Abstract The Grande-Motte port and seafront development project on the French Mediterranean coastline entailed evaluating wave impact loads pressures and forces on the new beach seawall and comparing the resulting scour potential at the base of the existing and new seawall.
A physical model was built at ARTELIA's hydraulics laboratory in Grenoble France to provide insight into: wave and setup at the beach, the evolution of scour over time at the front of the wall, quasi-static and impulsive wave force intensity and distribution on the wall, and water and sand overtopping discharges over the wall. Light-weight sediment physical model and pressure and force measurements were performed with scale References G.
Forgot your password? The results show that scours around the tripod foundation do not only occur directly around the foundation piles, but also in the near-field of the structure. Compared to first in-situ measured scours in the test site, at least a good qualitative agreement of the modeled scour depths and evolutions could be shown.
References DHI. Scour Manual. Balkema, Rotterdam Lambers-Huesmann, M. Personal communication on scours measured in the German offshore test site alpha ventus Rolfes, R. Park Passes. News Releases. Featured Stories. Science Snippets. Technical Announcements. Employees in the News. Get Our News. Media Contacts. I'm a Reporter. Staff Profiles. Social Media. Contact Us. About Us. Survey Manual. Key Officials. Careers and Employees. Doing Business. Emergency Management.
Overview Publications Partners The primary objective of this project is to develop an integrated procedure for assessing scour potential at riverine bridges in South Carolina utilizing the regional bridge-scour envelope curves developed in the three previous field investigations.
March 28, Modification of selected South Carolina bridge-scour envelope curves Historic scour was investigated at bridges in the Piedmont and Coastal Plain physiographic provinces of South Carolina by the U. Some limitations to using historic shoreline change rates to estimate future shoreline position include:. Local sediment budgets play a large role in the dynamics of shoreline change.
Sediment budgets describe the input, transport, storage, and export of sediment along the shoreline. Whether evaluated quantitatively or qualitatively, all sediment budgets are conceptually understood by a continuity equation stating that during a given time period, the amount of sediment coming into the area minus the amount leaving the area equals the change in the amount of stored sediment. Historical aerial imagery as well as survey can be used to evaluate long-term trends in the shoreline as mentioned above but review of the sediment budget can also be used to estimate future shoreline positions.
Sediment budgets typically require much more data and analysis than simple shoreline change extrapolation. Aerial photography and remote sensing can be used to quantify visual and volumetric changes in sediment along a shoreline. In addition, sediment sampling in the water column and along the seafloor can be combined to develop data needed for sediment transport models.
In the mapping or quantifying of sediment transport, specific erosion problems can be identified or better understood in order to develop appropriate site-specific solutions.
Figure is an example of a sediment budget evaluation and map. The sediment budgets were determined through volumetric methods that evaluated the beach profile changes from In addition to prorating historical trends of shoreline change, numerical models have been developed to estimate future shoreline positions.
Few numerical models can accommodate all of the design factors discussed in this chapter within the same model. Models also vary in their degree of complexity, ranging from 1D to 3D capabilities. Figure shows inputs per level of analysis and available modeling for each level. The most common method for estimating future shoreline positions is direct extrapolation of historic shoreline change rates to the present shoreline from historic maps and aerials.
Shortcomings in this method include the fact that shorelines change processes may not be linear with time; it is difficult to tie the shorelines to a specific datum, engineering may have impacted shoreline change in the past and may impact future change.
If an area is rural and has experienced minimal engineering design along its coast, then historic maps and aerials can be appropriate for shoreline change. If shoreline change and modeling is required for a large study area with many engineered structures and recorded shoreline change, it is usually necessary to use a highly advanced model to achieve the sediment transport detail needed for design.
Dredging can play a large role in shoreline change and especially in sites adjacent to the GIWW. Sargent Bridge in Texas is an example of an abutment being designed for future dredging depth and impacts, rather than current conditions.
This bridge site and the large area impacted by repeated or planned dredging would be a candidate for advanced modeling to evaluate shoreline change and sediment transport. The type of project may dictate when to choose between a long-term and a short-term analysis.
When evaluating short-term shoreline change due to extreme events, such as hurricanes, available data may limit the type of approach. The validation and calibration of such short-term shoreline change models is only possible when the available data, such as shoreline positions and elevations, are available both before and after the storm event.
Modeling a short-term change is needed to calibrate the model to review long-term changes. Long-term change models can then include several probable storm events. Such data has become more common thanks to technological advancements in elevation data collection. Pre-storm and post-storm shoreline position and elevation data are available in limited locations for some recent storms in the form of coastal LiDAR data.
Roadways and other transportation assets along the coast are vulnerable to shoreline change Figure Once shoreline change has been identified as a design factor impacting a roadway asset, the vulnerability should be assessed. One method to determine vulnerability is to map the elevation and shoreline positions near structures versus the long-term recession rate the long-term recession rate is the long-term shoreline change at an area that is determined to be recessing landward , using methods previously outlined.
The less time a structure has until exposed by shoreline recession, the greater the potential vulnerability. This approach should also be combined with consideration of short-term or storm-induced erosion to help prioritize structures with a high potential for exposure to erosion. Early consideration is highly beneficial for planning repair, protection, or relocation strategies.
If possible, transportation structures vulnerable to shoreline change should be considered for relocation to a landward position.
However, if relocation is not an option due to adjacent private property, environmental concerns, or other issues, engineered shoreline stabilization combined with monitoring may provide long-term protection. Due to shoreline retreat, it is not viable to be rebuilt in its current location. Examples of Roadways affected by Shoreline Change. As discussed in the Scour Mitigation Measures subsection, stabilization or remediation can be achieved through both hard engineering e.
A combination of techniques is often most effective in ensuring success. Mitigation measures for shoreline stabilization are similar to mitigation for scour but should be viewed on a broader scale in terms of sediment transport. Right-of-ways are often narrow, and joint efforts or partnerships may be required for roadway revetment and combination of hard and soft protection. Search for the word or phrase:.
Help Advanced. Anchor: i Section 6: Erosion Erosion in the coastal environment can take many forms, with the most common issues for coastal roadways resulting from scour and shoreline change. Anchor: i Scour Scour is addressed elsewhere in this Manual for cases involving hydraulics for bridges Chapter 9 , reservoirs Chapter 12 , and storm water management Chapter Scour Mechanisms Scour results from the erosive action of flowing water, which may remove and carry away material from the bed, banks of waterway, and from around coastal structures, such as piers and abutments.
Additional Coastal Scour Mechanisms. Search for the word or phrase: Help Advanced. Search in: this manual only. Erosion along toe of highway embankment. Erosion of embankment due to overtopping flow. Long term vertical degradation of stream bed.
Horizontal migration of stream banks. A - Partial embankment damage caused by wave attack. B - Example of the weir-flow damage mechanism as it occurs. D - Two bridges destroyed by wave loads in Hurricane Katrina. E - Wave scour hole formed by Hurricane Katrina.
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