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At least 1,261 records · Page 70Linked to original sources
USGS2019

Response of tidal marsh vegetation to pulsed increases in flooding and nitrogen

Worldwide, human activities have modified hydrology and nutrient loading regimes in coastal wetlands. Understanding the interplay between these drivers and subsequent response of wetland plant communities is essential to informing wetland management and restoration efforts. Recent restoration strategies in Louisiana proposes to use sediment diversions from the Mississippi River to build land in adjacent wetlands and reduce the rate of land to open water conversion. In conjunction with sediment delivery, diversions can increase nutrient loads and water levels in the receiving basins. We conducted a greenhouse mesocosm experiment in which we exposed three common tidal freshwater and brackish marsh plants ( Panicum hemitomon, Sagittaria lancifolia, and Spartina patens ) to two nitrate loading rates [high (35 g N m 2 year −1 ) and low (0.25 g N m 2 year −1 )], and two flooding treatments (with and without diversion pulsing). Experimental units were set at two different elevations within the treatment tanks to simulate both a healthy and degraded marsh. Plant growth metrics and soil physicochemical properties were measured monthly. Final total biomass was determined at the study’s conclusion. Growth responses differed between species but were not significantly influenced by the treatments. Soil redox potential decreased significantly following the increase in flooding associated with the diversion pulse, but recovered to pre-diversion levels after a 3-month recovery period. Our study suggests short flooding pulses with a recovery period may be key for maintaining healthy marshes, however there remains a need for longer-term empirical studies to understand marsh response to pressures associated with river sediment diversions over time.

Louisiana↗
USGS2012

Antarctic and Southern Ocean influences on Late Pliocene global cooling

The influence of Antarctica and the Southern Ocean on Late Pliocene global climate reconstructions has remained ambiguous due to a lack of well-dated Antarctic-proximal, paleoenvironmental records. Here we present ice sheet, sea-surface temperature, and sea ice reconstructions from the ANDRILL AND-1B sediment core recovered from beneath the Ross Ice Shelf. We provide evidence for a major expansion of an ice sheet in the Ross Sea that began at ~3.3 Ma, followed by a coastal sea surface temperature cooling of ~2.5 °C, a stepwise expansion of sea ice, and polynya-style deep mixing in the Ross Sea between 3.3 and 2.5 Ma. The intensification of Antarctic cooling resulted in strengthened westerly winds and invigorated ocean circulation. The associated northward migration of Southern Ocean fronts has been linked with reduced Atlantic Meridional Overturning Circulation by restricting surface water connectivity between the ocean basins, with implications for heat transport to the high latitudes of the North Atlantic. While our results do not exclude low-latitude mechanisms as drivers for Pliocene cooling, they indicate an additional role played by southern high-latitude cooling during development of the bipolar world.

PNAS↗
USGS2010

Predictions of turbidity due to enhanced sediment resuspension resulting from sea-level rise on a fringing Coral Reef: Evidence from Molokai, Hawaii

Accelerating sea-level rise associated with global climate change will affect sedimentary processes on coral reefs and other shoreline environments by increasing energy and sediment resuspension. On reefs, sedimentation is known to increase coral stress and bleaching as particles that settle on coral surfaces interfere with photosynthesis and feeding, and turbidity induced by suspended sediment reduces incident light levels. Using relationships developed from observations of wave orbital velocity, water-surface elevation, and suspended-sediment concentration on a fringing reef flat of Molokai, Hawaii, predictions of the average daily maximum in suspended-sediment concentration increase from ~11 mg/l to ~20 mg/l with 20 cm sea-level rise. The duration of time concentrations exceeds 10 mg/l increases from 9 to 37. An evaluation of the reduction of wave energy flux through breaking and frictional dissipation across the reef flat shows an increase of ~80 relative to the present will potentially reach the shoreline as sea level increases by 20 cm. Where the shoreline exists on low, flat terrain, the increased energy could cause significant erosion of the shoreline. Considering the sediment budget, the sediment flux is predicted to increase and removal of fine-grained sediment may be expedited on some fringing reefs, and sediment in storage on the inner reef could ultimately be reduced. However, increased shoreline erosion may add sediment and offset removal from the reef flat. The shifts in sediment availability and transport that will occur as result of a modest increase in sea level have wide application to fringing coral reefs elsewhere, as well as other shoreline environments. ?? 2010 the Coastal Education & Research Foundation (CERF).

