scholarly journals AN ENERGETIC TYPE MODEL FOR THE CROSS-SHORE DISTRIBUTION OF TOTAL LONGSHORE SEDIMENT TRANSPORT

2012 ◽  
Vol 1 (33) ◽  
pp. 40 ◽  
Author(s):  
Cüneyt Baykal ◽  
Ayşen Ergin ◽  
Işıkhan Güler
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Field Measurements ◽  
Sediment Flux ◽  
Type Model ◽  
Main Mode ◽  
Total Load ◽  
Empirical Constant ◽  
Longshore Sediment Transport ◽  
Rate Of Dissipation

This paper presents an energetic-based simple approach for the computation of cross-shore distribution of total longshore sediment transport (LST) rates. The proposed approach (Baykal 2012) follows similar assumptions with the given formula of Bayram et al. (2007) for the total LST rate (Qlst,t) across the surf zone and is applied to investigate the relation between the rate of dissipation in wave energy flux due to wave breaking and total longshore sediment flux using the available laboratory measurements of Wang et al. (2002) and Gravens and Wang (2007) and the field measurements carried out at Duck site, North Carolina, USA between years 1995-1998 (Miller 1999). The proposed approach is also compared with some of the available distributed total load models. From the comparative studies, it is found that the proposed approach shows good agreement with both the laboratory and field measurements, using a single empirical constant, both qualitatively and quantitatively, especially for the cases where the wave conditions are highly energetic (both for plunging and spilling type breakers) and the suspended load is the main mode of sediment transport in the surf zone.

scholarly journals Toward a Better Understanding of Sediment Dynamics as a Basis for Maintenance Dredging in Nagan Raya Port, Indonesia

Fluids ◽  
2021 ◽  
Vol 6 (11) ◽  
pp. 397
Author(s):  
Muhammad Zikra ◽  
Shaskya Salsabila ◽  
Kriyo Sambodho
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Field Measurements ◽  
Wave Direction ◽  
Inlet Channel ◽  
Longshore Sediment Transport ◽  
Modeling Analysis ◽  
Aceh Province ◽  
Maintenance Dredging ◽  
Wave Induced

The Port of 2 × 110 MW Nagan Raya Coal Fired Steam Power Plant is one of the facilities constructed by the State Electricity Company in Aceh Province, Indonesia. During its operation, which began in 2013, the port has dealt with large amounts of sedimentation within the port and ship entrances. The goal of this study is to mitigate the sedimentation problem in the Nagan Raya port by evaluating the effect of maintenance dredging. Field measurements, and hydrodynamic and sediment transport modeling analysis, were conducted during this study. Evaluation of the wind data showed that the dominant wind direction is from south to west. Based on the analysis of the wave data, the dominant wave direction is from the south to the west. Therefore, the wave-induced currents in the surf zone were from south to north. Based on the analysis of longshore sediment transport, the supply of sediments to Nagan Raya port was estimated to be around 40,000–60,000 m3 per year. Results from the sediment model showed that sedimentation of up to 1 m was captured in areas of the inlet channel of Nagan Raya port. The use of a passing system for sand is one of the sedimentation management solutions proposed in this study. The dredged sediment material around the navigation channel was dumped in a dumping area in the middle of the sea at a depth of 11 m, with a distance of 1.5 km from the shoreline. To obtain a greater maximum result, the material disposal distance should be dumped further away, at least at a depth of 20 m or a distance of 20 miles from the coastline.

Longshore sediment transport in the surf zone based on different formulae: a case study along the central west coast of India

2017 ◽  
Vol 21 (1) ◽  
pp. 1-13 ◽  
Author(s):  
V. Sanil Kumar ◽  
P. R. Shanas ◽  
G. Udhaba Dora ◽  
Johnson Glejin ◽  
Sajiv Philip
Keyword(s):  
Sediment Transport ◽  
West Coast ◽  
Surf Zone ◽  
West Coast Of India ◽  
Longshore Sediment Transport

scholarly journals NONUNIFORM ALONGSHORE SEDIMENT TRANSPORT INDUCED BY COASTLINE CURVATURE

2012 ◽  
Vol 1 (33) ◽  
pp. 29 ◽  
Author(s):  
Alejandro López-Ruiz ◽  
Miguel Ortega-Sánchez ◽  
Asunción Baquerizo ◽  
David Navidad ◽  
Miguel Ángel Losada
Keyword(s):  
Sediment Transport ◽  
Wave Energy ◽  
Surf Zone ◽  
River Mouth ◽  
Type Model ◽  
Intensive Study ◽  
Different Types ◽  
Alongshore Sediment Transport ◽  
Line Type ◽  
Good Agreement

