Flow and sediment transport dynamics in a slot and cauldron blowout and over a foredune, Mason Bay, Stewart Island (Rakiura), NZ

This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (August 2017) in accordance with the publisher’s archiving policyThis study is the first to simultaneously compare flow and sediment transport through a blowout and over an adjacent foredune, and the first study of flow within a highly sinuous, slot and cauldron blowout. Flow across the foredune transect is similar to that observed in other studies and is primarily modulated by across-dune vegetation density differences. Flow within the blowout is highly complex and exhibits pronounced accelerations and jet flow. It is characterised by marked helicoidal coherent vortices in the mid-regions, and topographically vertically forced flow out of the cauldron portion of the blowout. Instantaneous sediment transport within the blowout is significant compared to transport onto and/or over the adjacent foredune stoss slope and ridge, with the blowout providing a conduit for suspended sediment to reach the downwind foredune upper stoss slope and crest. Medium term (4 months) aeolian sedimentation data indicates sand is accumulating in the blowout entrance while erosion is taking place throughout the majority of the slot, and deposition is occurring downwind of the cauldron on the foredune ridge. The adjacent lower stoss slope of the foredune is accreting while the upper stoss slope is slightly erosional. Longer term (16 months) pot trap data shows that the majority of foredune upper stoss slope and crest accretion occurs via suspended sediment delivery from the blowout, whereas the majority of the suspended sediment arriving to the well-vegetated foredune stoss slope is deposited on the mid-stoss slope. The results of this study indicate one mechanism of how marked alongshore foredune morphological variability evolves due to the role of blowouts in topographically accelerating flow, and delivering significant aeolian sediment downwind to relatively discrete sections of the foredune

Coastal Dune Restoration: Trends and Perspectives

Sandy coasts are distributed worldwide and they are all heterogeneous ecosystems in terms of morphology, vegetation, and dynamics. Psammophytes are common in these environments. Besides these widespread attributes, sandy beaches and coastal dunes also share the intense impact of humans. Because of their privileged location at the coast, they are preferred sites for urban and maritime development, destinations for tourists, and locations for many other human activities. Thus, over the years (but especially during the last few decades) many of the previously natural dunescapes have been lost to urban, tourist, and industrial developments. Furthermore, a recurring problem of many coastal dune systems is over-stabilization, which is mostly the result of human actions. The urgent need to preserve the natural and valuable coastal dune remnants and, as much as possible, restore those that have been degraded, is evident. There are many different and contrasting actions that have been followed during restoration activities. Restoration actions have involved “soft” methods, such as sand fences, and “hard” methods, such as geotubes and herbicides. Also, restoration may lead not only to the stabilization of dunes, but also to the re-mobilization of sand. On n overcrowded planet where the coasts are ecosystems to which humans gravitate, conservation and restoration actions become exponentially important

Editorial: The History and Evolution of the Journal of Sorority and Fraternity Life Research and Practice

Individuals involved in the founding of the Oracle: The Research Journal of the Association of Fraternity/Sorority Advisors (Oracle), former Oracle editors and Adam M. McCready, Editor of Journal of Sorority and Fraternity Life Research and Practice share the history and evolution of the journal over the past two decades

