Shoreline Erosion Rates Research Articles

Contribution of shoreline erosion to nutrient loading of the Lake Diefenbaker reservoir, Saskatchewan, Canada

The nutrient budget of the Lake Diefenbaker reservoir (SK, CAN) is being developed as part of a larger multi-faceted trophic status study. However, it is currently unknown if shoreline erosion from the near vertical banks serves as a source of nutrients to the reservoir. Thus, the objective of this study was to quantify the annual nutrient loading to the reservoir through shoreline erosion, and the relative magnitude of erosion-derived inputs versus nutrient loading through the major tributary, the South Saskatchewan River (SSR). Nutrient status measurements indicate that Lake Diefenbaker algal populations would be responsive to additional inputs of phosphorus (P). We measured the total carbon (TC), total nitrogen (TN), Mehlich 3 P, and iron oxide strip extracted (FeO) P nutrient content by weight in the bank soils along the reservoir. Combined with shoreline erosion rates and lengths, the mean annual nutrient inputs for TC, TN, M3P, and FeO P were 57,500 kg year − 1 , 2100 kg year − 1 , 49.8 kg year − 1 and 30.0 kg year − 1 , respectively. We also compared nutrient content and inputs across bank classifications and land uses to identify factors contributing to nutrient loading through erosion and to determine potential areas for mitigation efforts. Relative to the primary nutrient loading from the SSR, bank soils represent less than 1% of the overall load. These measurements of nutrient inputs will allow us to assess the relative contribution of soil nutrients to prairie reservoirs and will serve as important baseline data for the reservoir. • Carbon, nitrogen, and phosphorus soil concentrations were measured around the reservoir. • Bank-specific erosion rates were used to determine annual nutrient input rates. • Nutrient input rates were compared between bank classifications and land uses. • Nutrient input through shoreline erosion was < 1% of the annual load. • Implications for reservoir management were identified.

Influence of storms on coastal retreat in SW Spain

Puig, M., Del Río, L., Plomaritis, T.A., Benavente, J., 2014. Influence of storms on coastal retreat in SW Spain. Proceedings 13th International Coastal Symposium (Durban, South Africa), Journal of Coastal Research, Special Issue No. 70, pp. 193–198, ISSN 0749-0208.Natural and anthropogenic controls contribute to coastal change at diverse temporal and spatial scales. This study presents an analysis of storminess and a correlation with the medium-term shoreline erosion rates in two sand spits of the Gulf of Cadiz (SW Spain). Recession rates were assessed by means of aerial photographs and orthophotographs considering the dune foot as an appropriate proxy. Storm events were obtained from a combination of coastal wave buoy data and the hindcast database of the HIPOCAS project. The characteristics of the storms were compared with shoreline changes determined using the aerial photographs, and the correlation between them was estimated and discussed. The best agreement between storms and shoreline change was observed in section 1 of Sancti Petri sand spit, while Valdelagrana sand spit showed a lower dependence between shoreline erosion and storminess. This is related to the contrasting exposure of both sites, with Sancti Petri being more exposed and thus more sensitive to storm impact. It is suggested that the main causes of retreat in Valdelagrana are human interventions performed on the coast and in the nearby rivers (breakwaters, jetties and dams). Nevertheless, storminess contributes to modulate recession rate, so that erosion rates increase when the number of storms is higher.

Shoreline dynamics and littoral transport around the tidal inlet at Pulicat, southeast coast of India

