Shoreline Erosion Rates Research Articles

Upland and Coastal Sediment Sources in a Chesapeake Bay Estuary

Abstract Rapid sedimentation in the upper and central portions of tributary estuaries of the Chesapeake Bay typically has been attributed to clearing of land and subsequent upland erosion since European settlement. New data from the South River, Maryland and re-examination of existing literature suggest that coastal erosion may be the dominant process driving sediment inputs along the entire length of many tributary estuaries of the Chesapeake over the past several centuries. Shoreline erosion rates derived from historical shoreline maps and aerial photographs, coupled with information on fluvial inputs obtained from sediment rating curves, indicate that coastal contributions to the estuarine sediment budget of the South River are 4 to 12 times higher than fluvial inputs. Rates of subtidal accumulation estimated from pollen and 210Pb dating of cores and changes in estuarine bathymetry suggest that most sediment from streams is trapped in river mouth marshes and subtidal storage within 1 km of river mouths. Sediment inputs from streams therefore have little direct effect on sediment accumulation in the majority of the South River estuary. These findings imply that existing runoff-based efforts to control estuarine sedimentation also need to include nonstructural measures to reduce shoreline erosion in order to alleviate sediment-related problems in tributary estuaries of the western Chesapeake.

Barrier-beach erosion and rising sea level

For an equilibrium cross-shore profile, a kinematic model has been constructed that predicts the rate of shoreline erosion in response to rising sea level. Model predictions are reasonably close to observed erosional rates for several state shorelines bordering the United States coast of the Atlantic Ocean and Gulf of Mexico.

Preliminary assessments of the occurrence and effects of utilization of sand and aggregate resources of the Louisiana inner shelf

Louisiana is experiencing the most critical coastal erosion and land loss problem in the United States. Shoreline erosion rates exceed 6 m/yr in more than 80% of the Louisiana coastal zone and can be up to 50 m/yr in areas impacted by hurricanes. The barrier islands have decreased in area by some 40% since 1880. Land loss from coastal marshlands and ridgelands from both natural and human-induced processes is estimated to exceed 100 km 2/yr. In response, a two-phase plan has been established, calling for barrier-island restoration and beach nourishment, both requiring large amounts of sand. The plan will be cost-effective only if sand can be found offshore in sufficient quantities close to project sites. To locate such deposits, the Louisiana Geological Survey is conducting an inventory of nearshore sand resources on the Louisiana continental shelf. Exploration for offshore sand deposits is conducted in two phases, with high-resolution seismic reflection profiling to locate potential sand bodies followed by vibracoring to confirm seismic intepretations and obtain samples for textural characterization. As part of the initial stages of the program, reconnaissance high-resolution seismic investigations of three areas of the continental shelf representing different stages in the evolutionary sequence of barrier shorelines were carried out. The Timbalier Islands, flanking barriers of the eroding Caminada-Moreau headland, contain potential sand resources associated with buried tidal and distributary channels. The Chandeleur Islands, a barrier-island arc, have potential offshore sands in the form of truncated spit and tidal inlet deposits, submerged beach ridges, and distributary channels. Trinity Shoal, an inner shelf shoal, is an offshore feature containing up to 2 × 10 9 m 3 of material, most of which is probably fine sand. These reconnaissance surveys have demonstrated the occurrence of sand resources on the Louisiana continental shelf. Utilization of such deposits for island restoration or beach nourishment raises the question of potential adverse effects on the shoreline due to alteration of the inner shelf bathymetry by removing material or deposition of spoil in the process of dredging. Wave refraction analysis models provide a means by which hypothetical wave energy distribution can be determined and possible changes due to resource utilization assessed. A preliminary assessment of the consequences of using sand from Ship Shoal, a large shore-parallel feature, as borrow material for beach nourishment was conducted. Initial results indicate that the shoal serves to attenuate storm waves, and removal of this feature would result in increased erosion and overwash on the adjacent Isles Dernieres barrier-island shoreline. These findings illustrate the need to determine optimum dredging configurations if environmentally deleterious effects of utilization of offshore and aggregate resources are to be minimized.

