Impacts of Human Modifications and Natural Variations on Short-Term Morphological Changes in Estuarine Tidal Flats

This study evaluated the impact of human modifications and natural variations (e.g., seasonal riverine fluxes, plant growth, and estuarine environments) on the short-term morphological changes in estuarine tidal flats. Central to the study was an embankment, constructed in 2014, which changed the path of a tidal flat evolution in the Yangtze Estuary and resulted in a remarkable shift of the erosion-deposition pattern in the study area. To examine the embankment’s impact, we used a terrestrial laser scanner to collect seven topographic data sets for the tidal flat, during different seasons from 2012 to 2016. The rates of elevation change varied from − 19.3 cm year⁻¹ before embankment construction to 17.2 cm year⁻¹ after embankment construction. The field measurements also showed that the new embankment led to an increase of suspended sediment concentration from 1.4 to 2.7 kg m⁻³ on average in the mudflat and from 1.0 to 2.6 kg m⁻³ in the salt marsh. These results indicated that the increase in sediment availability caused by human modifications played an important role in tidal flat evolution and were able to promote the accretion of the tidal flats. Furthermore, there were significant spatiotemporal variations in the morphological changes in different regions of the tidal flat. Depositional changes were more likely to occur during the wet seasons and salt marshes were more stable than mudflats and tidal creeks.