Elwha River plume, Washington
Our group conducts research all over the globe. Since 2000, we have carried out studies in Italy, Papua New Guinea, New Zealand, Chile, Brazil, Hawaii, Washington, Utah, and Alaska. Read on for more information about present and past research projects.
The largest dam removal project in U.S. history is underway on the Elwha River in northwest Washington State. Our group is studying the fate of mud released from the former reservoirs to the coastal ocean. This system provides an opportunity to study tidally dominated dispersal of fine-grained sediments, which has implications for signatures of natural and anthropogenic events like landslides, river floods, and dam removal in energetic coastal environments. We are nearing the end of a two-year field effort, and finding interesting patterns in sediment migration and deposition. Throughout 2014, we will continue to monitor for high discharge events (from winter storms and the spring freshet) in hopes of capturing a high-density gravity flow, and will also continue to track seabed changes as the river erodes reservoir sediment.
Funding source: National Science Foundation
People: Andrea Ogston, Chuck Nittrouer, Kristen Lee, Emily Eidam
Formation, reworking and accumulation of sedimentary deposits, Waipaoa Rver Shelf, New Zealand
This research examines dispersal processes and sediment dynamics that control strata production on the Waipaoa River margin, New Zealand, a MARGINS Source-to-Sink (S2S) focus site where discrete event beds have been found. This research combines numerical modeling of sediment dynamics, sediment-transport observations, and time-series coring with high-resolution sampling. A hydrodynamic / sediment transport model for the continental shelf is being developed to examine event- and seasonal-timescale dispersal and deposition. Seasonal variations in sediment transport and deposition across the Waipaoa River shelf are being studied during three ~4-month deployments of three near-bed tripods. During instrument site visits, shallow seabed coring is being conducted to reveal recently deposited strata using X-radiography, sedimentology, macrofaunal-density and radiochemistry.
Hale, R.P., Ogston, A.S., Walsh, J.P., Orpin, A.R., Sediment Transport and Event Deposition on the Waipaoa River Shelf, New Zealand. Continental Shelf Research (accepted, in press).
Funding source: National Science Foundation
People: Andrea Ogston, Rip Hale
Learn more about our work on the Amazon Tidal River at the ATRAM website.
Observing and modeling the transport and accumulation of glacially produced sediment in fjords
This research focuses on the processes and time scales of sediment production, transport, and accumulation near the calving fronts of retreating tidewater glaciers. Depositional rates and spatial patterns merit close attention because they can affect glacier stability by reducing the water depth that controls the calving rate, the surface area available for submarine melting, and the ability of tidewater glaciers to advance into deep water. The sediments produced by these glaciers also archive a high-fidelity record of changes in glacial, environmental, and tectonic conditions. We use physical measurements of ice, meltwater, sediment and seawater, seismic observations of the seabed, and seabed sampling for sediment fluxes and the preserved record of glacial retreat. These measurements are integrated into a numerical model to relate known changes in the glacial terminus position and ice speed to sediment transport and accumulation in the fjord during the period of retreat.
Boldt, K.V., Nittrouer, C.A., Hallet, B., Koppes, M., Forrest, B., Wellner, J., Anderson, J., 2013. Modern rates of glacial sediment accumulation along a 15˚ S-N transect in fjords from the Antarctic Peninsula to southern Chile, Journal of Geophysical Research- Earth Surface, 118: 1-17, doi: 10.1002/jgrf.20145.
Funding source: Quaternary Research Center
People: Chuck Nittrouer, Katie Boldt
Geologists have long recognized the importance of both river deltas and deep-ocean sedimentary systems as major sinks for large quantities of land-derived sediment, and as important components in the integrated source-to-sink transit of terrestrial sediments. Relatively few studies, however, have directed their attention at the linkage between the two, despite the fact that deltaic dynamics are almost always intimately related to deep marine sediment transport systems. This project examines the relationship between deltaic and deep- water sedimentation in Lake Chelan, WA, where the external forces acting on the system are relatively well constrained, and the river is directly linked to deeper water.