This work proposes an expression for the alongshore sediment transport and a one-line type model to analyze the importance that the curvature of the shoreline and the bathymetric contours, and the associated alongshore wave energy gradients have in the evolution of the coastline and in the development of shoreline undulations. This model characterizes the alongshore wave energy gradients by means of the surf zone width variations and does not make any restriction on the shoreline curvature. The shoreline undulations of two different types of coast are investigated: a curvilinear coast in a prograding spit front, and an erosional stretch of coast adjacent to a river mouth. The results for the first one are in good agreement with observations. For the erosional coast good qualitative results are obtained, although a more intensive study is required.

Magnitude of sediment transport due to extreme windthrow event in small catchments in the Tatra Mountains

2020 ◽  
Author(s):  
Dariusz Strzyżowski
Keyword(s):  
Sediment Transport ◽  
Field Measurements ◽  
Field Work ◽  
Sediment Flux ◽  
Tatra Mountains ◽  
Mountain Areas ◽  
Wind Events ◽  
Tree Uprooting ◽  
The Tatra Mountains ◽  
Root Plate

<p>In the forested mountain areas tree uprooting plays important role among many other geomorphic processes. In some cases, during extreme wind events, large patches of forest may be destroyed, which causes transport of significant amount of sediment.</p><p>The aim of this research was to investigate magnitude of sediment transport during one intense windthrow event, which took place on 25 December 2013 in the Tatra Mountains, southern Poland. The research was conducted in three second- to third-order catchments (16-81 ha), in which 34 to 94 percent of their areas were affected by windthrow. This was achieved by combining field measurements and GIS analyses. During field work root plates located within selected research polygons were measured in order to recognize the amount of sediment transported by a single uprooted tree. Then, each root plate located in the investigated catchments was mapped in GIS software using high-resolution (40 mm) orthophoto. Based on this, total volume of sediment displaced by uprooted trees within each catchment was estimated. Next, taking into account directions of tree fall and slope inclination within each uprooted tree, sediment flux by windthrow event in 2013 was calculated.</p><p>In total 211 uprooted trees were measured in the field. Mean volume of measured root plates was 1.84 m<sup>3</sup>. It was assumed that half of that value is accounted for roots of a tree, thus on average 0.92 m<sup>3</sup> of sediment was transported by each root plate. Analysis of the orthophoto allowed for identification of 4650 uprooted trees located in the investigated catchments. Most of the trees have fallen in downslope direction. Sediment flux by windthrow event in 2013 calculated for each catchment was 1.0–4.6 × 10<sup>–3</sup> m<sup>3</sup> m<sup>–1</sup>.</p>

scholarly journals SUSPENDED SEDIMENT AND LONGSHORE SEDIMENT TRANSPORT DATA REVIEW

1972 ◽  
Vol 1 (13) ◽  
pp. 51 ◽  
Author(s):  
M.M. Das
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Field Measurements ◽  
Field Studies ◽  
Volume Transport ◽  
Transport Rate ◽  
General Validity ◽  
Average Percentage ◽  
Longshore Sediment Transport ◽  
Semi Empirical

A review of laboratory and field studies on suspended sediment under waves shows that although about five analytical or semi-empirical approaches have been attempted to predict the vertical distribution of suspended sediment, none of the approaches has had its general validity proven. This is mainly due to the lack of knowledge about the characteristics of turbulence of the wave boundary layer and to the lack of a suitable suspended sediment measuring technique for use in waves. Six different suspended sediment measuring techniques have been used in the studies previewed. Although none of them gives completely reliable laboratory or field measurements, an optical system appears to show promise in obtaining information on the mechanics of suspension under waves. The reanalysis of longshore sediment transport data and tests of the relationships Q = A..E , Q = A,,E , and I = A„E , where Q is volume transport rate in cubic yards per day, E is longshore component of wave energy flux in lbs per day per foot of beach and I is immersed weight transport rate in lbs per day, for different subsets of data and using the method of least squares, showed that a single set of A-, A„ and B does not fit all subsets of data with minimum average percentage deviation of observed values from those predictable by the relationships. The subset of data consisting of all but the observations with light weight sediments can be described by the line of fit, Q =1.93 X 10-4E , with the observed data differing from the predicted ones by 74 percent on the average.

