Print Email Facebook Twitter Accretion-erosion conversion in the subaqueous Yangtze Delta in response to fluvial sediment decline Title Accretion-erosion conversion in the subaqueous Yangtze Delta in response to fluvial sediment decline Author Luan, Hua Long (East China Normal University; Changjiang River Scientific Research Institute (CRSRI)) Ding, Ping Xing (East China Normal University) Yang, Shi Lun (East China Normal University) Wang, Zhengbing (TU Delft Coastal Engineering; East China Normal University; Deltares) Date 2021 Abstract Identifying the pattern of delta morphological change under decreasing sediment flux due to dam construction is essential for sustainable management in such densely populated coastal areas. In this study, we investigated the morphological processes of the Yangtze mouth bar and prodelta based on bathymetric data on a decadal-interannual scale (1958, 1978, 1997, 2002, 2007, 2010, 2013 and 2015). We found that strong accretion (205.1 Mm3 yr−1) occurred during 1958–1978, when a high sediment load (465 Mt yr−1) was supplied by the Yangtze. Afterwards, the net accumulation rate decreased to 31.9 Mm3 yr−1 in 1978–1997 and 114.6 Mm3 yr−1 in 1997–2002 as a result of riverine sediment loads decreasing to 390 Mt yr−1 and 314 Mt yr−1, respectively. Surprisingly, the net accumulation rate increased to 130.8 Mm3 yr−1 in 2002–2007, though the sediment load sharply decreased to 177 Mt yr−1. This anomaly was attributed to the construction of training walls within the mouth bar area, which induced significant accretion in groyne-sheltered areas and nearby regions. Along with a further decrease in sediment load, the entire study area converted to net erosion of −200.4 Mm3 yr−1 in 2007–2010 and −152.2 Mm3 yr−1 in 2010–2013. Stronger erosion in the former period was partly caused by intensive dredging activities in the mouth bar area. The critical sediment discharge for the Yangtze mouth bar and prodelta to retain net accretion was estimated to be ca. 218 Mt yr−1. If deducting the impacts of estuarine engineering projects on accretion/erosion during 1997–2010, the critical sediment discharge is adjusted to ca. 234 Mt yr−1. In combination with previously reported accretion-erosion conversion elsewhere in the Yangtze Delta, we inferred that most portion of the subaqueous delta has most likely converted from net accretion to net erosion in response to fluvial sediment decline, and the mouth bar area showed the latest conversion among portions of the delta. Integrated assessment and adaptive strategies are urgently required for the Yangtze Delta to survive the coming erosional stage. Subject Accretion-erosion conversionEstuarine engineering projectsFluvial sediment declineYangtze Delta To reference this document use: http://resolver.tudelft.nl/uuid:8abdbcdc-eb51-43f7-b5db-5a8169d7bdfa DOI https://doi.org/10.1016/j.geomorph.2021.107680 Embargo date 2023-03-13 ISSN 0169-555X Source Geomorphology, 382, 1-10 Bibliographical note Accepted author manuscript Part of collection Institutional Repository Document type journal article Rights © 2021 Hua Long Luan, Ping Xing Ding, Shi Lun Yang, Zhengbing Wang Files PDF Proof_Manuscript_clean20210311.pdf 2.09 MB Close viewer /islandora/object/uuid:8abdbcdc-eb51-43f7-b5db-5a8169d7bdfa/datastream/OBJ/view