Empirical modelling of beach evolution: implementation of coupled cross-shore and longshore approaches

2020 ◽  
Author(s):  
Teddy Chataigner ◽  
Marissa Yates ◽  
Nicolas Le Dantec
Keyword(s):  
Morphological Evolution ◽  
Computational Cost ◽  
Sandy Beaches ◽  
Sediment Flux ◽  
Beach Profile ◽  
Change Models ◽  
Empirical Modelling ◽  
Spatial And Temporal Scales ◽  
Shoreline Evolution

<p>Understanding shoreline evolution, and in particular, the consequences of shoreline erosion is a<br>major societal concern that threatens to become even more important in the future with the impacts<br>of climate change. Thus, it is necessary to improve both knowledge of the dominant physical processes<br>controlling medium to long-term shoreline evolution and the capabilities of morphological evolution<br>models to simulate beach changes at these spatial and temporal scales.<br>Empirical models may be an ideal choice for modelling complex and dynamic environments such as<br>sandy beaches at large spatial (beach) and long temporal (years to decades) scales. They reproduce<br>the effects of the main morphodynamical processes with low computational cost and relatively high<br>accuracy, in particular when high quality, long-term data are available for calibration.<br>Here, to broaden its range of application, a cross-shore equilibrium model, which has demon-<br>strated its accuracy and efficiency in reproducing shoreline and intertidal beach profile changes at<br>several micro and macrotidal beaches, is extended to couple it with a longshore beach evolution<br>modelling approach. The selection of a particular longshore model (based on a one-line approach),<br>and its implementation and validation with benchmark test cases of shoreline evolution caused by<br>the effects of diffusion, high angle wave instabilities, and coastal structures are presented.<br>The new hybrid model is applied at Narrabeen beach to reproduce the long-term evolution of<br>beach contours near the shoreline. The model is calibrated and tested using the 40-year timeseries of<br>monthly subaerial beach profile surveys conducted along 5 cross-shore profiles along the 3.6km-long<br>Narrabeen-Collaroy embayment. The novelty of the current work is to focus on reproducing changes<br>at different altitudes, with the objective of assessing the cross-shore variability of the longshore<br>sediment flux, which is assumed constant in most one-line longshore transport models. The coupled<br>model performance is discussed, and the results are compared to existing studies that have simulated<br>shoreline evolution at Narrabeen using other morphological change models.</p>

scholarly journals EQUILIBRIUM MODELING OF CURRENT AND FUTURE BEACH EVOLUTION: VOUGOT BEACH, FRANCE

2020 ◽  
pp. 17
Author(s):  
Teddy Chataigner ◽  
Marissa Yates ◽  
Nicolas Le Dantec ◽  
Serge Suanez ◽  
France Floch ◽  
...  
Keyword(s):  
Climate Change ◽  
Morphological Changes ◽  
Wave Climate ◽  
Optimal Choice ◽  
Physical Processes ◽  
Change Models ◽  
Spatial And Temporal Scales ◽  
Shoreline Evolution ◽  
Impacts Of Climate Change

The impacts of climate change, including sea level and wave climate changes, may increase future erosion risks. Thus, it is important to improve knowledge of the dominant physical processes controlling medium- to long-term shoreline evolution, as well as the performance of beach evolution models reproducing past observations and predicting future changes. Empirical equilibrium beach change models may be an optimal choice at these spatial and temporal scales. Here, morphological changes at Vougot Beach (Brittany, France) are analyzed by evaluating the cross-shore evolution of contour elevations (-1 to 6m) along six intertidal beach profiles using observations and an equilibrium beach change model, and then three methods for estimating the impacts of climate change are applied and compared.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/p70KuzjR1kU

scholarly journals SIMULATION OF LONG-TERM SHORELINE CHANGE DRIVEN BY LONGSHORE AND CROSS-SHORE SEDIMENT TRANSPORT

2020 ◽  
pp. 31
Author(s):  
Yan Ding ◽  
Sung-Chan Kim ◽  
Richard B. Styles ◽  
Rusty L. Permenter
Keyword(s):  
Sediment Transport ◽  
Shoreline Change ◽  
Breaking Wave ◽  
Beach Profile ◽  
Shoreline Evolution ◽  
Longshore Sediment Transport ◽  
Wave Energy Flux ◽  
Semi Empirical ◽  
Evolution Modeling

