大量采沙对东江下游及东江三角洲河床地形和潮汐动力的影响

通过分析东江下游及东江三角洲的采沙情况、采沙对河床演变和潮汐动力的影响。近几十年来东江下游及东江三角洲采沙量巨大,1980~2002年22年间采沙总量达到了3.32亿m³。大量采沙对河床演变的主要影响是：大幅度扩大了河槽容积、河床平均高程显著降低、水深明显增加、纵比降减小。东江下游及东江三角洲潮汐动力的变化主要表现在：网河区上段及东江下游潮水位明显降低,潮差增大,涨潮历时延长,主要分潮振幅加大;潮汐传播速度加快;潮区界、潮流界、咸潮界上移;网河区上段及东江下游潮汐动力得到明显增强,潮汐动力作用范围向上延伸,导致这种变化的主要原因是大量挖沙所导致的河床剧烈变化。

Impacts of Huge Amount of Sand Dredging on Riverbed Morphology and Tidal Dynamics of the Lower Reaches of the Dongjiang River and the Dongjiang River Delta

The sand dredging and its impacts on riverbed evolution and changes of the tidal dynamic in the Dongjiang River network and lower reaches of the Dongjiang River are analyzed in this paper.The huge amount of sand,totally 0.332 billion m3 from 1980 to 2002,was mined from the riverbed of the Dongjiang River network and lower reaches of the Dongjiang River.The main impacts of sand dredging on the riverbed evolution include increasing substantially of the channel capacity,lowering of the average riverbed elevation,and deepening of the water depth and decreasing of the longitudinal riverbed gradient.The main tidal dynamic changes are as follows:(1) In the upper part of the Dongjiang River network and lower reaches of the Dongjiang River,the tidal water level drops apparently,the tidal range widens,the flood tidal duration goes longer and the amplitudes of the main tidal components become bigger.(2) The tidal wave spreads faster.(3) The limits of the tidal level,tidal current and salt water move upwards.(4) The tidal dynamic in the upper part of the Dongjiang river network and lower reaches of the Dongjiang River intensifies greatly.The above changes are mainly caused by the dramatic change of riverbed topographic alteration shaped as a result of the huge amount of sand dredging.