scholarly journals Downscaling Future Longshore Sediment Transport in South Eastern Australia

2019 ◽  
Vol 7 (9) ◽  
pp. 289 ◽  
Author(s):  
Julian O’Grady ◽  
Alexander Babanin ◽  
Kathleen McInnes
Keyword(s):  
Sediment Transport ◽  
Climate Model ◽  
Global Climate ◽  
Transport Processes ◽  
Type Model ◽  
South Eastern ◽  
Wave Transport ◽  
Longshore Sediment Transport ◽  
Eastern Australia ◽  
South Eastern Australia

Modelling investigations into the local changes in the shoreline resulting from enhanced atmospheric greenhouse gas concentrations and global climate change are important for supporting the planning of coastal mitigation measures. Analysis of Global Climate Model (GCM) and Regional Climate Model (RCM) simulations has shown that Lakes Entrance, a township located at the northern end of Ninety Mile Beach in south-eastern Australia, is situated in a region that may experience noticeable future changes in longshore winds, waves and coastal currents, which could alter the supply of sediments to the shoreline. This paper will demonstrate a downscaling procedure for using the data from GCM and RCM simulations to force a local climate model (LCM) at the beach scale to simulate additional nearshore wind-wave, hydrodynamic and sediment transport processes to estimate future changes. Two types of sediment transport models were used in this study, the simple empirical coastline-type model (CERC equation), and a detailed numerical coastal area-type model (TELEMAC). The two models resolved transport in very different ways, but nevertheless came to similar conclusions on the annual net longshore sediment transport rate. The TELEMAC model, with the Soulsby-Van Rijn formulation, showed the importance of the contribution of storm events to transport. The CERC equation estimates more transport during the period between storms than TELEMAC. The TELEMAC modelled waves, hydrodynamics and bed-evolutions are shown to agree well with the available observations. A new method is introduced to downscale GCM longshore sediment transport projections using wave-transport-directional change parameter to modify directional wave spectra. We developed a semi-empirical equation (NMB-LM) to extrapolate the ~3.7-year TELEMAC, storm dominated transport estimates, to the longer ~30-year hindcast climate. It shows that the shorter TELEMAC modelled period had twice as large annual net longshore sediment transport of the ~30 year hindcast. The CERC equation does not pick up this difference for the two climate periods. Modelled changes to the wave transport are shown to be an order of magnitude larger than changes from storm-tide current and mean sea level changes (0.1 to 0.2 m). Discussion is provided on the limitations of the models and how the projected changes could indicate sediment transport changes in the nearshore zone, which could impact the coastline position.

scholarly journals COASTAL ARMORING: EFFECTS, PRINCIPLES AND MITIGATION

1986 ◽  
Vol 1 (20) ◽  
pp. 135 ◽  
Author(s):  
R.G. Dean
Keyword(s):  
Sediment Transport ◽  
Adverse Effects ◽  
Field Data ◽  
Surf Zone ◽  
Local Scour ◽  
Longshore Sediment Transport ◽  
Longshore Transport ◽  
Severe Erosion ◽  
Substantial Distance ◽  
Factual Data

An attempt is made to conduct a rational assessment of the potential adverse effects of coastal armoring on adjacent shorelines and to propose methodology for mitigation, where appropriate. Specific attention is directed toward claims that armoring causes: profile steepening, increased longshore sediment transport, intensified local scour, transport of sand to substantial offshore distances, etc. The assessment presented here is based on a combination of sound principles and the availability or lack, of laboratory and field data to either support or refute the claims. Although it is found that data relating to coastal armoring effects are sparse, conclusions can be drawn. There seems to be no factual data to support the contentions that armoring causes profile steepening, increased longshore transport, transport of sand to a substantial distance offshore, or significantly delayed profile recovery following a severe erosion event. Armoring does have the potential to cause intensified local scour both in front of and at the ends of an armored segment. Reasons for these effects, based on knowledge of response of a natural profile, are presented. Additionally, armoring which projects into the active surf zone can act as a partial barrier to the net longshore sediment transport, thereby causing downdrift erosion. Methodology is presented for quantifying the appropriate mitigation for a particular armoring situation. The proposed mitigation is the annual placement of sand in the vicinity of the armoring to offset its potential adverse effects. The two potential adverse effects addressed in the methodology include the reduction of sediment supplied to the system as a result of the armoring and the blockage of longshore sediment transport by a protruding armoring installation.

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