scholarly journals Investigating Changes in Aeolian Sediment Transport at Coastal Dunes and Sand Trapping Fences: A Field Study on the German Coast

2020 ◽  
Vol 8 (12) ◽  
pp. 1012
Author(s):  
Christiane Eichmanns ◽  
Holger Schüttrumpf
Keyword(s):  
Sediment Transport ◽  
Wind Profile ◽  
Field Experiments ◽  
Coastal Dunes ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Coastal Protection ◽  
Protection Measures ◽  
Law Of The Wall ◽  
Aeolian Sediment

For the restoration and maintenance of beach and dune systems along the coast, knowledge of aeolian sediment transport and its interaction with coastal protection measures is required. As a nature-based solution, sand trapping fences can be an integral part of coastal protection measures initiating foredune development. There are few detailed studies on aeolian sediment transport rates on coastal dunes and sand trapping fences available to date. Thus, in this work, we present the results of field experiments conducted at the beach, coastal dune, and sand trapping fence on the East Frisian island Langeoog. The vertical sediment flux profile was measured by vertical mesh sand traps, and saltiphones measured the instantaneous sediment transport. A meteorological station was set up to obtain wind data. On the beach, dune toe, and dune crest, the stationary wind profile can be described well by the law of the wall. Saturated aeolian sediment transport rates on the beach and dune toe were predicted by widely used empirical models. Between the sand trapping fence, these empirical transport models could not be applied, as no logarithmic wind profile existed. The upwind sediment supply reduced after each brushwood line of the sand trapping fence, thereby, leading to increased deviation from the saturated conditions.

scholarly journals Influence of Sand Trapping Fences on Dune Toe Growth and Its Relation with Potential Aeolian Sediment Transport

2021 ◽  
Vol 9 (8) ◽  
pp. 850
Author(s):  
Christiane Eichmanns ◽  
Holger Schüttrumpf
Keyword(s):  
Sediment Transport ◽  
Meteorological Data ◽  
Coastal Dunes ◽  
Sediment Supply ◽  
Minor Role ◽  
Digital Elevation ◽  
Lower Permeability ◽  
Aerial Vehicle ◽  
A Minor ◽  
Aeolian Sediment

This study provides insights into dune toe growth around and between individual brushwood lines of sand trapping fences at the dune toe of coastal dunes using digital elevation models obtained from repeated unmanned aerial vehicle surveys. Prevailing boundary conditions, especially sediment supply, as well as the porosity and arrangement of the installed sand trapping fences significantly influence the effectiveness of different configurations of sand trapping fences. The dune toe growth is significant immediately after constructing a new sand trapping fence and decreases over time. According to the results presented in this study, for sand trapping fences that have been in place longer, the protruding branch height and the porosity of the remaining branches play a minor role in trapping sand. Sand trapping fences with lower permeability favour localized coastal dune toe growth directly at their brushwood lines, whereas fences with higher porosity allow for more sediment deposition further downwind. The trend in dune toe changes can be roughly predicted by integrating potential sediment transport rates calculated with hourly meteorological data.

scholarly journals Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

2020 ◽  
Vol 12 (22) ◽  
pp. 3689
Author(s):  
Iain Fairley ◽  
Jose Horrillo-Caraballo ◽  
Ian Masters ◽  
Harshinie Karunarathna ◽  
Dominic E. Reeve
Keyword(s):  
Spatial Scales ◽  
Coastal Dunes ◽  
Sediment Supply ◽  
Tidal Range ◽  
Coastal Protection ◽  
Dune System ◽  
Pressure Transducers ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore variation in dune response to morphodynamic forcing, which can occur over small spatial scales. In this paper, a fixed wing unmanned aerial vehicle (UAV), is used to measure the longshore variation in evolution of a dune system in a megatidal environment. Dune sections to the east and west of the study site are prograding whereas the central portion is static or eroding. The measured variation in dune response is compared to mesoscale intertidal bar migration and short-term measurements of longshore variation in wave characteristics during two storms. Intertidal sand bar migration is measured using satellite imagery: crescentic intertidal bars are present in front of the accreting portion of the beach to the west and migrate onshore at a rate of 0.1–0.2 m/day; episodically the eastern end of the bar detaches from the main bar and migrates eastward to attach near the eastern end of the study area; bypassing the central eroding section. Statistically significant longshore variation in intertidal wave heights were measured using beachface mounted pressure transducers: the largest significant wave heights are found in front of the dune section suffering erosion. Spectral differences were noted with more narrow-banded spectra in this area but differences are not statistically significant. These observations demonstrate the importance of three-dimensionality in intertidal beach morphology on longshore variation in dune evolution; both through longshore variation in onshore sediment supply and through causing longshore variation in near-dune significant wave heights.