Pulicat is India׳s second largest brackish water lagoon with its mouth opening in the Bay of Bengal. The dynamics of the tidal inlet at Pulicat has been reported in this study on the basis of long term analysis using satellite remote sensing aided with Geographical Information System (GIS) and berm crest data. In addition, the short term analysis was carried out using monthly in situ Global Positioning System (GPS) profiling and sediment grain size analysis. The study of the shoreline dynamics along the inlet using the Linear Imaging Self – Scanning Sensor (LISS) – III along with the Survey of India toposheet of 1954 reveals that the inlet once with a single mouth is divided into two, over the period of time with the southern mouth migrating towards north with an inconsistent migration pattern of the northern mouth. The overall extent of migration is found to be within 3km. The outcome of the 25 year berm crest data starting from 1978 revealed the coastline around Pulicat is eroding upto 1990 and thereafter it is accreting with the net shoreline erosion rate of 20.34m/yr. The monthly in situ beach profiling studies from August 2004 to July 2005 revealed that the Pulicat inlet follows a variable migratory pattern with a shift of upto 914m North during August to December with a reversal migration of 600m thus leading to a net migration towards the north. The grain size analysis has unravelled the sediment transport around Pulicat inlet. The study of the inlet using satellite imagery during monsoon has clearly justified the dominant fresh water inflow regulatory force over the tidal forces and the positive influence of the Tsunami on opening the inlet during monsoon failure.

National evaluation of Chinese coastal erosion to sea level rise using a Bayesian approach

In this paper a Causal Bayesian network is developed to predict decadal-scale shoreline evolution of China to sea-level rise. The Bayesian model defines relationships between 6 factors of Chinese coastal system such as coastal geomorphology, mean tide range, mean wave height, coastal slope, relative sea-level rise rate and shoreline erosion rate. Using the Bayesian probabilistic model, we make quantitative assessment of china's shoreline evolution in response to different future sea level rise rates. Results indicate that the probability of coastal erosion with high and very high rates increases from 28% to 32.3% when relative sea-level rise rates is 4~6mm/a, and to 44.9% when relative sea-level rise rates is more than 6mm/a. A hindcast evaluation of the Bayesian model shows that the model correctly predicts 79.3% of the cases. Model test indicates that the Bayesian model shows higher predictive capabilities for stable coasts and very highly eroding coasts than moderately and highly eroding coasts. This study demonstrates that the Bayesian model is adapted to predicting decadal-scale Chinese coastal erosion associated with sea-level rise.

Variable response of coastal environments of the northwestern Gulf of Mexico to sea-level rise and climate change: Implications for future change