Driven by wave and current, sediment transport alongshore and cross-shore induces shoreline changes in coasts. Estimated by breaking wave energy flux, longshore sediment transport in littoral zone has been studied for decades. Cross-shore sediment transport can be significant in a gentle-slope beach and a barred coast due to bar migration. Short-term beach profile evolution (typically for a few days or weeks) has been successfully simulated by reconstructing nonlinear wave shape in nearshore zone (e.g. Hsu et al 2006, Fernandez-Mora et al. 2015). However, it is still lack of knowledge on the relationship between cross-shore sediment transport and long-term shoreline evolution. Based on the methodology of beach profile evolution modeling, a semi-empirical closure model is developed for estimating phase-average net cross-shore sediment transport rate induced by waves, currents, and gravity. This model has been implemented into GenCade, the USACE shoreline evolution model.

scholarly journals Morphodynamic Acceleration Techniques for Multi-Timescale Predictions of Complex Sandy Interventions

2019 ◽  
Vol 7 (3) ◽  
pp. 78 ◽  
Author(s):  
Arjen Luijendijk ◽  
Matthieu Schipper ◽  
Roshanka Ranasinghe
Keyword(s):  
Time Scales ◽  
Morphological Evolution ◽  
Computational Cost ◽  
Wave Climate ◽  
Sandy Beaches ◽  
Brute Force ◽  
Morphological Response ◽  
Acceleration Techniques ◽  
Long Time ◽  
Wave Conditions

Thirty one percent (31%) of the world’s coastline consists of sandy beaches and dunes that form a natural defense protecting the hinterland from flooding. A common measure to mitigate erosion along sandy beaches is the implementation of sand nourishments. The design and acceptance of such a mitigating measure require information on the expected evolution at time scales from storms to decades. Process-based morphodynamic models are increasingly applied, together with morphodynamic acceleration techniques, to obtain detailed information on this wide scale of ranges. This study shows that techniques for the acceleration of the morphological evolution can have a significant impact on the simulated evolution and dispersion of sandy interventions. A calibrated Delft3D model of the Sand Engine mega-nourishment is applied to compare different acceleration techniques, focusing on accuracy and computational times. Results show that acceleration techniques using representative (schematized) wave conditions are not capable of accurately reproducing the morphological response in the first two years. The best reproduction of the morphological behavior of the first five years is obtained by the brute force simulations. Applying input filtering and a compression factor provides similar accuracy yet with a factor five gain in computational cost. An attractive method for the medium to long time scales, which further reduces computational costs, is a method that uses representative wave conditions based on gross longshore transports, while showing similar results as the benchmark simulation. Erosional behavior is captured well in all considered techniques with variations in volumes of about 1 million m 3 after three decades. The spatio-temporal variability of the predicted alongshore and cross-shore distribution of the morphological evolution however have a strong dependency on the selected acceleration technique. A new technique, called ’brute force merged’, which incorporates the full variability of the wave climate, provides the optimal combination of phenomenological accuracy and computational efficiency (a factor of 20 faster than the benchmark brute force technique) at both the short and medium to long time scales. This approach, which combines realistic time series and the mormerge technique, provides an attractive and flexible method to efficiently predict the evolution of complex sandy interventions at time scales from hours to decades.

scholarly journals A Study of UVER in Santiago, Chile Based on Long-Term In Situ Measurements (Five Years) and Empirical Modelling

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 368
Author(s):  
Lisdelys González-Rodríguez ◽  
Amauri Pereira de Oliveira ◽  
Lien Rodríguez-López ◽  
Jorge Rosas ◽  
David Contreras ◽  
...  
Keyword(s):  
Urban Areas ◽  
Solar Spectrum ◽  
Sun Exposure ◽  
Great Accuracy ◽  
In Situ Measurements ◽  
Uv Index ◽  
Empirical Modelling ◽  
The People

