scholarly journals A SYSTEM OF RADIO-LOCATION USED IN THE DELTA AREA

2011 ◽  
Vol 1 (7) ◽  
pp. 59
Author(s):  
R.H.J Morra
Keyword(s):  
Tidal Flow ◽  
Fine Sand ◽  
Considerable Change ◽  
Sand Transport ◽  
Delta Area ◽  
Independent Expert ◽  
Survey System ◽  
Good Repeatability ◽  
Sand Movement ◽  
Radio Location

In the South-Western part of the Netherlands the Delta project is being carried out consisting inter alia of k main dams closing k large inlets (fig.1). Through the four tidal inlets to be closed about 1800 million cubic metres of water run into the Delta area during flood tide and flow out again during ebb tide. This means about 7000 million cubic metres daily. The bottom of the inlets and the sea-bottom consist of fine sand (deQ = .100 - .2500 mm), which is in constant movement. During the past centuries considerable changes in the bottom contour have taken place. Yearly many millions of cubic metres of sand are moved by the water. The bottom is a very complicated system of gullies and sandbanks which has evolved down the centuries and is ever changing. It is evident that the dams under construction will out off the tidal flow into and out of the area and that this will result in a considerable change in the sand movement. The underwater estuary extending as far as 20-25 km seawards from the dams will probably have to adapt itself rather suddenly, i.e., within a few decennia. This can be dangerous for the Western extremities of the islands. The whole combination of phenomena concerned has to be studied and watched very carefully. Basic information concerning the sand movement and its consequences is given by soundings. A long term of frequent and accurate soundings with very good repeatability i3 required for the entire coastal area of the estuary. However, the meteorological conditions for sounding are such that good conditions only obtain on about 20 days a year, because good visibility and a quiet sea must occur simultaneously. Moreover, there is a serious shortage of landmarks and at distances seawards of less than 10 km from the shore visual location is impossible. The only solution is to make the location independent of visibility. For these reasons it was decided that a system of radio-location should be devised. We were advised by an independent expert to adopt the Decca survey system. With such a system it is possible to make frequent soundings with very good repeatability and with a reasonably low number of launches, because many more suitable days (and nights) become available. This system of radio-location is called the Delta chain. The system is also used for special purposes (velocity and sand transport measurements).

scholarly journals SHEETFLOW SEDIMENT TRANSPORT UNDER SKEWED - ASYMMETRIC WAVES AND CURRENTS

2012 ◽  
Vol 1 (33) ◽  
pp. 50 ◽  
Author(s):  
Le Phuong Dong ◽  
Shinji Sato
Keyword(s):  
Sediment Transport ◽  
Laboratory Experiments ◽  
Fine Sand ◽  
Sand Transport ◽  
Phase Lag ◽  
Half Cycle ◽  
Experimental Conditions ◽  
Wide Range ◽  
Waves And Currents ◽  
Asymmetric Flows

Prototype scale laboratory experiments have been conducted to investigate the sheetflow sediment transport of uniform sands under different skewed-asymmetric oscillatory flows. Experimental results reveal that in most of the case with fine sand, the “cancelling effect”, which balances the on-/off-shore net transport under pure asymmetric/skewed flows and results a moderate net transport, was developed for combined skewed-asymmetric flow. However, under some certain conditions (T > 5s) with coarse sands, the onshore sediment transport was enhanced by 50% under combined skewed-asymmetric flows. Sand transport mechanism under oscillatory sheetflow conditions is also studied by comparing the maximum bed shear stress and the phase lag parameter at each half cycle. A comparison of measurements including the new experimental data with a number of practical sand transport formulations shows that the Dong et al. (2013) formulation performs the best in predicting the measured net transport rates over a wide range of experimental conditions

scholarly journals LABORATORY STUDY ON SAND TRANSPORT OVER RIPPLES DUE TO ASYMMETRIC OSCILLATORY FLOWS

1986 ◽  
Vol 1 (20) ◽  
pp. 109 ◽  
Author(s):  
Shinji Sato ◽  
Kiyoshi Horikawa
Keyword(s):  
Laboratory Study ◽  
Oscillatory Flow ◽  
Transport Rate ◽  
Sand Transport ◽  
Hydraulic Parameters ◽  
Oscillatory Flows ◽  
Sand Transport Rate ◽  
Bed Forms ◽  
Sand Movement

