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At least 631 records · Page 35Linked to original sources
USGS2002

Success of artificial bird nests in burned Gulf Coast Chenier Plain marshes

Wildlife managers in the Gulf Coast Chenier Plain of Louisiana and Texas frequently burn marshes during winter to improve habitat for wintering waterfowl and furbearers. Such fires dramatically alter vegetation structure and cover, although such changes are generally temporary. However, if vegetation cover does not recover sufficiently by the start of the subsequent breeding season, nests of marsh birds could be exposed to increased predation rates. We examined effects of burning on 2 measures of vegetation structure and on 2 types of artificial bird nests during breeding seasons (May and June) before and after experimental winter burns (December and January). We found that vegetation structure did not differ between burned and non-burned marshes at 5 months post-burn. Similarly, depredation rates of artificial sparrow and duck nests did not differ between burned and non-burned marshes during the post-burn breeding season. We recommend that managers complete burning programs by the end of January so that sufficient nesting cover develops before the start of the breeding season.

Southwestern Naturalist↗
USGS2003

Morphological variation in glochidia shells of six species of Elliptio from Gulf of Mexico and Atlantic Coast drainages in the southeastern United States

The genus Elliptio, with 36 currently recognized species, is the largest genus in the family Unionidae in North America. The genus is represented by two species, Elliptio crassidens and E. dilatata, in the Interior Basin and 34 species in drainages of the eastern Gulf of Mexico and Atlantic Coast. The paucity and variation of conchological characters in the genus Elliptio makes it extremely difficult to define species and determine relationships. We examined glochidia from six species of Elliptio in an effort to determine if there are useful characteristics for species level identification and/or characters for identification of species groups. Elliptio species were selected to represent different morphological groups from four drainages in the southeastern United States. The glochidia from E. crassidens, E. dariensis, E. hopetonensis, E. icterina, E. shepardiana, and E. mcmichaeli were qualitatively compared, using scanning electron microscopy, with each other and with descriptions of these and other Elliptio glochidia described in the literature. Two groups were identified. The crassidens group, including E. crassidens, E. dariensis, and E. mcmichaeli, had subtriangular glochidia with a triangular styliform hook extending from the ventral margin of the valve and rough exterior valve sculpturing. Adults of this group had wrinkled or corrugated sculpturing on the posterior slope of the shell. The complanata group, including E. hopetonensis, E. icterina, and E. shepardiana, had subelliptical glochidia with a broad flange extending the entire ventral margin and loose-looped exterior valve sculpturing. Adults of this group lack sculpturing on the posterior slope of the shell. Differences in glochidial morphometrics were found, however, additional work is needed to determine if they are reliable for species level identification.

Proceedings of the Biological Society of Washingto↗
USGS2003

Effects of structural marsh management and salinity on invertebrate prey of waterbirds in marsh ponds during winter on the Gulf Coast Chenier Plain

Aquatic invertebrates are important food resources for wintering waterbirds, and prey selection generally is limited by prey size. Aquatic invertebrate communities are influenced by sediments and hydrologic characteristics of wetlands, which were affected by structural marsh management (levees, water-control structures and impoundments; SMM) and salinity on the Gulf Coast Chenier Plain of North America. Based on previous research, we tested general predictions that SMM reduces biomass of infaunal invertebrates and increases that of epifaunal invertebrates and those that tolerate low levels of dissolved oxygen (O2) and salinity. We also tested the general prediction that invertebrate biomass in freshwater, oligohaline, and mesohaline marshes are similar, except for taxa adapted to specific ranges of salinity. Finally, we investigated relationships among invertebrate biomass and sizes, sediment and hydrologic variables, and marsh types. Accordingly, we measured biomass of common invertebrate by three size classes (63 to 199 ??m, 200 to 999 ??m, and ???1000 ??m), sediment variables (carbon content, C:N ratio, hardness, particle size, and O, penetration), and hydrologic variables (salinity, water depth,temperature, 02, and turbidity) in ponds of impounded freshwater (IF), oligohaline (IO), mesohaline (IM), and unimpounded mesohaline (UM) marshes during winters 1997-1998 to 1999-2000 on Rockefeller State Wildlife Refuge, near Grand Chenier, Louisiana, USA. As predicted, an a priori multivariate analysis of variance (MANOVA) contrast indicated that biomass of an infaunal class of invertebrates (Nematoda, 63 to 199 ??m) was greater in UM marsh ponds than in those of IM marshes, and biomass of an epifaunal class of invertebrates (Ostracoda, 200 to 999 ??m) was greater in IM marsh ponds than in those of UM marshes. The observed reduction in Nematoda due to SMM also was consistent with the prediction that SMM reduces invertebrates that do not tolerate low salinity. Furthermore, as predicted, an a priori MANOVA contrast indicated that biomass of a single invertebrate class adapted to low salinity (Oligochaeta, 200 to 999 ??m) was greater in ponds of IF marshes than in those of IO and IM marshes. A canonical correspondence analysis indicated that variation in salinity and O2 penetration best explained differences among sites that maximized biomass of the common invertebrate classes. Salinity was positively correlated with the silt-clay fraction, O2, and O2 penetration, and negatively correlated with water depth, sediment hardness, carbon, and C:N. Nematoda, Foraminifera, and Copepoda generally were associated with UM marsh ponds and high salinity, whereas other invertebrate classes were distributed among impounded marsh ponds and associated with lower salinity. Our results suggest that SMM and salinity have relatively small effects on invertebrate prey of wintering waterbirds in marsh ponds because they affect biomass of Nematoda and Oligochaeta, and few waterbirds consume these invertebrates. ?? 2003, The Society of Wetland Scientists.

