scholarly journals MODELLING OF A NEARSHORE PLACED SAND MOUND

2012 ◽  
Vol 1 (33) ◽  
pp. 35
Author(s):  
Ernest R. Smith ◽  
Felice D'Alessandro ◽  
Giuseppe Roberto Tomasicchio ◽  
Joseph Z. Gailani
Keyword(s):  
Numerical Model ◽  
Numerical Solutions ◽  
Numerical Models ◽  
Open Water ◽  
Beach Nourishment ◽  
The United States ◽  
Water Levels ◽  
Beach Profile ◽  
Near Shore ◽  
Model C

Nearshore placement of sand is becoming a more popular option in two related types of coastal engineering projects: beach nourishment and inlet dredging. Placing the sand in the nearshore instead of directly on the beach can reduce the costs of a beach nourishment project (Douglass 1995); furthermore, the environmental impact to the beach and dune ecosystem may be perceived to be less for open-water disposal with subsequent migration than for direct placement on the beach. Nearshore placement of sand is also an option in navigation dredging projects for similar reasons. Several design and planning questions relate to the fate of dredged sand placed in the nearshore. Can we economically use profile nourishment, and what is the certainty that a constructed submerged feature will move onshore or remain in place? And if it will move, what is the rate of its movement? Another question concerns how deep material should be placed. In order to answer these questions, together with physical model experiments, several empirical/numerical models have been developed in the past in the United States as a part of the Corps of Engineers ‘Dredging Research Program’ (DRP) (Hands 1991, Larson and Kraus 1992). Hydrodynamic modelling of the nearshore environment has reached a verifiable level of maturity in the last decades as a result of well-defined equations, established numerical solutions and quality laboratory and field data. On the contrary, modelling of sediment transport and beach profile evolution has not yet approached a similar level of accuracy. Most commonly applied models to predict beach profile modifications and to estimate the migration rate of nearshore constructed sand mounds rely on empirical relationships (Douglass 1995). More recently, the numerical model C-SHORE (Kobayashi et al. 2007; Figlus et al. 2011) was developed resulting in simple, practical and accurate code that predicts beach–dune profile evolution over the near-shore region in response to waves, currents and water levels. In the present work, a calibration and verification procedure is considered for the numerical model C-SHORE (Kobayashi et al. 2007) and the empirical model (Douglass 1995).

A RANS numerical model for cross-shore beach profile evolution

2020 ◽  
Author(s):  
Julio Garcia-Maribona ◽  
Javier L. Lara ◽  
Maria Maza ◽  
Iñigo J. Losada
Keyword(s):  
Sediment Transport ◽  
Numerical Model ◽  
Transport Model ◽  
Numerical Models ◽  
Computational Cost ◽  
Physical Modelling ◽  
Computational Effort ◽  
Beach Profile ◽  
Time Step ◽  
Wave Conditions

