人类活动对磨刀门水道河床地形和潮汐动力的影响

基于实测地形和水文资料,探讨人类活动对近期磨刀门水道河床地形和枯季潮汐动力变化的影响。研究结果表明:(1) 磨刀门上游河段大规模河床挖沙引起河床高程显著降低,水深增大,河槽容积增加,底坡降减小;口门围垦整治导致磨刀门口门区水域面积变小,入海口门向海延伸,入海水道增深。(2) 磨刀门水道河床地形变化引起枯季潮汐动力发生变化:上游河段低潮位降低,潮差增大,进潮量增加,潮汐动力明显增强;口门区潮差减小,横洲水道潮能汇聚,水位壅高;水面坡降减小,潮波传播速度增加,咸水界上移。

Impacts of Large-scale Human Activities on Riverbed Morphology and Tidal Dynamics at Modaomen Estuary

Modaomen estuary is one of the main outlets of the Zhujiang (Pearl) River. Since the 1980s, large-scale human activities such as riverbed sand dredging and estuary regulation, had lead to some changes of channel topography and hydrodynamic. Based on field data such as topographic data and water data from different years, this paper provide some primarily conclusions as follows: (1)large-scale sand dredging at Modaomen waterway resulted in riverbed deepening and channels volume increasing. Due to estuary regulation, the shallow sea at Modaomen estuary turned into two waterways regulated by artificial banks. As a result, water area and channel volume were reduced. Riverbed of the waterway became deepening. (2) During dry season in recent years, Topographic change in Modaomen waterway lead to tidal dynamic enhancing apparently at Zhuyin station, the upper reaches of Modaomem estuary, with low water level dropping, tidal range increasing and tidal influx increasing. As well, at Dahengqin station, near the outlet of Modaomen estuary, water level rise with tidal assembly and tidal range decreasing. Phase difference between Dahengqin and Zhuyin reduced, and tidal wave propagation velocity increased with saline water intruding frequently.