Lake Chelan sits in a fjord-like basin most recently scoured by a combination of the Chelan Glacier and Okanagan Lobe of the Cordilleran ice sheet during the Last Glacial Maximum. Lake Chelan sits 335 meters above sea level and reaches a depth of nearly 450 meters. The northern end of the lake is fed by the Stehekin River, which has produced a delta that has prograded some four kilometers in the last 9000 years.
In summer 2010 we completed bathymetric and sub-bottom surveys of the northern five kilometers of the lake. We also collected lake bed grab samples and gravity cores for grain size and geochemical analysis in order to characterize the transport and fate of sediment near the Stehekin Delta. The bathymetric and sub-bottom surveys reveal large-scale bedforms on the lake floor, likely the product of density currents produced during high river flows or as a consequence of failure on the delta front.
Funding source: University of Washington Royalty Research Fund
People: Chuck Nittrouer, Aaron Fricke
Laboratory study: Sediment transport in wave-supported gravity currents
A number of recent observational studies on continental shelves have observed high rates of cross-shelf transport in thin layers of highly concentrated fine-grained sediment. These gravity currents are sustained by the combined action of their negative buoyancy and supplemental shear stress provided by surface waves. Wave-supported gravity currents (WSGC) have been identified as an important mechanism for cross-shelf sediment transport on many shelves, yet our understanding of WSGC is limited to observational studies that cannot resolve the velocity or density structure within them.
The goals of this work are to determine the structure and transport in WSGC using a combination of laboratory experiments and prior field observations. The laboratory experiments are being conducted in a 5-m long sediment/wave flume constructed expressly for these experiments and proven to realistically reproduce conditions in the oceanic wave boundary layer. Evaluation of the laboratory results will be guided and motivated by field observations of such flows in three shelf systems (Eel and Po River margins, and Gulf of Papua).
People: Andrea Ogston, Alex Horner-Devine (UW CEE), Abbas Hooshmand (UW CEE)
Predictions of turbidity due to enhanced sediment resuspension resulting from sea-level rise on a fringing coral reef: evidence from Molokai, HI
The UW Sediment Dynamics group has been involved in the USGS Coral Reef studies on the Molokai, HI reef flat focusing on the evaluation of sediment-transport conditions, mechanisms, and impacts on depositional processes, and ultimately coral reef health. A specific goal of this work is to evaluate the sedimentary processes in light of projected sea-level rise. Discussion about effect of climate change on coral reef health and sustainability has largely focused on the effects of rising sea-surface temperature. However, increased sedimentation has also been correlated to coral stress and bleaching. The presence of suspended sediment may stress corals by reducing incident light levels, and moreover, particles that settle on coral surfaces interfere with photosynthesis and hinder feeding. The effects of increased water-surface elevation on coral reefs can be varied, and include increased circulation due to broader interaction with offshore water and changes in exposure to dissolved and particulate matter. Increased water-surface elevation will also change rates of erosion, resuspension and transport of terrigenous sediment on fringing reefs, and these impacts on turbidity are explored in this study.
Field, M.E., Ogston, A.S., Storlazzi, C.D. (2012) Rising sea level and increased turbidity on fringing coral reefs. EOS Transactions, AGU, 93, 23.
Ogston, A.S., Field, M.E. (2010) Predictions of turbidity due to enhanced sediment resuspension resulting from sea-level rise on a fringing coral reef: evidence from Molokai, HI. Journal of Coastal Research 26; 1027-1037.
Presto, M.K., Ogston, A.S, Storlazzi, C.D., Field, M.E., (2006) Seasonal variation of sediment transport on a fringing reef. Estuarine, Coastal and Shelf Science 67: 67-81.
Ogston, A.S., Storlazzi, C.D., Field, M.E. and Presto, M.K. (2004). Sediment resuspension and transport patterns on a fringing reef flat, Molokai, Hawaii, Coral Reefs 23: 559-569.
