Sand Dune Erosion Research Articles

Observations of wave run-up affected by dune scarp during storm conditions: a two dimensional large-scaled movable bed experiment

Artificial dunes serve as essential nature-based defenses against the increasing threats posed by climate change and rising sea levels along coastal regions. However, these man-made dunes are particularly susceptible to erosion during severe storm events, necessitating careful consideration of their design for effective coastal protection. Among the myriad factors influencing artificial dune design, wave run-up stands out as a paramount concern. Not only is wave run-up crucial in assessing the extent of coastal flooding, but it also plays a significant role in shaping shoreline dynamics. During intense storm events, wave run-up amplification leads to substantial erosion of sand dunes, forming dune scarps that resemble cliffs. To address these challenges, we conducted a series of innovative two-dimensional large-scale laboratory experiments using movable beds. These experiments aimed to provide a quantitative understanding of wave run-up characteristics on dune scarps. Additionally, our study explored the feasibility of using existing empirical formulas to predict the 2% exceedance of wave run-up (referred to as R2%) in such scenarios. Our results revealed a consistent trend in R2% values, irrespective of variations in the surf similarity parameter when wave run-up was influenced by a dune scarp. Notably, our findings recommend the adoption of the Stockdon empirical formula, incorporating beach slope from the still water level to the dune scarp toe, as an effective method for predicting R2% during highly erosive conditions. This approach can significantly enhance the design and functionality of artificial dunes, bolstering their capacity to safeguard coastal areas from the impacts of severe storms and erosion, thus contributing to resilient coastal ecosystems and sustainable coastal management.

Climate change, site formation, and indigenous use of coastlines in Barbuda

This article explores the landscape dynamics at the island of Barbuda in the context of changing climate to understand (1) the environmental setting of indigenous settlements; (2) the impacts of current coastal processes; and (3) the potential threats moving forward toward increasing pressure of climate change. Focusing on the site of Seaview, on the east coast of Barbuda, we use geoarchaeological methods to reconstruct the ancient geomorphological setting, investigate changes post-abandonment, and identify the hazards faced under future sea-level projections. Our study shows that (1) sea level stabilization after the Mid-Holocene allowed the formation of coral reefs, seagrass beds and other benthic ecosystems that allowed for biogenic sediment accumulation and growth of sand dune retention ridges. (2) These environmental characteristics, including rich marine food sources, supported the establishment and flourishing of Seaview starting ca. 160 BC. (3) Occupation ended at some point between AD960 and 1000. This change coincided with a period of increased storminess, higher SSTs, and possible coral reef mortality that affected both food availability and sediment supply. (4) Lack of sediments triggered progressive sand dune erosion that continues today and has left the sand dune ridge past the tipping point of erosion. (5) Looking into a future of rapidly changing climate, sea level rise poses a severe and devastating threat to the land- and seascapes of Barbuda. With the lowland coastal plain at or only slightly above current sea level, a rate of SLR comparable to Mid-Holocene rates, and rapid loss of sand dune ridges and coral reefs as natural barriers, it is just a matter of time before the lowlands become transformed beyond recognition. The results of this analysis can be used to improve long-term management of the heritage resources of Barbudans and shed light on parallel challenges experienced on other tropical coastal locations.

An experimental study of mitigating coastal sand dune erosion by microbial- and enzymatic-induced carbonate precipitation

Due to more extreme weather events and accelerating sea-level rise, coastal sand dunes are subjected to more frequent storm wave inundation and surge impacts, which contribute to widespread coastal erosion problems. In this study, two novel bio-mediated methods, microbial-induced carbonate precipitation (MICP) and enzymatic-induced carbonate precipitation (EICP), were investigated and compared for their effectiveness in mitigating sand dune erosion under wave attack. Small-scale laboratory model tests were performed on MICP-treated, EICP-treated, and untreated sand dunes at dune slope angles and two wave intensities for up to 2 h. The cross-shore profile was captured continuously during the course of the erosion test. The erosion volume above the still water level (SWL) and landward retreat distance at the SWL were calculated based on the captured bed profiles. The results show that both EICP and MICP could substantially reduce sand dune erosion at mild-to-moderate wave and dune slope conditions. However, the effectiveness of MICP treatment deteriorated at steeper dune slopes with longer period of wave attack. Under the most adverse condition (i.e., steepest dune slope, biggest wave, and longest period of wave attack), neither EICP nor MICP could effectively mitigate erosion. Fundamentally, the variable effectiveness of MICP and EICP treatment for sand dune erosion control was attributed to the spatial distribution pattern of formed calcite precipitation, which was determined by the way how EICP and MICP were applied. The calcite precipitation was relatively uniform in EICP-treated sand dunes. In MICP-treated ones, however, substantial calcite precipitation concentrated in the shallow surface layer as confirmed by the surface penetration test and SEM observation.