The results from nearly three decades of marine geological research in the northwestern Gulf of Mexico are compiled in an effort to understand those factors (e.g., sea-level rise, sediment supply, subsidence, antecedent topography) that influenced coastal evolution during the last eustatic cycle (~ 120 ka to Present). Armed with this information, we evaluate coastal response to variable sea-level rise of the Holocene and accelerated rise during historical time to gain a better understanding of how the coast is likely to respond to future changes. The early Holocene evolution of northwestern Gulf of Mexico bays was punctuated by rapid and possibly synchronous flooding events that are interpreted as resulting from episodes of rapid sea-level rise. Two of these events, one between ~ 8.4 and 8.0 ka and the other between ~ 7.4 and 6.8 ka, were associated with known episodes of ice sheet retreat in North America and Antarctica, respectively. During the middle and late Holocene, the east Texas and western Louisiana coasts experienced episodes of stability and growth followed by rapid shoreline retreat, while the central Texas coast remained relatively stable. This variability in coastal response to sea-level rise resulted mainly from differences in sediment supply and the highly irregular antecedent topography on which coastal environments formed. Sand that nourished the evolving east and south Texas, as well as westernmost Louisiana, coasts was derived mainly from transgressive ravinement of deltas that were formed during the falling stage of sea level (MIS5e–MIS2). The loci of these deltas controlled the spatial variability of this offshore sand supply. Sand supply to the central Texas coast has been dominated by converging longshore currents and throughout the middle to late Holocene was large enough to keep pace with sea-level rise. Moreover, sand supply from rivers has varied considerably in response to climate change. During the early Holocene, when the average rate of linear sea-level rise was 4.2 mm/yr, the Brazos, Colorado and Rio Grande Rivers all formed deltas on the inner continental shelf. Today, only the Brazos contributes enough sediment to the Gulf of Mexico to form a delta, but its sand delivery is minimal. A reversal from late Holocene growth of western Louisiana–east Texas and south Texas barrier islands and peninsulas to erosion occurred during the last ~ 2.0 ka, after the rate of sea-level rise began to decelerate. The actual timing of this reversal was diachronous across the coast and was caused by a decrease in sediment supply once offshore sand sources were bypassed by the landward-advancing shoreface (transgressive ravinement). Differences in the exact timing and rate of retreat also reflect variability in the offshore profiles of these barriers and their thickness, which results from the underlying relief on the Pleistocene surface. The late Holocene was also the time of chenier plain development in western Louisiana and east Texas that was marked by localized differences in growth and retreat. The current rate of eustatic sea-level rise in the northern Gulf of Mexico is in the range of 2.0 and 3.0 mm/yr and is approaching rates of the early Holocene. This is on average about five times the long-term rate of the past 4.0 ka. This larger rate is associated with an increase in coastal erosion in historical time relative to long-term rates. Current rates of Gulf shoreline erosion are approaching rates of the early to mid-Holocene and the rate of retreat of some barriers is not sustainable. Core transects off central Texas reflect a late Holocene history of shoreface progradation, but the modern shoreline is currently eroding, albeit at slower rates than elsewhere along the coast. Overall, the sand supply needed to sustain the Gulf shoreline is lacking. Likewise, baylines are experiencing erosion rates that are faster than the late Holocene average and bayhead deltas are at the tipping point of catastrophic retreat. Spatial variability in erosion rates highlights the importance of factors such as sediment supply, subsidence, and anthropogenic influences on coastal evolution. Tropical storms and hurricanes, while exerting the most noticeable coastal change, merely exacerbate overall shoreline retreat and migration. Along the entire northwestern Gulf Coast, the impact of human intervention to natural processes is particularly evident, primarily due to alterations in river discharge and sediment supply to the coast, interruptions in along-shore and cross-shore sand transport, and increases in rates of subsidence through fluid withdrawal. Compared to natural changes that took place during the Holocene, the impacts of human activity have been virtually instantaneous. The geological record indicates that the ongoing increase in the rate of sea-level rise, coupled with diminished sediment supply and human intervention, will continue to severely impact the low-gradient coastal environments of the northwestern Gulf of Mexico.

Effects of oil on the rate and trajectory of Louisiana marsh shoreline erosion

Oil can have long-term detrimental effects on marsh plant health, both above- and belowground. However, there are few data available that quantify the accelerated rate of erosion that oil may cause to marshes and the trajectory of change. Between November 2010 and August 2012, we collected data on shoreline erosion, soil strength, per cent cover of Spartina alterniflora, and marsh edge overhang at 30 closely spaced low oil and high oil sites in Bay Batiste, Louisiana. Surface oil samples were taken one meter into the marsh in February 2011. All high oiled sites in Bay Batiste were contaminated with Macondo 252 oil (oil from the Deepwater Horizon oil spill, 20 April–15 July 2010). The results suggest that there is a threshold where soil parameters change dramatically with a relatively small increase in oil concentration in the soil. Heavy oiling weakens the soil, creating a deeper undercut of the upper 50 cm of the marsh edge, and causing an accelerated rate of erosion that cascades along the shoreline. Our results demonstrate that it could take at least 2 yr to document the effects heavy oiling has had on the marsh shoreline. The presence of aboveground vegetation alone may not be an appropriate indicator of recovery.

Effects of shoreline erosion on salt-marsh floral zonation

The loss of salt-marsh habitat is proceeding at an alarming rate worldwide, resulting in the loss of ecosystem function and reduced exchange with adjacent habitats. The immediate result of shoreline erosion is the loss of fringing vegetation, but it is unclear how, and at what temporal scale, intertidal floral zones respond to shoreline loss. Using a transect-based approach over a 3 yr period, we compared community composition among 3 intertidal salt marshes in coastal Alabama that differ in the intensity of wave-generated disturbance. Each study marsh exhibited net annual rates of shoreline retreat, but differed in its exposure to wave-induced disturbance and erosional state. We also examined whether wave attenuation by oyster break waters reduced annual rates of shoreline erosion, providing a means to test whether the intensity of shoreline erosion affects inter-annual patterns of marsh zonation. Community composition differed across sites, but not between breakwater treatments and site-specific rates of shoreline loss, suggesting that differences in community composition are not due to differences in erosion intensity, but to other contrasts across sites. The cohesive nature of the floral communities at each site suggests that marshes maintain their zonation structure by migrating inland as the shoreline recedes. The inland migration of marsh zones will, however, ultimately be limited by the lack of area available for marsh colonization. The preservation of coastal salt marshes is, therefore, vitally contingent on effective shoreline management strategies.