<p>The evolution of the cross-shore beach profile is tightly related to the evolution of the coastline in both small and large time scales. Bathymetry changes in extreme maritime events can also have important effects on coastal infrastructures such as geotechnical failures of foundations or the modification of the incident wave conditions towards a more unfavourable situation.</p><p>The available strategies to study the evolution of beach profiles can be classified in analytical, physical and numerical modelling. Analytical solutions are fast, but too simplistic for many applications. Physical modelling provides trustworthy results and can be applied to a wide variety of configurations, however, they are costly and time-consuming compared to analytical strategies. Finally,  numerical approaches offer different balances between cost and precision depending on the particular model.</p><p>Some numerical models provide greater precision in the beach profile evolution, but incurring in a prohibitive computational cost for many applications. In contrast, the less expensive ones assume simplifications which do not allow to correctly reproduce significant phenomena of the near-shore hydrodynamics such as wave breaking or undertow currents, neither to predict important features of the beach profile like breaker bars.</p><p>In this work, a new numerical model is developed to reproduce the main features of the beach profile and hydrodynamics while maintaining an affordable computational cost. In addition, it is intended to reduce to the minimum the number of coefficients that the user has to provide to make the model more predictive.</p><p>The model consists of two main modules. Firstly, the already existing 2D RANS numerical model IH2VOF is used to compute the hydrodynamics. Secondly, the sediment transport model modifies the bathymetry according to the obtained hydrodynamics. The new bathymetry is then considered in the hydrodynamic model to account for it in the next time step.</p><p>The sediment transport module considers bedload and suspended transports separately. The former is obtained with empirical formulae. In the later,the distribution of sediment concentration in the domain is obtained by solving an advective-diffusive transport equation. Then, the sedimentation and erosion rates are obtained along the seabed.<br>Once these contributions are calculated, a sediment balance is performed in every seabed segment to determine the variation in its level.</p><p>With the previously described strategy, the resulting model is able to predict not only the seabed changes due to different wave conditions, but also the influence of this new bathymetry in the hydrodynamics, capturing features such as the generation of a breaker bar, displacement of the breaking point or variation of the run-up over the beach profile. To validate the model, the numerical results are compared to experimental data.</p><p>An important novelty of the present model is the computational effort required to perform the simulations, which is significantly smaller than the one associated to existing models able to reproduce the same phenomena.</p>

scholarly journals FINAL DESIGN OF THE NAGS HEAD BEACH NOURISHMENT PROJECT USING A LONGSHORE NUMERICAL MODEL

2012 ◽  
Vol 1 (33) ◽  
pp. 64 ◽  
Author(s):  
Haiqing Liu Kaczkowski ◽  
Timothy W Kana
Keyword(s):  
Numerical Model ◽  
Large Scale ◽  
Numerical Models ◽  
Normal Wave ◽  
Beach Nourishment ◽  
Shoreline Evolution ◽  
Longshore Transport ◽  
Final Design ◽  
Model Setup ◽  
The Impact

Nags Head, located at the northeastern part of North Carolina in the U.S., has sustained chronic erosion over the past 50 years. In 2005, Coastal Science & Engineering (CSE) was retained by the town of Nags Head to develop an interim beach restoration plan. Profile volume change was used in the planning and preliminary design of the project, and longshore and cross-shore numerical models were used in the final design to refine the preliminary nourishment plan and increase potential longevity of the project. This paper focuses on the key factors of the longshore numerical model setup for the project. These include model selection, input data and parameters, model calibration, and applications under different design alternatives. The Generalized Model for Simulating Shoreline Changes (GENESIS) was used in this study to evaluate shoreline evolution under normal wave conditions during various stages of the design life following the beach nourishment project. The model was used to identify the potential occurrence of erosional hotspots and to optimize the nourishment design so that the effects of such hotspots could be avoided or minimized where possible. Model results were also used to evaluate the impact of borrow area dredging on longshore transport in the project area and the impact of nourishment on shoaling in the adjacent inlet. The project encompasses 10.11 miles (mi) (16.28 kilometers-km) of ocean shoreline, and the design nourishment volume is based on the total permitted volume of 4 million cubic yards (cy) (3 million cubic meters-m³). [Note: As-built length was 10.0 mi and volume was 4.615 million cubic yards.] The final design has fill densities varying from north to south in relation to historical erosion rates and model projections. The average fill density is 75 cubic yards per foot (cy/ft) (188 m³/m) and ranges from 38 cy/ft to 150 cy/ft (95 m³/m to 375 m³/m). In conclusion, it is shown that the numerical model selected in this study was capable of predicting the overall performance of the large scale beach nourishment project in Nags Head as well as the performance at a particular location within or adjacent to the project, and its design methods can offer guidance to future projects.

scholarly journals A MODEL TO SIMULATE BEACH PROFILE EVOLUTION INDUCED BY STORMS

2018 ◽  
pp. 10
Author(s):  
Jie Zhang ◽  
Magnus Larson ◽  
Zhenpeng Ge
Keyword(s):  
Sediment Transport ◽  
Numerical Models ◽  
Model Development ◽  
High Water ◽  
Water Levels ◽  
Evolution Model ◽  
Beach Erosion ◽  
Beach Profile ◽  
Dune Erosion ◽  
Profile Change