Dynamics of a northern barrier beach: Nauset Spit, Cape Cod, Massachusetts

Research Article| January 01, 1986 Dynamics of a northern barrier beach: Nauset Spit, Cape Cod, Massachusetts STEPHEN P. LEATHERMAN; STEPHEN P. LEATHERMAN 1Department of Geography, University of Maryland, College Park, Maryland 20742 Search for other works by this author on: GSW Google Scholar ROBERT E. ZAREMBA ROBERT E. ZAREMBA 2Nature Conservancy, Cold Spring Harbor, New York 11724 Search for other works by this author on: GSW Google Scholar Author and Article Information STEPHEN P. LEATHERMAN 1Department of Geography, University of Maryland, College Park, Maryland 20742 ROBERT E. ZAREMBA 2Nature Conservancy, Cold Spring Harbor, New York 11724 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1986) 97 (1): 116–124. https://doi.org/10.1130/0016-7606(1986)97<116:DOANBB>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation STEPHEN P. LEATHERMAN, ROBERT E. ZAREMBA; Dynamics of a northern barrier beach: Nauset Spit, Cape Cod, Massachusetts. GSA Bulletin 1986;; 97 (1): 116–124. doi: https://doi.org/10.1130/0016-7606(1986)97<116:DOANBB>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Quantitative analysis of historical shoreline (ocean and bay) and coastal environments (dune, salt marsih, shrub, washover, and sandy beach) change data for Nauset Spit, Cape Cod, Massachusetts are described in this paper. There are marked differences in the relative role of the landward sediment transport processes along the Nauset barrier chain. In general, the barriers have been narrowing during thi; past century, and bayshore accretion has not been equal to ocean shoreline erosion rates. Inlets are largely responsible for bayside sedimentation, whereas over-wash is not effective in maintaining width until the barrier sllims considerably. While salt marshes form on intertidal washover deposits, the vast expanse of barrier-related marshes have developed atop of flood-tidal deltas, and overwash subsequently has buried and killed the marshes. Therefore, massive washovers eventually become the sites of new dunes, often at trie expense of marshes in the cyclic events of barrier evolution. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Shoreline Erosion and Restabilization in the Southern Indian Lake Reservoir

Prior to a 3-m impoundment in 1976, bedrock comprised 76% of the shoreline of Southern Indian Lake in northern Manitoba. This was reduced to only 14% of the shoreline as the water level rose above the wave-washed zone and flooded into the predominantly fine-grained, frozen overburden materials. Twenty monitoring sites were surveyed annually to determine rates of permafrost melting and solifluction and shoreline erosion. The sequence of shoreline erosion in permafrost materials was found to be cyclic, consisting of melting and undercutting of the backshore zone, massive faulting of the overhanging shoreline, and removal of the melting and fractured debris. Rates of shoreline erosion varied widely, depending on the exposure of the site to wave action and the composition of the backshore materials. At sites in fine-grained frozen silts and clays, representative of over three quarters of the postimpoundment shoreline, rates of retreat of up to 12 m∙yr−1were observed. The total volume of shoreline materials removed varied from less than 1 to over 23 m3∙m shoreline length−1∙yr−1. Clearing of the forested backshore prior to flooding did not affect the erosion rates. The index of erosion based on the hindcast wave energy component perpendicular to the shoreline was 0.00035 m3∙t-m wave energy−1(0.036 m3∙MJ−1). The minimum period of restabilization of the shoreline based on the volume of backshore materials that must be eroded before bedrock conditions are reestablished was estimated to be 35 yr for three quarters of the shoreline surrounding the lake.

Breakdown of Conifer Needle Debris in a New Northern Reservoir, Southern Indian Lake, Manitoba

Formation of the Southern Indian Lake reservoir, northern Manitoba, added an estimated 5.4 × 105 t of Picea mariana (black spruce) needles to the lake. The breakdown of needles in the lake was measured by stringing needles on monofilament line, placing the strings into 3-mm mesh bags, and situating the bags along four shorelines representing high and low shoreline erosion rates (clay vs. bedrock) and wave exposures (highly exposed vs. protected). Sampling was done in phases of 0–41 and 328–384 d. Effects of excluding macroinvertebrates were tested by using needle strings placed in 50-μm mesh bags at the clay low exposure shoreline. Needle breakdown apparently occurred in two stages. Initially, weight losses were due primarily to leaching and microbial conditioning. Subsequently, weight losses were due primarily to feeding by macroinvertebrates. Processing coefficients (k) ranged from 0.0011∙d−1 for the 50-μm mesh bags to 0.0097∙d−1 for the 3-mm mesh bags at the bedrock high exposure shoreline. The presence of macroinvertebrates and exposure to waves enhanced needle breakdown. Macroinvertebrate colonization of needle strings occurred rapidly [Formula: see text] and was mainly by chironomid larvae. Phaenopsectra punctipes (Wied.) and Brillia flavifrons (joh.) larvae fed directly on needle tissue. Macroinvertebrates accounted for ~ 40% of total weight losses and, apparently, were active over the winter. Leaching and microbial conditioning each accounted for ~ 30% of total weight losses. Values of k for Southern Indian Lake most resembled those for conifer needle breakdown recorded in streams, indicating the significance of wave action in the lake. The breakdown of P. mariana needles in Southern Indian Lake appeared to be a significant source of carbon during the year following impoundment, and needles may have been an important habitat for macroinvertebrates within localized areas.

