新入海水沙情势下黄河口的地貌演变

Processes of the Yellow River Mouth on new water and sediment condition

近年来,受流域气候变化和强烈的人类活动干预,黄河入海水沙情势出现了新的变化,河口区地貌演变也随之改变。为了解新入海水沙情势下现行黄河口地貌演变特征,基于利津站水沙数据和现行河口实测水下地形资料,运用统计学方法进行分析研究。结果表明:黄河入海水沙情势由'水少沙多'向'枯水少沙'转变,入海泥沙持续减少,悬沙浓度降低,泥沙颗粒粗化;2002-2015年持续调水调沙的14年间入海泥沙共19.79亿t,其中有8.34亿m^3(13.09亿t)泥沙沉积在现行河口滨海区,而2016年由于水量极枯调水调沙首次中断,河口滨海区大面积蚀退,净蚀退量达0.72亿m^3(1.13亿t),现行河口2~5 m水深平均侵蚀厚度为0.38 m,对入海水沙锐减的响应最为突出;维持现行河口滨海区冲淤平衡的入海泥沙通量临界值为1.3亿t/a,黄河入海水沙情势的改变使河口地貌演变将出现新的态势。

Runoff and sediment load in the Yellow River underwent dramatic changes due to the climate change and human activities in the past few decades,which resulted a new pattern of its delta morphological evolution.In order to find out the relationship between evolution of Yellow River Mouth and new regime of fluvial sediment delivered to the sea,the time series variation trends of water and sediment discharge at Lijin Hydrological Station and river mouth morphology are analyzed by means of statistics.Results show that there is a sharp decline of sediment into the sea and Water-Sediment Regulation Scheme(WSRS)is stopped in 2016 as the absence of water discharge.Since WSRS came into operation in 2002,there were decline in sediment input and suspended sediment concentration,and coarser sediment from lower Yellow River watershed.During 2001-2015,the total sediment discharge is 19.79×10~8 t,of which 8.34×10~8 m^3(13.09×10~8 t)sediment deposited in the River Mouth.In 2016,the subaqueous delta experienced great erosion with a net volume of 0.72×10~8 m^3(1.13×10~8 t).The underwater topography between 2 m and 5 m isobaths is the most sensitive geomorphology unit to the decline of sediment with an average erosion rate 0.38 m/a.It is estimated that the sediment discharge threshold of deposition of subaqueous morphology is 1.3×10~8 t/a.The new regime of water and sediment will lead to an evolution pattern of the Yellow River mouth.