河床演变时间滞后与空间联动的耦合机理

An important characteristic of the fluvial system is its delayed response to allogenic disruptions, and this characteristic has been widely studied. Autogenic control within the system results in the spatial correlation of the upstream and downstream channel reaches. Thus far, the coupled mechanism of the delayed response and spatial correlation of the fluvial processes has not yet been investigated sufficiently. To bridge this gap, research in three aspects will be carried out. The channel reaches at the downstream of the Three Gorges Dam and the lower Wei River, among others, are taking as typical cases, where the fluvial systems are influenced by relatively simple disruptions with great magnitude. The spatial correlation length (SCL) is defined as the extension length of the progressive/retrogressive erosion/aggradation processes. (1) The spatial and temporal evolution processes of the selected channel reaches will be analyzed to identify the impact factors for the heterogeneous adjustment along the channels and those disrupting the spatial correlation of the fluvial systems. SCL and its rates will be estimated based on the results of flume experiments and observations in the selected natural channel reaches. By incorporating theory and methods concerning with the equilibrium slope of river channel, a method will be developed for SCL. (2) Delayed response model along with the related theories on the equilibrium of rivers will be used to calculate the delayed response time of channel reaches impacted by different magnitudes of disturbances. The relation between the magnitudes of disturbances and delayed response time will also be discussed. (3) By combining the calculation methods for the SCL and the delayed response model, a method for fluvial processes coupled with the temporal lag and spatial correlation will be proposed, applied and verified. The results of this research project will contribute to the development of the basic theories of the self-regulation and non-equilibrium adjustment of the fluvial system.

冲积河流对外部扰动具有滞后响应的特征，同时河流系统内部上、下游河段之间具有联动性，以往研究多关注前者，缺乏考虑时间滞后和空间联动耦合机制的河床演变研究。本项目以沿程或溯源冲淤占主导的强非平衡态河床演变过程为对象，选取三峡坝下游、渭河下游等河道为典型实例；定义河道沿程或溯源冲淤影响范围为空间联动步长，分析河道时空冲淤演变规律，辨识河道沿程不均衡调整和空间联动受阻的影响因子；结合概化水槽试验，研究空间联动步长随时间的变化规律，基于冲淤平衡比降等理论和方法，建立空间联动步长及其变化速率的计算方法；采用滞后响应模型和河流平衡态的表达方法，计算不同强度影响下河道的滞后响应时间，探讨扰动强度与滞后时间的关系；将滞后响应模型与空间联动速率的计算方法结合，建立考虑时间滞后与空间联动耦合作用的河床演变计算方法，并对其进行应用与验证。研究成果对发展冲积河流自动调整作用和非平衡态河床演变的基础理论具有重要意义。

冲积河流对外部扰动具有滞后响应的特征，同时河流系统内部上、下游河段之间具有联动性，以往研究多关注前者，缺乏考虑时间滞后和空间联动耦合机制的河床演变研究。本项目以沿程或溯源冲淤占主导的强非平衡态河床演变过程为对象，分别选取了受三峡水库运用和水沙变异影响的宜昌至城陵矶河段、受上游来水来沙与下游水库运用协同作用的三门峡库区及渭河下游河道、受上游水沙和下游河长延伸共同影响的黄河口清水沟河道为研究对象，研究了河道时间滞后与空间联动的演变规律，揭示了受不同影响因素影响的河道时空演变机理，为水库运用及河道管理等提供了重要科学参考。研究成果共发表期刊论文18篇，其中SCI论文8篇，EI论文2篇，中文核心期刊论文6篇（含1篇录用），培养研究生3名，超额完成预期目标。