People: Andrea Ogston
Shoreline armoring is thought to be a key factor disrupting natural ecosystem processes in nearshore environments yet there are surprisingly few data documenting actual negative impacts of armoring on the health of Puget Sound. This project involves coordinated and intensive biological, geological, and oceanographic studies at armored and un-armored sites in south-central Puget Sound, emphasizing the linkages between physical processes, organisms, and ecosystems. The objectives of the Sediment Dynamics lab in this study of paired unarmored/armored beaches are 1) to examine the slope, grain size, wave energy relationships of mixed sand and gravel beaches, 2) to evaluate the observable impacts of armoring on geomorphic features of the beach and the relationships, and 3) to provide a baseline database for management of armoring regulations on beaches such as these.
Heerhartz, S.M., Dethier, M.N., Toft, J.D., Cordell, J.R., Ogston, A.S. (in review) Effects of shoreline armoring on beach wrack subsidies to the nearshore ecotone. Estuaries and Coasts.
Toft, J., Ogston, A., Heerhartz, S., Cordell, J., Flemer, E., (2013) Shoreline enhancements within urban constraints: Biological and physical developments at an armored shoreline in Puget Sound, WA. Ecological Engineering 57: 97-108.
Processes controlling transfer of fine-grained sediment within and between channels and flats on intertidal flats
To understand the source-to-sink sediment transfer from rivers to marine deposition, we must develop our understanding of the gateway between the land and ocean -- shallow-water regions spanning the tidally influenced river to the inner shelf. Here, the processes that transport and package sediment in suspension undergo dramatic changes. Tidal flats represent one type of environment found in this shallow-water realm. The transport and deposition of fine-grained sediment varies over the global range of tidal flats, which consists of systems that predominantly import or export sediment, yet our understanding of why these differ is limited. This project seeks to explore: 1) local transfer of sediment between the water column and seabed in both channel and flat environments, 2) the environmental linkages, or exchange of sediment, between channel and flat environments, and 3) place those in the long-term cycle in relation to river discharge, wind, and wave forcing.
Boldt, K.V., Nittrouer, C.A., Ogston, A.S., 2013. Seasonal transfer and net accumulation of fine sediment on a muddy tidal flat: Willapa Bay, WA, Continental Shelf Research, 60S: 157-172, doi: 10.1016/j.csr.2012.08.012.
Nowacki, D.J., Ogston A.S., 2012, Water and sediment transport of channel-flat systems in a mesotidal mudflat: Willapa Bay, Washington, Continental Shelf Research, doi:10.1016/j.csr.2012.07.019.
Webster, K.L., Ogston, A.S., Nittrouer, C.A. (2013) Delivery, reworking and export of fine sediment across the Skagit tidal flats: implications for the fate of fluvial discharge. Continental Shelf Research 60: S58-S70.
Hsu, T-J., Chen, S-N., Ogston, A.S. (2013) A numerical investigation of fine sediment transport across intertidal flats. Continental Shelf Research 60: S85-S98.
Funding source: Office of Naval Research
People: Chuck Nittrouer, Andrea Ogston, Kristen Lee, Katie Boldt, Dan Nowacki
Sediment deposit generated by gravity flow in a submarine canyon
This project was designed to characterize sediment accumulation in a submarine canyon with no major river source on an active continental margin. In collaboration with several Taiwanese scientists, we investigated the effects of a 2006 earthquake and 2009 typhoon in Fangliao Canyon, SW Taiwan. The work was funded by the US NSF and the Taiwan NSC, through the EAPSI fellowship. We found evidence of gravity flows generated by the earthquake and storm processes, through the investigation of a series of short (<50 cm) sediment cores. We used a suite of textural, radiochemical, and geochemical tracers to identify events, and attempt to determine the specific type of gravity flow responsible. This research emphasizes the importance of gravity flows on sediment transport, as well as the role that seemingly dormant submarine canyons can play as conduits for material from the terrestrial to deep-marine environments.
Hale, R., Nittrouer, C., Liu, J.T., Keil, R.G., Ogston, A.S., Effects of a Major Typhoon on Sediment Accumulation in Fangliao Submarine Canyon, SW Taiwan, Marine Geology (2012).
