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.).

Development of hybrid aeolian dunes: the William River dune field, northwest Saskatchewan, Canada

1986 ◽  
Vol 23 (12) ◽  
pp. 1974-1990 ◽  
Author(s):  
M. A. Carson ◽  
P. A. MacLean
Keyword(s):  
Large Scale ◽  
Sand Dunes ◽  
Progressive Increase ◽  
Sand Transport ◽  
Asymmetric Distribution ◽  
Wind Regime ◽  
The North ◽  
Field Evidence ◽  
Aeolian Dunes ◽  
Sand Movement

Observations have been made on the structure, morphology, and pattern of sand movement on large-scale, roughly elongate, northwest–southeast-aligned aeolian sand dunes in a desert area of northern Saskatchewan, Canada. Transverse profiles show steeper northeast flanks, the lower parts of which are covered with psammophilous grasses. Dune structure is dominated by northeast-dipping accretion laminae, and 14C dates of organic material trapped between such exposed laminae on the southwest flank indicate migration to the northeast at about 0.5 m/year in the last few centuries. On the other hand, there is a progressive increase in height, bulk, symmetry, and peakedness of the dunes from northwest to southeast, suggestive of substantial along-dune sand movement. The present-day wind regime shows a potential resultant sand-transport vector to the southeast, virtually parallel to the dune axis; winds from the north-northeast and northeast dominate the first 6 months of the year, followed by winds from the west-southwest in the latter half. Field evidence of airflow and sand-movement patterns upon the surfaces of two dunes also indicates a strong along-dune component. The dunes are interpreted as hybrid landforms reflecting both transverse and longitudinal processes acting at the present time. Of particular sedimentological significance is the discordance between dune stratigraphy and the wind regime. Dune structure is controlled by a southwest–northeast imbalance in sand movement assumed to result from an asymmetric distribution of sand-trapping vegetation and from a seasonal contrast in sand mobility that partly correlates with seasonality in the wind regime. Both factors promote northeast migration normal to the potential resultant of effective winds.

Wind regime and sand transport in the Sistan and Registan regions (Iran/Afghanistan)

2019 ◽  
Vol 62 (1) ◽  
pp. 41-57 ◽  
Author(s):  
Hamidreza Abbasi ◽  
Christian Opp ◽  
Micheal Groll ◽  
Azadeh Gohardoust
Keyword(s):  
Sand Transport ◽  
Wind Regime

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 Development of Desertification Indicators for Desertification Monitoring from Landsat Images Using Python Programming

2022 ◽  
Vol 8 (2) ◽  
pp. 99-114
Author(s):  
Lamyaa Gamal EL-Deen Taha ◽  
Manar A. Basheer ◽  
Amany Morsi Mohamed
Keyword(s):  
Sand Dune ◽  
Sand Dunes ◽  
Landsat Images ◽  
Image Differencing ◽  
Layer Stacking ◽  
Southern Side ◽  
Sand Movement ◽  
Dune Migration ◽  
Desertification Assessment ◽  
Python Programming

Nowadays, desertification is one of the most serious environment socioeconomic issues and sand dune advances are a major threat that causes desertification. Wadi El-Rayan is one of the areas facing severe dune migration. Therefore, it's important to monitor desertification and study sand dune migration in this area. Image differencing for the years 2000 (Landsat ETM+) and 2019 (OLI images) and Bi-temporal layer stacking was performed. It was found that image differencing is a superior method to get changes of the study area compared to the visual method (Bi-temporal layer stacking). This research develops a quantitative technique for desertification assessment by developing indicators using Landsat images. Spatial distribution of the movement of sand dunes using some spectral indices (NDVI, BSI, LDI, and LST) was studied and a Python script was developed to calculate these indices. The results show that NDVI and BSI indices are the best indices in the identification and detection of vegetation. It was found that mobile sand dunes on the southern side of the lower Wadi El-Rayan Lake caused filling up of large part of the lower lake. The indices results show that sand movement decreased the size of the lower Wadi El-Rayan Lake and there are reclamation activities in the west of the lower lake. The results show that a good result could be achieved from the developed codes compared to ready-made software (ENVI 5).

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.

Wind regime and sand transport in China’s Badain Jaran Desert

2015 ◽  
Vol 17 ◽  
pp. 1-13 ◽  
Author(s):  
Zhengcai Zhang ◽  
Zhibao Dong ◽  
Chunxiao Li
Keyword(s):  
Sand Transport ◽  
Badain Jaran Desert ◽  
Wind Regime

Dunes and associated sand transport in a tidally influenced sand-bed channel: Fraser River, British Columbia

2003 ◽  
Vol 40 (1) ◽  
pp. 115-130 ◽  
Author(s):  
P V Villard ◽  
M Church
Keyword(s):  
British Columbia ◽  
Rapid Change ◽  
Sand Transport ◽  
Fraser River ◽  
Flow Conditions ◽  
Material Transport ◽  
Coefficients Of Variation ◽  
Dune Migration ◽  
And Migration ◽  
Dune Height

Dunes form annually on the sand bed of the tidally influenced South Arm of Fraser River, British Columbia. Bathymetric surveys along the center of the main channel throughout a snow-melt freshet provided measurements of dune geometry and migration. Dune length, height, and steepness all increase with river discharge. However, lag between the highest flow conditions and development of the largest, steepest dunes reflects the influence of antecedent flow conditions on dune geometry. Population averages of dune height and steepness ratio change more rapidly than dune length, whilst coefficients of variation of dune height, length, and steepness ratio indicate high variability in dune geometry within the estuarine reach during periods of dune growth and decay. Unlike dune geometry, dune migration rates display little lag with flow conditions. The largest coefficients of variation for dune migration occur during periods of rapid change in discharge and tidal fall, corresponding to the onset of rapid change in dune geometry on both rising and falling limbs. Migration rate estimates and geometry measurements are used to estimate associated sand transport. In the absence of hydraulic measurements in the estuary, Mission and Hope discharges are adopted to drive simple statistical models of sand transport as a function of discharge and tidal fall. The models cover 65–70% of the transport, and tidal fall is only marginally significant. Comparison with historical direct measurements indicates that the dune-associated transport coincides with bed-load transport in the estuary, and arguments are made that it constitutes the preponderance of all bed-material transport.

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.

Sign in / Sign up

Export Citation Format

Share Document