崇明东滩北侧拦门沙浅滩涨落潮和大小潮冲淤过程及机制分析

doi:10.3969/j.issn.1000-5641.2025.04.015

摘要/Abstract

摘要：

河口拦门沙冲淤变化是河口地貌和河势演变的基础与关键机制. 以往的研究主要借助海图和沉积测年资料, 来揭示拦门沙年际或季节性冲淤变化, 但对涨落潮及大小潮的冲淤变化研究尚不充分. 以长江口崇明东滩北部的潮滩前缘为例, 基于对涨落潮、大小潮水沙动力及地形变化的高精度观测, 发现: ① 潮周期内, 流速在涨潮与落潮过程中的增减变化, 导致拦门沙浅滩在涨潮期冲刷、落潮期淤积, 共形成4个阶段的冲淤变化. ② 涨潮期间, 来自口外浅滩的高悬沙流输入形成涨急悬沙峰, 其泥沙在涨憩后快速淤积, 导致涨潮过程呈现净淤积; 落潮期间, 近底层水流因长时间的落急冲刷形成落急悬沙峰, 导致落潮过程呈现净冲刷. ③ 大小潮周期内, 小潮至大潮潮差增加, 涨潮流中来自浅滩的泥沙输入虽增加但总体较小, 导致涨潮淤积小于落潮冲刷, 拦门沙浅滩呈冲刷趋势; 大潮至小潮潮差减小, 口外冲淡水滞留效应导致涨潮流中来自浅滩的泥沙输入急剧增加, 使得涨潮淤积超过落潮冲刷, 拦门沙浅滩呈淤积趋势. 上述发现为深入理解河口冲淤和演变提供了参考.

关键词: 河口拦门沙, 崇明东滩, 涨落潮, 大小潮, 沉积动力

Abstract:

The erosion-deposition processes of estuarine bars are the basis of estuarine geomorphology and channel evolution. Most studies revealed the annual or seasonal change in deposition-erosion of estuarine bars based on chart data and sedimentary dating. However, understanding of erosion-deposition changes during the flood-ebb tide and spring-neap tide cycles is insufficient. This study conducted high-resolution in-situ observations of hydrodynamics and bedform changes on the tidal flat front of northern Chongming Dongtan, using bottom-mounted tripods over 15 flood–ebb tide cycles and one spring–neap tide cycle. The study found increases and decreases in velocity in four erosion-deposition phases over one flood-ebb cycle: flood tide erosion, flood tide deposition, ebb tide erosion, and ebb tide deposition. In addition, the flood flow originating from offshore shoals caused a high suspended sediment peak (SSP), which settled rapidly and formed the major silting layer after flood slack. The ebb flow caused another SSP and formed the major scouring layer due to long-term scouring by high velocity flow during the rapid ebb flow stage. From neap tide to spring tide, the bed exhibited a scouring trend due to the generally low suspended sediment concentration (SSC) of flood flow from offshore shoals. However, from spring tide to neap tide, the bottom showed a depositional trend due to a high and increasing SSC of flood flow from shoals. The above findings provide a reference for further understanding of estuarine erosion-deposition and evolution processes.

Key words: mouth bar, Chongming Dongtan, flood-ebb tide cycle, spring-neap tide cycle, sediment dynamics

中图分类号:

P731.2

谭子杰, 牛淑杰, 李茂田, 李为华, 刘晓强, 宋艳, 姚慧锟, 张雯彦, 彭旦, 陈欣洁. 崇明东滩北侧拦门沙浅滩涨落潮和大小潮冲淤过程及机制分析[J]. 华东师范大学学报（自然科学版）, 2025, 2025(4): 147-157.

Zijie TAN, Shujie NIU, Maotian LI, Weihua LI, Xiaoqiang LIU, Yan SONG, Huikun YAO, Wenyan ZHANG, Dan PENG, Xinjie CHEN. Analysis of erosion–deposition processes and mechanisms during flood–ebb and spring–neap tides over the mouth bar shoal on the northern side of Chongming Dongtan[J]. J* E* C* N* U* N* S*, 2025, 2025(4): 147-157.