Wetlands↗
USGS2004

Status and reproduction of Gulf coast strain walleye in a Tombigbee River tributary

Walleye (Sander vitreus [Mitchill]) are native to rivers and streams in the Mobile River basin in Mississippi and Alabama. These populations comprise a genetically unique strain (Gulf coast walleye, GCW) and represent the southernmost distribution of walleye in the United States. Luxapallila Creek was considered an important spawning site for GCW prior to and shortly after impoundment of the Tombigbee River in 1980. Extensive sampling in Luxapallila Creek in 2001 and 2002 collected only one larval walleye. Microsatellite DNA analysis suggested 14 of 16 adult walleye from Luxapallila Creek were hatchery-produced fish or their progeny. Controlled angling catch rates of adult walleye have declined since 1997. The scarcity of wild-spawned walleye and the similarity of wild-caught and hatchery broodstock walleye indicates that the GCW population in, or spawning in, Luxapallila Creek is sustained by stocking and recruitment from these stocked fish may be diminishing.

Southeastern Naturalist↗
USGS2004

Composition of breeding bird communities in Gulf Coast Chenier Plain marshes: Effects of winter burning

Marsh managers along the Gulf Coast Chenier Plain frequently use winter burns to alter marsh vegetation and improve habitat quality for wintering waterfowl. However, effects of these burns on marsh avifauna are not well documented. We recorded abundances of breeding bird species and vegetation structure in burned and unburned control marshes during one breeding season before (1996) and two breeding seasons after (1997, 1998) experimental winter burns. We used non-metric multidimensional scaling analysis to assess the extent and direction of changes in bird community compositions of burned and unburned control marshes and to investigate the influence of vegetation structure on bird community composition. Overall, we found that Seaside Sparrows (Emberizidae: Ammodramus maritimus [Wilson]) and Red-winged Blackbirds and Boat-tailed Grackles (Icteridae: Agelaius phoeniceus [L.] and Quiscalus major Vieillot, respectively) comprised > 85% of observed birds. In burned marshes during the first breeding season following experimental burns (1997), icterid abundance increased while Seaside Sparrow abundance decreased relative to pre-burn (1996) conditions. This pattern was reversed during the second breeding season post-burn. No obvious patterns of change in avian abundance were detected in unburned control marshes over the 3-year period. Qualitative changes in breeding bird community composition were related to effects of winter burning on percent cover of dead vegetation and Spartina patens (Aiton) Muhl.

Southeastern Naturalist↗
USGS2006

A geochronological approach for cave evolution in the Cantabrian Coast (Pindal Cave, NW Spain)

Some of the oldest speleothems in the North Cantabrian Coast (Spain) are reported for the first time in this work. Pindal Cave is developed at 24 m above sea level, in a karstic massif reaching its highest surface in a marine terrace (rasa) located at 50-64 m above the present sea level. Several phases of evolution were previously recognized into the cave, including block collapse of the roof, episodic flooding and detrital sedimentation, and chemical precipitation of at least four speleothem generations over both alluvial and collapse deposits. Three of these speleothem generations have been dated by U/Th. The first generation yielded ages from 124,2 ?? 1, 5 ka BP to 73,1 ?? 0,9 ka BP, giving a minimum age for the main detritic sediments in the cave. The second one is not dated. The third generation gives an age of 3,71 ?? 0,4 ka BP (mathematically corrected to 2.7 ?? 0.5 ka BP), while for the youngest generation, with actively growing stalagmites in the cave, basal ages of 200 years BP are estimated by counting annual laminae. The data suggest a tentative maximum elevation rate close to 0, 2 mm/yr for the Cantabrian Margin in this area, although further chronological studies will be needed to check this hypothesis. ?? 2006 Gebru??der Borntraeger.

