scholarly journals Paleotsunami Inundation of a Beach Ridge Plain: Cobble Ridge Overtopping and Interridge Valley Flooding in Seaside, Oregon, USA

2010 ◽  
Vol 2010 ◽  
pp. 1-22 ◽  
Author(s):  
Curt D. Peterson ◽  
Harry M. Jol ◽  
Tom Horning ◽  
Kenneth M. Cruikshank
Keyword(s):  
Shear Stresses ◽  
Before Present ◽  
Beach Ridge ◽  
Beach Ridges ◽  
Cobble Beach ◽  
Bed Shear Stresses ◽  
Beach Plain

The Seaside beach ridge plain was inundated by six paleotsunamis during the last ~2500 years. Large runups (adjusted >10 m in height) overtopped seawardmost cobble beach ridges (7 m elevation) at ~1.3 and ~2.6 ka before present. Smaller paleotsunami (6–8 m in height) likely entered the beach plain interior (4-5 m elevation) through the paleo-Necanicum bay mouth. The AD 1700 Cascadia paleotsunami had a modest runup (6-7 m height), yet it locally inundated to 1.5 km landward distance. Bed shear stresses (100–3,300 dyne cm−2) are estimated for paleotsunami surges (0.5–2 m depths) that flowed down slopes (0.002–0.017 gradient) on the landward side of the cobble beach ridges. Critical entrainment shear stresses of 1,130–1,260 dyne cm−2 were needed to dislodge the largest clasts (26–32 cm diameter) in paleotsunami coulees that were cut (100–200 m width) into the landward side of the cobble ridges.

scholarly journals Beach-ridge architecture constrained by beach topography and ground-penetrating radar, Itilleq (Laksebugt), south-west Disko, Greenland – implications for sea-level reconstructions.

2018 ◽  
Vol 66 ◽  
pp. 167-179
Author(s):  
Priscila E. Souza ◽  
Aart Kroon ◽  
Lars Nielsen
Keyword(s):  
Ground Penetrating Radar ◽  
Abrupt Change ◽  
Beach Ridge ◽  
Sediment Grain Size ◽  
Beach Ridges ◽  
Reflection Data ◽  
South West ◽  
Tide Level ◽  
Ground Penetrating ◽  
Reflection Characteristics

Detailed topographic data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach ridges at Itilleq, south-west Disko, West Greenland. In the western part of the study area, the present low-tide level is well defined by an abrupt change in sediment grain size between the sandy foreshore and the upper shoreface that is characterised by frequently occurring large clasts. The main parts of both fine and large clasts appear to be locally derived. Seaward-dipping reflections form downlap points, which are clearly identified in all beach-ridge GPR profiles. Most of them are located at the boundary between a unit with reflection characteristics representing palaeo-foreshore deposits and a deeper and more complex radar unit characterised by diffractions; the deeper unit is not penetrated to large depths by the GPR signals. Based on observations of the active shoreface regime, large clasts are interpreted to give rise to scattering observed near the top of the deeper radar unit. We regard the downlap points located at this radar boundary as markers of palaeo-low-tide levels. In some places, scattering hyperbolas are more pronounced and frequent than in others, suggesting differences in the occurrence of large boulders.

scholarly journals Applying of depth-averaged hydrodynamic modeling with different methods of turbulence closure for flow near channel groyne. Part I – hydrodynamic background

2018 ◽  
Vol 23 ◽  
pp. 00009
Author(s):  
Ryszard Ewertowski
Keyword(s):  
Eddy Viscosity ◽  
Rectangular Channel ◽  
Simulation Models ◽  
Shear Stresses ◽  
Research Activity ◽  
Simulation Experiments ◽  
Hydrodynamic Simulation ◽  
Training Structures ◽  
Averaged Model ◽  
Bed Shear Stresses

Training structures in flow stream play an important role in shaping flow and bed properties. Planning to introduce such training elements like groins or dikes into the river stream one need to know consequences they may introduce into flow field and bed shear stresses. These consequences can be investigated by laboratory experiments on hydraulic models or by numerical modelling using hydrodynamic simulation models. In the paper the second possibility is exploited by applying two-dimensional depth-averaged model for straight rectangular channel with a groyne. This paper contains the first part of the research results and it describes hydrodynamic background of the flow phenomenon, concentrating on hydrodynamic equations for depth-averaged flow, types of eddy viscosity method used and kind of boundary conditions applied. Based on the hydrodynamic descriptions, different simulation experiments have been conducted for the flow problem and the whole analysis of simulation results for flow in channel near groyne is contained in the second part of the research activity (Part II = Analysis of simulation).