Tsunami Inundation and Maritime Hazard Modelling for a Maximum Credible Tsunami Scenario in Southeast Tasmania, Australia

The east coast of Tasmania is directly exposed to tsunamis originating from the Puysegur subduction zone, off New Zealand’s southwest coast. However, the potential impacts of tsunami inundation for coastal communities and Hobart Airport, and risks to maritime operations in Hobart Port, are poorly understood. The purpose of this project is to simulate a maximum credible earthquake/tsunami/high tide scenario (a Mw 8.7 rupture of the Puysegur subduction zone) across a 17,000 km2 model area and provide outputs that can inform local hazard management plans. Modelling was performed using the ANUGA hydrodynamic library, along with a detailed elevation model constructed from LiDAR, photogrammetric contours and bathymetric datasets. The modelling strategy comprised three primary scenarios: a 13 h simulation of tsunami activity focusing on maritime hazard from waves and currents, with two further 4 h simulations focusing on coastal inundation for 71 coastal communities and Hobart Airport. The models were run on a variable triangulated mesh with a detailed Manning’s n surface roughness model. Tsunami erosion of sand dunes was accounted for through the development of an erosion operator. Results predict severe inundation (> 4 m flow depth) in exposed east-facing areas and the maritime hazard assessment advises that water disturbance would pose a significant threat to marine craft. The assessment suggests that the feasibility of shipping evacuation from Hobart port is questionable, given the timeframes involved and the nature of simulated water disturbance. Modelling results suggest that the dune line in front of Hobart Airport would not be breached in this instance and so inundation would not occur.

Numerical Simulation and Large-Scale Physical Modelling of Coastal Sand Dune Erosion

Do, K.; Shin, S.; Cox, D., and Yoo, J., 2018. An international comparison of drowning in South Korea. In: Shim, J.- S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 196–200. Coconut Creek (Florida), ISSN 0749-0208.Coastal sand dune system is important in the nearshore environment for sand supply, ecosystem, and hazard mitigation. In this study, a process-based morphological model was performed and the results were compared with large-scale laboratory experimental data. Two-dimensional large-scale laboratory experiments were conducted with 1:6 geometric scale in the large wave flume (104m (L) × 3.7 m (W) × 4.6 m (D)) of the Hinsdale Wave Research Laboratory at Oregon State University (Maddux et al, 2006). Several different wave conditions were used with different water levels in this experiment including pre-storm, storm, and post storm based on random wave time series by using TMA spectrum. The data set included cross-shore Wave heights, fluid velocities, and the profile changes of the beach and dune. The process based model, XBeach (Roelvink et al., 2009) was used to simulate the nearshore hydrodynamics and bed level change during storm wave condition. Several semi-empirical parameters were used in the XBeach model to predict morphodynamic process (Roelvink et al., 2009) and recently the updated parameters (WTI settings) were suggested based on the results of field observations. The present study ran the XBeach model by using both default and WTI settings and compared with the results from the experiments. The results showed that the model results with WTI settings showed good agreement with the measured beach profile while the model results with default settings over-predicted the offshore sediment transport and dune erosion. Especially, the wave skewness (facSk) and asymmetry (facAs) gave the highest contribution to predict dune erosion.

Drivers of alongshore variable dune erosion during a storm event: Observations and modelling

The ability to understand and predict alongshore-variable sand dune erosion is key to better coastal management. This study utilizes detailed observations (immediately pre, during and post-storm topography, waves and water levels) collected over a 6-day period at the 3.6 km long Narrabeen-Collaroy beach in south-east Australia, to identify and explore drivers of the highly variable alongshore dune erosion caused by an East Coast Low storm in June 2011. Key characteristics of the immediately pre-storm subaerial morphology obtained by airborne Lidar (beach slope, dune toe elevation, dune height) varied considerably alongshore. Daily airborne Lidar surveys conducted at low tide indicated considerable temporal variability in the evolution of the subaerial beach profile. Despite considerable alongshore variability in the magnitude of modelled inshore wave heights during the storm, it was instead observed that the predominant determinant of maximum dune erosion was the pre-storm dune toe elevation. A simple dune impact model forced with local alongshore-variable inshore wave modelling was found to successfully predict up to 85% of the observed alongshore variability in dune erosion at this site, with this erosion tidally modulated over the 6 days to time periods when the waves were directly impacting the dune. Importantly, alongshore variation in wave height is shown to account for just 10% of the alongshore variability in dune erosion during this storm. These results reconfirm that knowledge of the pre-storm subaerial morphology, in particular the elevation of the dune toe with respect to time-varying water levels during a storm, is a key driver of alongshore variability in the erosion response along dune-backed sandy coastlines.

