黄河下游滩区行洪和沉沙功能演变分析

Analysis of the Evolution of the Flood Discharging and Sediment Deposition Function in the Floodplain of the Lower Yellow River

黄河下游滩区的行洪和沉沙作用未来究竟有多大,是滩区治理战略方向确定的关键依据。利用实测资料,系统分析了黄河下游实测洪水泥沙变化、滩区不同时期行洪和泥沙淤积变化。结果表明:受洪水量级大幅减小、河道整治工程相对完善以及滩区生产堤建设等综合因素影响,1986年以来滩区行洪和沉沙功能与历史时期相比已显著减弱。采用数学模型对比分析了下游河道"现状格局"和"彻底废除生产堤"两个方案滩区的沉沙作用,结果表明:在潼关年均来沙3亿t条件下,未来50 a内滩区基本不发挥沉沙作用;来沙6亿t条件下,未来50 a内滩区发挥一定的沉沙作用;从滩区泥沙淤积比例这个关键指标看,"废除生产堤"方案仅比"现状格局"方案高2%。提出了重新对滩区行洪和沉沙功能进行战略定位的建议。

It is the key basis to determine the strategic direction of the floodplain management that how much is the effect of the flood dischar-ging and sediment deposition in the floodplain of the Lower Yellow River. Based on the field data , the flood and sediment variation and flood discharging and sediment deposition of the floodplain in different periods were systematically analyzed. The results indicate that the flood dis-charging and sediment deposition function of the floodplain have degraded since 1986 compared with that in history which is affected by the reduction of flood discharge , the completion of the river regulation works and the construction of the farming levees. Base on the numerical model , the sediment deposition function in floodplain under two schemes were compared and analyzed which were the scheme of current sitva-tion and the scheme of dismantling the farming levee thoroughly. The results show that , under the circumstance of the incoming sediment is 0.3 billion tons at Tongguan Station , there is no sediment deposited in the floodplain in 50 years;under the circumstance of the incoming sediment is 0.6 billion tons at Tongguan Station , only a few of sediment deposited in the floodplain in 50 years that means it will not give nota-ble improvement to the transverse distribution of the sediment deposition in the downstream channel by means of dismantling the farming levees. It follows that a proposal is put forward which is to re-orientate strategically the function of flood discharging and sediment deposition in the floodplain.