387 / 2024-09-15 23:47:31

A comparison of sedimentary records and channel evolution during the Song dynasty in two tide-dominated river mouths on the East China coast

Climate warming; Storm tide; Salinity intrusion; Fluvial-tidal interaction

It is recorded in literature that high frequency of storm tides occurred on the East China Coast in Song dynasty which corresponds to the Medieval Climate Anomaly in Europe. The archaeological excavation of two ancient ports, i.e., the Qinglonggang in the palaeo-Wusong River mouth of southern Yangtze Delta plain and Shuomen in the Oujiang River mouth in recent years provides chances to study the sedimentary records and reveal the response of navigation channels in the tide-dominated river mouths to the intensified storms under the background of climate warming. The investigation of sedimentary records demonstrates that a domination of tidal processes and intensified salinity intrusion led to the rapid infilling of Qinglonggang in the Song dynasty. Rapid deposition due to extreme storm events were also identified in the sedimentary successions at the palaeo-Shuomen port. However, fluvial and tidal processes alternatively prevailed in the navigation channel of the Oujiang River mouth, which might explain the long-lasting history of Shuomen port there. It is suggested that the mountain stream of Oujiang produces much stronger fluvial processes than the Wusong River in delta plain, which is beneficial to maintain the water depth for navigation channel in the tide-dominated river mouth. Therefore, the balance of fluvial-tidal interaction is a key for the management of navigation channel in facing the challenge of climate warming.