scholarly journals Ground Penetrating Radar Investigation of Late Pleistocene Shorelines of Pluvial Lake Clover, Elko County, Nevada, USA

Quaternary ◽  
2020 ◽  
Vol 3 (1) ◽  
pp. 9
Author(s):  
Jeffrey S. Munroe
Keyword(s):  
Late Pleistocene ◽  
Ground Penetrating Radar ◽  
Land Surface ◽  
Primary Objective ◽  
Water Levels ◽  
Beach Ridge ◽  
Beach Ridges ◽  
Sand And Gravel ◽  
Ground Penetrating ◽  
Topographic Surveys

Beach ridges constructed by pluvial Lake Clover in Elko County, Nevada during the Late Pleistocene were investigated with ground-penetrating radar (GPR). The primary objective was to document the internal architecture of these shorelines and to evaluate whether they were constructed during lake rise or fall. GPR data were collected with a ground-coupled 400-Mhz antenna and SIR-3000 controller. To constrain the morphology of the ridges, detailed topographic surveys were collected with a Topcon GTS-235W total station referenced to a second class 0 vertical survey point. GPR transects crossed the beach ridge built by Lake Clover at its highstand of 1725 m, along with seven other ridges down to the lowest beach at 1712 m. An average dielectric permittivity of 5.0, typical for dry sand and gravel, was calculated from GPR surveys in the vicinity of hand-excavations that encountered prominent stratigraphic discontinuities at known depths. Assuming this value, consistent radar signals were returned to a depth of ~3 m. Beach ridges are resolvable as ~90 to 150-cm thick stratified packages of gravelly sand overlying a prominent lakeward-dipping reflector, interpreted as the pre-lake land surface. Many ridges contain a package of sediment resembling a buried berm at their core, typically offset in a landward direction from the geomorphic crest of the beach ridge. Sequences of lakeward-dipping reflectors are resolvable beneath the beach face of all ridges. No evidence was observed to indicate that beach ridges were submerged by higher water levels after their formation. Instead, the GPR data are consistent with a model of sequential ridge formation during a monotonic lake regression.

AMS Radiocarbon Dating of Lake Michigan Beach-Ridge and Dune Development

1997 ◽  
Vol 48 (1) ◽  
pp. 137-140 ◽  
Author(s):  
John Lichter
Keyword(s):  
Radiocarbon Dating ◽  
Lake Level ◽  
Sand Dune ◽  
Lake Michigan ◽  
Beach Ridge ◽  
Radiocarbon Dates ◽  
Beach Ridges ◽  
Ams Radiocarbon Dating ◽  
Climate Fluctuations ◽  
Radiocarbon Chronology

Strandplains of shore-parallel beach ridges bordering the Great Lakes are valuable for reconstructing histories of climate-related lake-level fluctuations. However, imprecise radiocarbon dates of ridge formation have frustrated development of dependable chronologies from which information about variation in the frequency of ridge formation and inferred climate fluctuations can be obtained. The resolution and precision of radiocarbon chronologies can be improved with AMS 14C dates of roots and rhizomes of plant species associated with the formation and growth of the sand-dune caps of breach ridges. These dates reliably estimate the timing of shore progradation when the base of the previously established beach ridge becomes inundated by the water table. An AMS radiocarbon chronology of beach-ridge formation in northern Lake Michigan shows that information about variation in the frequency of ridge formation is important for paleoclimatic interpretation.

Holocene Coastal Environments near Pompeii before the A.D. 79 Eruption of Mount Vesuvius, Italy

2001 ◽  
Vol 55 (1) ◽  
pp. 77-85 ◽  
Author(s):  
Tullio Pescatore ◽  
Maria Rosaria Senatore ◽  
Giovanna Capretto ◽  
Gaia Lerro
Keyword(s):  
Coastal Plain ◽  
Sedimentary Basin ◽  
Coastal Environments ◽  
Present Position ◽  
Beach Ridge ◽  
Pyroclastic Material ◽  
Beach Ridges ◽  
Shoreline Progradation ◽  
The City ◽  
Sarno River