Assessment of the sensitivity of the southern coast of the Gulf of Corinth (Peloponnese, Greece) to sea-level rise

Abstract The eustatic sea-level rise due to global warming is predicted to reach approximately 18–59 cm by the year 2100, which necessitates the identification and protection of sensitive sections of coastline. In this study, the classification of the southern coast of the Gulf of Corinth according to the sensitivity to the anticipated future sealevel rise is attempted by applying the Coastal Sensitivity Index (CSI), with variable ranges specifically modified for the coastal environment of Greece, utilizing GIS technology. The studied coastline has a length of 148 km and is oriented along the WNW-ESE direction. CSI calculation involves the relation of the following physical variables, associated with the sensitivity to long-term sea-level rise, in a quantifiable manner: geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height. For each variable, a relative risk value is assigned according to the potential magnitude of its contribution to physical changes on the coast as the sea-level rises. Every section of the coastline is assigned a risk ranking based on each variable, and the CSI is calculated as the square root of the product of the ranked variables divided by the total number of variables. Subsequently, a CSI map is produced for the studied coastline. This map showed that an extensive length of the coast (57.0 km, corresponding to 38.7% of the entire coastline) is characterized as highly and very highly sensitive primarily due to the low topography, the presence of erosionsusceptible geological formations and landforms and fast relative sea-level rise rates. Areas of high and very high CSI values host socio-economically important land uses and activities.

Degradation and resilience in Louisiana salt marshes after the BP–Deepwater Horizonoil spill

More than 2 y have passed since the BP-Deepwater Horizon oil spill in the Gulf of Mexico, yet we still have little understanding of its ecological impacts. Examining effects of this oil spill will generate much-needed insight into how shoreline habitats and the valuable ecological services they provide (e.g., shoreline protection) are affected by and recover from large-scale disturbance. Here we report on not only rapid salt-marsh recovery (high resilience) but also permanent marsh area loss after the BP-Deepwater Horizon oil spill. Field observations, experimental manipulations, and wave-propagation modeling reveal that (i) oil coverage was primarily concentrated on the seaward edge of marshes; (ii) there were thresholds of oil coverage that were associated with severity of salt-marsh damage, with heavy oiling leading to plant mortality; (iii) oil-driven plant death on the edges of these marshes more than doubled rates of shoreline erosion, further driving marsh platform loss that is likely to be permanent; and (iv) after 18 mo, marsh grasses have largely recovered into previously oiled, noneroded areas, and the elevated shoreline retreat rates observed at oiled sites have decreased to levels at reference marsh sites. This paper highlights that heavy oil coverage on the shorelines of Louisiana marshes, already experiencing elevated retreat because of intense human activities, induced a geomorphic feedback that amplified this erosion and thereby set limits to the recovery of otherwise resilient vegetation. It thus warns of the enhanced vulnerability of already degraded marshes to heavy oil coverage and provides a clear example of how multiple human-induced stressors can interact to hasten ecosystem decline.

Statistical model predicts shoreline erosion rates due to sea level rise

While sea level rise in the face of global warming is a well‐acknowledged threat, providing estimates of the local impact—the information needed by planners to develop effective strategies against the rising waters—has been difficult. Many attempts treat the global ocean as a giant bathtub, where increased water volume simply rises up and floods the land. Understandably, these approaches fall short of accurately estimating the impact of storms, sea level rise, and human influence on coastlines. The next extension toward an accurate longterm prediction of shoreline change necessarily includes a representation of the dynamic interaction between coastal features and the rising water.

