Longshore sediment transport is important on most of the coastline; the direction of the net longshore sediment transport of the coastline may be manifested from natural features and by the accumulation of sediment behind obstacles such as harbours, breakwalls and groynes. Interference with the natural longshore sediment transport is the cause of human-induced problems.
The coastal sector of Castellammare di Stabia Gulf is the minor physiographic unit of the main one located in the Napoli Gulf. It consists of a narrow sandy beach, surrounded by the artificial harbours of Torre Annunziata to the Northwest and Castellammare di Stabia to the Southeast, and cut in the middle by the Sarno River mouth. The presence of artificial harbours located at the extremes of the units implies a different transport by wave-generated longshore currents, that causes a weak rotation of the shoreline towards the East, linked to an overall erosion on the downdrift side of the sandy beach, which is more evident on its Southern sector. Therefore, the changes carried out by human activities on the coastal system are studied with the same methods used for the investigation of other coastal areas.
Author(s) Details:
Giuseppe Pecoraro
Giunta Regione Lombardia, Milano, Italy.
Micla Pennetta
Università degli Studi di Napoli “Federico II”, Napoli, Italy.
Recent global research developments in Human Impacts on Longshore Sediment Dynamics: A Case Study of Castellammare di Stabia Gulf
1. Longshore Sediment Transport Direction:
- The study confirms that longshore sediment transport along the coast of the Napoli Gulf occurs from Northwest (NW) to Southeast (SE).
- Sediments are moved by longshore currents parallel to the coastline.
2. Integrated Sedimentological and Geomorphological Study:
- Researchers conducted an integrated study combining sedimentology and geomorphology.
- They performed a bathymetric survey and sampled bottom sediments to understand sediment dynamics.
3. Morphological Evolution:
- Historical data reveal that in 1865, the sandy littoral in the Castellammare di Stabia Gulf was wide and in its natural state.
- However, the construction of the Torre Annunziata harbor in 1871 led to sediment trapping.
- Sediments transported by the NW-SE longshore drift became trapped, resulting in the formation of a new wide, triangular-shaped beach on the updrift side (NW) of the harbor breakwall.
- Unfortunately, this process also induced significant shoreline retreat in the southeast sector of the littoral.
4. Beach Erosion Patterns:
- Widespread beach erosion is more pronounced in the southern portion of the coastal physiographic unit of Castellammare di Stabia Gulf (bounded by two ports).
- The shoreline shows a slight rotation toward the East and a general trend of regression.
- Triangular-shaped beaches at the end of the falcate widened significantly due to reduced sediment input.
- The Sarno River and its tributaries provide limited sediment load, affecting the sedimentary budget.
5. Human Interventions:
- Besides sediment trapping, other human interventions further modified the morphological characteristics of both emerged and submerged beaches.
- Intense land use impacted the fluvial course and river mouth, indirectly affecting the shoreline and drainage network of the Sarno River.
References
1. Pennetta M. 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. 2018; 8(7):235. https://doi.org/10.3390/geosciences8070235
2. Araújo MAVC, Wallbridge S, Fernand L. A Methodology to Predict the Impact of a Marine Structure on Longshore Dynamics and Shoreline Evolution. Water. 2024; 16(5):705. https://doi.org/10.3390/w16050705
3. Moran, Kelli, “Sediment Transport and Geomorphological Evolution in the Northern Gulf of Mexico” (2023). LSU Doctoral Dissertations. 6047. https://repository.lsu.edu/gradschool_dissertations/6047
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