图/表 6

图1

图2

表1

潮周期涨落潮2个过程4个阶段的底床冲淤、流速、悬沙和盐度变化量统计"

潮周期序列	Tn1			Tn2			Tn3			Tn4			潮周期净变化
	涨潮增速阶段			涨潮减速阶段			落潮增速阶段			落潮减速阶段			涨潮				落潮
	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	盐度 (psu)	冲淤/ mm	流速/ (m/s)	悬沙/ (g/L)	盐度 (psu)
T1	–4.60	0.30	0.60	3.30	0.31	0.73	–10.00	0.36	0.84	4.80	0.45	0.96	–1.30	0.30	0.65	26.80	–5.20	0.39	0.91	24.50
T2	–6.50	0.30	0.89	6.80	0.39	0.44	–5.10	0.34	0.45	3.20	0.42	1.29	0.30	0.35	0.66	24.90	–1.90	0.37	0.78	23.10
T3	–3.20	0.38	1.57	3.20	0.28	0.81	–4.90	0.41	0.74	8.20	0.40	1.53	0.00	0.35	1.27	25.10	3.30	0.40	1.00	22.90
T4	–8.20	0.36	3.41	11.40	0.34	3.18	–13.00	0.35	3.60	6.50	0.36	2.92	3.20	0.35	3.29	24.00	–6.50	0.35	3.35	25.40
T5	–4.90	0.42	4.34	4.90	0.33	1.31	–3.20	0.36	1.57	3.20	0.42	2.11	0	0.38	2.95	25.00	0	0.38	1.77	23.90
T6	–4.60	0.41	3.01	4.60	0.29	2.07	–6.70	0.37	2.84	4.60	0.34	3.81	0	0.35	2.61	23.70	–2.10	0.36	3.15	21.10
T7	–6.50	0.45	6.26	8.60	0.37	2.93	–6.70	0.41	6.74	4.60	0.41	3.72	2.10	0.41	4.29	23.60	–2.10	0.41	5.45	20.00
T8	–4.40	0.47	5.32	11.40	0.31	3.86	–12.00	0.36	6.76	1.40	0.35	6.39	7.00	0.40	4.69	22.70	–10.00	0.36	6.64	18.80
T9	–5.00	0.55	7.15	13.70	0.35	6.20	–12.00	0.38	9.03	2.80	0.42	9.60	8.70	0.44	6.61	23.60	–8.80	0.39	9.24	19.50
T10	–3.30	0.41	13.10	15.40	0.30	7.45	–14.00	0.34	5.60	3.20	0.33	8.61	12.10	0.35	10.10	21.10	–11.00	0.34	6.68	20.50
T11	–3.00	0.43	10.60	11.90	0.29	4.05	–12.00	0.42	5.33	3.20	0.41	8.88	8.90	0.37	7.74	22.10	–8.90	0.41	6.34	18.30
T12	–2.80	0.39	12.10	10.00	0.28	4.58	–10.00	0.36	7.06	3.00	0.37	15.80	7.20	0.33	8.32	21.30	–7.20	0.36	10.40	20.20
T13	–3.00	0.36	9.36	10.20	0.25	5.56	–12.00	0.41	6.54	8.20	0.37	11.50	7.20	0.31	7.50	21.50	–3.90	0.39	8.42	20.60
T14	–4.40	0.36	11.80	16.80	0.21	6.09	–15.00	0.30	2.78	1.40	0.37	8.14	12.40	0.29	9.01	20.30	–14.00	0.33	5.31	22.20
最小值	–8.20	0.30	0.60	16.80	0.21	0.24	–15.00	0.30	0.45	8.20	0.33	0.96	12.40	0.29	0.65	20.30	0	0.33	0.78	18.30
最大值	–2.80	0.55	13.10	3.20	0.39	7.45	–3.20	0.42	9.03	1.40	0.45	15.80	0	0.44	10.10	25.10	–14.00	0.41	10.40	25.40
平均值	–4.60	0.40	6.38	9.40	0.31	3.52	–9.60	0.37	4.28	4.10	0.39	6.08	4.80	0.36	4.98	23.30	–5.60	0.37	5.04	21.50

表1

图3

图4

图5

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