强人类活动下伶仃洋河口湾沉积地貌格局演化规律

Evolution of sedimentology and geomorphology in the Lingding Bay under anthropogenic impact

基于伶仃洋河口湾1965—2016年不同年代水深数据,结合不同年代沉积物数据,分析了伶仃洋沉积地貌格局的演化规律,讨论了人类活动对伶仃洋沉积地貌格局的影响作用。结果表明:(1)过去40年,伶仃洋地形边界主要受围垦影响而大幅度变窄,河口湾滩槽格局整体受到挤压并向东偏移;在航道开挖、浚深以及河口采砂等人类活动的叠加影响下,水域面积减小、水体容积增加,地貌形态向窄深化发展;(2)从不同年代表层沉积物空间分布来看,1975年和2003—2004年沉积物由北往南呈粗-细-粗的分布规律,粒度参数整体呈条带状分布。2016年沉积物在南北方向上的分布规律不显著,细颗粒沉积物主要沿西滩、东滩分布,粗颗粒的陆源沉积物主要以斑块状分布于中滩、东槽的采砂坑以及外伶仃洋的深槽末段;粒度参数的空间分布由条带状转变为斑块状,整体沉积环境由单一向复杂转变。(3)新格局下河口湾存在3个沉积中心,即中滩北部的内伶仃洋沉积中心,外伶仃洋西侧、淇澳岛以南的西滩沉积中心以及伶仃航道末段的外伶仃洋沉积中心;它们与各区域的冲淤格局相对应。由此可见,过去40年,人类活动显著地影响了珠江伶仃洋河口湾的沉积地貌格局,本研究有助于揭示伶仃洋河口湾地貌演变趋势,对珠江河口综合治理、水资源高效利用管理与开发具有重要的实践意义。

Based on water depth datasets between 1965 and 2016 in the Lingding Bay and the sedimentary data in different years,the evolution patterns of sedimentology and geomorphology of Lingding Bay under the impact of human activities were analyzed.Results show that:(1)Over the past 40 years,the geomorphological boundaries of Lingding Bay have been significantly narrowed,and the overall shoal-trough scheme of the estuary has been compressed and moved eastward.The water surface area has been decreased,while the water volume increased.The geomorphology of the estuary has become narrowed and deepened.(2)In terms of spatial distribution of surface sediment in different years,the grain size of sediment in 1975 and 2003—2004 exhibited a coarse-fine-coarse distribution pattern from north to south,and grain parameters showed a banded distribution.After 2016,the north-south distribution pattern was no longer prominent.Fine sediments were distributed mainly along the western and eastern shoals,while coarse-grained sediments were distributed in the middle shoal in patch,in the dredging pits in the eastern trough,and in the end of the deep trough in outer Lingding Bay.Spatial distribution of grain parameters had shifted from banded to patchy pattern,indicating a transition from a simple to a more complex sedimentary environment.(3)Under the new pattern,three depocenters occurred in the bay:the inner Lingding Bay depocenter in the northern part of the middle shoal,the western shoal depocenter in the south of Qi'ao Island on the western side of the outer Lingding Bay,and the depocenter at the end of the Lingding Channel in the outer Lingding Bay;and they correspond to the scouring and silting schemes in each region.Human activities have significantly influenced the sedimentation and geomorphology of the Lingding Bay over the past 40 years.This study helps to reveal the geomorphological evolution trends of the Lingding Bay and has important practical implications for the integrated management of the Pearl River Delta,as well as the efficient utilization and management of regional water resources.