Hydrogeomorphic processes of thermokarst lakes with grounded‐ice and floating‐ice regimes on the Arctic coastal plain, Alaska

AbstractThermokarst lakes cover &gt; 20% of the landscape throughout much of the Alaskan Arctic Coastal Plain (ACP) with shallow lakes freezing solid (grounded ice) and deeper lakes maintaining perennial liquid water (floating ice). Thus, lake depth relative to maximum ice thickness (1·5–2·0 m) represents an important threshold that impacts permafrost, aquatic habitat, and potentially geomorphic and hydrologic behaviour. We studied coupled hydrogeomorphic processes of 13 lakes representing a depth gradient across this threshold of maximum ice thickness by analysing remotely sensed, water quality, and climatic data over a 35‐year period. Shoreline erosion rates due to permafrost degradation ranged from &lt; 0·2 m/year in very shallow lakes (0·4 m) up to 1·8 m/year in the deepest lakes (2·6 m). This pattern of thermokarst expansion masked detection of lake hydrologic change using remotely sensed imagery except for the shallowest lakes with stable shorelines. Changes in the surface area of these shallow lakes tracked interannual variation in precipitation minus evaporation (P − EL) with periods of full and nearly dry basins. Shorter‐term (2004–2008) specific conductance data indicated a drying pattern across lakes of all depths consistent with the long‐term record for only shallow lakes. Our analysis suggests that grounded‐ice lakes are ice‐free on average 37 days longer than floating‐ice lakes resulting in a longer period of evaporative loss and more frequent negative P − EL. These results suggest divergent hydrogeomorphic responses to a changing Arctic climate depending on the threshold created by water depth relative to maximum ice thickness in ACP lakes. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Beach morphology and change along the mixed grain-size delta of the dammed Elwha River, Washington

Sediment supply provides a fundamental control on the morphology of river deltas, and humans have significantly modified these supplies for centuries. Here we examine the effects of almost a century of sediment supply reduction from the damming of the Elwha River in Washington on shoreline position and beach morphology of its wave-dominated delta. The mean rate of shoreline erosion during 1939–2006 is ~ 0.6 m/yr, which is equivalent to ~ 24,000 m 3/yr of sediment divergence in the littoral cell, a rate approximately equal to 25–50% of the littoral-grade sediment trapped by the dams. Semi-annual surveys between 2004 and 2007 show that most erosion occurs during the winter with lower rates of change in the summer. Shoreline change and morphology also differ spatially. Negligible shoreline change has occurred updrift (west) of the river mouth, where the beach is mixed sand to cobble, cuspate, and reflective. The beach downdrift (east) of the river mouth has had significant and persistent erosion, but this beach differs in that it has a reflective foreshore with a dissipative low-tide terrace. Downdrift beach erosion results from foreshore retreat, which broadens the low-tide terrace with time, and the rate of this kind of erosion has increased significantly from ~ 0.8 m/yr during 1939–1990 to ~ 1.4 m/yr during 1990–2006. Erosion rates for the downdrift beach derived from the 2004–2007 topographic surveys vary between 0 and 13 m/yr, with an average of 3.8 m/yr. We note that the low-tide terrace is significantly coarser (mean grain size ~ 100 mm) than the foreshore (mean grain size ~ 30 mm), a pattern contrary to the typical observation of fining low-tide terraces in the region and worldwide. Because this cobble low-tide terrace is created by foreshore erosion, has been steady over intervals of at least years, is predicted to have negligible longshore transport compared to the foreshore portion of the beach, and is inconsistent with oral history of abundant shellfish collections from the low-tide beach, we suggest that it is an armored layer of cobble clasts that are not generally competent in the physical setting of the delta. Thus, the cobble low-tide terrace is very likely a geomorphological feature caused by coastal erosion of a coastal plain and delta, which in turn is related to the impacts of the dams on the Elwha River to sediment fluxes to the coast.

