Добірка наукової літератури з теми "Windblown sand action"

A model for predicting 3-D beach changes in an extensive area including beach and backshore areas was developed, taking the effects due to both waves and windblown sand into account. In the calculation of beach changes, the BG model (a model for predicting beach changes based on Bagnold's concept) was employed, and a cellular automaton method was used to calculate the backshore changes due to the effect of windblown sand. To validate the model applicability, a reproduction calculation was carried out for the beach formed at the corner of Futtsu new port. The calculation results were in good agreement with the measurement results.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/905aRlNAOjA

Salients were formed in the lee of two artificial reefs (submerged breakwaters) constructed on Kimigahama Beach in Chiba Prefecture, Japan, owing to the wave-sheltering effect of the reefs, and then, a significant amount of fine sand was transported inland from the salients by wind action. In this study, not only shoreline changes after the installation of the two artificial reefs but also beach changes caused by windblown sand were predicted using a model, in which the BG model (a model for predicting three-dimensional beach changes due to waves based on Bagnold’s concept) is combined with a cellular automaton method. Reproduction calculation was carried out on the basis of field data. Beach changes after the artificial reefs were removed were also predicted and the effect of beach nourishment was investigated. It was concluded that landward sand transport by wind is accelerated when wave-sheltering structures such as an artificial reef are constructed on a coast composed of fine sand, and such an effect can be successfully predicted by using the present model.

Our next major question is, how can we characterize the sediment as a habitat for biota? Marine sediments range from coarse gravels in areas subjected to much wave and current action, to muds typical of low-energy estuarine areas and to fine silts and clays in deep-sea sediments. The settling velocity of those particles and the ability of any particle to be re-suspended, moved, and redeposited depends on the prevailing hydrographic regime (e.g. see Open University 2002). The latter will in turn influence the transport of a species´ dispersal stages, especially larvae which will then be allowed to settle following metamorphosis under the appropriate hydrographic conditions (defined as hydrographic concentration). Hence the presence of fine sediments will indicate the depositing/accreting areas which may also be suitable for passively settling organisms. Clearly the particle size is of major importance in characterizing sediments, although sediments can also be categorized by their origin (fluvial, biogenic, cosmogenic, etc.) and their material (quartz, carbonates, clays, etc.) (Open University 2002). On a typical sandy beach the coarsest particles lie at the top of the beach and grade down to the finest sediments at the waterline. The top of the beach is dry and there is much windblown sand, since coarse sands drain rapidly, whereas at the lower end of the beach the sediments are wet, with frequent standing pools. Coarse sediment is found at the top of the shore because as the waves break on the beach the heaviest particles sediment out first. Finer particles remain in suspension longer and are carried seaward on the wave backwash. Beaches change their slope over the seasons, being steeper in winter and shallower in summer. A greater degree of wave energy will produce steeper beaches, as particles are pushed up the beach and so may be stored there, whereas gentle waves produce shallow, sloping beaches. Waves hitting the shore obliquely will create sediment movement as longshore drift. Subtidally, waves are important in distributing and affecting sediments down to depths of 100 m, but the effect decreases exponentially with depth and so the dominant subtidal influences on sediment transport are currents.