Ultraviolet radiation is a highly energetic component of the solar spectrum that needs to be monitored because is harmful to life on Earth, especially in areas where the ozone layer has been depleted, like Chile. This work is the first to address the long-term (five-year) behaviour of ultraviolet erythemal radiation (UVER) in Santiago, Chile (33.5° S, 70.7° W, 500 m) using in situ measurements and empirical modelling. Observations indicate that to alert the people on the risks of UVER overexposure, it is necessary to use, in addition to the currently available UV index (UVI), three more erythema indices: standard erythemal doses (SEDs), minimum erythemal doses (MEDs), and sun exposure time (tery). The combination of UVI, SEDs, MEDs, and tery shows that in Santiago, individuals with skin types III and IV are exposed to harmfully high UVER doses for 46% of the time that UVI indicates is safe. Empirical models predicted hourly and daily values UVER in Santiago with great accuracy and can be applied to other Chilean urban areas with similar climate. This research inspires future advances in reconstructing large datasets to analyse the UVER in Central Chile, its trends, and its changes.

scholarly journals Impact of the COVID-19 pandemic: a perspective from industry

2020 ◽  
Vol 22 (Supplement_P) ◽  
pp. P56-P59
Author(s):  
Nick E J West ◽  
Wai-Fung Cheong ◽  
Els Boone ◽  
Neil E Moat
Keyword(s):  
Care Delivery ◽  
Models Of Care ◽  
Medium Term ◽  
Change Models ◽  
New Device ◽  
Supply Chain Logistics ◽  
Cardiovascular Patients ◽  
Medical Crisis ◽  
Device Industry

Abstract The global COVID-19 pandemic has led to unprecedented change throughout society.1 As the articles in this supplement outline, all segments of the broader cardiovascular community have been forced to adapt, to change models of care delivery, and to evolve and innovate in order to deliver optimal management for cardiovascular patients. The medtech/device industry has not been exempt from such change and has been forced to navigate direct and indirect COVID-associated disruption, with effects felt from supply chain logistics to the entire product lifecycle, from the running of clinical trials to new device approvals and managing training, proctoring and congresses in an increasingly-online world. This sea-change in circumstances itself has enforced the industry, in effect, to disrupt its own processes, models and activities. Whilst some of these changes may be temporary, many will endure for some time and some will doubtless become permanent; one thing is for sure: the healthcare ecosystem, including the medical device industry, will never look quite the same again. Although the pandemic has brought a short- to medium-term medical crisis to many countries, its role as a powerful disruptor cannot be underestimated, and may indeed prove to be a force for long-term good, given the accelerated innovation and rapid adaptation that it has cultivated.

scholarly journals Guideline concordance and outcome in long-term naturalistic treatment of bipolar disorder - a one-year longitudinal study using latent change models

2020 ◽  
Author(s):  
Joannes W. Renes ◽  
Dominique F. Maciejewski ◽  
Eline J. Regeer ◽  
Adriaan W. Hoogendoorn ◽  
Willem A. Nolen ◽  
...  
Keyword(s):  
Bipolar Disorder ◽  
Longitudinal Study ◽  
Change Models ◽  
One Year

scholarly journals Long-Term Observations of Beach Variability at Hasaki, Japan

2020 ◽  
Vol 8 (11) ◽  
pp. 871
Author(s):  
Masayuki Banno ◽  
Satoshi Nakamura ◽  
Taichi Kosako ◽  
Yasuyuki Nakagawa ◽  
Shin-ichi Yanagishima ◽  
...  
Keyword(s):  
Morphological Change ◽  
High Frequency ◽  
Climate Changes ◽  
Wave Climate ◽  
Time Interval ◽  
Observation Data ◽  
Beach Profile ◽  
Water Level Variations ◽  
Monthly Variations

Long-term beach observation data for several decades are essential to validate beach morphodynamic models that are used to predict coastal responses to sea-level rise and wave climate changes. At the Hasaki coast, Japan, the beach profile has been measured for 34 years at a daily to weekly time interval. This beach morphological dataset is one of the longest and most high-frequency measurements of the beach morphological change worldwide. The profile data, with more than 6800 records, reflect short- to long-term beach morphological change, showing coastal dune development, foreshore morphological change and longshore bar movement. We investigated the temporal beach variability from the decadal and monthly variations in elevation. Extremely high waves and tidal anomalies from an extratropical cyclone caused a significant change in the long-term bar behavior and foreshore slope. The berm and bar variability were also affected by seasonal wave and water level variations. The variabilities identified here from the long-term observations contribute to our understanding of various coastal phenomena.

