Storms impacts on a sandy beach including seasonal recovery: alongshore variability and management influences
5
Citation
21
Reference
10
Related Paper
Citation Trend
Abstract:
Despite a global context of shoreline retreat, coastal areas and in particular sandy coasts are increasingly attractive. To handle the problem of coastline retreat different management strategies are deployed and among them soft methods as windbreakers or hard ones as seawalls. But all those methods are known to interfere in the natural evolution of the beach/dune systems at different timescales. To underline potential influences of management strategies on erosion and recovery periods, high frequency DGPS surveys coupled with video images are recorded at a workshop-site exhibiting various management strategies, Biscarrosse beach (SW of France) from November 2015 until September 2016. Results for the winter 2016 highlight a global erosion of the beach associated to a dune foot retreat and an alongshore variability in the beach response to events. The same patterns can be observed during the seasonal recovery period (April to August), in particular a lag in the berm reconstruction in front of the seawall. The LVI (Longshore Variation Index) reflects possible sediment processes taking place between the different sections of the beach: while recovery seems to be dominated by cross-shore exchanges in the unmanaged section, longshore sediment processes seem to be the origin of the recovery in the managed section. This variability could be linked to a permanent rip current visible (98% of observation) in front of the seawall that could cause an offshore sediment export explaining both the lag in term of recovery timescale and the different sediment processes involved during the recovery period. During the erosion season, sediment exchanges between the beach and the dune are limited due to the presence of seawalls and beach erosion and dune retreat in the two ends on the wall accelerated.Keywords:
Seawall
Sedimentary budget
Beach nourishment
Berm
Coastal erosion
Beach morphodynamics
Beach ridge
Longshore drift
Coastal Management
Coastal geography
To address the issues of shore protection and "sediment starvation" along the Winthrop Beach shoreline, a beach nourishment project has been designed to return the shoreline to historic conditions. Unlike most beach nourishment projects in the United States, the beach compatible material needed for restoration of Winthrop Beach consists of mixed gravel and sand sediments. Based upon observations from similar regional beach systems, it is anticipated that the coarse fraction of the nourishment material will be naturally sorted by wave action and form a gravel berm along the upper portion of the beach. Formation of these gravel berms during the winter months will significantly enhance the design life of the project by increasing wave energy dissipation due to the high porosity of the berm and reduce storm-induced erosion of the finer-grained material underlying the gravel. Due to the unique conditions of Winthrop Beach, an offshore borrow site was determined to be the most cost-effective and the only feasible method for providing nourishment material to the beach.
Berm
Beach nourishment
Dredging
Coastal erosion
Beach ridge
Cite
Citations (0)
Beach width is an important factor for tourists’ comfort, and the backshore is a swash zone where sediment moves quickly. Artificial sandy beaches focus on beach width stability and evolution. This paper is based on an artificial beach project in Haikou Bay, where, in view of the existing conditions, a new type of beach profile that can protect beach berm and width without being eroded by large wave action. Numerical simulation based on XBeach model were conducted to predict the morphodynamical responses of the beach, including a diagnosis of the erosion spots under storm and normal wave events, respectively. Sediment fluxes along and across the shoreline under varied scenarios, dependent on profile width and backshore slope, were discussed. It was found that normal waves with lower heights and longer periods can induce stronger erosion than storm waves due to the landform of the inner-bay in Haikou Bay. Engineering and biological methods to reduce beach erosion during wave action were discussed. Biological methods such as green-plants-root-system can retain berm surface sediment without allowing it to be transported offshore by wave action. The design concept of this artificial beach project may inspire more beach design and protection projects in coastal zones.
Berm
Swash
Coastal erosion
Beach nourishment
Landform
Plage
Beach ridge
Coastal engineering
Surf zone
Wave height
Beach morphodynamics
Cite
Citations (5)
Use of the term 'beach ridge' is confusing in the literature because definitions of beach ridges are highly variable and are commonly used interchangeably with 'berm' and sometimes 'foredune'. Thus, the definitions of sand beach ridges are briefly reviewed, and beach ridges are re-defined as entirely wave formed deposits. Berms and foredunes are also defined. Modes of sand beach ridge formation are also reviewed, with four primary modes identified.
Berm
Beach ridge
Foredune
Beach nourishment
Beach morphodynamics
Plage
Cite
Citations (43)
Gravel beach shows more dynamic profile change than sand beach, and is vulnerable to erosion. An artificial reef may be a structure to reduce beach erosion. However, there are many cases still suffering from beach erosion after installation of artificial reefs, indicating that more studies about beach processes are required. This study aims to investigate shoreline change at Shichirimihama Beach by using WEB camera system and beach profile changes based on field observation. Results showed that high energy wave during typhoon is the main reason leading to the continuous shoreline retreat. High wave approaching from E-SSE direction leaded to the formation of berm on the top of beach face at the location without artificial reef. In the area behind artificial reef, berm formation was not observed and shoreline almost stood by at its orginal position. However, when highwave approached to the coast from S-SW direction, sediment on beach face was washed out and the shoreline reatreated on the entire study area. This results indicated that in Shichirimihama beach wave direction also plays an important role on beach morphology change
Berm
Beach nourishment
Coastal erosion
Typhoon
Beach ridge
Plage
Cite
Citations (6)
Beach nourishment is increasingly seen as an appropriate management solution in areas which are experiencing beach erosion. Such a scheme has been implemented along the Lincolnshire coast between Skegness and Mablethorpe, on the east coast of England, since 1994. Poorly sorted, gravelly sandy sediment has been placed on the beaches in a gently sloping seaward profile to raise beach levels and protect the hard defences from wave attack. Grain size analysis of beach sediments, topographic profiling and remote sensing have been used to monitor the beach response. After nourishment, wave reworking caused a rapid redistribution of sediment over the beach profile during the succeeding weeks. Coarse sediment has remained on the beach berm, while finer sediment has migrated to the lower beach and sub-tidal zone. The berm face has correspondingly become steeper, producing more wave reflectance, and further scour and erosion of lower beach sediment, although there appears to have been little alongshore sediment transport. The most severe sediment loss has occurred around promontories and on the central portion of the convex-shaped coast which experiences greatest wave exposure. While the nourishment scheme has improved the standard of defence, further sediment losses could be reduced by nourishing the beach with a more natural size grading, promoting a flatter beach profile and increasing the dissipation of wave energy. Unless stabilization of the beach profile can be achieved, further periodic renourishment will be required to maintain relatively high beach levels.
Berm
Beach nourishment
Beach ridge
Coastal erosion
Beach morphodynamics
Plage
Surf zone
Dredging
Longshore drift
Cite
Citations (22)
In this paper,taking the west beach of Beidaihe as an example,we analyzed the evolutionary features after beach nourishment through study of the changes in beach geomorphology and sediments distribution.One year after the beach nourishment project,the beach was obviously eroded.The average erosional volume per unit width was 44.8 m3/m and the average erosion distance of the beach berm was up to 15m.The erosion rate of eastern part of the beach was higher than that of the western part.Beach sediments were changed from coarse to fine in grain size and became well sorted.Four months after the nourishment project,the net transport tendency of the sediments was mainly alongshore in a direction from NE to SW.The beach off submerged breakwaters was eroded more severely without the protection of the offshore submerged breakwaters and there formed erosion hotspots as the result.One year after the beach nourishment project,76% of the filling sands were retained and the beach geomorphology was similar to the expected.As a whole,the beach nourishment is rather successful.
Beach nourishment
Berm
Coastal erosion
Breakwater
Plage
Beach ridge
Beach morphodynamics
Cite
Citations (0)