城市河流形态及稳定性演变研究进展

Progress on Urban Stream Transformation of Critical Forms and Stability Relationships

人为干扰导致的城市河流退化在地理科学和水文学领域引发了广泛关注,针对城市河流形态及演变过程的研究成为退化河流生态修复的一项重要内容,然而,目前国内相关基础理论的系统梳理相对缺乏。本文回顾了半个多世纪以来城市河流形态及稳定性演变的研究成果,从研究内容和方法两方面对不同城市化阶段河流形态及稳定性变化的特征和原因进行总结,同时评述了不同研究方法的特点与局限。本文认为,城市化进程改变了河流自然演化过程,破坏了河流原有形态及稳定性,其中,沉积和径流体系变化是其根本原因。为了更好地运用河流演变机理进行河流修复,学者们发展了河流分类体系,主要包括形态导向法、过程导向法和综合分类法,重点从河流退化的地貌形态、沉积和径流变化过程、河流演变的时间周期等方面概述各分类体系的优缺点,阐述具有预测功能的河流分类体系不断完善的过程。本文通过梳理城市河流演变的研究成果,以期为中国城市河流修复与管理提供科学依据和现实借鉴。

Urban river degradation under human impacts has aroused wide attention in the areas of geography science and hydrology. But in domestic academic field there is still a lack of systematic theory study on fluvial geomorphology and process which is the important work in river restoration design. Based on the study of river geomorphology and stabilization for nearly half a century, this paper reviews the research results from the con-tent and method, summarizes the features and reasons about river changes in the process of urbanization, and an-alyzes the advantages and limitations of river classification. In conclusion, urbanization has transformed river landscapes across the Earth＇ s surface, caused great damage to fluvial equilibrium, and highly altered river natu-ral progress. The main parameters include river enlargement, reductions in sinuosity, an overall increase in drain- age densities, and a tendency for bed material to coarsen. The root cause of these changes is the change of hydro- logic suystem and sediment discharge regiments in that urban construction can induce river aggradation due to soil erosion at the beginning of urbanization; and accompanied by the gradual completion of the construction, channel erosion has been the main source of river sediment; and that hydrological system is upset by a decrease in the perviousness of the catchment, driven by land-use changes. Therefore, scholars have been studying the classification of river evolution on form and stability. In this paper, a summary of existing urban stream classifi-cation systems can be classified primarily into three broad types by synthesizing literature methods： form-based method, process-based method and synthesis method. Form-based method is appropriate for concluding river morphological characteristics, but the classification scheme lacks significant explanation and has a limited basis in channel processes and stability. Process-based method can provide important information at the stage of evolu-tion and the dominant channel processes that can help predict the future response to changing sediments and dis- charge inputs. However, it ignores the correlation between river degradation, adjustment time and different stag-es of urbanization. The synthesis method with form and process-based feature, which is currently widely used, avoids the lack in application of above two methods and emphasizes the theory period of river adjustment which include three phases ＂the onset of a morphological response-significant morphology change-a new equilibrium＂, but still needs future quantitative research. Combing the existing experiences is beneficial to provide a scientific basis and practical references for watershed restoration and management in China.