scholarly journals EXPERIMENTAL INVESTIGATION ON DYNAMIC EQUILIBRIUM BAY SHAPE

2012 ◽  
Vol 1 (33) ◽  
pp. 37
Author(s):  
Sutat Weesakul ◽  
Somruthai Tasaduak
Keyword(s):  
Experimental Investigation ◽  
Sediment Transport ◽  
Dynamic Equilibrium ◽  
Shoreline Change ◽  
Sediment Supply ◽  
Coastal Protection ◽  
Supply Source ◽  
Wave Condition ◽  
Longshore Sediment Transport

Equilibrium bay is a bay that its shoreline is stable and does not change with time in long term. This concept can be applied for coastal protection. Experiments on dynamic equilibrium bay planform are conducted in a laboratory. There is one location of sediment supply source into a bay near upcoast headland and its magnitude vary from case to case. Wave obliquity varies from small to moderate values. These are two main parameters while wave condition is kept constant. The final bay planforms are investigated and recorded once they reach equilibrium with condition that sediment transport gradient approaches zero and no further shoreline change are observed. The parabolic equation similar to that for static equilibrium is newly proposed. The coefficients are originally derived and found to be a function of wave obliquity and the ratio of sediment supplied into bay to longshore sediment transport. The new dynamic equilibrium bay equation can be used and applied to study morphology change with variation of supplied sediment from inland.

Aeolian sediment transport on a beach with a varying sediment supply

2014 ◽  
Vol 15 ◽  
pp. 235-244 ◽  
Author(s):  
S. de Vries ◽  
S.M. Arens ◽  
M.A. de Schipper ◽  
R. Ranasinghe
Keyword(s):  
Sediment Transport ◽  
Sediment Supply ◽  
Aeolian Sediment

scholarly journals River sediment transport and coastal erosion in the southeastern Black Sea rivers / Transport riečnych sedimentov a erózia pobrežia riek krajiny v juhovýchodnej časti čierneho mora

2012 ◽  
Vol 60 (4) ◽  
pp. 299-308 ◽  
Author(s):  
Mehmet Berkun ◽  
Egemen Aras
Keyword(s):  
Sediment Transport ◽  
Black Sea ◽  
Coastal Erosion ◽  
The Black Sea ◽  
Coastal Protection ◽  
Anthropogenic Pressure ◽  
Hydroelectric Power ◽  
Protection Measures ◽  
Black Sea Region ◽  
Bed Material

In the Southeastern Black Sea Region, rivers are dammed for hydroelectric power and irrigation. The natural course of fluvial alluvium transport is almost completely altered because of planned and constructed dams and coastal protection measures. Decreasing volume of sediment carried to the sea cause intensification of the shore erosion. The Black Sea Rivers and coastal areas of Turkey and Georgia are under heavy anthropogenic pressure because of the bed material extraction and coastal erosion rate. In this study, environmental effects of dams and related effects of sediment transport on coastal erosion in the Eastern Black Sea region are discussed.

scholarly journals AEOLIAN SEDIMENT TRANSPORT AT A MAN-MADE DUNE SYSTEM; BUILDING WITH NATURE AT THE HONDSBOSSCHE DUNES

2018 ◽  
pp. 83 ◽  
Author(s):  
Marloes Wittebrood ◽  
Sierd De Vries ◽  
Petra Goessen ◽  
Stefan Aarninkhof
Keyword(s):  
Sediment Transport ◽  
Transport Model ◽  
Morphological Changes ◽  
Morphological Evolution ◽  
Sediment Supply ◽  
Dune System ◽  
Morphological Response ◽  
Profile Type ◽  
Building With Nature ◽  
Aeolian Sediment

This paper presents the influence of aeolian sediment transport on the initial morphological evolution of beach and dunes at the man-made dune system ‘Hondsbossche Dunes’ at the Dutch coast. In total 35 million m^3 dredged material was used for the construction of a beach, dune and foreshore system. This study focused on differences in morphological response within the five different realized dune profile types. A conceptual framework was developed, based on the assessment of (1) environmental forcing, (2) sediment supply from aeolian and marine sources and (3) dune types. These three components were quantified from an analysis of measured profile evolution and the application of an aeolian sediment transport model for the first 19 months since the project delivery date in May 2015. Morphological changes were most pronounced in the first seven months after construction. Dune growth of a profile type at this location is determined by a temporal and alongshore variability in local processes that determines the aeolian sediment supply towards the dunes and the dune geometry that determines the capacity of the profile type to capture the sediments. The model simulations managed to qualitatively reproduce alongshore variations in dune growth as a result of spatial variations in sediment availability, grain size, profile shape and interaction with vegetation. Overall, this study shows the relevance of both marine and aeolian processes in such man-made dynamic systems that are comparable to natural systems. Continuing the monitoring and modelling of this system will improve the quantitative knowledge for design optimization of the Building with Nature philosophy.

