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Xu, Y.; Cheng, L.; Zheng, J.; Zhu, Y.; Wu, Y.; Shi, J., and Zhang, W., 2019. Intensive anthropogenic influence on the morphological evolution of estuarine tidal channels. Journal of Coastal Research, 35(6), 1237–1249. Coconut Creek (Florida), ISSN 0749-0208. Long-term and large-scale morphological consequences of human activities are important to consider during human settlement construction around estuarine environments. Thus the rapid human-induced changes in the geomorphology of estuarine areas commands a growing socio-economic and scientific interest. Lingding Bay, a part of the Pearl River estuary, is one of the areas that draws much attention in this respect. By using admiralty charts and topographic maps since the 1960s, decadal timescale morphological changes are investigated to understand the effects of human activities on estuarine tidal channels. The results show that the estuarine channels have undergone overall net erosion over this 50 year period, with a sequence of alternating erosion and deposition phases. On basis of the variations of aspect ratios and thalweg movements, five types of stable channels are identified. The upstream part of the east channel is the most unstable region defined as type 5, where the significant topographical change is principally associated with the unplanned sand mining activities. The whole west tidal channel is approaching relative stability because it was deepened as the main navigational channel, with the thalwegs being straighter. Based on empirical orthogonal function analysis, the anthropogenic effects, including the dredging, sand excavation, and land reclamation, are found to be of relatively major importance in the morphological evolution process of the estuarine channels. [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on identifying changes in the tidal range and the duration of the flood tide in the Pearl River Delta region, China. Mann–Kendall test and regression methods are employed to verify the existence of trends in the annual tidal range and duration series (from the 1950s to 2005) at 17 stations in the 3 major tributaries of the delta. The research results indicate that generally there is an increasing trend in the tidal range and flood tide duration at most of the stations in the channel network. Moreover, the more upstream the location of the station, the more obvious the change in trend is, and these increasing trends are all significant at the stations in the upper part of the delta. Specifically, the tidal range at Shilong station in the East River has increased abruptly since the middle of the 1980s such that the mean level of post-1990 data is approximately three times that for pre-1985. Most stations near the mouth of the estuary show significant downward trends in the tidal range and flood tide duration. Results of the intersection point of the Mann–Kendall test curves for these Pearl River Delta stations appear mostly in 1980s–1990s, indicating that a noticeable change point occurs during this period. Human activities in the Pearl River Delta reached their peak during the 1980s. Among these, large-scale and long-term sand excavation modified the hydrodynamic regime dramatically in a way that increased the water depth and lowered the level of the riverbed, leading to an increased tidal prism and upstream movement of the tidal limit. Land reclamation is also likely to have had a relatively large effect on the tidal range and flood tide duration at stations near to the estuary mouth. Changes in other factors, such as freshwater flow and sea-level rise, seem to be of relatively minor importance. It is noteworthy that in a dry season the tidal dynamics are greatly enhanced and has resulted in strong saltwater intrusion into the estuary in recent years. [Copyright &y& Elsevier]