Decadal behaviour of a washover fan, Skallingen Denmark

2019 ◽  
Author(s):  
Troels Aagaard ◽  
Aart Kroon
Keyword(s):  
Washover Fan

scholarly journals Storm Driven Migration of the Napatree Barrier, Rhode Island, USA

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 330
Author(s):  
Bryan A. Oakley
Keyword(s):  
Rhode Island ◽  
Shoreline Change ◽  
Aerial Photographs ◽  
Tropical Storms ◽  
Lower Intensity ◽  
Storm Activity ◽  
The Impact ◽  
Washover Fan

Napatree Point, an isolated barrier in southern Rhode Island, provides a case study of barrier spit migration via storm driven overwash and washover fan migration. Documented shoreline changes using historical surveys and vertical aerial photographs show that the barrier had little in the way of net change in position between 1883 and 1939, including the impact of the 1938 hurricane. The barrier retreated rapidly between 1945 and 1975, driven by both tropical and extra-tropical storms. The shoreline position has been largely static since 1975. The removal of the foredune during the 1938 hurricane facilitated landward shoreline migration in subsequent lower intensity storms. Dune recovery following the 1962 Ash Wednesday storm has been allowed due to limited overwash and barrier migration over the last several decades. Shoreline change rates during the period from 1945–1975 were more than double the rate of shoreline change between 1939 and 2014 and triple the rate between 1883 and 2014, exceeding the positional uncertainty of these shoreline pairs. The long-term shoreline change rates used to calculate coastal setbacks in Rhode Island likely underestimate the potential for rapid shoreline retreat over shorter time periods, particularly in a cluster of storm activity. While sea-level rise has increased since 1975, the barrier has not migrated, highlighting the importance of storms in barrier migration.

scholarly journals Impact of historical tsunamis on a sandy coastal barrier: an example from the northern Gargano coast, southern Italy

2001 ◽  
Vol 1 (4) ◽  
pp. 213-219 ◽  
Author(s):  
F. Gianfreda ◽  
G. Mastronuzzi ◽  
P. Sansò
Keyword(s):  
Northern Coast ◽  
Deep Trench ◽  
Tsunami Waves ◽  
Coastal Barrier ◽  
Severe Erosion ◽  
Gargano Promontory ◽  
Historical Times ◽  
Roman Age ◽  
Washover Fan ◽  
Radiometric Data

Abstract. The Lesina coastal barrier is characterized by the presence of three wide washover fans. They were formed by three distinct tsunamis which struck the northern coast of the Gargano Promontory (Apulia, Italy) during historical times. A model for their formation is presented. It takes into account the geomorphological data collected and some reports about the effect of recent tsunamis on coastal barriers and beaches. Washover fans were produced by tsunami waves which ran through coseismic cracks developed on dune ridges shaping a narrow, straight and relatively deep trench which constitutes the fan throat. Moreover, each tsunami event most likely caused severe erosion of the coastal barrier, shaping erosive grooves across the dune ridges, causing beach cliffs and causing the nourishment of submarine offshore bars. After the tsunami, a phase of coastal barrier recovery began, forming new dune ridges and closing washover fan throats. Morphological, archeological and radiometric data indicate a pre-Roman age for the oldest event, which was dated at 2430 years BP. The second tsunami struck the Lesina coastal barrier with similar magnitude 1550 years BP; it was caused by the strong earthquake that occurred at Gargano Promontory in the year 493 AD as reported by a medieval sacred legend. The smallest and more recent fan formed following the tsunami that hit the northern coast of Gargano on 30 July 1627.

scholarly journals The Gyra washover fan in the Lefkada Lagoon, NW Greece—possible evidence of the 365 AD Crete earthquake and tsunami

2012 ◽  
Vol 64 (10) ◽  
pp. 859-874 ◽  
Author(s):  
Simon Matthias May ◽  
Andreas Vött ◽  
Helmut Brückner ◽  
Alessandra Smedile
Keyword(s):  
Crete Earthquake ◽  
Washover Fan

Washover fan and brackish bay sedimentation in the Berriasian-Valanginian of Bornholm, Denmark

Sedimentology ◽  
1988 ◽  
Vol 35 (2) ◽  
pp. 197-217 ◽  
Author(s):  
NANNA NOE-NYGAARD ◽  
FINN SURLYK
Keyword(s):  
Washover Fan

Spatial and temporal controls on overwash occurrence on a Great Lakes barrier spit

1992 ◽  
Vol 29 (1) ◽  
pp. 102-117 ◽  
Author(s):  
Robin G. D. Davidson-Arnott ◽  
John D. Fisher
Keyword(s):  
Lake Level ◽  
Field Measurements ◽  
High Water ◽  
Water Phase ◽  
Storm Events ◽  
North Shore ◽  
The North ◽  
High Lake Level ◽  
Washover Fan

Field measurements from 1985 to 1990 and sequential aerial photography since 1945 show that overwash plays an extremely important role in the dynamics of Long Point, a large barrier spit on the north shore of Lake Erie. Overwash occurs primarily in the transgressive proximal and central zones of the spit, which together account for some 65% of the total shoreline length of 41 km. During periods of high lake level, over 50% of the shoreline in these zones may be overwashed. Washover morphology ranges from continuous washover terraces in areas of low foredunes to isolated washovers with narrow throats and distinct fans where breaching has occurred through high dunes. Individual overwash events commonly produce deposits on the fan surface 0.25–0.75 m or more in thickness. Washover-fan sediments are dominated by nearly horizontal planar bedding, with deposits near the fan margins often having foreset bedding, reflecting deposition in standing water of the bay or of interdune ponds.The frequency of overwash occurrence is strongly influenced by long-term lake-level fluctuations, which produce a distinct cycle of overwash activity. During the high-water phase more than 40% of the shoreline may consist of active washover fans or inlet breaches. Even storms with a return frequency of 1–2 per year can lead to significant overwash activity, and the washovers are generally reactivated several times in a 2 or 3 year period around the peak water level. During the low-water phase wider beaches offer protection against even extreme storm events, resulting in washover healing and restoration of a continuous foredune.

scholarly journals Low resistance to overwash promotes sustained accretion of a washover fan on a transgressive barrier island during non-stormy periods

2020 ◽  
Author(s):  
Antonio B Rodriguez ◽  
Ethan J Theuerkauf ◽  
Justin T Ridge ◽  
Beth M VanDusen ◽  
Stephen R Fegley
Keyword(s):  
Barrier Island ◽  
Low Resistance ◽  
Washover Fan

scholarly journals BARRIER ISLAND DYNAMICS: OVERWASH PROCESSES AND SOLIAN TRANSPORT

1976 ◽  
Vol 1 (15) ◽  
pp. 113 ◽  
Author(s):  
Stephen P. Leatherman
Keyword(s):  
Barrier Island ◽  
Sediment Budget ◽  
Time Interval ◽  
Dune Field ◽  
Assateague Island ◽  
Washover Fan ◽  
Island Dynamics

The northern 5 miles of shoreline at Assateague Island, Maryland are presently being eroded. During storms, swash surges are able to overtop the most landward (storm) berm as overwash with deposition occurring on the barren flats. Where primary barrier dunes still exist, sediment-charged surges are funneled through breaches in the dune field for deposition of the entrained material on the washover fan. Sediment budget computations show that there has been a small net loss of material at each washover area, in spite of 7 discrete overwash events during a 26 month time interval. The predominant northwest winds effectively eroded the overwash material, transporting the majority of the sand back to the beach. This analysis indicates that there exists a balance between overwash and eolian processes with wind transport being slightly dominant.

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