AbstractStudies of some 70 bore holes around ancient Pompeii, on the southwestern slope of the Somma-Vesuvius volcano, allow the reconstruction of Holocene environments earlier than the A.D. 79 eruption. This eruption produced about 10 km3 of pyroclastic material that buried the Roman cities of Pompeii, Herculaneum, and Stabiae and promoted a shoreline progradation of 1 km. The Sarno coastal plain, in a post-Miocene sedimentary basin, has been affected by Somma-Vesuvius volcanic activity since the late Pleistocene. At the Holocene transgressive maximum, the sea reached an area east of ancient Pompeii and formed a beach ridge (Messigno, 5600 and 4500 14C yr B.P.) more than 2 km inland from the present shore. Progradation of the plain due to high volcanic supply during the following highstand resulted in a new beach ridge (Bottaro-Pioppaino, 3600 14C yr B.P.) 0.5 km seaward of the Messigno ridge. Ancient Pompeii was built as the shoreline continued to prograde toward its present position. Deposits of the A.D. 79 eruption blanketed the natural levees of the Sarno River, marshes near the city and on the Sarno's floodplain, the morphological highs of Messigno and Bottaro-Pioppaino beach ridges, and the seashore. That shore was probably 1 km landward of the present one.

scholarly journals Investigation of bed shear stresses subject to external turbulence

2003 ◽  
Vol 24 (6) ◽  
pp. 816-824 ◽  
Author(s):  
Nian-Sheng Cheng ◽  
B.Mutlu Sumer ◽  
Jørgen Fredsøe
Keyword(s):  
Shear Stresses ◽  
External Turbulence ◽  
Bed Shear Stresses

scholarly journals VESSEL WAKE INDUCED SEDIMENT MOBILITY AT EAGLE HARBOR, WASHINGTON, USA

2012 ◽  
Vol 1 (33) ◽  
pp. 58
Author(s):  
David Michalsen ◽  
Zeki Demirbilek ◽  
Okey Nwogu
Keyword(s):  
Puget Sound ◽  
Critical Shear Stress ◽  
Washington State ◽  
Shear Stresses ◽  
Difference Model ◽  
Stability Model ◽  
Sediment Mobility ◽  
Bed Stress ◽  
Passenger Ferry ◽  
Bed Shear Stresses

Eagle Harbor is a small natural harbor located in central Puget Sound on the eastern side of Bainbridge Island, Washington State, USA. Over a period of about 80 years, the harbor was severely contaminated. Approximately 28.3 hectares of the contaminated harbor were capped with dredged and upland sediments from 1993 to 2008. Recent monitoring data has concluded portions of the subtidal cap has eroded and may not be physically stable. Erosion in the vicinity of the car passenger ferry sailing line suggests the cap material may not be of sufficient size to achieve the objectives of providing a physical barrier for chemical isolation. Here, a two-dimensional finite difference model using a coupled Boussinesq-Panel method is used to investigate bed shear stresses on the existing sediment cap to analyze cap stability. Model results indicate the subtidal cap experiences over 100 Pa of bed stress within a 30 meter swath of the ferry sailing line. These bed stresses significantly exceed the critical shear stress of the original cap material indicating the cap is not physically stable.

scholarly journals BEACHFACE EVOLUTION UNDER TWO SWASH EVENTS BY TWO SOLITARY WAVES

2018 ◽  
pp. 16
Author(s):  
Fangfang Zhu ◽  
Nicholas Dodd
Keyword(s):  
Energy Dissipation ◽  
Sediment Transport ◽  
Numerical Simulations ◽  
Morphological Change ◽  
Solitary Waves ◽  
Shear Stresses ◽  
Swash Zone ◽  
Numerical Work ◽  
Shock Interactions ◽  
Bed Shear Stresses

Swash zone morphodynamics is of great signi cance for nearshore morphological change, and it is important to provide reliable numerical prediction for beachface evolution in the swash zone. Most of the numerical work on swash zone morphodynamics carried out so far has focused primarily on beach evolution under one single swash event. In reality, multiple swash events interact, and these swash interactions have been recognised as important in the beachface evolution. Swash-swash interactions leads to energy dissipation, enhanced bed shear stresses and sediment transport (Puleo and Torres- Freyermuth, 2016). In this paper, we investigate the beachface evolution under two swash events using numerical simulations, in which shock-shock interactions are described by dam-break problems.

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