Reclamation-induced sedimentary changes and management recommendations of the marginal shoals along the Huangmao Estuary, Pearl Delta

Studying the sedimentary changes and land resource variation trends of the marginal shoals influenced by human activities plays significant guiding role for the protection and efficient utilization of coastal resources. Based on multi-decadal topographic data (1940−2015) and remote sensing images, this study systematically investigates the impacts of reclamation on the sedimentary regime and land resource variations of the Huangmao Estuary’s marginal shoals, hence proposes targeted management recommendations. The results indicate that: ①While the marginal shoals overall maintained a progradational trend, high−intensity reclamation caused dramatic seaward advancement of coastlines on both sides of the estuary, leading to a sharp decline in Huangmao Estuary’s marginal shoal resources (with the area above −1 m and −2 m decreasing by 29 km² and 73 km², respectively). This even resulted in the complete absence of the −1 m isobaths shoal throughout the estuary during the 1990s. ②Reclamation altered the spatial distribution of the Huangmao Estuary’s marginal shoal resources. Accretion along the eastern bank slowed and the proportion of land resources thus decreased, due to the constraint of the navigation channel. Meanwhile, the marginal shoals extended significantly downstream after 2000 because of insufficient progradation space in the mid−upper sections. ③Reclamation reduced the estuarine tidal prism, which was overall beneficial for the accretion of the Huangmao Estuary’s marginal shoals. However, such impacts varied significantly at local scales and exhibited a clear time-lagged effect. This paper proposed management recommendations based on the research above, including altering reclamation intensity according to marginal shoal accretion rates, avoiding reclamation at sensitive areas (e.g., the entrance of estuaries), and adapting industrial layouts within reclamation zones. This study provides a scientific basis for estuarine resource exploitation and sustainable management.