| 1. |
- Larson, Magnus, et al.
(författare)
-
An analytical model to predict dune and cliff notching due to wave impact
- 2010
-
Ingår i: Proceedings of 32nd Conference on Coastal Engineering. - : Coastal Engineering Research Council. - 0161-3782. - 9781629931210 - 9780989661102
-
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.
|
|
| 2. |
- Hanson, Hans, et al.
(författare)
-
Modeling long-term beach change under interacting longshore and cross-shore processes
- 2010
-
Ingår i: Proceedings of 32nd Conference on Coastal Engineering. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661102
-
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.
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Hallin, Caroline, et al.
(författare)
-
Enhance dune-building processes with nature-based nourishment design
- 2020. - 2020
-
Ingår i: Proceedings of virtual Conference on Coastal Engineering, 2020. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661157 ; 36
-
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
|
|
| 7. |
- Hoan, Le Xuan, et al.
(författare)
-
Modeling shoreline response and inlet shoal volume development on long Island Coast, United States
- 2010. - 32
-
Ingår i: Proceedings of the Coastal Engineering Conference : 32nd International Conference on Coastal Engineering, ICCE 2010 - 32nd International Conference on Coastal Engineering, ICCE 2010. - 0161-3782.
-
Konferensbidrag (refereegranskat)abstract
- A new numerical model was developed to simulate regional sediment transport, shoreline response in the vicinity of tidal inlets, and inlet shoal volume growth based on the one-line model of shoreline change combined with the reservoir concept for volumetric evolution of inlet shoals. Sand bypassing onshore and sheltering effects on wave action from the inlet bar and shoals were taken into account. The model was applied to unique field data from the south coast of Long Island, United States, including inlet opening and closure. The simulation area extended from Montauk Point to Fire Island inlet, including Shinnecock and Moriches Inlets (Figure 1). A 20-year time series of hindcast wave data at three stations along the coast were used as input data to the model. Several types of sediment sources and sinks were represented, including beach fills, groin systems, jetty blocking, inlet bypassing, and flood shoal and ebb shoal feeding. The model simulations were validated against annual net longshore transport rates reported in the literature, measured shorelines, and recorded sediment volumes in the flood and ebb shoal complexes. Overall, the model simulations were in good agreement with the measured data.
|
|
| 8. |
- Marinho, Bárbara, et al.
(författare)
-
Long-term coastal evolution modelling of longshore bars
- 2018. - 2018
-
Ingår i: Proceedings of 32nd International Conference on Coastal Engineering. - 0161-3782. ; 36
-
Konferensbidrag (refereegranskat)abstract
- An extended version of a numerical model introduced by Larson et al. (2013) to simulate long-term cross shore material exchange for the subaqueous portion of the profile has been developed. Efforts have focused on improving the model to better account for beach systems consisting of two bars (inner and outer bar), as well as simulating the feeder response over time of nearshore dredged material bars, intended to function as beach nourishment. The theory for the evolution of a single-bar to a two-bar system was modeled, considering an inner and an outer bar, where the outer bar is of primary interest with the purpose of predicting the behavior of placed dredged material. The cross-shore sediment transport rate is based on the evolution equation for the bar system response to the hydrodynamic forcing by reference to its equilibrium condition, where the change in the bar volume is based on a set of wave criteria, describing the onset of a new breaking zone when the outer bar forms. Empirical formulas are employed for the bar equilibrium volume and for coefficients determining the bar response rate. In this study, a description of the extended model and the results from the model component validation at two different sites in USA (Duck, North Carolina, and Cocoa Beach, Florida) are presented. Duck measurements have detected that some bars form in the nearshore and move all the way offshore (eventually deflating by non-breaking waves). At the same time, it was equally observed that a lot of inner bars formed in shallow water do not move offshore but remain as inner bars all the time. According to this, the developed model considers that the inner bar will not become the outer bar, but material previously dedicated to the inner bar will be available for the outer bar. Overall, the present study demonstrates the potential for using rather simple models, based on the definition of an equilibrium state that is compared to the current state and the magnitude of offshore wave forcing to drive the changes in the profile. The methodology employed here allowed to quantitatively reproduce the main trends in the subaqueous beach profile response in a long-term perspective as a function of the bar volumes disequilibrium, the magnitude of the incident wave height and the dimensionless fall velocity to move the sand with a time varying forcing.
|
|
| 9. |
- Palalane, Jaime, et al.
(författare)
-
Analytical model of sand spit evolution
- 2014
-
Ingår i: Proceedings of 34th Conference on Coastal Engineering, Seoul, Korea, 2014. - : Coastal Engineering Research Council. - 0161-3782. - 9780989661126 ; 2014-January
-
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.
|
|
| 10. |
|
|