Conference Paper↗
USGS2007

Stable isotope data from deep-water antipatharians: 400-Year records from the southeastern coast of the United States of America

In this study, time-series stable isotope results (δ 13 C and δ 15 N) from three deep-water Leiopathes glaberrima (Esper, 1788) specimens Collected off the southeastern Coast of the United States of America and one specimen from the Gulf of Mexico are presented. The specimens were Collected live in 2004 and are estimated to be 200–500 yrs old based on 210 Pb measurements and band Counts. The δ 13 C and δ 15 N long-term trends are reproducible within and among specimens from a similar location, suggesting a common environmental influence. Three western Atlantic specimens have average δ 13 C values of −15.7‰, −16.3‰, and −16.1‰, with the most depleted values from the oldest specimen. The oldest specimen records an enrichment in 13 C of 0.5‰ corresponding to the Little Ice Age. All three specimens show a depletion of 13 C over the past 150 yrs Corresponding to the δ 13 C Suess Effect. The fourth specimen from the Gulf of Mexico has an average δ 13 C value of −16.4‰ and shows no trend in 13 C value with time. All four specimens Contain an enrichment in 15 N over the most recent 75 yrs, with the largest enrichment (3‰) in the Gulf of Mexico specimen. This enrichment is likely a result of increased terrestrial effluent (sewage and manure) reaching the offshore specimens.

Bulletin of Marine Science↗
USGS2008

δ 15 N patterns of Douglas-fir and red alder riparian forests in the Oregon Coast Range

We used naturally occurring stable isotopes of N to compare N dynamics in near-stream and upslope environments along riparian catenas in N-fixing red alder (Alnus rubra) and Douglas-fir (Pseudotsuga menziesii) forests in the Coast Range of western Oregon. Based on the existing literature, we expected soil δ 15 N to be enriched closer to streams owing to inputs of isotopically heavy, marine-derived N by spawning salmon, higher rates of denitrification near the stream, or both. However, it has been unclear what effect red alder might have on soil δ 15 N patterns near streams. We found a consistent −1‰ δ 15 N signature in red alder foliage, and δ 15 N of total N in soils under red alder averaged 2.2‰ along sampling transects extending 20 m upslope from the stream. Surprisingly, δ 15 N of total N in soil under Douglas-fir was progressively depleted nearer to streams, opposite from the pattern expected from N losses by denitrification or N inputs from anadromous salmon. Instead, δ 15 N of total N in soil under Douglas-fir converged toward soil δ 15 N values typical of red alder sites. We consider that the historic presence of red alder may have contributed a legacy of lower soil δ 15 N nearer to streams on sites that are currently dominated by young Douglas-fir forest.

Oregon↗
USGS2008

USGS: Building on leadership in mapping oceans and coasts

The US Geological Survey (USGS) offers continuously improving technologies for mapping oceans and coasts providing unique opportunity for characterizing the marine environment and to expand the understanding of coastal and ocean processes, resources, and hazards. USGS, which has been designated as a leader for mapping the Exclusive Economic Zone, has made an advanced strategic plan, Facing Tomorrow's Challenges- US Geological Survey Science in the Decade 2007 to 2017. This plan focuses on innovative and transformational themes that serve key clients and customers, expand partnerships, and have long-term national impact. The plan includes several key science directions, including Understanding Ecosystems and Predicting Ecosystem Change, Energy and Minerals for America's Future, and A National Hazards, Risk, and Resilience Assessment Program. USGS has also collaborated with diverse partners to incorporate mapping and monitoring within interdisciplinary research programs, addressing the system-scale response of coastal and marine ecosystems.