Autogenic progradation of Bayhead deltas during sea-level rise wIthin incised valleys : theory, experiment and field examples    

2021 ◽  
Author(s):  
Laure Guerit ◽  
Brady Foreman ◽  
Chen Chen ◽  
Chris Paola ◽  
Sébastien Castelltort
Keyword(s):  
Sediment Transport ◽  
Sea Level Rise ◽  
Sea Level ◽  
Large Scale ◽  
Sediment Supply ◽  
Sediment Flux ◽  
Surface Evolution ◽  
Sequence Stratigraphic ◽  
Incised Valleys ◽  
The Trinity

<p>The evolution of sedimentary landscapes is primary driven by the interplay between the rate of accommodation creation A, controlled by sea-level and subsidence, and the rate of sediment supply S, controlled by erosion and sediment transport. In simple terms, the balance between A and S can be used to predict periods of progradation (when sediment supply exceeds accommodation) and periods of retrogradation (when accommodation exceeds sediment supply). However, a growing list of observations show that internal feedbacks within the sediment transport system can generate large-scale, autogenic stratigraphic patterns that are not anticipated by the A/S theory. These observations call for a reanalysis of several sequence stratigraphic precepts that assume a deterministic relationship between external forcings and stratigraphic products. Here, we focus on the filling of incised valleys during constant sea-level rise, and by a constant sediment flux. We develop a simple conceptual model of valley filling and we show that the classic sequence stratigraphic phenomenon of bayhead deltaic systems can be generated by purely autogenic progradation during the late stage of valley flooding. This transient “auto-advance” event results from a strong decrease of in-valley accommodation as base-level rises towards the valley apex. To test this model, we build a laboratory experiment that successfully reproduces the dynamics predicted by the model. Finally, we apply our model to two similar field examples, the Trinity and Brazos rivers incised valleys (Texas, USA). There systems are broadly similar in dimension and sea-level history but were filled at different sediment rates. We propose that this led to auto-advance event in the Trinity River valley while no advance is observed in the Brazos system. We thus show by conceptual, experimental and natural examples that auto-advance can produce out-of-sequence regressive bayhead diastems during highstands similar to a transient change in allogenic forcing. Combined with other recent studies, our findings support the idea that meso-scale autogenic patterns are ubiquitous in the fluvio-deltaic record, and need to be more extensively incorporated into reconstructions of Earth surface evolution and reservoir models.</p>

VARIAÇÃO MORFOSSEDIMENTAR DO SETOR EXTREMO OESTE DA PRAIA DO ICARAÍ, CAUCAIA-CE

2019 ◽  
Vol 21 (2) ◽  
pp. 364-380
Author(s):  
Antônio Emanuel dos' Santos Silva ◽  
Matheus Silveira Pinheiro ◽  
Davis Pereira de Paula
Keyword(s):  
Civil Society ◽  
Coastal Erosion ◽  
Field Experiments ◽  
Coastal Protection ◽  
Dune System ◽  
Built Heritage ◽  
General Terms ◽  
Methodological Procedures ◽  
Sociedad Civil