Rates and Trends of Coastal Change in California and the Regional Behavior of the Beach and Cliff System

The U.S. Geological Survey (USGS) recently completed an analysis of shoreline change and cliff retreat along the California coast. This is the first regional, systematic measurement of coastal change conducted for the West Coast. Long-term (∼120 y) and short-term (∼25 y) shoreline change rates were calculated for more than 750 km of coastline, and 70 year cliff-retreat rates were generated for 350 km of coast. Results show that 40% of California's beaches were eroding in the long term. This number increased to 66% in the short term, indicating that many beaches have shifted toward a state of chronic erosion. The statewide average net shoreline change rates for the long and short term were 0.2 m/y and −0.2 m/y, respectively. The long-term accretional signal is likely related to large coastal engineering projects in some parts of the state and to large fluxes of sediment from rivers in other areas. The cliff-retreat assessment yielded a statewide average of −0.3 m/y. It was found that Northern California has the highest overall retreat rates, which are influenced by erosion hot spots associated with large coastal landslides and slumps. The databases established as part of the shoreline change and cliff-retreat analyses were further investigated to examine the dynamics of the beach/cliff system. A correlation analysis identified a strong relationship between the geomorphology of the coast and the behavior of the beach/cliff system. Areas of high-relief coast show negative correlations, indicating that higher rates of cliff retreat correlate with lower rates of shoreline erosion. In contrast, low-to moderate-relief coasts show strong positive correlations, wherein areas of high shoreline change correspond to areas of high cliff retreat.

Controls on coastal dune morphology, shoreline erosion and barrier island response to extreme storms

Abstract The response of a barrier island to an extreme storm depends in part on the surge elevation relative to the height and extent of the foredunes which can exhibit considerable variability alongshore. While it is recognized that alongshore variations in dune height and width direct barrier island response to storm surge, the underlying causes of the alongshore variation remain poorly understood. This study examines the alongshore variation in dune morphology along a 11 km stretch of Santa Rosa Island in northwest Florida and relates the variation in morphology to the response of the island during Hurricane Ivan and historic and storm-related rates of shoreline erosion. The morphology of the foredune and backbarrier dunes was characterized before and after Hurricane Ivan using Empirical Orthogonal Function (EOF) analysis and related through Canonical Correlation Analysis (CCA). The height and extent of the foredune, and the presence and relative location of the backbarrier dunes, varied alongshore at discrete length scales (of ~ 750, 1450 and 4550 m) that are statistically significant at the 95% confidence level. Cospectral analysis suggests that the variation in dune morphology is correlated with transverse ridges on the inner-shelf, the backbarrier cuspate headlands, and the historical and storm-related trends in shoreline change. Sections of the coast with little to no dune development before Hurricane Ivan were observed in the narrowest portions of the island (between headlands), west of the transverse ridges. Overwash penetration tended to be larger in these areas and island breaching was common, leaving the surface close to the watertable and covered by a lag of shell and gravel. In contrast, large foredunes and the backbarrier dunes were observed at the widest sections of the island (the cuspate headlands) and at crest of the transverse ridges. Due to the large dunes and the presence of the backbarrier dunes, these areas experienced less overwash penetration and most of the sediment from the beachface and dunes was deposited within the upper-shoreface. It is argued that this sediment is returned to the beachface through nearshore bar migration following the storm and that the areas with larger foredunes and backbarrier dunes have smaller rates of historical shoreline erosion compared to areas with smaller dunes and greater transfer of sediment to the washover terrace. Since the recovery of the dunes will vary depending on the availability of sediment from the washover and beachface, it is further argued that the alongshore pattern of dune morphology and the response of the island to the next extreme storm is forced by the transverse ridges and island width through alongshore variations in storm surge and overwash gradients respectively. These findings may be particularly important for coastal managers involved in the repair and rebuilding of coastal infrastructure that was damaged or destroyed during Hurricane Ivan.