Beach profile change induced by storms is a common and complex process in coastal engineering. Storms often bring high water levels and large waves, which erode the berm and dune, carrying large quantities of sand offshore, often causing severe damage to coastal properties. Thus, considerable research has been carried out to determine storm impact. Early studies mainly focused on laboratory investigations and analysis of field data. Since the 1980’s, many engineering numerical models of beach profile change have been developed. Kriebel and Dean (1985) proposed a model (EBEACH) to simulate the beach profile evolution with focus on dune erosion during storms, using the concept of an equilibrium beach profile (EBP). However, features such as bars and berms are not described in this model. Larson and Kraus (1989) developed an empirically based model (SBEACH) for describing the formation of bars and berms, also applying the EBP concept. Steetzel (1990) developed a model for cross-shore transport during severe storms that focuses on offshore transport and erosion. Johnson et al. (2012) developed a CS profile evolution model, CSHORE, that is mainly used to predict beach erosion under the combined effect of waves and currents. Although the model provided satisfactory performance in simulating measured berm and dune erosion in field applications, further improvements in dealing with the sediment transport in the intermittently wet-dry areas are desirable. At present, XBeach proposed by Roelvink et al. (2009) is the most popular and widely used model together with SBEACH. Although the objective of the XBeach model is to predict the profile evolution along the entire profile, i.e., both in the subaerial and subaqueous regions, the processes in the former region are less well described from a physics point of view compared to the latter. The response of the subaerial region in XBeach, including the foreshore, berm, and dune, relies on rather ad-hoc empirical sediment transport formulations. This study presents a profile evolution model that is based on the work by Larson et al. (2015). The emphasis of the model development is physically based descriptions of the subaerial profile response induced by storms. Focus of the model validation here is the berm and foreshore region.

scholarly journals DEVELOPMENT OF DYNAMIC SEDIMENT BUDGET TO PREDICT FUTURE SHORELINE POSITIONS ON A SAND LIMITED SHORELINE IN LOUISIANA

2012 ◽  
Vol 1 (33) ◽  
pp. 104
Author(s):  
Arpit Agarwal ◽  
Josh Carter ◽  
Matt Campbell ◽  
Hugo Bermudez
Keyword(s):  
Numerical Models ◽  
Beach Nourishment ◽  
Shoreline Change ◽  
Sediment Budget ◽  
Army Corps ◽  
Storm Events ◽  
Beach Profile ◽  
Change Analysis ◽  
Sediment Wave ◽  
Project Site

A shoreline change analysis was performed along the shoreline of the chenier plain in southwestern Louisiana in an attempt to forecast future shoreline position and to determine the performance of a proposed sand beach nourishment project along the shoreline which extends 14 km west of the western jetty of Calcasieu Pass, Louisiana and runs through the community of Holly Beach, Louisiana. Observations of shoreline morphology revealed a solitary sediment wave traversing the project site from east to west since the 1960’s. The genesis of the sediment wave is unknown and is unexplored in this work. The presence of the sediment wave masked the long-term shoreline change rates along the project site and therefore biased the predictions of future shoreline positions due to the transient nature of the sediment wave morphology. Standard coastal engineering methods used to predict future shoreline positions include simple translation of the shoreline based on measured shoreline change rates (referred to herein as historical linear progression or HLP) and one-line numerical models. For the project site, due to the presence of this sediment wave the HLP approach to predict future shoreline positions is not applicable. One-line shoreline morphology models such as the US Army Corps of Engineer's GENESIS model require the assumption that the beach profile can be represented by an equilibrium beach profile which was developed for sand rich shorelines. The project site profile composition of a sandy veneer extending to a depth of approximately -1.2 to -2 m over a muddy bottom violates this assumption, and therefore the traditional one-line model cannot be applied. Therefore, a dynamic sediment budget (DSB) method was developed to predict future shoreline positions based on available historical data, longshore transport rates, known morphological processes, statistical estimates of storm events, beach nourishment diffusion, and a relationship between volume change and shoreline change based on existing profile composition. This method was validated with existing data and was able to predict 20 years of morphology within ±15 m of measured shoreline positions.

