长江口深水航道整治工程影响下北槽河床冲淤变化分析

Analysis of influence of Deep Waterway Project on morphological change in North Passage of Changjiang Estuary

根据长江口深水航道整治工程前后(1998年1月与2008年2月)的地形测图,定量分析工程影响下的北槽河床冲淤变化,结果表明:1)10年间,研究区域内泥沙淤积总量高达3.37亿方,平均淤积厚度1.03m,其中入口段、上段、中段及下段的淤积量分别占淤积总量的16.5%、32.1%、29.6%与21.8%,淤积厚度分别为1.23m、1.12m、1.39m与0.65m;2)坝田泥沙淤积总量3.50亿方,其中航道北侧淤积量占58.3%,淤积分布特征为上段淤积厚度最大,下段次之,中段最小,分别为3.94m、2.44m和0.92m,航道南侧从上游向下淤积厚度逐渐减小,分别为3.32m、3.10m与1.87m;3)主槽整体净冲刷,泥沙冲刷总量0.68亿方,其中航道北侧冲刷量占87.9%,主槽上段冲刷深度最大,平均1.40m,下段次之(南侧0.10m北侧0.79m),中段淤积(南侧1.28m北侧0.59m)。此外,还发现北槽河床冲淤分布,主要受整治工程影响,疏浚抛泥仅影响贮泥坑和抛泥区附近的局部区域,流域来沙量变化对北槽淤积量变化影响很小。

Based on the bathymetry data of the North Passage of the Changjiang Estuary, surveyed in Jan. 1998 and Feb. 2008, respectively, the characteristics of erosion and deposition distribution in the North Passage are discussed quantitatively in this paper. It is found that the morphology in the North Passage has been significantly changed due to the Deep Waterway Project. Major features of the erosion and deposition patterns are summarized as follows. 1 ） The total volume of deposition was 3.37 × 10^8m^3 in the study area with the average deposition thickness up to 1.03 m during ten years from Jan. 1998 to Feb. 2008. The volumes of deposition in the entrance, upper, middle and lower regions of the North Passage were about 16.5% , 32.1% , 29.6% and 21.8% of the total deposition volume, with the deposition thickness about 1.23m, 1.12m, 1.39m and O. 65m, respectively; 2） The total volume of deposition within the dikes and groins was 3.50×10^8m^3, in which 58.3% deposited in the north region of the navigation channel. The deposition thickness of the upper, middle and lower sections in north region was 3.94m, 2.44m and 0.92m, respectively. The deposition thickness of the upper, middle and lower sections in south region was 3.32m, 3. lm and 1.87m respectively; 3） The main channel of the North Passage was mainly eroded, with the erosion thickness 1.40m in the upper section, and 0. 1-0.79m in the lower section, except the middle section with the deposition thickness 1.28 m in the south part and 0.59m in the north one. The morphological change in the North Passage was mainly influenced by the Deep Waterway Project, especially the construction of dikes and groins. The dredging along the navigation channel and sediment dumping at several locations only affected the local sedimentation. The change of sediment load from the Changjiang River had no significant effect on the morphological change in the North Passage.