城市化流域暴雨径流对“源-汇”景观格局的时空响应研究

The “source-sink” theory is an effective way to couple landscape patterns and ecological processes, which could be applied to the study of rainfall-runoff issue and express the ecological relationship between landscape pattern and hydrological response of urbanized watershed efficiently. However, for rainfall-runoff process, the “source/sink” function of the same type of landscape element may vary with different rainfall conditions. Therefore, how to effectively identify and quantify the “source” and “sink” landscapes and their ecological functions is the key point of using “source-sink” theory. In view of this, this research hopes to carry out a case study in the Wenyu river watershed of Beijing based on “source-sink” theory, in order to seek the ecological solutions to the risk of urban flood and provide a new method for urban hydrological study. This study tends to identify and quantify the “source” and “sink” landscape and its ecological functions related to rainfall-runoff process under different rainfall scenarios. Then, a “pattern-process” model will be generalized with a new source-sink function distribution index (i.e., location-weighted Landscape Contrast Index), to explore the mechanism of the “source” and “sink” landscape pattern affecting on hydrological process. On this basis, the dynamics of rainfall-runoff process and its spatiotemporal heterogeneity of the study watershed will be discussed by adopting an appropriate spatial discretization method, which could help identify the key region of rainfall-runoff alteration in a watershed and suggest a better govern plan.

源汇景观理论是耦合景观格局与生态过程的有效途径，将其应用于暴雨径流研究，可以直观表达城市化流域“景观格局-水文响应”的生态学联系。在源汇分析中，同一类型景观要素的源/汇功能可能会随降雨条件不同而发生改变，因此如何有效识别并量化流域源汇景观类型及其功能强度，是正确运用源汇景观理论解释流域景观动态与暴雨径流响应之间“格局-过程”关系的关键和难点。本项目以北京市温榆河流域作为研究区，开展源汇景观理论案例研究：综合遥感监测、GIS分析和模型模拟等手段，通过情景分析建立流域各景观要素在不同降雨条件下源汇功能类型及强度的动态识别方法，量化表达流域源汇景观格局特征，探讨城市化流域源汇景观分布模式对暴雨径流过程的影响机制。在此基础上，优化流域空间离散化方法，从时间和空间两个维度分析城市化过程中流域暴雨径流响应的异质性特征，识别风险关键区域，为流域暴雨径流治理提供直观依据。

城市化过程所引起的景观格局变化是改变城市区域原有降雨径流响应过程的重要原因之一，如何有效的量化并分析城市化流域内不同的“源”、“汇”景观对降雨径流过程的潜在影响是科学认识和完善城市雨洪水管理工作的关键。本项目通过综合遥感监测、GIS分析和水文模型模拟等手段，从多个尺度分析北京市温榆河流域内城市化区域内的降雨径流过程。研究结果显示：总体上来讲，不透水面是城市化流域降雨径流过程变化的重要“源”景观，而城市绿地及一些绿色基础设施则充当为关键的“汇”景观。具体来讲，从城区尺度来看，城市内不同功能区域由于其各自异质性的源汇景观比例而使得不同功能区之间的降雨-产流风险差异显著；从局地尺度上来看，绿色基础设施的布设在小型城市化汇水区域内可以有效的削减降雨径流过程的影响，通过优化其空间布局还可以进一步改善其径流削减效果。上述结果有助于掌握城市化区域内暴雨径流响应的异质性特征，为流域水风险关键区域识别、景观格局优化以及雨洪水管理提供科学依据。