A numerical model of coastline deformation for sandy beach at downstream of a jetty

A reformed numerical model based on the 'one-line theory' for beach deformation is presented. In this model, the change of beach slope during coastline procession is considered.A wave numerical model combined with wave refraction, diffraction and reflection is used to simulate wave climate to increase numerical accuracy.The results show that the numerical model has a good precision based on the adequate field data. The results can be applied to practical engineering.

Application of the Static Headland-Bay Beach Concept to a Sandy Beach: A New Elliptical Model

The headland-bay beach is one of the most common coastal types in the world.Its morphology reflects the changes that occurred during long-term evolution of the sandy coast.Several headland-bay beach models have been proposed to simulate the coastline’s configuration in equilibrium.In this paper,a new elliptical model is proposed,described,and applied.On the east coast of Laizhou Bay in Shandong Province from Longkou Port to Diaolongzui,four typical headland-bay beaches have developed,and four headland-bay beach models are used in this paper to simulate the morphology of these beaches to assess the applicability of each model.The simulation results of the elliptical model verify that it is applicable to the study area.In addition,the elliptical model is easy to use.Through simulation and field investigations,we concluded that most of the coastal segments in this area will remain in an erosion state,and the human activity has a significant impact on the shoreline’s evolution.

Did Species and Functional Diversities of Sandy Intertidal Marine Nematodes Reveal Similar Response to Environmental Changes?

Free living marine nematodes were sampled from two sandy beaches in Dalian City,in December of 2015,and April,July,and October of 2016.The spatial and seasonal variations of marine nematode species diversity(based on species abundance dataset)and functional diversity(based on functional traits dataset:feeding types and life history strategies)were investigated to understand the environmental drivers and how they respond to specific environmental variations.Sediment granularity was revealed to be the main environmental factor causing spatial differences in nematode diversity indices between the two beaches.Species diversity indices,namely species number,Margalef index,Shannon-Wiener diversity index(H’),were higher in fine-grained sediments,while the functional diversity indices,including functional evenness,functional dispersion,and Rao’s quadratic entropy index(RaoQ),were higher in coarse-grained sediments.Nematode species diversity indices also fluctuated with seasonal variations of temperature,dissolved oxygen,pH,salinity,and sediment chlorophyll-a within the study beaches.However,functional diversity indices did not show significant seasonal variations and exhibited weak correlation with the studied environmental variables.Overall,the functional diversity indices were negatively correlated with the species diversity indices,suggesting an inconsistent response to environmental changes.A decrease in nematode species diversity in coarse sands,accompanied by an increase in functional diversity,can be regarded as an early warning signal of environment disturbance.If more biological traits are involved in calculating functional diversity indices,it will be helpful for the future study of the internal connections of species diversity and functional diversity.

Analysis of wave shoaling and shore-breakers on a low tide terrace beach based on in-situ measurements at Xisha Bay on South China coast

Low tide terrace beach is a main beach type along South China coasts with strong tidal actions.How strong tides affect wave transformations on low tide terrace beach still remains unclear.In this study,in-situ measurements are conducted on the low terrace beach at Xisha Bay to provide quantitative descriptions of wave shoaling and shore-breaker phenomena under the tidal effects.It is found that wave breaking is unsaturated on the low tide terrace beach at Xisha Bay.Magnitudes of wave skewness and asymmetry increase as wave shoals and achieve the maximum value at the shore-breaker,and then decrease rapidly.Mean energy dissipation rates of shore-breakers are tide-modulated since the bottom slope changes at the shoreward boundary of wave propagation in a tidal cycle.The remaining wave energy flux at the initialization of the shore-breaker is 1%–12%of offshore wave energy flux,and the energy flux ratio decreases with increasing offshore wave heights.Wave attenuation at shore-breakers can be estimated directly from offshore wave conditions based on findings in this study,favoring designs of seawalls or beach nourishment projects.Field datasets on wave transformations can also be used for verifications of wave numerical models.

Siltation Prediction for Navigation Channels and Harbour Basins on Muddy Beach

This paper, after briefly reviewing the experimental research on sediment transport on muddy beach since the 1950s, improves and perfects the method for forecasting siltation in navigation channels and harbour basins which was first put forward in China by the authors. In consideration of silty sediment and sand, some factors in forecasting methods have been changed and modified. Consequently, the modified methods can be used either to compute siltation in navigation channels and harbour basins on muddy beach or to compute siltation and scouring in navigation channels and harbour basins on both silty beach and sandy beach. The verification of field data from eleven large, medium and small natural harbours shows a good agreement between the forecasting by the modified method and the natural conditions. Finally, the paper deals with the rational utilization of water area after the construction of the West Dyke in Lianyungang, the maintenance of water depth of the navigation channel at the entrance, siltation distribution, siltation in the navigation channel and harbour basin for ships of 100 thousand tonnnage. Results once again prove that the prospect of constructing Lianyungang Harbour into a deepwater harbour is bright.