Aeolian dynamics of beach scraped ridge and dyke structures

Where urban areas are situated close to a beach, sand dunes act as protection from flooding and erosion.When a dune has been removed or damaged by erosion, dune, ridge or dyke re-building using heavymachinery, a process known as beach scraping, is a common method of restoration. Following construction, natural accretion of sediment on the backshore is preferable as it facilitates sustained natural dune building, growth of vegetation, and habitat creation and reduces the need for further beach scraping. This study investigates the near surface flowand transport potential for three artificial structure designs: a single ridge, a double ridge and a dyke. The three shapes contained an identical volume of sand and were preceded by 50mof beach at an angle of 3°. A computational fluid dynamic model (CFD)was created for each scenario to calculatewind flowand shear velocity from 4 differentwind directions at 22.5° intervals from 0° (onshore) to 67.5°. From this data sediment flux was predicted along a two dimensional transect for each of the scenarios. For all structures, shear velocity on the beach and stoss slope decreased as incident wind direction became more oblique; conversely shear velocity in the lee of the crest increased. A reduction in shear velocity at the foot of each structure also occurred and appears related to stoss slope,with the greatest reduction at the toe of the dyke structure (stoss slope 34°) and the least before the single ridge (stoss slope 17°). Specifically the results suggest that the double ridge structure is the most resilient to aeolian erosion. Shear velocity reduction on the back beach is comparable to the dyke and sediment flux fromthe stoss slope of the double ridge structure may become trapped in the swale between the two ridges encouraging sediment deposition, thus reducing sediment transport beyond the dunes and backshore. Although the dyke structure underwent the greatest reduction in shear velocity on the back beach it experienced substantial sediment flux at the crest and along the top of the structure, making it susceptible to erosion during a strongwind event. The highest sediment transport rate was calculated at the crest of the single ridge, and the single ridge structure also created the smallest reduction of shear velocity on the back beach, thus making it less desirable than the double ridge

Biogeomorphological processes in an arid transgressive dunefield as indicators of human impact by urbanization

This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. This author accepted manuscript is made available following 24 month embargo from date of publication (August 2018) in accordance with the publisher’s archiving policyUrban and tourist developments can have long-lasting impacts on coastal environments and fundamentally alter the evolution of coastal dune systems. This is the case of the Maspalomas dunefield (Gran Canaria, Canary Islands), hosting one of the largest tourist resorts in Spain. The resort was built on top of a sedimentary terrace at 25 m above sea level (El Inglés) in the 1960s, and has subsequently affected local winds and therefore aeolian sediment transport patterns. Buildings on the terrace deflect the winds to the south of the dunefield, where the rate of sediment transport accelerated. A shadow zone appeared to the lee side of the resort with a consequent decrease in wind speed and aeolian sediment transport and an increase in vegetation cover. In this paper, first we characterize the environmental changes around El Inglés terrace in recent decades, and describe the changes in the shadow zone through an analysis of the evolution of sedimentary volumes and vegetation characteristics (density, spatial patterns, and plants communities). A series of historical aerial photographs, recent orthophotos and digital elevation models obtained by digital photogrammetry and LiDAR, as well as fieldwork were used to characterize plant communities and spatial-temporal changes in erosive landforms. Results show changes in the pattern and migration rates of dunes located at the southern edge of the urbanization, as well as the formation of blowouts and large deflation areas, where the vegetation increases in density and number of plant communities. We discuss eco-anthropogenic factors that have produced these environmental changes.This work is a contribution of projects CSO2013-43256-R and CSO2016-79673-R (National R & D & I Plan) co-financed with ERDF funds and a PhD contract of the Canary Islands Agency for Research, Innovation and Information Society and by the European Social Fund (ESF)

Three years of morphologic changes at a bowl blowout, Cape Cod, USA

© 2017 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (July 2017) in accordance with the publisher’s archiving policyThis study presents measurements of blowout topography obtained with annual terrestrial laser surveys carried out over a three-year period at a single, large bowl blowout located in the Provincelands Dunes section of Cape Cod National Seashore, in Massachusetts. The study blowout was selected because its axis is aligned with northwest winds that dominate the region, and because it was seemingly interacting with a smaller saucer blowout that had recently formed on the southern rim of the primary feature. Assuming that blowouts enlarge both horizontally and vertically in response to the wind regime, the objectives of the study were to determine both the amount of horizontal growth that the blowout experiences annually and the spatial patterns of vertical change that occur within the blowout. Changes to the blowout lobe surrounding the feature were also determined for areas with sparse enough vegetation cover to allow laser returns from the sand surface. The results show that the blowout consistently expanded outward during the three years, with the greatest expansion occurring at its southeast corner, opposite the prevailing winds. The most significant occurrence was the removal, in the first year, of the ridge that separated the two blowouts, resulting in a major horizontal shift of the southern rim of the new combined blowout. This displacement then continued at a lesser rate in subsequent years. The rim also shifted horizontally along the northwest to northeast sections of the blowout. Significant vertical loss occurred along the main axis of the blowout with the greatest loss concentrated along the southeast rim. On the lobe, there were large areas of deposition immediately downwind of the high erosion zones inside the blowout. However, there were also small erosion areas on the lobe, extending downwind from eroding sections of the rim. This study shows that: 1. blowouts can experience significant areal and volumetric changes in short periods of time; 2. significant changes may occur relatively suddenly when adjacent blowouts combine into a single feature; and 3. the sediment transport paths are highly controlled by the topography. The joining of two blowouts not only creates a new larger feature, but it also releases large amounts of sediment that are then distributed across the landscape downwind, creating a potential for major changes to a landscape over the longer term