Ambientalmente as dunas frontais constituem estruturas verdes de proteção costeira contra o avanço do mar, em muitos casos, são responsáveis pela manutenção do equilíbrio sedimentar do sistema praia-duna, impedindo que processos como a erosão costeira e a inundação marinha se tornem danosos a sociedade civil e ao patrimônio construído. O objetivo deste estudo foi monitorar as variações morfológicas e sedimentares do sistema praia-duna entre os anos de 2016 e 2018, no trecho extremo oeste da Praia do Icaraí, através da determinação das taxas granulométricas, volumétricas e morfológicas do sistema praia-duna na Praia do Icaraí. Os procedimentos metodológicos foram divididos em três etapas principais: levantamento bibliográfico, geocartográfico e experimentos de campo. Considerou-se que as forçantes oceanográficas foram as principais responsáveis pela erosão e solapamento das dunas frontais presentes na área de estudo. Em linhas gerais, os resultados deste trabalho significam um importante instrumento de análise dos impactos das condicionantes oceanográficas e antrópicas sobre uma praia que sofre de erosão costeira acentuada. O estudo em um trecho mais preservado dessa praia indicou de forma direta os impactos sofridos em um litoral que vem passando por transformações contínuas em suas praias, como é o caso do litoral de Caucaia.Palavras-chave: Morfodinâmica; Sistema Praial; Dunas Frontais. ABSTRACTEnvironmentally the frontal dunes constitute green structures of coastal protection against the advance of the sea, in many cases, they are responsible for the maintenance of the sedimentary balance of the beach-dune system, preventing that processes such as coastal erosion and marine flooding become harmful to civil society and built heritage. The objective of this study was to monitor the morphological and sedimentary variations of the beach-dune system between the years 2016 and 2018, in the extreme west section of Icaraí Beach, by determining the granulometric, volumetric and morphological rates of the beach-dune system in Praia of Icaraí. The methodological procedures were divided into three main stages: bibliographic survey, geocartographic and field experiments. It was considered that the oceanographic forcings were the main responsible for the erosion and overlap of the frontal dunes present in the study area. In general terms, the results of this work represent an important instrument for analyzing the impacts of oceanographic and anthropogenic conditions on a beach that suffers from marked coastal erosion. The study in a more preserved stretch of this beach indicated in a direct way the impacts suffered on a coast that has undergone continuous transformations in its beaches, as is the case of the coast of Caucaia.Keywords: Morphodynamics; Praial System; Fore Dunes. RESUMENAmbientalmente, las dunas frontales son estructuras verdes de protección costera contra el avance del mar. En muchos casos, son responsables de mantener el equilibrio sedimentario del sistema de dunas de playa, evitando que procesos como la erosión costera y las inundaciones marinas dañen a la sociedad civil. y el patrimonio construido. El objetivo de este estudio fue monitorear las variaciones morfológicas y sedimentarias del sistema de dunas de playa entre 2016 y 2018, en el extremo occidental de Praia do Icaraí, determinando el tamaño de partícula, las tasas volumétricas y morfológicas del sistema de dunas de playa en Praia de Icaraí Los procedimientos metodológicos se dividieron en tres etapas principales: estudio bibliográfico, geocartográfico y experimentos de campo. El forzamiento oceanográfico se consideró el principal responsable de la erosión y el debilitamiento de las dunas frontales presentes en el área de estudio. En general, los resultados de este trabajo representan un instrumento importante para analizar los impactos de las condiciones oceanográficas y antropogénicas en una playa que sufre una severa erosión costera. El estudio en un tramo más preservado de esta playa indicó directamente los impactos sufridos en una costa que ha sufrido cambios continuos en sus playas, como es el caso de la costa de Caucaia.Palabras claves: Morfodinámica; Sistema de playa; Dunas frontales.

scholarly journals Morphodynamic Evolution of a Nourished Beach with Artificial Sandbars: Field Observations and Numerical Modeling

2021 ◽  
Vol 9 (3) ◽  
pp. 245
Author(s):  
Cuiping Kuang ◽  
Xuejian Han ◽  
Jiabo Zhang ◽  
Qingping Zou ◽  
Boling Dong
Keyword(s):  
Sediment Transport ◽  
Tidal Current ◽  
Model Simulation ◽  
Morphological Changes ◽  
Current Model ◽  
Beach Nourishment ◽  
Tidal Range ◽  
Coastal Protection ◽  
Field Observations ◽  
One Year

Beach nourishment, a common practice to replenish an eroded beach face with filling sand, has become increasingly popular as an environmentally friendly soft engineering measure to tackle coastal erosion. In this study, three 200 m long offshore submerged sandbars were placed about 200 m from the shore in August 2017 for both coastal protection and beach nourishment at Shanhai Pass, Bohai Sea, northeastern China. A series of 21 beach profiles were collected from August 2017 to July 2018 to monitor the morphological changes of the nourished beach. Field observations of wave and tide levels were conducted for one year and tidal current for 25 h, respectively. To investigate the spatial-temporal responses of hydrodynamics, sediment transport, and morphology to the presence of three artificial submerged sandbars, a two-dimensional depth-averaged (2DH) multi-fraction sediment transport and morphological model were coupled with wave and current model and implemented over a spatially varying nested grid. The model results compare well with the field observations of hydrodynamics and morphological changes. The tidal range was around 1.0 m and the waves predominately came from the south-south-east (SSE) direction in the study area. The observed and predicted beach profiles indicate that the sandbars moved onshore and the morphology experienced drastic changes immediately after the introduction of sandbars and reached an equilibrium state in about one year. The morphological change was mainly driven by waves. Under the influences of the prevailing waves and the longshore drift toward the northeast, the coastline on the leeside of the sandbars advanced seaward by 35 m maximally while the rest adjacent coastline retreated severely by 44 m maximally within August 2017–July 2018. The model results demonstrate that the three sandbars have little effect on the tidal current but attenuate the incoming wave significantly. As a result, the medium-coarse sand of sandbars is transported onshore and the background silt is mainly transported offshore and partly in the longshore direction toward the northeast. The 2- and 5-year model simulation results further indicate that shoreline salient may form behind the sandbars and protrude offshore enough to reach the sandbars, similar to the tombolo behind the breakwater.

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