Differences of post-restoration evolution of beaches maintained with sediments of different particle sizes: a case study of Dong’ao and Tulongdi beach restoration projects in Dongtou district, Wenzhou City
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Graphical Abstract
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Abstract
The post-restoration evolution characteristics of beaches maintained with sediments of different grain sizes exhibit notable disparities. Taking the example of beach restorations at Dong’ao and Tulongdi beaches in Dongtou District, Wenzhou City, this study analyzed the progression of shoreline and profile morphology and the changes in related contrast indexes based on post-project data from multi-phase shoreline and profile surveys. The study revealed distinct evolution characteristics between restored sand beach and restored shingle beach. The shoreline width retention rates of sand beach and shingle beach were 87.10% and 121.35%, respectively, indicating that the beaches were generally in a relatively stable state. The shingle beach demonstrated lateral migration and accretion of shingle towards the shoreline, resulting in the formation of shingle ridges along the seaward beach berm. This process was accompanied by augmented beach shoulder dimensions and a more pronounced incline in the underwater beach face. In contrast, the sandy beach exhibited offshore sediment transport, beach face erosion, subaqueous sediment deposition, and a reduction in beach berm width coupled with a modest elevation in beach berm height during evolutionary phases. Overall, compared with fine-grained sandy beaches, coarse-grained shingle beaches showed comparatively minor mean variations in beach profiles under similar coastal topography and hydrodynamic settings. Therefore, utilizing coarser sediments such as gravel for beach maintenance and restoration can serve as an effective method to alleviate beach erosion.
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