Sea Technology↗
USGS2009

Monitoring and modeling shoreline response due to shoreface nourishment on a high-energy coast

Shoreface nourishment can be an efficient technique to feed sediment into the littoral zone without the order of magnitude cost increase incurred by directly nourishing the beach. An erosion hot spot at Ocean Beach in San Francisco, California, USA, threatens valuable public infrastructure as well as safe recreational use of the beach. In an effort to reduce the erosion at this location, a new beneficial reuse plan was implemented in May 2005 for the sediment dredged annually from the main shipping channel at the mouth of San Francisco Bay. From 2005 to 2007, approximately 230,000 m of sand was placed annually at depths between 9 and 14 m, in a location where strong tidal currents and open-ocean waves could potentially feed sediment onto the section of beach experiencing critical erosion. The evolution of the disposal mound and adjacent beach were monitored with 12 multibeam bathymetric surveys, and over 40 high-resolution beach topographic surveys. In addition, sediment transport processes were investigated using sediment grab samples, acoustic Doppler profilers, and two separate models: a cross-shore profile model (UNIBEST-TC) and a coastal area model (Delft3D). The results of the monitoring and modeling demonstrate that the disposal mound may be effective in dissipating wave energy striking this vulnerable stretch of coast with negligible shadowing effects, but a positive shoreline response can only be achieved by placing the sediment in water depths less than 5 m.

California↗
USGS1980

Paleoecological evaluation of Late Eocene biostratigraphic zonations of the Pacific Coast of North America

The late Eocene zonal criteria of the west coast of North America are to a large extent controlled by paleoecology and, therefore, the correlation of coeval but environmentally different benthic foraminiferal faunas cannot be achieved before paleoecological control of the biostratigraphy is understood. The faunal trends, morphology, characteristic occurrences and estimated upper depth limits of the benthic foraminifers and associated microfossils in the Oregon and Washington study sections lead to the recognition of paleoecologic facies. The interpretation of these late Eocene facies as bathymetric and low-oxygen facies is based on analogous late Eocene and Holocene assemblages. The paleoecologic facies criteria are often identical to the stage and zonal criteria. In the California zonal schemes, the Narizian zones are identified by lower and middle bathyal faunas whereas the Refugian zones are identified by outer neritic and upper bathyal faunas. The Washington late Eocene zones are identified by middle bathyal and transported neritic faunas. Modifications of the existing zonal schemes such that time and not paleoecology is the controlling factor results in a zonation that synthesizes the existing zonal schemes, recognizes regional stratigraphic ranges of diagnostic species, and removes paleoecologically controlled species occurrences. The late Narizian encompasses a bathyal and a neritic facies. The bathyal facies is correlative with a modified Bulimina corrugata Zone of California and the Uvigerina cf. U. yazooensis Zone of Washington. The neritic late Narizian facies corresponds to a modified Bulimina schencki-Plectofrondicularia cf. P. jenkinsi Zone of Washington and a modified Amphimorphina jenkinsi Zone of California. The Refugian can also be divided into a neritic and a bathyal facies. Although the early and late subdivisions of this stage are tentative, the early Refugian is equivalent to the modified versions of the Cibicides haydoni and the Uvigerina atwilli Subzones of the Valvulineria tumeyensis Zone and the Uvigerina vicksburgensis Zone (in part) of California and the modified version of the Sigmomorphina schencki Zone of Washington. The late Refugian is equivalent to modified versions of the California Uvigerina vicksburgensis Zone (in part) and the Washington Cassidulina galvinensis Zone. The Cibicides haydoni Subzone is the neritic facies of the Refugian Stage, whereas the faunas of the Uvigerina atwilli Subzone and the Uvigerina vicksburgensis, Sigmomorphina schencki and Cassidulina galvinensis Zones represent the bathyal Refugian facies.

Paleontological Monograph↗
USGS2010

Impacts of climate change on Oregon's coasts and estuaries

Earth’s changing climate is expected to have significant physical impacts along the coast and estuarine shorelands of Oregon, ranging from increased erosion and inundation of low lying areas, to wetland loss and increased estuarine salinity. The environmental changes associated with climate change include rising sea levels, increased occurrences of severe storms, rising air and water temperatures, and ocean acidification. The combination of these processes and their climate controls are important to beach and property erosion, flood probabilities, and estuarine water quality, with the expectation of significant changes projected for the 21st century. In the following sections we attempt to summarize the most recent literature documenting historical changes as well as what may be expected to occur in response to climate change. Where little information is available we draw preliminary conclusions about the potential for specific impacts. When possible we highlight what research is needed to bridge knowledge gaps to improve our ability to identify climate change impacts more precisely, ultimately allowing for future projections.

Oregon↗
USGS2013

Fish: Section 4.8 in Climate change and the Olympic Coast National Marine Sanctuary: Interpreting potential futures.

