利津水位对河口演变响应的计算方法

Calculation method for water stage at Lijin in response to delta evolution

本文分析了黄河口的演变特征及其对利津3000 m3/s同流量水位的影响。黄河口每次改道后尾闾河道的河长突然缩短，比降陡增，之后河长以先快后慢的速率增长，尾闾河道比降则呈指数衰减，经过约5~6年调整至平衡比降，其变化过程反映了典型的河床演变滞后响应特性。基于黄河口河道的演变特征，提出了河口河道水位和纵比降变化的概化模式，并采用滞后响应模型建立了河口河道同流量水位的计算方法，较好地计算了1954—2012年间黄河下游利津3000 m3/s同流量水位的变化过程。该计算方法不仅考虑了河床演变的滞后响应特性，而且反映了来水来沙和河道淤长与蚀退对利津同流量水位的共同影响，能够连续地模拟河口淤积延伸及改道过程中河口河道特征水位的长期变化过程。研究成果可为分析黄河口淤积延伸与下游河道相对侵蚀基准面的变化关系提供参考。

This study analyzed the characteristics of the evolution of the Yellow River delta and its impact on water stage at Lijin at a discharge of 3 000 m3/s （denoted by H3000）. Every time after channel avulsion at the Yellow River delta, the river length downstream of the diversion point was suddenly shortened and chan-nel slope increased steeply, then channel length increased with a decreasing rate while channel slope de-creased with a rate decaying exponentially with time and adjusted to equilibrium slope after 5~6 years. Such phenomenon typically reflected the significant characteristic of delayed response of the fluvial system. Based on these characteristics of the evolution of Yellow River delta channel, generalized models for the changes of channel slope and water surface at the delta channel were proposed. Based on the proposed con-ceptual models, equations for calculating water stages at the same discharge along the delta channel were developed by using the delayed response model for modelling morphological responses of fluvial rivers to perturbations. H3000 at Lijin during 1954 and 2012 was calculated well. The proposed methods consider the characteristic of delayed response of fluvial system and the impacts of water and sediment conditions and delta evolution on the changes of the local base level of the Lower Yellow River（LYR）, which makes them applicable to the whole evolution processes of the degradation, extension,swift and avulsion of the del-ta channel. This study provides references for studying the relationship between delta extension and accre-tion and the changes of local base level of the LYR.