Containment, closure and red deer

Erosion of sand dunes in the Bay of Skaill, close to the Neolithic site at Skara Brae, exposed a spread of faunal remains and stone tools representing a Late Neolithic butchery site separated by a wall from a deposit of articulated red deer bone. This is an unusual and significant bone assemblage comprising both fragmented and articulated remains of red deer together with some domesticates. Also a whale mandible was closely associated with the butchery area. An interpretation of the site incorporates a reappraisal of the role of red deer and cattle elsewhere in Late Neolithic Orkney.

Erosional Impact on Caspian Sea Coasts Stability Capacity

Stability capacity determination of beach against marine erosion forces in the southern coasts of the Caspian Sea (Babolsar to Noor) is the main target in this paper. By dividing study areas to 14 zones, shoreline displacement rate, land covering deformation and sand dune erosion vulnerability tendency have been measured with remote sensing and the geographical information system. In field monitoring, the geometric structure of the beach was mapped and 42 sediment samples have been obtained from the beach zone (Berm, shoreline, 0.5 meter depth). Then the beach stability capacity levels that due to several criterions such as: (sediment texture, geometry structure, sand dune accumulation, and land use development and land cover changes) have been calculated by GIS in universal ranking system model (URSM). Results showed that the highest stability capacity rates belong to Talar beach (zone 1) and Arabkheil beach (zone 2) and the eastern part of Mahmoodabad beach (zone 9). By contrast, Mahmoodabad (zone 10) and Noor (zone 14) were the most unstable regions against sea-levels and hydrodynamic forces.

浜崖後退抑止工の波浪安定性についての水理模型実験および現地試験

Two-dimensional tank experiments were conducted to establish a method for assessing the stability of a sand-pack structure on a beach. The results of 89 experimental cases showed that piping out of nourished sand and pulling out of a sand-pack on a slope were typical collapsing processes, and these were caused by the return flow of a wave over topping. Lifting up of the seaward tip of the sand-pack by wave run-up was also observed. The desirable weight of a sand-pack for avoiding these pulling out and lifting up behaviors was investigated. Based on these findings, structures for moderating sand dune erosion were designed, and a field experiment was conducted. Through the one-year-long field experiment, the developed structures were confirmed to endure against even high typhoon-induced waves.

Critical storm thresholds for the generation of significant dune erosion at Dziwnow Spit, Poland

Storm influence on the southern Baltic coast was examined for a 14-km long section of the Polish coast along the Dziwnow Spit based on 30years of post-storm dune erosion observations. In this study, we assumed that a significant storm causes noticeable sand dune erosion. Significant changes of the coast after each major storm were analysed based on reports from 1978 to 2008 provided by the Maritime Office, Szczecin. Thirty-two storms that caused dune losses were chosen for analysis. Correlation and hierarchical cluster analysis allowed us to distinguish three groups of storms that caused varying amounts of dune erosion: G1 (small), G2 (medium), and G3 (large). Sea level is the main parameter that influences the amount of dune erosion caused by storms on the southern Baltic coast. Factors such as maximum significant wave height, mean wave direction, storm energy and duration can also, but less significantly, influence dune erosion. The study area was divided into two sections: Dziwnow, where there are many protection measures in place, and Miedzywodzie, which has no protection measures in place. In both areas, we observed differences in the impact of sea level and significant wave height and storm groupings. Approximate minimum sea level and significant wave height thresholds were defined for particular storm groups.

Thickness and grain-size distribution of the 2004 Indian Ocean tsunami deposits in Periya Kalapuwa Lagoon, eastern Sri Lanka