Journal of Coastal Research↗
USGS2000

Geographic signatures of North American West Coast estuaries

West Coast estuaries are geologically young and composed of a variety of geomorphological types. These estuaries range from large fjords to shallow lagoons; from large to low freshwater flows. Natural hazards include E1 Niños, strong Pacific storms, and active tectonic activity. West Coast estuaries support a wide range of living resources: five salmon species, harvestable shellfish, waterfowl and marine birds, marine mammals, and a variety of algae and plants. Although populations of many of these living resources have declined (salmonids), others have increased (marine mammals). West Coast estuaries are also centers of commerce and increasingly large shipping traffic. The West Coast human population is rising faster than most other areas of the U.S. and Canada, and is distributed heavily in southern California, the San Francisco Bay area, around Puget Sound, and the Fraser River estuary. While water pollution is a problem in many of the urbanized estuaries, most estuaries do not suffer from poor water quality. Primary estuarine problems include habitat alterations, degradation, and loss; diverted freshwater flows; marine sediment contamination; and exotic species introductions. The growing West Coast economy and population are in part related to the quality of life, which is dependent on the use and enjoyment of abundant coastal natural resources.

British Columbia;California;Oregon;Washington↗
USGS2016

Effect of wastewater treatment facility closure on endocrine disrupting chemicals in a Coastal Plain stream

Wastewater treatment facility (WWTF) closures are rare environmental remediation events; offering unique insight into contaminant persistence, long-term wastewater impacts, and ecosystem recovery processes. The U.S. Geological Survey assessed the fate of select endocrine disrupting chemicals (EDC) in surface water and streambed sediment one year before and one year after closure of a long-term WWTF located within the Spirit Creek watershed at Fort Gordon, Georgia. Sample sites included a WWTF-effluent control located upstream from the outfall, three downstream effluent-impacted sites located between the outfall and Spirit Lake, and one downstream from the lake's outfall. Prior to closure, the 2.2-km stream segment downstream from the WWTF outfall was characterized by EDC concentrations significantly higher ( α = 0.05) than at the control site; indicating substantial downstream transport and limited in-stream attenuation of EDC, including pharmaceuticals, estrogens, alkylphenol ethoxylate (APE) metabolites, and organophosphate flame retardants (OPFR). Wastewater-derived pharmaceutical, APE metabolites, and OPFR compounds were also detected in the outflow of Spirit Lake, indicating the potential for EDC transport to aquatic ecosystems downstream of Fort Gordon under effluent discharge conditions. After the WWTF closure, no significant differences in concentrations or numbers of detected EDC compounds were observed between control and downstream locations. The results indicated EDC pseudo-persistence under preclosure, continuous supply conditions, with rapid attenuation following WWTF closure. Low concentrations of EDC at the control site throughout the study and comparable concentrations in downstream locations after WWTF closure indicated additional, continuing, upstream contaminant sources within the Spirit Creek watershed. 

Georgia↗
USGS1995

Effect of increased water depth on growth of a common perennial freshwater-intermediate marsh species in Coastal Louisiana

The response of Sagittaria lancifolia to increased water depths of 7.5 and 15 cm was examined in this field study. Water-depth treatments were achieved by digging sods containing one or two individual plants or ramets of S. lancifolia from the marsh, removing sediment from the resulting hole, and replacing the sods in their original location at the appropriate lower elevation. Plants subjected to increased water depth of 15 cm had higher mean and maximum leaf heights than disturbed control plants. Aboveground biomass was not affected by water-depth treatment; however, 15-cm treatment plants had reduced root biomass and lowered leaf tissue concentrations of Ca, Cu, Fe, Mg, and Zn. Marsh sods at 15 cm below the marsh surface had the lowest redox potential and highest interstitial water sulfide concentration, indicating that this treatment created the most stressful belowground environment. Sagittaria lancifolia plants responded to the level of stress imposed by the experimental conditions with an altered growth form of increased leaf height.