Funding source: National Science Foundation, Taiwan NSC
People: Chuck Nittrouer, Rip Hale
Processes controlling depositional signals for environmental change in the Fly River sediment dispersal system: Mechanisms and rates of shelf clinoform development
This study was part of MARGINS Source-to-Sink (S2S) investigation of the Gulf of Papua, which is a foreland basin receiving large quantities of siliciclastic sediment. The energetic character of the setting imparts strong sedimentary signals to the fate of particles in its dispersal systems. The largest of these is the Fly River, which drains the rain-drenched highlands of Papua New Guinea. Its fluvial load enters the gulf, where tidal currents are strong and the variability of winds, waves and circulation is driven by seasonal changes from trade-wind to monsoon conditions. The wet-tropical setting causes river discharge to be relatively constant during most years. However, the proximity to the equatorial warm pool intensifies the impact of El Nino periods, when rainfall is dramatically decreased and so is river discharge.
The Gulf of Papua provided a valuable opportunity to study continental-shelf sedimentation, because it has a rich assortment of active processes and preserved stratigraphy. The focus of this investigation was on active sedimentation associated with the clinoform found on the inner and middle shelf, and the relationship of this sedimentation to the rest of the dispersal system.
Crockett, J.S., Nittrouer, C.A., Ogston, A.S., Goni, M.A. (2009) Variable Styles of Sediment Accumulation Impacting Strata Formation on a Clinoform: Gulf of Papua, Papua New Guinea. In: The Fly River: natural and human aspects of a complex fluvial system. B.R. Bolton, Ed.
Crockett, J. S., Nittrouer, C.A., Ogston, A.S., Walsh, J.P., Naar, D., Donahue, B (2008). Morphology and filling of incised submarine valleys on the continental shelf near the mouth of the Fly River, Gulf of Papua. Journal of Geophysical Research 113: F01512.
Goni, M.A., Monacci, N., Gisewite, R., Nittrouer, C., Crockett, J., Ogston, A. (2008) Terrigenous organic matter in sediments from the Fly River delta (Papua New Guinea). Journal of Geophysical Research 113: F01510. doi:10.1029/2006JF000653.
Martin, D.P., Nittrouer, C.A., Ogston, A.S., Crockett, J.S. (2008) Tidal and seasonal dynamics of a muddy inner-shelf environment, Gulf of Papua. Journal of Geophysical Research 113: F01507. doi:10.1029/2006JF000681.
Ogston, A.S., Sternberg, R.W., Nittrouer, C.A., Martin, D.P., Goni, M.A., Crockett, J.S., (2008) Sediment delivery from the Fly River tidally dominated delta to the nearshore marine environment and the impact of El Nino. Journal of Geophysical Research 113: F01511. doi:10.1029/2006JF000669.
Slingerland, R., Selover, R.W., Ogston, A.S., Keen, T.R., Driscoll, N.W., Milliman, J.D. (2008) Role of coastal flows in building the holocene clinoform in the Gulf of Papua. Journal of Geophysical Research 113: F01514. doi.10.1029/2006JF000680.
Goni, M.A., Monacci, N., Gisewite, R., Ogston, A., Nittrouer, C., Crockett, J. (2006) Distribution and Sources of Particulate OM in the Water Column and Sediments of the Fly River Delta, Gulf of Papua (Papua New Guinea). Estuarine Coastal and Shelf Science 69: 225-245.
Crockett, J., Nittrouer, C., Ogston, A. Sternberg, R., Driscoll, N., Babcock, J., Milliman, J., Slingerland, R., Naar, D., Donahue, B., Walsh, J., Dietrich, W., Parker, G., Bera, M., Davies, H., Harris, P., Goni, M., Aller, R., and J. Aller. (2005). Where rivers and oceans collide: geological complexities of this interace revealed by the NSF MARGINS program. EOS, Transactions, American Geophysical Union, 86:3.
Funding source: National Science Foundation
People: Chuck Nittrouer, Andrea Ogston, Dick Sternberg