In this paper we describe the sedimentary characteristics of the 2004 Indian Ocean tsunami deposits in and around Periya Kalapuwa Lagoon, Sri Lanka. Periya Kalapuwa is a coastal lagoon of about 13 km 2 area and has an average depth of about 1 m. It is separated from the Indian Ocean by coastal barrier sand dunes of up to 9-m elevation through which two inlet channels open the lagoon to the ocean. This region was hit by three waves during the 2004 Indian Ocean tsunami. The second wave was largest (4–6 m) and entered the lagoon not only via the two inlet channels, but also by flowing over the sand dunes. Erosive scars were found on the sand dunes adjacent to the two inlets. Twenty-seven core samples, along with trenching and hand-auger data, show that the tsunami deposits are 9 cm thick on average (up to 35 cm in the lagoon and up to 66 cm on the shore) and are composed mainly of medium sand (mean grain size 1.06 φ) with low mud content (0.61 wt.%), which is similar to the composition of sand from near the erosive scars in the sand dunes (mean grain size 0.94 φ), but different from the lagoon deposits (mean grain size 1.68 φ; mud content 4.7 wt.%). The distribution of the tsunami deposits was limited to within about 1 km from each inlet. The tsunami deposits become thinner and finer grained with increasing distance from the inlets. Most of the tsunami deposits are massive, but some show sedimentary structures: single or multiple-graded bedding structures, parallel laminations defined by layers of heavy minerals, and muddy laminations. Our observations and analyses suggest that the tsunami deposits were formed mainly from sand eroded from sand dunes near the two inlets. We estimated the total volume of tsunami sediments to be 83 000 m 3. By assuming that the sediments of the tsunami deposits were supplied only by erosion of sand dunes from near the two inlets, this is equivalent to erosion of 83 m 3 of sand per meter of sand dune traversed by the tsunami wave.

Human impact on fixed sand dunes revealed by morphometric analysis

AbstractThe Nyírség is the second largest alluvial fan in Hungary covered by fixed sand dunes. The primary aim of the paper is to describe the morphology of dunes in the region and classify them based on their morphometric characteristics. The other major aim is to select those dunes which were exposed to significant anthropogenic impact, and to determine the spatial and temporal differences in the intensity of human activity. The following dune types were separated: valley‐marginal, transitional valley‐marginal, transitional parabolic, filled, partially and unfilled parabolic dunes. After defining different dune types and their parameters, certain dunes were selected based on exposure to significant anthropogenic impact. Definite connection was demonstrated between the intensity of human environmental impact and the rate of erosion on fixed sand dunes. The erosion of sand dunes was most intensive in Medieval times, most likely due to concentration of agricultural land use. Copyright © 2009 John Wiley & Sons, Ltd.

Phytolith assemblages as indicators of coastal environmental changes and hurricane overwash deposition

We demonstrate that phytolith assemblages are a useful proxy for reconstructing coastal environmental changes and for validating the overwash origin of sand layers in palaeotempestology studies. Phytolith analysis was conducted on 50 topsoil or surface sediment samples collected from a variety of coastal plant communities or depositional environments in the southeastern USA. The data suggest that different coastal subenvironments can be distinguished by their modern phytolith assemblages. For example, coastal marsh samples contain a diverse phytolith assemblage dominated by smooth-elongate and square morpho-types and maritime forest samples are dominated by phytoliths from palms and broadleaf dicotyledonous plants. Remarkably, the phytolith assemblages from sand dunes are characterized by high percentages of two-horned-tower, flat-tower, spool/horned-tower and short-saddle types. Phytolith analysis of three prehistoric sand layers in a sediment core from Western Lake, northwestern Florida, shows that they contain a phytolith assemblage similar to those characteristic of sand dunes and interdune meadows. These observations are confirmed by the results of principal components analysis and discriminant analysis on the modern and fossil phytolith data sets. Our study results support the interpretation that the sand layers in Western Lake were indeed formed by the erosion of sand dunes during overwash processes caused by landfalling catastrophic hurricanes.

Monitoring sand dune erosion on the clwyd coast, North Wales

Monitoring sand dune erosion on the clwyd coast, North Wales

BEACH AND DUKE EROSION TESTS

In the Netherlands a large part of the country lying below sea level is protected by sand dunes. The erosion of sand dunes during storms at the North Sea, by which the strong wave action is attended with a high sea level, is therefore of extreme importance in the Netherlands. It is almost impossible to do adequate measurements along the coast during storms. Accordingly the Delft Hydraulics Laboratory was requested by the Public Works Department of the Dutch government to investigate in a model a number of matters related to both the maintenance of existing dunes and the design of artificial sand dunes as sea defence works. The investigations reported in this paper are concerned with the following problems a) the influence of the height of sand dunes upon the amount of coastal recession during storm conditions. b) the influence of the wave characteristics upon the amount of coastal recession. c) the differences in coastal recession and profiles obtained with regular waves and those obtained with wind waves. The reproduction on scale of the phenomena m the surf zone is a difficult matter. Many investigators have come to the conclusion that there are several scale effects. Till now our knowledge is not sufficient to determine the magnitude of the scale effects. Owing to this the described tests can give only qualitative information.

Beach and Sand Dune Erosion Control

Beach and Sand Dune Erosion Control