturbation events

Progressing from multidisciplinary to interdisciplinary restoration science: monitoring and applied studies on the Nisqually River Delta

Restoration science is often described as an ultimate test of ecological theory; assessing the value of restoration actions is challenged by difficulties in measuring complex interactions between restored physical processes and the response of biological resources. Yet, demonstrating the value of restoration is a key to sustaining future public investment, especially in light of uncertainty of future climate change effects. At the Nisqually River Delta, a restoration partnership between the U. S. Fish and Wildlife Service Nisqually National Wildlife Refuge (Refuge), the Nisqually Indian Tribe (Tribe), and Ducks Unlimited culminated in re-established tidal flow to 360 ha of historic floodplain and delta representing the largest estuarine restoration in the Pacific Northwest. Restoration of this large delta was expected to result in a substantial improvement in ecological functions and services in southern Puget Sound. The goal of our scientific team, led by the U. S. Geological Survey (USGS) for the project partners, was to assess the biophysical response to restoration. Science objectives were built into a monitoring framework to include hydrodynamics, geomorphology, sedimentation and nearshore processes with vegetation, invertebrate food resources, waterbird, and fisheries. Our science partners included the U. S. Geological Survey, Refuge, Tribe, non-governmental organizations, and universities representing several disciplines. Funding the science was challenging, since as with most wetland restoration projects, adequate funds are rarely included in costs. Instead, the managers and scientists worked together to raise funds through special funds and competitive grants including addressing climate change. With this funding model, a major challenge for the team was communicating and sustaining a vision to make separate multidisciplinary efforts into unified interdisciplinary science. Here, we use lessons learned from early results of the Nisqually River Delta restoration to discuss restoration science in planning processes, funding costs and approaches, monitoring versus applied studies, and advancing interdisciplinary findings from multidisciplinary efforts

Wind and tidal forcing of a buoyant plume, Mobile Bay, Alabama

Abstract AVHRR satellite imagery and in situ observations were combined to study the motion of a buoyant plume at the mouth of Mobile Bay, Alabama. The plume extended up to 30 km from shore, with a thickness of about 1 m. The inner plume, which was 3–8 m thick, moved between the Bay and inner shelf in response to tidal forcing. The tidal prism could be identified through the movement of plume waters between satellite images. The plume responded rapidly to alongshore wind, with sections of the plume moving at speeds of more than 70 cm s−1, about 11% of the wind speed. The plume moved predominantly in the direction of the wind with a weak Ekman drift. The enhanced speed of the plume relative to normal surface drift is probably due to the strong stratification in the plume, which limits the transfer of momentum into the underlying ambient waters

Habitat suitability for eelgrass following large scale tidal restoration on the Nisqually Delta

Large-scale estuary restoration, such as the removal of dams or dikes, can alter nearshore processes and provide an opportunity to study how ecosystems respond to changes in the physical environment. In this study, we quantify changes in the spatial distribution of eelgrass Zostera marina following a 2009 dike-removal project that restored tidal processes to over 350 ha of the Nisqually River delta. We produced high resolution maps of eelgrass percent cover, depth distribution, and nearshore bathymetry from surveys performed in 2012 and 2014 using a Biosonics 430 kHz single-beam echosounder and survey-grade global navigation satellite system. A coupled hydrodynamic and sediment transport model is used to characterize hydrodynamics (water levels, tidal currents, waves) and water column properties (salinity and turbidity) before and after dike removal. Model simulations suggest that removal of the dikes increased the tidal prism and altered sediment transport pathways on the delta. We explore how modeled changes in the hydrodynamics, turbidity, and morphology following restoration relate to eelgrass cover, depth distribution, and habitat suitability for eelgrass on the Nisqually delta. Such relationships provide insight into the physical mechanisms driving ecosystem responses and can improve the capacity to predict changes in nearshore habitats following restoration or other land-scape modifications including climate change