Louisiana↗
USGS2010

Seabed photographs, sediment texture analyses, and sun-illuminated sea floor topography in the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts

The U.S. Geological Survey, in collaboration with National Oceanic and Atmospheric Administration's National Marine Sanctuary Program, conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary region from 1993 to 2004. The mapped area is approximately 3,700 km (1,100 nmi) in size and was subdivided into 18 quadrangles. An extensive series of sea-floor maps of the region based on multibeam sonar surveys has been published as paper maps and online in digital format (PDF, EPS, PS). In addition, 2,628 seabed-sediment samples were collected and analyzed and are in the usSEABED: Atlantic Coast Offshore Surficial Sediment Data Release. This report presents for viewing and downloading the more than 10,600 still seabed photographs that were acquired during the project. The digital images are provided in thumbnail, medium (1536 x 1024 pixels), and high (3071 x 2048) resolution. The images can be viewed by quadrangle on the U.S. Geological Survey Woods Hole Coastal and Marine Science Center's photograph database. Photograph metadata are embedded in each image in Exchangeable Image File Format and also provided in spreadsheet format. Published digital topographic maps and descriptive text for seabed features are included here for downloading and serve as context for the photographs. An interactive topographic map for each quadrangle shows locations of photograph stations, and each location is linked to the photograph database. This map also shows stations where seabed sediment was collected for texture analysis; the results of grain-size analysis and associated metadata are presented in spreadsheet format.

Data Series↗
USGS2010

Bank erosion, mass wasting, water clarity, bathymetry and a sediment budget along the dam-regulated Lower Roanoke River, North Carolina

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability, floodplain inundation patterns, and channel morphology. Most of the world's largest rivers have been dammed, which has prompted management efforts to mitigate dam effects. Three high dams (completed between 1953 and 1963) occur along the Piedmont portion of the Roanoke River, North Carolina; just downstream, the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, more than 700 bank erosion pins were installed along 124 bank transects. Additionally, discrete measurements of channel bathymetry, water clarity, and presence or absence of mass wasting were documented along the entire 153-kilometer-long study reach. Amounts of bank erosion in combination with prior estimates of floodplain deposition were used to develop a bank erosion and floodplain deposition sediment budget for the lower river. Present bank erosion rates are relatively high [mean 42 milimeters per year (mm/yr)] and are greatest along the middle reaches (mean 60 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates such that erosion rate maxima have migrated downstream. Mass wasting and water clarity also peak along the middle reaches.