scholarly journals Event-Driven Simulation Scheme for Spiking Neural Networks Using Lookup Tables to Characterize Neuronal Dynamics

2006 ◽  
Vol 18 (12) ◽  
pp. 2959-2993 ◽  
Author(s):  
Eduardo Ros ◽  
Richard Carrillo ◽  
Eva M. Ortigosa ◽  
Boris Barbour ◽  
Rodrigo Agís
Keyword(s):  
Synaptic Plasticity ◽  
High Speed ◽  
Large Scale ◽  
Computational Cost ◽  
Brain Structures ◽  
Spike Timing ◽  
Neuronal Dynamics ◽  
Event Driven ◽  
Synaptic Dynamics

Nearly all neuronal information processing and interneuronal communication in the brain involves action potentials, or spikes, which drive the short-term synaptic dynamics of neurons, but also their long-term dynamics, via synaptic plasticity. In many brain structures, action potential activity is considered to be sparse. This sparseness of activity has been exploited to reduce the computational cost of large-scale network simulations, through the development of event-driven simulation schemes. However, existing event-driven simulations schemes use extremely simplified neuronal models. Here, we implement and evaluate critically an event-driven algorithm (ED-LUT) that uses precalculated look-up tables to characterize synaptic and neuronal dynamics. This approach enables the use of more complex (and realistic) neuronal models or data in representing the neurons, while retaining the advantage of high-speed simulation. We demonstrate the method's application for neurons containing exponential synaptic conductances, thereby implementing shunting inhibition, a phenomenon that is critical to cellular computation. We also introduce an improved two-stage event-queue algorithm, which allows the simulations to scale efficiently to highly connected networks with arbitrary propagation delays. Finally, the scheme readily accommodates implementation of synaptic plasticity mechanisms that depend on spike timing, enabling future simulations to explore issues of long-term learning and adaptation in large-scale networks.

scholarly journals Emergence and Migration of a Nearshore Bar: Sediment Flux and Morphological Change on a Multi-Barred Beach in the Great Lakes

2007 ◽  
Vol 60 (1) ◽  
pp. 31-47 ◽  
Author(s):  
Brian Greenwood ◽  
Allana Permanand-Schwartz ◽  
Christopher A. Houser
Keyword(s):  
Great Lakes ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sandy Beaches ◽  
Sediment Flux ◽  
Accommodation Space ◽  
Longshore Transport ◽  
Sediment Balance ◽  
And Migration ◽  
Equilibrium Morphology

Abstract Burley Beach (southeastern Lake Huron) exhibits a multi-barred shoreface, the long-term equilibrium morphology characteristic of many low angle, sandy beaches in the Canadian Great Lakes. During a single major storm, a new bar emerged 50-60 m offshore as an irregular trough-crest form, through differential erosion of an existing shore terrace. Emergence, bar growth and offshore migration were associated with: (a) an overall negative sediment balance in the inner surf zone initially (‑2.30 m3>/m beach width), but with a large positive sediment balance (+5.10 m3/m) subsequent to the storm peak and during the storm decay; (b) progradation of the beach step to produce a new shore terrace; and (c) offshore migration of the two outer bars to provide the accommodation space necessary for the new bar. The primary transport mechanisms accounting for emergence of the new bar, its growth and migration were: (a) the mean cross-shore currents (undertow), which always transported suspended sediment offshore; and (b) the onshore transport of suspended sediment by incident gravity wave frequencies early in the storm and subsequently by infragravity waves (at the storm peak and the decay period). The longshore transport of sediment was significant in terms of the gross transport, although the net result was only a small transport to the south-west (historic littoral transport direction). It did not cause bar initiation, but it may have supplied some of the sediment for bar growth. The primary mechanism for bar initiation and growth was the cross-shore displacement of sediment by wave-driven (oscillatory) transport and cross-shore mean currents (undertow).

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