Environmental variables affecting an arid coastal nebkha

Foredunes in arid coastal dune systems comprise nebkhas, which originate by interactions between vegetation and aeolian sedimentation. While continuous foredunes in temperate climates have been widely studied, knowledge of interactions between biotic and abiotic drivers in foredunes formed by nebkha is still scarce. With the aim of exploring variables affecting arid foredunes, a range of morphological, sedimentological, and vegetation characteristics were measured on a single nebkha formed by a Traganum moquinii plant located in the foredune of Caleta de Famara beach (Lanzarote, Canary Islands). Variables were sampled at 120 plots in a 0.5 × 0.5 m square grid. A two-step process using multiple linear regression (MLR) analyses was developed to characterize 1) the influence that morphological variables and distance from the sea have on plant and sediment patterns on nebkha, and 2) the influence of plants on depositional sediment characteristics. Results indicate close relationships between distance from the sea, plant coverage, and sediment patterns. Empirical results were used to develop a conceptual model that explains the spatial distribution of bio- and geo-morphological characteristics of an arid nebkha foredune.Spanish Ministry of Economy, Industry and Competitiveness contract (BES-2017-082733

Foredune morphodynamics and sediment budgets at seasonal to decadal scales: Humboldt Bay National Wildlife Refuge, California, USA.

© 2018 Elsevier. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.0/ This author accepted manuscript is made available following 24 month embargo from date of publication (June 2018) in accordance with the publisher’s archiving policyCoastal foredunes are shore-parallel ridges that form in the backshore and their morphodynamics are controlled partly by seasonal and spatial variations in the coastal (onshore) sediment budget that, in turn, are driven by oceanic and atmospheric processes and interactions, including regional wave and wind regimes, climatic variability events (e.g., ENSO), sediment availability, beach characteristics (e.g., width, slope), and vegetation type and cover in the backshore. Previous studies on shoreline change in Northern California report only broad rates of erosion and accretion related to regional meteorological regimes. This study presents a more detailed, multi-decadal to seasonal account of shoreline response and foredune morphodynamics along a 2.5 km stretch of coast in the Humboldt Bay National Wildlife Refuge (HBNWR). Analysis of historical aerial photography (1939–2014) reveals trends in shoreline position that are coupled with more detailed assessments of foredune morphodynamics and seasonal scale volumetric changes from cross-shore topographic profiles``. These findings set the historical context of foredune morphodynamics and allow exploration of the implications of seasonal meteorological variation on long-term (75-year) foredune evolution and development at the HBNWR. DSAS describes maximum foredune progradation in the north (up to +0.51 m a−1) and maximum foredune retreat in the south (up to −0.49 m a−1). Aerial photograph analysis (2004–2014) shows statistically significant larger erosive features in the southern zone than in the northern and central zones. Seasonal volume calculations from cross-shore profiles indicate statistically significant differences in alongshore transect elevation and foredune volume, with larger elevations and volumes in the northern and central zones than in the southern. Combined with evidence of seasonal bidirectional littoral drift, these data support a north to south gradient in sediment availability, foredune position and resulting stages of established foredune development. Seasonal storm energies and climate forcing events introduce variability in erosive patterns but support the persistence of alongshore developmental stages. Future research should explore foredune morphodynamics on a smaller spatial scale and changes related to the presence/absence of multiple vegetation assemblages