Mechanism of sand movement due to asymmetric oscillatory flows was investigated through experiments. Measurements of bed forms, suspended sand concentration and net sand transport rate were carried out by using an oscillatory flow tunnel. The process of entrainment and suspension of sand above asymmetric ripples was quantitatively described. The geometry of ripples and the net sand transport rate in regular and irregular flows were expressed in terms of hydraulic parameters characterizing the oscillatory flow. Two-dimensionality of ripples was found to be an important factor in the estimation of the net sand transport rate.

scholarly journals CALCULATION OF ON-OFFSHORE SAND MOVEMENT AND WAVE DEFORMATION ON TWO-DIMENSIONAL WAVE-CURRENT COEXISTENT SYSTEM

1988 ◽  
Vol 1 (21) ◽  
pp. 90
Author(s):  
Koichi Kinose ◽  
Shuji Okushima ◽  
Masahito Tsuru
Keyword(s):  
Wave Height ◽  
Experimental Results ◽  
Breaking Point ◽  
Transport Rate ◽  
Sand Transport ◽  
Height Distribution ◽  
Wave Deformation ◽  
Sand Transport Rate ◽  
Sand Drift ◽  
Sand Movement

In this paper, we proposed a method of calculation to predict quantitatively the on-offshore sand movement and the wave deformation on a wave-current coexistent system by assuming a river mouth. And the calculated results were compared with the experimental data obtained for the coexistent system in a twodimensional wave tank. The distribution of wave height on the breaker zone was analyzed by use of BORE MODEL. It was required for the calculation of the sand transport rate. The model was established on the assumption that the value of energy loss in a breaking wave was equivalent to that of bore. The wave height distribution on the offshore side of breaking point was presumed employing the third order approximate solution of Stokian wave on the coexistent system. The breaking point was obtained by use of Miche's criteria equation. The local sand transport rate could be calculated by use of POWER MODEL. The predominant direction of sand drift was recognized using relations for judgement which were derived from the experimental results. The transformation of sea bottom and river one was estimated on the basis of the calculated distributions of the wave height and the sand transport rate. The results obtained by this analytical method agreed well with the experimental results.

scholarly journals MODE AND PERIOD OF SAND TRANSPORT IN THE SURF ZONE

1974 ◽  
Vol 1 (14) ◽  
pp. 47 ◽  
Author(s):  
Benno M. Brenninkmeyer
Keyword(s):  
Deep Water ◽  
Water Wave ◽  
Surf Zone ◽  
Sediment Concentration ◽  
Sand Transport ◽  
Bed Load ◽  
Measuring Devices ◽  
Load Movement ◽  
Sand Movement ◽  
Deep Water Wave

Three almometers-water opacity measuring devices-emplaced perpendicular to the beach, measure instantaneously and continuously the sediment concentration across the surf zone. Most of the variance of the sand movement is centered in frequencies of less than 0.25 Hz and between 1.15 and 1.25 Hz. Modes and frequency of sand transport differ within each of the dynamic zones of the surf. The motion of sediment in the inner and outer surf zones is small and virtually independent of the deep water wave periods. Outside the breaker zone, bed load movement is somewhat coincident with the prevailing swell period. Lighter concentrations move predominantly with a 0.8-0.9 second periodicity. In the breaker zone, sand moves along the bottom with frequencies equal to that of both the swell and sea, but most of the power is in lower frequencies. In the breaker zone sand is rarely thrown into suspension. In the transition zone, sediment motion is largely by suspension with a period a little longer than the swell.

scholarly journals A STUDY OF CRITICAL DEPTH AND MODE OF SAND MOVEMENT USING RADIOACTIVE GLASS SAND

