Disturbance in natural longshore drift currents.

• Author: Sherazi, Sadia

Byline: Sadia Sherazi

Longshore sediment transport is important on most of the coastline; the direction of the longshore sediments may be manifested from natural features and by the accumulation of sediment behind obstacles such as harbors, breakwalls and groynes. Interference with the natural longshore sediments transport is caused by human-induced problems.(Pennetta, 2018).

The expansion in infrastructure of ports are massively impact on the longshore drift in coastal areas. These types of developments and expansions are threatening to longshore drift and also in shore's movements. Disturbance in longshore drift is the main reason of changing of sedimentation patterns and result of erosion in coastal system.

One more disturbance in coastal areas through coastal erosion is caused by various factors, such as decreases in the supply of sediments coming from rivers due to the construction of dams and changes in the flow of drifting sand caused by the construction of ports. Coastal erosion manifests as changes in the shoreline, and, therefore, wide area monitoring of shorelines has become more important for identifying the factors causing coastal erosion and for establishing effective countermeasures. Monitoring requires continuous observation in wide areas. (Ohkura, 2018).

Long shore drift consists of the transportation of sediments along a coast, which is dependent on prevailing wind directions, swash and backwash.

These different processes are known as littoral drift, longshore current or longshore transport. Shoreline structures are built to change the effects of ocean waves, currents and sand movements in coastal areas.

Development of the ports also involve in the dredging and disposal activities to maintain the required depths for navigation. Construction of the break waters is major disturbance in natural long shore current.

The physical processes and water mass dynamics of coastal areas profoundly affect biological, chemical, geological, metrological conditions and as such have a direct and definite bearing on the development and management of the coastal...