| 1. |
- Hallin, Caroline, et al.
(författare)
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Enhance dune-building processes with nature-based nourishment design
- 2020. - 2020
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Ingår i: Proceedings of virtual Conference on Coastal Engineering, 2020. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661157 ; 36
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Konferensbidrag (refereegranskat)abstract
- Vast coastal stretches around the world rely on dunes for flood protection. At the same time, the protection level of many dune systems can be undermined due to coastal erosion, sea-level rise, and greater population densities. To enhance dune building processes and the growth of coastal dunes, nature-based solutions, such as multi-purpose sand nourishments, are increasingly being implemented. However, the performance of the nourishment projects in terms of dune growth do not always match the expectations due to unforeseen supply-limiting factors (Hoonhout and de Vries, 2019). Sediment on a beach should be within a site-specific range of grain sizes to be available for pick up by the wind and deposition in the dunes. However, the grain-size characteristics do also influence several other supply-limiting factors, e.g., surface moisture, crust development, and beach slope, making nourishment design complicated. The process-based model Aeolis has been developed to predict aeolian transport rates considering several supply limiting factors. In this study, we introduce a new surface moisture functionality in Aeolis and demonstrate how the model can be used to optimize nourishment designs with respect to dune build-up. A number of test cases are presented to illustrate how grain size, sorting, and beach morphology are influencing aeolian transport rates.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/K_eiZ5kPk2g
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| 2. |
- Hanson, Hans, et al.
(författare)
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Modeling long-term beach change under interacting longshore and cross-shore processes
- 2010
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Ingår i: Proceedings of 32nd Conference on Coastal Engineering. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661102
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Konferensbidrag (refereegranskat)abstract
- This paper presents mathematical formulations and a new numerical model GenCade that simulates beach and dune change in response to cross-shore processes of dune growth by wind and dune erosion by storms, and by gradients in longshore sand transport that will also alter shoreline position. The berm plays a central role since the potential for sand to be transported to the dune by wind depends on berm width, and sand lost in erosion of the dune during storms will widen the berm. Morphologic equilibrium considerations are introduced to improve reliability of predictions and stability of the non-linear model. An analytical solution is given to illustrate properties of the model under simplified conditions. Sensitivity tests with the numerical solution of the coupled equations demonstrate model performance. Finally, the numerical model is applied to examine the consequences of groin shortening at Westhampton Beach, Long Island, New York, as an alternative for providing a sand supply to the down-drift beach. Results indicate that the sand will be released over several decades as the shoreline and dune move landward in adjustment to the new equilibrium condition with the shortened groins.
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| 3. |
- Larson, Magnus, et al.
(författare)
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An analytical model to predict dune and cliff notching due to wave impact
- 2010
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Ingår i: Proceedings of 32nd Conference on Coastal Engineering. - : Coastal Engineering Research Council. - 0161-3782. - 9781629931210 - 9780989661102
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Konferensbidrag (refereegranskat)abstract
- A model was developed to calculate the evolution of a notch in a dune or cliff due to wave impact. Analytical solutions were derived to the model for schematized conditions regarding forcing and dune/cliff properties. Comparisons were made with laboratory experiments where the time evolution of the notch was measured. Values of the transport coefficients in the analytical solutions were determined by least-square fitting the solutions to the laboratory data. Some of these coefficients could be related to the ratio between parameters describing the forcing and the dune/cliff strength. The evolution of the dune notch displayed a linear behavior at short times, whereas the cliff notch showed a more complex response for cases where a feedback between the notch and a beach formed seaward of the cliff occurred.
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| 4. |
- Palalane, Jaime, et al.
(författare)
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Analytical model of sand spit evolution
- 2014
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Ingår i: Proceedings of 34th Conference on Coastal Engineering, Seoul, Korea, 2014. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661126 ; 2014-January
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Konferensbidrag (refereegranskat)abstract
- Spits typically consist of sand or gravel and are commonly occurring morphological features at inlets, river mouths, and the down-drift ends of barrier islands. Thus, they may form at the ocean-, lake-, or bay-side of inlets, entrances, and river mouths. Apart from the scientific interest in spits and their evolution, engineers have often studied spits with regard to their penetration into river mouths or inlets, restricting the flow rate and possibly even causing closure of the inlet (river mouth). Governing processes for spit growth under a predominant longshore transport, causing down-drift accumulation of sand, were reviewed. Based on this review, equations for the simulation of spit growth from former studies were improved, and their analytical solutions employed to build a model able to reproduce linear spit elongation. Major modifications were introduced in the equations to account for variation in spit cross-section with time, and to better describe the increase in active profile height and transport at the down-drift end of the spit as it elongates through the inlet channel. The analytical solutions were compared with data from the laboratory and field case studies. The case studies represent situations of unrestricted and restricted growth, including time-varying cross-sectional spit area and increasing active profile height. Results showed that the generalized expression for time-varying spit cross-sectional area enabled the adoption of a more realistic trapezoidal cross-section for the modeled spits. The model also contributed to estimate the net longshore sediment transport rates, facilitating comparison with observations from the different case studies. For unrestricted spit growth, it was possible to give a satisfactory representation of spit elongation over the analyzed periods, although for some study areas a single elongation rate could not accurately predict increasing spit lengths over long periods of analysis, i.e., above 50 years. Nevertheless, the model has a high potential to make rapid quantitative predictions, being a useful and valid tool for initial estimates in engineering projects.
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| 5. |
- Westergren, Sofia, et al.
(författare)
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An analytical tool for long-term dune management
- 2014
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Ingår i: Proceedings of 34th Conference on Coastal Engineering. - : Coastal Engineering Research Council. - 0161-3782. ; 2014-January
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Konferensbidrag (refereegranskat)abstract
- Climate change calls for coastal management to consider longer time scales. The main objective of this study is to develop an analytical tool for long-term dune management to help evaluate the risk associated with high water levels, high waves, and their joint probability, as well as the probability of dune erosion, overwash, and breaching to occur. The tool also aims to identify vulnerable dune sections. A case study was made in Ystad Sandskog beach located on the south coast of Sweden. Data covering 20 years were used to investigate probabilities and consequences resulting from extreme waves and water levels. The data were also manipulated in order to indicate future implications in the context of climate change. The analytical tool turns out to be easy to implement and to interpret. The case study shows that Ystad Sandskog beach is subject to dune erosion and that many houses and infrastructure located behind the dunes may be exposed to more frequent flooding in the future.
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