Summary Decreased ocean survival of Chinook and coho salmon in the coastal waters of Washington, Oregon, and California is likely based on historical and present day observations during conditions of unusually high water temperatures and reduced or delayed upwelling. Based on observations during conditions of unusually high water temperatures and reduced or delayed upwelling, highly migratory southern species including Pacific hake, jack and Pacific chub mackerel, and Pacific sardine will likely become more abundant and distributed closer to shore off Washington. In contrast, resident forage fish including northern anchovy, Pacific herring, and smelts (surf and whitebait) may become less abundant. Small pelagic fish (i.e. forage fish and mackerel) respond more rapidly to climaterelated changes in ocean conditions than benthic fish. Distribution and abundance of benthic fish reflect average ocean conditions over periods of many years. A key question for groundfish is how long term, sustained changes in ocean conditions will affect the current spatial configuration of habitats and fish communities, and the productivity of those habitats and communities. Little is known about effects of ocean acidification on northeast Pacific fish; however, work with tropical reef fish suggests that increased acidity impairs larval fish behavior (their ability to find suitable reef habitat from olfactory and auditory cues) and ultimately their survival. Response of benthic fish in the OCNMS to future increases in hypoxia will likely be similar to those for fish off the central Oregon coast where hypoxia developed each summer starting in 2002. Abundance and condition of fish will decline in hypoxic areas. Fish will move inshore seeking higher oxygen concentrations. Species adapted to low oxygen environments, for example Dover sole, will be less affected.

California, Oregon, Washington↗
USGS1980

Modern sedimentary facies of the open Pacific coast and Pleistocene analogs from Montery Bay, California

Depositional processes and sedimentary structures of wave-dominated Pacific coastal environments vary systematically with water depth. The depth-limited open-coast facies identifiable by their sedimentary structures are the inner shelf, barred or nonbarred nearshore, beach, and coastal dune facies. These facies are most commonly preserved in shallowing-upward progradational sequences. The vertical sequence of sedimentary structures preserved in marine terrace deposits in the northern Monterey Bay region is very similar to that predicted on the basis of the modern facies. Few marine sediments deposited during the marine transgression that accompanied rising sea level were preserved. Most of the the marine and eolian sediments form a progradational sequence deposited mainly during intervals of falling sea level. In contrast, the sediments that form the adjacent fluvial terraces were deposited mainly during periods of rising sea level and became entrenched during the subsequent lowering of sea level. In combination, these fluvial, marine, and eolian deposits provide a record of a complete eustatic cycle. The recognition of the role of changing sea level in controlling patterns of coastal sedimentation and landform development during the Quaternary allows the development of a generalized model for Quaternary sedimentation along a wave-dominated coastline. The application of this model has aided in the interpretation of older Pleistocene sediments in the region (e.g. the Aromas Sand). It also has resulted in the recognition of at least eleven glacio-eustatic cycles preserved in the stratigraphic record of the Monterey Bay area during the Quaternary.

California↗
USGS2007

Survey report of NOAA Ship McArthur II cruises AR-04-04, AR-05-05 and AR-06-03: habitat classification of side scan sonar imagery in support of deep-sea coral/sponge explorations at the Olympic Coast National Marine Sanctuary

Habitat mapping and characterization has been defined as a high-priority management issue for the Olympic Coast National Marine Sanctuary (OCNMS), especially for poorly known deep-sea habitats that may be sensitive to anthropogenic disturbance. As a result, a team of scientists from OCNMS, National Centers for Coastal Ocean Science (NCCOS), and other partnering institutions initiated a series of surveys to assess the distribution of deep-sea coral/sponge assemblages within the sanctuary and to look for evidence of potential anthropogenic impacts in these critical habitats. Initial results indicated that remotely delineating areas of hard bottom substrate through acoustic sensing could be a useful tool to increase the efficiency and success of subsequent ROV-based surveys of the associated deep-sea fauna. Accordingly, side scan sonar surveys were conducted in May 2004, June 2005, and April 2006 aboard the NOAA Ship McArthur II to: (1) obtain additional imagery of the seafloor for broader habitat-mapping coverage of sanctuary waters, and (2) help delineate suitable deep-sea coral-sponge habitat, in areas of both high and low commercial-fishing activities, to serve as sites for surveying-in more detail using an ROV on subsequent cruises, Several regions of the sea floor throughout the OCNMS were surveyed and mosaicked at 1-meter pixel resolution. Imagery from the side scan sonar mapping efforts was integrated with other complementary data from a towed camera sled, ROVs, sedentary samples, and bathymetry records to describe geological and biological (where possible) aspects of habitat. Using a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999), we created a preliminary map of various habitat polygon features for use in a geographical information system (GIS). This report provides a description of the mapping and groundtruthing efforts as well as results of the image classification procedure for each of the areas surveyed.