North Carolina↗
USGS2015

Southern Salish Sea Habitat Map Series: Admiralty Inlet

In 2010 the Environmental Protection Agency, Region 10 initiated the Puget Sound Scientific Studies and Technical Investigations Assistance Program, designed to support research in support of implementing the Puget Sound Action Agenda. The Action Agenda was created in response to Puget Sound having been designated as one of 28 estuaries of national significance under section 320 of the U.S. Clean Water Act, and its overall goal is to restore the Puget Sound Estuary's environment by 2020. The Southern Salish Sea Mapping Project was funded by the Assistance Program request for proposals process, which also supports a large number of coastal-zone- and ocean-management issues. The issues include the recommendations of the Marine Protected Areas Work Group to the Washington State Legislature (Van Cleve and others, 2009), which endorses a Puget Sound and coast-wide marine conservation needs assessment, gap analysis of existing Marine Protected Areas (MPA) and recommendations for action. This publication is the first of four U.S. Geological Survey Scientific Investigation Maps that make up the Southern Salish Sea Mapping Project. The remaining three map blocks to be published in the future, located south of Admiralty Inlet, are shown in figure 1. Puget Sound is a deep, fjord-type estuary covering an area of 2,330 km 2 in the Pacific Northwest region of the United States (fig. 1). It is connected to the ocean by the Strait of Juan de Fuca, a turbulent passage approximately 160 km in length and 22 km wide at its west end, expanding to over 40 km wide at its east end (Thomson, 1994). During the Pleistocene, the area was occupied several times by lobes of continental ice, resulting in a complex basin-fill of glacial and interglacial deposits that are locally as thick as 1100 m (Johnson and others, 2001). The last glaciation, called the Fraser glaciation, began after 28,800±740 14 C yr B.P. when ice started a slow expansion (Clague, 1981). At peak advance the westward Juan de Fuca lobe reached the edge of the continental shelf through the Juan de Fuca Strait shortly before 14,460±200 14 C yr B.P. (Herzer and Bornhold, 1982). The southward Puget lobe advanced to its terminal position in Puget Sound by around 14,150 14 C yr B.P. (Porter and Swanson, 1998). Ice retreated from its maximum to northern Whidbey Island by 13,650±350 14 C yr B.P. (Dethier and others, 1995). Retreating glaciers resulted in a thick sequence of ice-contact, glacial-marine sediment, and early post-glacial sediments (Linden and Schurrer, 1988). These deposits have experienced the effects of a marine transgression followed by regression, resulting in a sea-level several tens of meters lower than the present day (Linden and Schurrer, 1988). A second transgression brought sea level to about the present level by around 5,470±120 14 C yr B.P. (Clague and others, 1982) establishing the present oceanographic and geologic environment Puget Sound is separated into four interconnected basins; Whidbey, Central (Main), Hood Canal, and South (Thomson, 1994). The Whidbey, Central, and Hood Canal basins are the three main branches of the Puget Sound estuary and are separated from the Strait of Juan de Fuca by a double sill at Admiralty Inlet. The Admiralty Inlet map area includes the Inlet and a portion of the Whidbey Basin (fig. 1). The shallower South Basin is separated by a sill at Tacoma Narrows and is highly branched with numerous finger inlets. Flow within Puget Sound is dominated by tidal currents of as much as 1 m/s at Admiralty Inlet, reducing to approximately 0.5 m/s in the Central Basin (Lavelle and others, 1988). The lack of silt and clay-sized sediments in the Admiralty Inlet map area is likely a result of the strong currents (see Ground-Truth Studies for the Admiralty Inlet Map Area, sheet 3). The subtidal component of flow reaches approximately 0.1 m/s and is driven by density gradients arising from the contrast in salty ocean water at the entrance and freshwater inputs from stream flow (Lavelle and others, 1988). The total freshwater input to Puget Sound is approximately 3.4 x 10 6 m 3 /day, primarily from the Skagit River (Cannon, 1983). The subtidal circulation mostly consists of a two-layered flow in the basins with fresher water exiting at the surface and saltier water entering at depth (Ebbesmeyer and Cannon, 2001). In general, surface waters flow north and deeper waters flow south; variations arise from wind effects that can drive a surface current in the same direction as the wind, and a baroclinic response in the lower layer to about 100-m depth (Matsuura and Cannon, 1997). Oceanographic properties are influenced by temporal forcing parameters such as reduced stream flow during the 2000-01 drought that increased surface salinity and decreased differences between surface and bottom waters (Newton and others, 2003). On offshore seismic-reflection profiles, Pleistocene strata (excluding latest Pleistocene glacial and post-glacial deposits) form a distinct seismic unit, bounded below by pre-Tertiary or Tertiary basement and above by typically flat-lying latest Pleistocene to Holocene deposits that fill in erosional or depositional relief (Johnson and others, 2001). Cores from central Puget Sound have accumulation rates that range from 85 to 1200 mg/cm 2 /yr, or 0.12 to 2.4 cm/yr; the highest accumulation rates are near the southern end of central Puget Sound (Carpenter and others, 1985). Carpenter and others (1985) un-weighted arithmetic mean of accumulation rates for central Puget Sound deeper stations is 480±340 (± one standard deviation) mg/cm 2 /yr. Lavelle and others (1985) also found rates as high as 1200 mg/cm 2 /yr over the past approximately 70 years in cores in the Central Basin off of and north and south of Elliott Bay. Puget Sound basin rates are comparable to rates in midshelf silt deposits on the Washington coast north of the Columbia River (Nittrouer and others, 1979). The deep subtidal (in other words, below SCUBA depths) habitats of Puget Sound are relatively poorly known. A few subtidal surveys exist for several habitat types from the 1960s and 1970s (reviewed in Dethier, 1990), using grab and box core data. The Dethier (1990) review divides habitat up into Coast and Marine Ecological Classification Standard (CMECS) substrate, water column energy, and depth zones but does not attempt to map these habitats, rather it is an inventory of habitats found in the area and the flora and fauna associated with each habitat. The approach of the Southern Salish Sea Mapping project is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data (the undersea equivalent of satellite remote-sensing data in terrestrial mapping), acoustic backscatter, seafloor video, seafloor photography, and bottom-sediment sampling data. This approach is based in part on methods presented and data collection and product needs identified at the Washington State Seafloor Mapping Workshop (Washington State Seafloor Mapping Workshop Steering Committee, 2008), attended by coastal and marine managers and scientists. The map products display seafloor geomorphology and substrate, and identify potential marine benthic habitats. It is emphasized that the more interpretive habitat and geology maps rely on the integration of multiple, new high-resolution datasets and that mapping at small scales would not be possible without such data. Oceanographic current and wave data is not included in this analysis, however, the accompanying geographic information system (GIS) data set is designed and intended to be combined with oceanographic and biologic data sets assembled by others in the future and some of the GIS data has already been incorporated in the unpublished Nature Conservancy Benthic Habitats of Puget Sound database. This publication includes four map sheets, explanatory text, and a descriptive pamphlet. Each map sheet is published as a portable document format (PDF) file. ESRI ArcGIS compatible geotiffs (for example, bathymetry) and shapefiles (for example video observation points) will be available for download in the data catalog associated with this publication (Cochrane, 2015). An ArcGIS Project File with the symbology used to generate the map sheets is also provided. For those who do not own the full suite of ESRI GIS and mapping software, the data can be read using ESRI ArcReader, a free viewer that is available at http://www.esri.com/software/arcgis/arcreader/index.html .