2011 ◽  
Vol 1 (8) ◽  
pp. 18
Author(s):  
Shoji Sato ◽  
Takeshi Ijima ◽  
Norio Tanaka
Keyword(s):  
Field Experiments ◽  
Sandy Beach ◽  
Sand Transport ◽  
Critical Depth ◽  
Radioactive Tracers ◽  
Construction Planning ◽  
The World ◽  
Glass Sand ◽  
Sand Movement ◽  
Qualitative Characteristics

In Japan, in order to get fundamental data for harbor construction planning, radioactive glass sand has been used on the coasts of Tomakomai Irako, Fukue, Isohama, Kashima and Niigata as shown in Figure 1, The authors have directed these field experiments excepting Tomakomai and been doing model experiments using radioactive glass sand. The field observation of sand movement using radioactive tracers has been already performed in several countries of the world and many works have been published. Authors have aimed to make clear the direction of sand transport in several depths of water and the critical water depth of sand movement where harbors are to be constructed, in order to get basic data for the best arrangement of breakwaters on sandy beach. The activity of radioactive glass sand ( Co-60 and Sc-46 ) used at one point was several millicuries in the inland coast and several tens millicuries in the open coast. In this paper, the qualitative characteristics of sand movement in the offshore and the breaker zone and the relations of waves, depth and bottom materials are estimated from the field experiments. Moreover, in the model test, the glass sand containing Cr-51 was used in order to study the mode of sand movement due to waves, in particular, the direction of ripple movement and sand transport.

scholarly journals WIND AND SEDIMENT MOVEMENT IN COASTAL DUNE AREAS

1980 ◽  
Vol 1 (17) ◽  
pp. 93 ◽  
Author(s):  
John R. Hails ◽  
John Bennett
Keyword(s):  
Surface Stress ◽  
Financial Support ◽  
South Australia ◽  
Sand Transport ◽  
Wind Regime ◽  
Interaction Processes ◽  
Local Topography ◽  
Windward Slope ◽  
Sand Movement ◽  
Dune Migration

Little is known about how air-sediment interaction processes control the differential rates and direction of dune migration along the coast of South Australia. Information is needed on sand transport and dune formation in order to establish better guidelines for conservation and agricultural management programmes in areas that are undergoing erosion. The writers, with financial support from the Coast Protection Board, Department for the Environment, South Australia, have commenced a pilot research project to examine dunes in the lower Coorong and adjacent areas in the southeast of the State (Figure 1). The aims of the project are - To determine: (a) instantaneous surface stress values on the windward slopes of active transgressive dunes; (b) sand movement over the crestline as a function of surface stress on the windward slope in order to establish the life expectancy of stability of individual dunes; (c) the extent to which the local topography affects the wind regime in the dunal areas. To obtain: (a) air trajectories over and around transgressive dunes; (b) information on dune geometry (slope inclinations, crest heights, base lengths, etc.).

scholarly journals SAND ACCUMULATION IN WAVE-SHELTER ZONE OF OHARAI PORT AND CHANGE IN GRAIN SIZE OF SEABED MATERIALS ON NEARBY COAST

2011 ◽  
Vol 1 (32) ◽  
pp. 63
Author(s):  
Takeo Matsu-ura ◽  
Takaai Uda ◽  
Takayuki Kumada ◽  
Michio Sumiya
Keyword(s):  
Fine Sand ◽  
Beach Erosion ◽  
Annual Rate ◽  
Sand Transport ◽  
The South ◽  
Bathymetric Survey ◽  
Deposition Zone ◽  
The Pacific ◽  
Sand Accumulation ◽  
The Pacific Ocean