Washington↗
USGS1997

Wetland losses related to fault movement and hydrocarbon production, southeastern Texas coast

Time series analyses of surface fault activity and nearby hydrocarbon production from the southeastern Texas coast show a high correlation among volume of produced fluids, timing of fault activation, rates of subsidence, and rates of wetland loss. Greater subsidence on the downthrown sides of faults contributes to more frequent flooding and generally wetter conditions, which are commonly reflected by changes in plant communities {e.g., Spartina patens to Spartina alterniflora) or progressive transformation of emergent vegetation to open water. Since the 1930s and 1950s, approximately 5,000 hectares of marsh habitat has been lost as a result of subsidence associated with faulting. Marsh- es have expanded locally along faults where hydrophytic vegetation has spread into former upland areas. Fault traces are linear to curvilinear and are visible because elevation differences across faults alter soil hydrology and vegetation. Fault lengths range from 1 to 13.4 km and average 3.8 km. Seventy-five percent of the faults visible on recent aerial photographs are not visible on photographs taken in the 1930's, indicating relatively recent fault movement. At least 80% of the surface faults correlate with extrapolated subsurface faults; the correlation increases to more than 90% when certain assumptions are made to compensate for mismatches in direction of displacement. Coastal wetlands loss in Texas associated with hydrocarbon extraction will likely increase where production in mature fields is prolonged without fiuid reinjection.

Texas↗
USGS1985

Processes on a glacier-dominated coast, Alaska

The 500 km long Gulf of Alaska coastline between Cape Suckling and Cape Spencer can be characterized by constant rapid change in an environment of glaciers, stormy climate, high relief, and extreme oceanographic parameters. During a more than 200-year history of observation, bays have completely filled with sediment, new bays have appeared, glaciers have advanced and retreated as much as 40 km, streams have been captured, and spits have grown as much as 10 km in length, earthquakes have uplifted the coast as much as 15 m, and in general, few features have been static. More than 250 km of coastline have undergone erosion and retreat, with maximum retreat exceeding 4 km at Icy Bay.

Alaska↗
USGS2010

Estimating salinity intrusion effects due to climate change along the Grand Strand of the South Carolina coast

The ability of water-resource managers to adapt to future climatic change is especially challenging in coastal regions of the world. The East Coast of the United States falls into this category given the high number of people living along the Atlantic seaboard and the added strain on resources as populations continue to increase, particularly in the Southeast. Increased temperatures, changes in regional precipitation regimes, and potential increased sea level would have a great impact on existing hydrological systems in the region. Six reservoirs in North Carolina discharge into the Pee Dee River, which flows 160 miles through South Carolina to the coastal communities near Myrtle Beach, SC. During the Southeast’s record-breaking drought from 1998 to 2002, salinity intrusions inundated a coastal municipal freshwater intake, limiting water supplies. Salinity intrusion results from the interaction of three principal forces - streamflow, mean tidal water levels, and tidal range. To analyze, model, and simulate hydrodynamic behaviors at critical coastal streamgages along the Atlantic Intracoastal Waterway (AIW) near Myrtle Beach, SC, data-mining techniques were applied to over 20 years of hourly streamflow, coastal water-quality, and water-level data. Artificial neural network (ANN) models were trained to learn the variable interactions that cause salinity intrusions. Streamflow from the 12,700 square-mile Pee Dee River Basin that flows into the AIW are input to the model as time-delayed variables and accumulated tributary inflows. Tidal inputs to the models were obtained by decomposing tidal water-level data into a “periodic” signal of tidal range and a “chaotic” signal of mean water levels. The ANN models were able to convincingly reproduce historical behaviors and generate alternative scenarios of interest. To evaluate the impact of climate change on salinity intrusion, inputs of streamflows and mean tidal water levels were modified to incorporate estimated changes in precipitation patterns and sea-level rise appropriate for the Southeastern United States. Changes in mean tidal water levels were changed parametrically for various sea-level rise conditions. Preliminary model results at the U.S. Geological Survey Pawleys Island streamgage (station 02110125) near a municipal freshwater intake indicate that a sea-level rise of 1 foot (ft, 30.5 centimeters [cm]) would double the frequency of water with a specific conductance value of 2,000 microsiemens per centimeter close to 4 percent. A 2 ft (61 cm) sea-level rise would quadruple the frequency to 9 percent.

South Carolina↗