Geospatial Analysis of Barrier Island Width of Two Segments of the Outer Banks, North Carolina, USA: Anthropogenic Curtailment of Natural Self-Sustaining Processes

A comparison of two sections of the Outer Banks, North Carolina, USA (Pea Island and Avon-Buxton areas), reveals the importance of the interplay between oceanic and estuarine shoreline dynamics to long-term changes in barrier island width. From 1852 to 1998, the northern portion of Pea Island experienced an average net increase in width of 431 m (3 m/y); this area experienced low to moderate rates of oceanic shoreline erosion and high rates of back-barrier land accretion via overwash and formation of flood tidal delta islands. In contrast, between 1852 and 1998, the width of the southern portion of Pea Island and the Avon-Buxton area decreased an average of 515 m (4 m/y) and 594 m (4 m/y), respectively, because of high rates of oceanic shoreline erosion and variable changes in estuarine shoreline accretion and erosion. Net gain or net loss of barrier island width is strongly dependent on the natural depositional processes of overwash and flood tide delta formation. Anthropogenic modifications to the barrier island, such as construction of barrier dune ridges, planting of stabilizing vegetation, and urban development, can curtail or even eliminate the natural, self-sustaining processes of overwash and inlet dynamics.

Colonization and substratum preference of an introduced burrowing crustacean in a temperate estuary

Habitat use in marine invertebrates is often influenced by multiple abiotic and biotic factors. Substratum composition is one factor known to have a dramatic effect on habitat selection. The Australasian burrowing isopod ( Sphaeroma quoianum, H. Milne Edwards 1840) is a common introduced species in many estuaries on the Pacific coast of North America. S. quoianum burrows into a variety of firm substrata including marsh banks (composed of peat, clay, and/or mud), wood, friable rock, and Styrofoam floats. In some areas, isopods achieve high densities and may accelerate the rate of shoreline erosion and damage marine structures; thus, understanding the substratum preference of this species may be important for conservation and management efforts. Field experiments were conducted in Coos Bay, Oregon to examine substratum preference, burrowing rates, and the life stage of colonizers. In three experimental trials (Fall 2005, Spring 2006, Fall 2006), replicates of four intertidal substrata (marsh banks, decayed wood, sandstone, Styrofoam) were deployed near intertidal populations of S. quoianum. The numbers of burrows created in each substratum were enumerated weekly or daily (depending on trial). After the trials were completed, the total numbers of isopods inhabiting each substratum were counted. In weeks, S. quoianum extensively burrowed the substrata but exhibited a distinct preference for decayed wood. Significantly more isopods were present in wood than the other substrata at the end of the experiments and rates of burrowing were greatest in wood, although significance varied across time in one trial. Nearly 90% of colonizing isopods were under 5 mm in length suggesting that juvenile isopods primarily colonize intertidal substrata. Differences between burrow densities measured in the field and the results from these preference trials may indicate other factors, such as relative availability of substrata, recruitment and dispersal limitations, and possible gregarious behavior also influence local isopod densities.

Useless arithmetic: why environmental scientists can't predict the future

Noted coastal geologist Orrin Pilkey and environmental scientist Linda Pilkey-Jarvis show that the quantitative mathematical models policy makers and government administrators use to form environmental policies are seriously flawed. Based on unrealistic and sometimes false assumptions, these models often yield answers that support unwise policies. Writing for the general, nonmathematician reader and using examples from throughout the environmental sciences, Pilkey and Pilkey-Jarvis show how unquestioned faith in mathematical models can blind us to the hard data and sound judgment of experienced scientific fieldwork. They begin with a riveting account of the extinction of the North Atlantic cod on the Grand Banks of Canada. Next they engage in a general discussion of the limitations of many models across a broad array of crucial environmental subjects. The book offers fascinating case studies depicting how the seductiveness of quantitative models has led to unmanageable nuclear waste disposal practices, poisoned mining sites, unjustifiable faith in predicted sea level rise rates, bad predictions of future shoreline erosion rates, overoptimistic cost estimates of artificial beaches, and a host of other thorny problems. The authors demonstrate how many modelers have been reckless, employing fudge factors to assure correct answers and caring little if their models actually worked.A timely and urgent book written in an engaging style, Useless Arithmetic evaluates the assumptions behind models, the nature of the field data, and the dialogue between modelers and their customers.