Washington↗
USGS2022

Preliminary geologic map of the Cherry Hill quadrangle, Dinwiddie, Sussex, and Greensville Counties, Virginia

The Cherry Hill 7.5-minute quadrangle straddles the Coastal Plain and Piedmont Provinces along the Tidewater Fall Line. Rocks of the eastern Piedmont Roanoke Rapids terrane crop out in the western part of the quadrangle and consist of greenschist- to amphibolite-facies Neoproterozoic felsic to intermediate metavolcanic rocks, some of which contain flattened quartz phenocrysts and are locally isoclinally folded; greenstone that locally preserves primary layering; and intrusive metadiorite and metagabbro, much of which has been altered to amphibolite. Most of these rocks are strongly foliated and jointed. Greenschist-facies metasiltstone that preserves primary bedding also occurs locally in the Roanoke Rapids terrane. Neoproterozoic mica schist, middle Paleozoic foliated metagranite, and late Paleozoic massive and porphyritic granite crop out in the eastern part of the quadrangle and are part of the Dinwiddie terrane and the late Paleozoic De Witt pluton. Upper greenschist- to lower amphibolite-facies mica schist consists of stringers and boudins of vein quartz and contains porphyroclasts of staurolite that preserve an earlier foliation as inclusion trails. Porphyroblasts of garnet, staurolite, and kyanite also occur locally. Foliation in granites of the De Witt pluton may be magmatic. Separating the Dinwiddie terrane from the Roanoke Rapids terrane are greenschist-facies, highly strained granitic mylonite and bodies of less deformed granite within the Nottoway River fault zone, which is a strand of the eastern Piedmont fault system. Paleozoic pegmatite dikes and quartz veins cross-cut rocks of the Dinwiddie terrane, and quartz veins and Jurassic diabase dikes cross-cut rocks of the Roanoke Rapids terrane. Sand and gravel deposits of the Atlantic Coastal Plain overlie Piedmont rocks. Two units assigned to the upper part of the Neogene Chesapeake Group occur at elevations up to 295 feet (90 meters) above sea level atop the Richmond plain in the central part of the quadrangle. Two units of the Quaternary Bacons Castle Formation occupy the Essex plain and Norge uplands at elevations up to 180 feet (55 meters) above sea level in the eastern part of the quadrangle. In the western part of the quadrangle, multiple levels of terrace deposits are the fluvial equivalent of estuarine to marine units of the Atlantic Coastal Plain to the east. Holocene alluvium occurs along creeks and the Nottoway River. Quaternary colluvial deposits occur locally. Numerous Carolina bays pock the landscape of the Richmond and Essex plains, and three abandoned channelways represent former locations of Sappony Creek, one of the major drainages of the quadrangle. Brittle faults juxtapose Piedmont basement rocks against Neogene sediments of the upper part of the Chesapeake Group. These Cenozoic faults were first uncovered in mine excavations in the late 1990s; new mapping indicates that many of these faults are reactivated silicified cataclasite zones that occur throughout the Piedmont basement rocks. Silicified cataclasites and associated quartz veins are typically mineralized with iron and iron sulfide minerals. The quadrangle was the focus of extensive mining for heavy minerals, including ilmenite and zircon, in upland Atlantic Coastal Plain deposits beginning in the mid-1990s. Other mineral resources, including precious metals, clay for structural brick, crushed stone, and building stone for millstones, have also been prospected or quarried in the quadrangle.

