Home / This Week / Cover Stories / Disturbance in natural longshore drift currents

Disturbance in natural longshore drift currents

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.

picshaz1

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.

picshaz2

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 area. These coastal structures and the dredging activities interfere in the coastal process and large impact on geomorphology of coastline. Major morphological impact is felt in the coastal region having high rate of longshore littoral drift (M D Kudale).

In conclusion, the maritime areas of Pakistan, including coastal waters and associated shelf systems, are both productive and vulnerable, as well. The degradation and over-utilization of the coastal belt in some of the areas are causing considerable economic and aesthetic loss. The present trend of unsustainable misuse of various environmental agents is showing up as diminished marine productivity, deforestation, desertification and other adverse environmental phenomena.

 

It is recommended that, coastal engineer has to foresee this and try to prevent such damage by adopting suitable shore protection procedures through EIA (Environmental Impact Assessment). The constructions of a port have changed significantly the pattern of sediments transportation inducing dramatic changes in coastline configuration. Therefore, the process of EIA must be carried out for all future developments in coastal management plans.

Bibliography

https://en.wikipedia.org/wiki/Longshore_drift. (n.d.).

Ohkura, T. F. (2018). Development of Shoreline Extraction Method Based on Spatial Pattern Analysis of Satellite SAR Images. International Journal of Molecular Sciences , 10.

Pennetta, M. (2018, June 27). Beach Erosion in the Gulf of Castellammare di Stabia in Response to the Trapping of Longshore Drifting Sediments of the Gulf of Napoli (Southern Italy). Geosciences, 8. Retrieved from https://doi.org/10.3390/geosciences8070235

The writer is a Senior Lecturer, Bahria University, Karachi) — sadiasherazi.ncmpr@bahria.edu.pk

Check Also

Industrialization through SMEs - must do for economic comeback

Industrialization through SMEs – must do for economic comeback

Pakistan is facing numerous challenges, which is not new for this country. The economic situation …

Leave a Reply