Influence of Stratification and Shoreline Erosion on Reservoir Sedimentation Patterns

Sedimentation in the main pool of a deep (maximum depth: 50 m ), 227 km2 hydropower reservoir was modeled using a three-dimensional numerical model of hydrodynamics and sedimentation for different wind, inflow, and outflow conditions. Short-term velocity measurements made in the reservoir were used to validate some aspects of the hydrodynamic model. The effects of thermal stratification on sedimentation patterns were investigated, since the reservoir is periodically strongly stratified. Stratification alters velocity profiles and thus affects sedimentation in the reservoir. Sedimentation of reservoirs is often modeled considering only the deposition of sediments delivered by tributaries. However, the sediments eroding from the shorelines can contribute significantly to sedimentation if the shorelines of the reservoir erode at sufficiently high rates or if sediment delivery via tributary inflow is small. Thus, shoreline erosion rates for a reservoir were quantified based on measured fetch, parameterized be...

Effect of El Niño (1997–98) on Beaches of the Peninsular Gulf Coast of Florida

During the winter of 1997–98, the El Niño weather pattern was a major influence on the beaches of the Gulf Coast of the Florida peninsula. Cyclonic storm patterns influenced by El Niño moved across the Gulf of Mexico from the southwest, approaching the coast of Florida from the southwest, a direction that differs from that of the usual winter frontal passage direction. The El Nino effects along the Florida Gulf Coast are in the form of subtropical, low-pressure systems including mild temperatures, frequent storms with sustained winds, high wave energy, and record amounts of rainfall. The winds and waves generated by these systems initially came from the south or west. As the storm passed over the coast, barometric pressure increased and winds shifted to the west or northwest. Ten occurrences of this weather pattern took place from late December 1997 through March 1998.An atypical south to north littoral drift was recognized in localized areas along the Florida Gulf Coast during the winter of 1997–98, instead of the typical winter pattern of north to south sediment transport. Evidence for this reversal of sediment transport is the accumulation of sediment and shoreline progradation along the southern face of coastal structures and in a concave area that is oriented northwest to south-southeast. Waves due to the El Niño winter storms approached ebb-tidal deltas at the mouth of inlets from the west or southwest. Beach shorelines on islands located adjacent to the inlets responded differently than their normal winter response as recorded in surveyed beach changes. Beaches with a north-northwest shoreline orientation (between 330 and 345 degrees) had an increased rate of shoreline erosion and volume loss. Other effects of El Niño-influenced weather included erosion at typically prograding areas, and progradation or reduced rates of erosion in typically eroding locations. Such deviations from normal patterns are important factors to include in long-term beach management plans, especially if the El Niño phenomenon continues to be a frequent occurrence.

Massive sediment bypassing on the lower shoreface offshore of a wide tidal inlet — Cat Island Pass, Louisiana

Analysis of a series of historical bathymetric and shoreline surveys along the Louisiana coast west of the Mississippi River mouth detected a large area of deposition in water depths of 2.0–8.5 m offshore of a 9-km-wide tidal inlet, the Cat Island Pass/Wine Island Pass system. A 59.9 · 106 m 3 sandy deposit formed from the 1930s–1980s, spanning 27 km in the alongshore direction, delineating the transport pathway for sediment bypassing offshore of the inlet on the shoreface. Bypassing connected the shorefaces of two barrier island systems, the Isles Dernieres and the Bayou Lafourche. The processes responsible for formation of this deposit are not well understood, but sediment-transport modeling suggests that sediment is transported primarily by wind-driven coastal currents during large storms and hurricanes. Deposition appears to be related to changes in shoreline orientation, closing of transport pathways into a large bay to the east and the presence of tidal inlets. This newly documented type of bypassing, an offshore bypassing of the inlet system, naturally nourished the immediate downdrift area, the eastern Isles Dernieres, where shoreface and shoreline erosion rates are about half of pre-bypassing rates. Erosion rates remained the same farther downdrift, where bypassing has not yet reached. As this offshore bypassing continues, the destruction of the Isles Dernieres will be slowed.