EMERGENCE OF CADDISFLIES (TRICHOPTERA) FROM ERODING AND NON-ERODING SHORELINES OF SOUTHERN INDIAN LAKE, MANITOBA, CANADA

AbstractEmerging Trichoptera were collected from the littoral zone of a newly-created reservoir, Southern Indian Lake, Manitoba, from 1977 to 1981. The relationship between caddisfly emergence and lake shoreline type, depth of sampling, and shoreline erosion rate was studied. Twenty-five species of Trichoptera were collected; six species of Polycentropodidae comprised almost 75% of the total number of individuals. Abundance and richness of Trichoptera were correlated with shoreline stability, with higher abundance and richness being found at more stable (i.e. lower erosion) shorelines. Highest numbers of Trichoptera emerged in 1981, 5 years after impoundment. Maximum abundance and richness of Trichoptera was found at 3.5 m depth, which is also the depth at which maximum deposition of organic matter occurred. Agrypnia straminea Hagen, a case-maker, dominated the trichopteran fauna at the marsh shoreline; species of net-spinning Polycentropodidae dominated at the clay shorelines. Patterns of species composition and abundance in 1982 artificial substrate collections were similar to those found in 1977–1981 emergence trap collections. Interspecific differences in Neureclipsis capture nets may explain the greater abundance of N. validus (Walker) than N. bimaculatus (L.) at a high erosion shoreline.

Shoreline erosion rates along barrier islands of the north central gulf of Mexico

Rates of shoreline change and overwash penetration distances were calculated for barrier islands along the Louisiana, Mississippi, and Alabama coasts with the orthogonal grid mapping system (OGMS). Average rates of shoreline change are exceptionally high in Louisiana, being of the order −4.7 to −7.4 m yr−1. Mississippi and Alabama recession rates are lower and range from −2.0 to −3.1 m yr−1 over the period of record. Erosion rates along the shorelines of these islands have remained relatively constant over the period of study with five exceptions in coastal Louisiana and the Chandeleur-Breton Islands Arc, and two exceptions along the Mississippi-Alabama barrier islands where they have accelerated. Mean overwash penetration is greatest along Dauphin Island, Alabama, and Cat Island, Mississippi: 207.6 and 197.9 m, respectively. The Chandeleur-Brenton Islands Arc range from 88.1 m at the central barrier to 180.4 along the flanks. The Mississippi islands range from 105.2 m on Ship Island to 200.5 m along central Horn Island. Mean overwash penetration along the Louisiana barriers is highly variable: 46.3 to 211.4 m.

Erosion of U.S. shorelines

We have assembled data on the rate of change of the U.S. shorelines, including those of the Great Lakes. Obtained from geologists and engineers, our data base covers 1689 sites. The national average (unweighted) shoreline erosion rate is 0.40 m/yr. Along the Atlantic coast the average rate of recession is 0.8 m/yr; the Gulf coast is 1.8 m/yr; and the Pacific coast rate, including Alaska, is 0.005 m/yr. Statistics for Delaware Bay, Chesapeake Bay, and the Great Lakes are also summarized.

Shoreline erosion rates along the middle Atlantic coast of the United States

Research Article| December 01, 1979 Shoreline erosion rates along the middle Atlantic coast of the United States Robert Dolan; Robert Dolan 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903 Search for other works by this author on: GSW Google Scholar Bruce Hayden; Bruce Hayden 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903 Search for other works by this author on: GSW Google Scholar Cary Rea; Cary Rea 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 229032Present addresses: (Rea) Naval Field Operational Intelligence Office, Attn: Code 33, Fort Meade, Maryland 20755; (Heywood) National Park Service-Department of the Interior, Box 25287, 655 Parfet Street, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Jeffrey Heywood Jeffrey Heywood 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 229032Present addresses: (Rea) Naval Field Operational Intelligence Office, Attn: Code 33, Fort Meade, Maryland 20755; (Heywood) National Park Service-Department of the Interior, Box 25287, 655 Parfet Street, Denver, Colorado 80225 Search for other works by this author on: GSW Google Scholar Author and Article Information Robert Dolan 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903 Bruce Hayden 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903 Cary Rea 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 229032Present addresses: (Rea) Naval Field Operational Intelligence Office, Attn: Code 33, Fort Meade, Maryland 20755; (Heywood) National Park Service-Department of the Interior, Box 25287, 655 Parfet Street, Denver, Colorado 80225 Jeffrey Heywood 1Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 229032Present addresses: (Rea) Naval Field Operational Intelligence Office, Attn: Code 33, Fort Meade, Maryland 20755; (Heywood) National Park Service-Department of the Interior, Box 25287, 655 Parfet Street, Denver, Colorado 80225 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1979) 7 (12): 602–606. https://doi.org/10.1130/0091-7613(1979)7<602:SERATM>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Robert Dolan, Bruce Hayden, Cary Rea, Jeffrey Heywood; Shoreline erosion rates along the middle Atlantic coast of the United States. Geology 1979;; 7 (12): 602–606. doi: https://doi.org/10.1130/0091-7613(1979)7<602:SERATM>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A method has been developed and tested for mapping shoreline changes using an orthogonal grid system and historical aerial photography. Our data base now includes rates and variances of shoreline change and storm-surge penetration at 100-m intervals along the coast for 630 km between New Jersey and North Carolina. Analysis of the data shows that the average rate of shoreline recession is 1.5 m/yr; however, variance along the 630-km reach is high, with rates of as much as 10 m/yr for the Virginia barrier islands. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Late Holocene history of the Central Texas coast from Galveston Island to Pass Cavallo