scholarly journals DUNE EROSION PHYSICAL, ANALYTICAL AND NUMERICAL MODELLING

2012 ◽  
Vol 1 (33) ◽  
pp. 32 ◽  
Author(s):  
Felice D'Alessandro ◽  
Giuseppe Roberto Tomasicchio ◽  
Fausta Musci ◽  
Andrea Ricca
Keyword(s):  
Large Scale ◽  
Laboratory Data ◽  
Water Levels ◽  
Data Sets ◽  
Dune System ◽  
Dune Erosion ◽  
Storm Waves ◽  
Near Shore ◽  
Recession Rates ◽  
Model C

The present paper provides an overview of the large-scale physical model experiments performed at the Canal d’Investigaciò i Esperimentaciò Marìtima (CIEM), Laboratori d’Enginyeria Marìtima (LIM), Universitat Politècnica de Catalunya (UPC), Barcelona, within the EU-Hydralab III Integrated Infrastructure Initiative. The model tests have been carried out in a flume with a sandy dune exposed to a combination of water levels and wave conditions. Different regimes of wave attacks on the sandy/beach dune system have been investigated; in particular, the study provides a unique set of large-scale physical data concerning the storm waves induced dune overwash (Tomasicchio et al. 2011a; Tomasicchio et al.2011b). The effects of various “load parameters” on the dune erosion process generation, including dune recession rates in terms of the retreat of the dune face, Δx, and the eroded volume, ΔV, have been investigated and discussed. The laboratory data sets have been adopted to calibrate and verify the analytical model proposed by Larson et al. (2004) in order to calculate the values of ΔV at specific time intervals. Furthermore, the profile measurements have been used to calibrate and verify the numerical model C-SHORE (Kobayashi et al. 2007) predicting the beach-dune profile modifications over the near-shore region (Tomasicchio et al. 2011a; Tomasicchio et al.2011b).

Dynamic Ice Breakup Control for the Connecticut River near Windsor, Vermont

1988 ◽  
Vol 19 (4) ◽  
pp. 245-258
Author(s):  
M. G. Ferrick ◽  
G. E. Lemieux ◽  
P. B. Weyrick ◽  
W. Demont
Keyword(s):  
United States ◽  
Open Water ◽  
The United States ◽  
River Regulation ◽  
Flood Damage ◽  
Water Levels ◽  
Connecticut River ◽  
Ice Breakup ◽  
Lower Stage ◽  
Ice Conditions

The Cornish-Windsor bridge is the longest covered bridge in the United States and has significant historical value. Dynamic ice breakup of the Connecticut River can threaten the bridge and cause flood damage in Windsor, Vermont. We monitored ice conditions throughout the 1985-86 winter, observed a mid­winter dynamic ice breakup, conducted controlled release tests during both open water and ice cover conditions, and analyzed more than 60 years of temperature and discharge records. River regulation presents alternatives for ice mangement that would minimize water levels during breakup. In this paper we develop the basis of a method to produce a controlled ice breakup at lower stage and discharge than occur during major natural events.

scholarly journals Analysis of estuarine flood levels based on numerical modelling. The Douro river estuary case study

2019 ◽  
Vol 23 ◽  
pp. 14
Author(s):  
Stênio De Sousa Venâncio ◽  
José Luís Pinho ◽  
José Manuel Vieira ◽  
Paulo Avilez-Valente ◽  
Isabel Iglesias
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Numerical Models ◽  
River Estuary ◽  
Northern Region ◽  
Complete Characterization ◽  
Water Levels ◽  
Flood Events ◽  
Douro River

