近期长江张家洲南水道强冲刷机理与趋势分析

Strong Erosion Mechanism and Trend Analysis of the South Zhangjiazhou Waterway of the Yangtze River

2016年9月利用多波束测深仪调查了张家洲河段河床微地貌的高分辨率形态与分布特征,结合1998年和2013年水下地形资料,分析了三峡截流以来该河段河槽的冲淤变化与演变趋势。结果表明:(1)张家洲河段整体呈冲刷状态,净冲刷量17. 2×10~6m^3。其中,张家洲南水道是强冲刷区,最大冲刷深度约9 m;(2)河槽表层沉积物中值粒径为149. 1～226. 3μm,与历史资料相比呈粗化趋势;(3)张家洲河段约82. 9%的主航道发育了沙波,约14. 0%的主航道发育了冲刷坑与冲刷槽,平床地形仅占3. 1%。流域来沙量减少是张家洲河段整体冲刷的主要原因,而河流控制工程稳定了河势,迫使水流归槽,加剧了张家洲南水道的冲刷。随着流域来沙量持续减少,张家洲南水道主航道有可能进一步冲刷。

The spatial distribution and high-resolution morphological of riverbed micro-morphology were observed using a RESON 7125 multi-beam during September 2016. Bathymetric data of the Zhangjiazhou reach in 1998 and 2013 were also used to analysis the channel volume change. Results show that：（ 1） strong riverbed erosion was experienced in the Zhangjiazhou segment and the net erosion volume was 17. 6 × 10^6 m^3 between 1998 and 2013. Several erosional holes were found in the South Zhangjiazhou Waterway which reach up to 9 m.（ 2）Medium grain size of the channel sediment sampled in 2016 changed from 149. 1 μm to 22. 3 μm were coarser than history before 2003.（ 3） Approximately 82. 9% main channel developed dunes while 14. 0% of the main channel developed erosional holes. The mainly reason of the strong erosion occurred in the Zhangjiazhou segment because of the sediment supply reduced. The river channel control engineering affected the river morphology and stabilized the river regime. The water was forced by these manmade projects to return to the river trough and exacerbated the erosion phenomenon. With the sediment supply reducing in the future,the main channel of the South Zhangjiazhou Waterway may erosion further.