Mid-Holocene facies underlying Matagorda Peninsula and Galveston Island record a complex history of transgressive and regressive fluvial, deltaic, and estuarine sedimentation along the central Texas coast. Data from 80 borings and jet-down holes reveal a dissimilar sequence of depositional events for northeastern and southwestern Matagorda Peninsula. Along northeastern Matagorda Peninsula and the area now occupied by the Colorado-Brazos delta plain, all major river valleys were flooded during the Holocene transgression; gulfward, a barrier system developed and was driven landward by rising sea level. As the rate of sea-level rise decreased, the Colorado and Brazos Rivers completely filled their common estuary and prograded across ancestral Matagorda and West Bays. Deltaic progradation terminated after the landward-migrating barrier system overrode the delta front; at that time, sediment was delivered directly to the Gulf of Mexico. Shortly thereafter, beach and shoreface progradation began along barrier island systems lateral to the now rapidly eroding deltaic headland. This was accompanied by renewed deposition of estuarine mud in Matagorda and West Bays. Facies underlying southwestern Matagorda Peninsula indicate Pass Cavallo was initially established over the axis of the Lavaca River valley. Southwestward migration of the pass accompanied by landward migration of the barrier peninsula has resulted in a well-preserved facies tract of bay, distal and proximal flood tidal delta, and spit-related sediments now underlying this coastal segment. Modern physiographic features, as well as rates of shoreline erosion and recession, are directly related to these middle and late Holocene depositional events.

Spatial and temporal analyses of shoreline variations

Using detailed data from historical aerial photography, high resolution (100-m) shoreline and storm surge penetration line rates-of-change and variance were calculated for 428 km of coast between New Jersey and Cape Lookout, North Carolina. Shoreline erosion rates along the U.S. mid-Atlantic coast average 0.6 m/yr but commonly vary (± 1 σ) along-the-coast from −3.6 m/yr to 2.4 m/yr and from −6.8 m/yr to 5.6 m/yr on a decade-to-decade basis. Spatial and temporal variances in shoreline change rates make the design of coastal experiments and systematic monitoring programs difficult. The precision of measurements of the rates of change of the shoreline and storm-surge penetration line decrease as the along-the-coast sampling interval increases. This decrease follows an hyperbolic tangent form of decline. For the U.S. mid-Atlantic coast a sample spacing of 500 m will provide an estimate of the mean shoreline rate-of-change to within ± 0.25σ of the higher resolution (100-m) estimate. The average standard deviation of shoreline change rates for the U.S. mid-Atlantic Coast is ± 3.01 m/yr. Consequently, a 500-m sampling spacing will result in a precision of ± 0.75 m/yr for shoreline change. In addition to the hyperbolic tangent decline of measurement precision, along-the-coast periodicities in shoreline and storm-surge penetration line rates of change occur. Accordingly, unless the objective of the measurement program is to define these periodicities, a constant interval sampling should be avoided.

Increasing Shoreline Erosion Rates with Decreasing Tidal Range in the Virginia Chesapeake Bay

The Virginia Chesapeake Bay has a large variation (200%) in tidal range (.36m to 1m) over a relatively short (120 km) distance. Analysis of a regional sampling of shoreline morphology and processes demonstrates that decreasing tidal ranges result in increasing long-term erosion rates. This results because larger tidal ranges form a higher elevation beach. Thus, in larger tidal range areas, water levels increased by storm surges have a lower probability of reaching the elevation of the fastland (bluff or dune) material to augment erosion. Secondly, the wave energy is distributed over a greater distance in the course of a tidal cycle.

STUDY OF EQUILIBRIUM BEACH PROFILES

The use of the dimensionless fall velocity for determining equilibrium foreshore slopes, -modeling of natural beaches in the laboratory, and for determining shoreline erosion rates is examined. Encouraging results are found for relating foreshore slope uniquely to the dimensionless fall velocity and possible model law is proposed.