Virginia↗
USGS2014

Coastal bathymetry and backscatter data collected in 2012 from the Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys off the northern Chandeleur Islands, Louisiana, in July and August of 2012. The objective of the study is to better understand barrier island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1-5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the second in a series of three planned surveys in this area. High resolution geophysical data collected in each of 3 consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1-5 years). This Data Series report includes the geophysical data that were collected during two cruises ( USGS Field Activity Numbers 12BIM03 and 12BIM04 ) aboard the RV Survey Cat and the RV Twin Vee along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz (kHz)), an EdgeTech 424 (4-24 kHz) chirp sub-bottom profiling system, and a Knudsen 320BP (210 kHz) echosounder. This report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, an acoustic backscatter mosaic, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. NOTE: These data are scientific in nature and are not to be used for navigation.

Louisiana↗
USGS2017

Coastal bathymetry data collected in 2013 from the Chandeleur Islands, Louisiana

As part of the Barrier Island Evolution Research Project, scientists from the U.S. Geological Survey (USGS) St. Petersburg Coastal and Marine Science Center conducted nearshore geophysical surveys around the northern Chandeleur Islands, Louisiana, in July and August of 2013. The objective of the study is to better understand barrier-island geomorphic evolution, particularly storm-related depositional and erosional processes that shape the islands over annual to interannual timescales (1‒5 years). Collecting geophysical data will allow us to identify relationships between the geologic history of the island and its present day morphology and sediment distribution. This mapping effort was the third in a series of three planned surveys in this area. High resolution geophysical data collected in each of three consecutive years along this rapidly changing barrier island system will provide a unique time-series dataset that will significantly further the analyses and geomorphological interpretations of this and other coastal systems, improving our understanding of coastal response and evolution over short time scales (1‒5 years). This data series includes the geophysical data that were collected during two cruises (USGS Field Activity Numbers (FAN) 13BIM02, 13BIM03, and 13BIM04, in July 2013; and FANs 13BIM07 and 13BIM08 in August 2013) aboard the R/V Sallenger , the R/V Jabba Jaw , and the R/V Shark along the northern portion of the Chandeleur Islands, Breton National Wildlife Refuge, Louisiana. Primary data were acquired with the following equipment: (1) a Systems Engineering and Assessment, Ltd., SWATHplus interferometric sonar (468 kilohertz [kHz]), (2) an EdgeTech 424 (4‒24 kHz) chirp sub-bottom profiling system, and (3) two Odom Hydrographic Systems, Incorporated, Echotrach CV100 single beam echosounders. This data series report serves as an archive of processed interferometric swath and single-beam bathymetry data. Geographic information system data products include an interpolated digital elevation model, trackline maps, and point data files. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata.

Louisiana↗
USGS1973

Hydrologic changes after clear-cut logging in a small Oregon coastal watershed

Preliminary graphical analysis indicates that clear-cut logging of a small Oregon watershed has significantly altered certain hydrologic characteristics. After logging, moderate increases were noted in annual runoff, but no significant changes were detected in either peak or minimum flow rates. Both the annual sediment yields and the maximum monthly water temperatures increased greatly after logging; sediment yields and temperatures in the unlogged control watershed actually decreased during the postlogging period.

Oregon↗
USGS2007

Forcing of large-scale cycles of coastal change at the entrance to Willapa Bay, Washington

Anomalous morphological features within large estuaries may be: (1) recorders of external forces that periodically overwhelm the normal morphodynamic responses to estuarine energy fluxes, and (2) possible predictors of cycles of future coastal change. At the entrance to Willapa Bay, Washington, chronic beach erosion and frequent coastal flooding are related to the historical northward channel migration that destroyed the protective sand spits of Cape Shoalwater. Northward channel migration since the late 1800s conforms to the long-term net sediment transport direction. What requires explanation is periodic southward relocation of the trunk channel by as much as 5 km, and attendant construction of moderately large sand spits on the north side of the bay such as Kindred Island, Tokeland Peninsula, and Cape Shoalwater. Both autocyclic and allocyclic processes may have been responsible for trunk channel realignment and associated spit deposition. Channel recycling may occur when the main channel becomes overextended to the north and the tidal flow is inefficient because of its decreased gradient and increased susceptibility to shoaling by the growth and migration of tidal sand ridges. Under those conditions trunk channel relocation would be facilitated by increased wave heights and water levels of El Niño winter storms. However, co-seismic subsidence is the most likely mechanism for abruptly increasing sand supply and longshore transport that would favor discrete periods of channel relocation and spit deposition. Unless external forcing changes sand supply and predominant sediment transport directions in the future, the relative rise in sea level, frequent winter storms, and local deficit in the sand budget assure that beach erosion will continue at the mouth of this large estuary.