Beach changes around Oharai Port facing the Pacific Ocean were investigated using bathymetric survey data collected over 25 years between 1979 and 2004. Between the south and offshore breakwaters of Oharai Port, 1.50×106 m3 of fine sand was deposited in this period, i.e., at an annual rate of 6.0×104 m3/yr, which was originally supplied from the Naka River 3 km north of the port. Also in the wave-shelter zone of the offshore breakwater south of the port, 7.0×106 m3 of fine sand was deposited between 1979 and 2004 at an annual rate of 2.8×105 m3/yr, which was transported by the northward longshore sand transport induced from outside to inside the wave-shelter zone of the offshore breakwater, resulting in severe beach erosion on the south coast outside the wave-shelter zone. Taking into consideration the fact that sand transport to the Kashimanada coast is now completely obstructed by the port breakwaters, sand bypassing and sand back passing to the coast from the sand deposition zone of Oharai Port are required.

scholarly journals O Controle da Deriva Litorânea no Desenvolvimento do Campo de Dunas e da Antepraia no Litoral Médio do Rio Grande do Sul

2006 ◽  
Vol 33 (2) ◽  
pp. 35 ◽  
Author(s):  
ELÍRIO TOLDO JR ◽  
LUIZ ALMEIDA ◽  
LUCIANO ABSALONSEN ◽  
NELSON GRUBER
Keyword(s):  
Sediment Transport ◽  
Surf Zone ◽  
Rio Grande ◽  
Fine Sand ◽  
Sediment Flux ◽  
Sand Transport ◽  
Rio Grande Do Sul ◽  
Coastal Jet ◽  
Longshore Transport ◽  
Alongshore Sediment Transport

Zones of erosion and accretion were delimited by comparing a DGPS shoreline mapping in 1997 and the beach line reproduced from the army chart collection of 1975. The results show extensive shore retreat along of Rio Grande do Sul central coast, while accretion was observed in Mostardas and Dunas Altas beach. Mathematical estimative of the regional longshore transport potential along the Rio Grande do Sul coast, a 630-km long holocenic fine sand barrier, resulted in a large net northward annual sand volume. Additionally, the estimated potential of sediment transport based on the CERC formula predicts a substantial variation of the energy flux into the surf zone, due to little changes in shoreline alignments and in the potential alongshore sediment transport. The reduction in the sediment flux due to changes in the shoreline alignment produce a jam in the longshore transport, meaning that part of the sediment arriving from the upstream stretch may be deposited or diverted offshore by coastal jet. Based on that, it is possible that changes in the net longshore sand transport are responsible for the increase in the shoreface width from less than 1 km to more than 3 km in Mostardas beach and Dunas Altas beach. Interesting to note that wider dune fields are associated to those beaches where shoreface is also wider. In this way, the volume of longshore sand transport and the sediment jam provide by changes on shoreline alignment in Mostardas and Dunas Altas beaches are important for both coastal dune fields and shoreface width.

scholarly journals Suspended sand transport in different conditions of temperature and salinity

2005 ◽  
Vol 27 (3) ◽  
pp. 140-148
Author(s):  
Dang Huu Chung
Keyword(s):  
Wave Height ◽  
Fine Sand ◽  
Coarse Sand ◽  
Effect Of Temperature ◽  
Sand Transport ◽  
Physical Parameters ◽  
Data Sets ◽  
Good Ability ◽  
Reference Concentration ◽  
Vertical Distributions

A study on the action of temperature and salinity on the distribution of suspended sand concentration and transport rate has been carried out through a lDV model with a proposed formula of the kinematic viscosity. Five tests of the data sets from the Delta flume with three different cases of temperature and salinity were used for the simulation. The results of computation showed that the vertical distributions of suspended sand concentration depend on salinity and specially, on temperature. When temperature increases or salinity decreases, the settling process of particles occurs faster. For fine sand, the discrepancy on transport rates due to temperature or salinity decreases with wave height. For coarse sand, the effect of temperature and salinity is not much affected by the wave height. The lDV model showed good ability to simulate the time-averaged suspended sand concentrations and hence the suspended transport in the ripple regime, provided that the reference concentration near the bed and the vortex-related mixing are represented with sufficient accuracy. Therefore; it can be used effectively to study the behaviour of some physical parameters on the transport.

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