Estuarine hydrodynamics present intermittent and complex circulation patterns. In this context, from the point of view of the coastal management associated with flood risks in riverine areas, numerical models allow predicting scenarios under specific hypotheses. This work simulates flood events occurring in the Douro river estuary recurring to numerical modelling tools. This estuary, located in the northern region of Portugal, periodically suffered severe flooding, with the associated losses and damages for the local protected landscape areas and hydraulic structures. The occurrence of these events justify the importance of a complete characterization of the areas that present risk of inundation and how they can be affected. A 2D-horizontal numerical model implemented with the Delft3D software was developed for this estuarine region including also the adjacent coastal zone. Available in-situ data were used for model calibration and validation processes. The obtained results are consistent with the in-situ measured water levels, allowing to understand the dynamics of the estuary during flood events. The robustness of the implemented numerical model allows to anticipate flood scenarios effects and associated water levels. The simulations results can then be used for sustainable management of this estuarine zone that presents high social, economic and environmental values.

scholarly journals GRAVEL BEACH PROFILE EVOLUTION IN WAVE AND TIDAL ENVIRONMENTS

2012 ◽  
Vol 1 (33) ◽  
pp. 15
Author(s):  
Mohamad Hidayat Jamal ◽  
David J. Simmonds ◽  
Vanesa Magar
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
Large Scale ◽  
Water Levels ◽  
Coarse Grained ◽  
Beach Profile ◽  
Model Simulations ◽  
Parameter Values ◽  
Future Work ◽  
Gravel Beach

This paper reports progress made in modifying and applying the X-Beach code to predict and explain the observed behaviour of coarse grained beaches. In a previous study a comparison of beach profile evolution measured during large scale experiments under constant water level with numerical model simulations was made. This placed particular emphasis on the tendency for onshore transport and profile steepening during calm conditions (Jamal et al., 2010). The present paper extends that investigation to study the influence of the advection of surf processes induced by tidal water level variations effects, on gravel beach profile evolution. The parameter values and numerical model used in the simulation is similar to that presented previously. It is assumed that, to good approximation, the groundwater interface inside the beach follows the tidally modulated water level. The results obtained from the model shows that the model provides reasonable simulations of beach profile change in a tidal environment. In comparison with simulations under stationary water levels, a larger berm is produced in agreement with literature. Finally, good agreement is obtained between the model simulations and an example of field observations from a beach at Milford on Sea, UK. Further developments are outlined for future work.

scholarly journals Transient Evolution of Inland Freshwater Lenses: Comparison of Numerical and Physical Experiments

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1154
Author(s):  
Rachel Rotz ◽  
Adam Milewski ◽  
Todd C Rasmussen
Keyword(s):  
Numerical Model ◽  
Arabian Peninsula ◽  
Transport Model ◽  
Numerical Models ◽  
Water Levels ◽  
Physical Models ◽  
Laboratory Model ◽  
Arid Environments ◽  
Model Simulations ◽  
Freshwater Lenses

Brackish to saline groundwater in arid environments encourages the development and sustainability of inland freshwater lenses (IFLs). While these freshwater resources supply much-needed drinking water throughout the Arabian Peninsula and other drylands, little is understood about their sustainability. This study presents a numerical model using the SEAWAT programming code (i.e., MODFLOW and the Modular Three-Dimensional Multispecies Transport Model (MT3DMS)) to simulate IFL transient evolution. The numerical model is based on a physical laboratory model and calibrated using results from simulations conducted in a previous study of the Raudhatain IFL in northern Kuwait. Data from three previously conducted physical model simulations were evaluated against the corresponding numerical model simulations. The hydraulic conductivities in the horizontal and vertical directions were successfully optimized to minimize the objective function of the numerical model simulations. The numerical model matched observed IFL water levels at four locations through time, as well as IFL thicknesses and lengths (R2 = 0.89, 0.94, 0.85). Predicted lens degradation times corresponded to the observed lenses, which demonstrated the utility of numerical models and physical models to assess IFL geometry and position. Improved understanding of IFL dynamics provides water-resource exploration and development opportunities in drylands throughout the Arabian Peninsula and elsewhere with similar environmental settings.

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