Washington↗
USGS2010

Limits on the adaptability of coastal marshes to rising sea level

Assumptions of a static landscape inspire predictions that about half of the world's coastal wetlands will submerge during this century in response to sea-level acceleration. In contrast, we use simulations from five numerical models to quantify the conditions under which ecogeomorphic feedbacks allow coastal wetlands to adapt to projected changes in sea level. In contrast to previous sea-level assessments, we find that non-linear feedbacks among inundation, plant growth, organic matter accretion, and sediment deposition, allow marshes to survive conservative projections of sea-level rise where suspended sediment concentrations are greater than ~20 mg/L. Under scenarios of more rapid sea-level rise (e.g., those that include ice sheet melting), marshes will likely submerge near the end of the 21st century. Our results emphasize that in areas of rapid geomorphic change, predicting the response of ecosystems to climate change requires consideration of the ability of biological processes to modify their physical environment.

Geophysical Research Letters↗
USGS2003

Longshore sediment transport rates on a microtidal estuarine beach

Longshore sediment transport rates were estimated on a microtidal estuarine beach in Great South Bay, N.Y., during two dyed sand tracer experiments using a temporal sampling method. Mean onshore wind speeds of 5.8 and 9.9 m/s resulted in root-mean-square wave heights of 0.07 and 0.08 m and wave angles of 3.0 and 10.1, causing transport rates of 0.468 and 0.972 m3/h. Rates were 3.1 to 6.5 times greater than predicted by existing equations using standard coefficients. Greater rates are attributed to the concentration of sediment transport in the energetic swash zone under plunging breakers.

Journal of Waterway, Port, Coastal and Ocean Engin↗
USGS2019

Tropical cyclones and the organization of mangrove forests: A review

Background Many mangrove ecosystems are periodically exposed to high velocity winds and surge from tropical cyclones and often recover with time and continue to provide numerous societal benefits in the wake of storm events. Scope This review focuses on the drivers and disturbance mechanisms (visible and functional) that tropical cyclones of various intensities have on mangrove ecosystem properties from around the world, as well as the potential ecosystem services role offered by mangroves along storm-ravaged coastlines. When viewed together, studies describe repeatable types of impact and a variety of responses of mangroves that make them ecologically resilient to high velocity winds, and which have served to advance the notion that mangroves are disturbance-adapted ecosystems. Conclusions Studies have documented massive tree mortality and forest structural shifts as well as high variability of spatial effects associated with proximity and direction of tropical cyclone trajectory that influence biogeochemical processes, recovery of individual trees, and forest regeneration and succession. Mangroves provide coastal protection through surge and wind suppression during tropical cyclones, and yet are able to overcome wind effects and often recover unless some alternate environmental stress is at play (e.g., hydrologic alteration or sedimentation). Structural elements of mangroves are influenced by the legacies imposed by past tropical cyclone injury, which affect their current appearance, and presumably function of mangroves, at any point in time. However, much is yet to be discovered about the importance of tropical cyclones on these fascinating botanical ecosystems including the role of storm-based sediment subsidies, and much more effort will be needed to predict future recovery patterns as frequency and intensity of tropical cyclones potentially change.

Annals of Botany↗
USGS1997

Bottom boundary layer in south San Francisco Bay, California

Detailed velocity distributions within the benthic turbulent boundary layer were measured by a Broad Band Acoustic Doppler Current Profiler (BB-ADCP) in South San Francisco Bay, California. In "mode 5", the BB-ADCP was able to measure velocity in 5 cm increments. The validation of these measurements was achieved by comparing the BB-ADCP measurements with the velocities measured by a Narrow Band Acoustic Doppler Current Profiler (NB-ADCP) in close proximity. There were thirty-three (33) velocity time-series measured by the BB-ADCP beginning at 7 cm above bed and extending to 175 cm in water column for about two weeks. The velocities from locations at 7 cm and 12 cm above the bed were determined to be of lower accuracy, and they were not used in estimates of friction velocity, u.. The values of u. at 95% confidence level were determined with relative error less than 20%. The time-series of u. varied with velocity outside of the boundary layer, and responded to spring-neap tidal variations. Attempts to use acoustic backscatterance echo intensity to measure suspended sediment concentration showed prom ise, and merit consideration in future studies.

California↗