A Gateway to Successful River Restorations: A Pre-Assessment Framework on the River Ecosystem in Northeast China

Abstract

Natural rivers have been disturbed for hundreds of years by human activities. Previous water conservancy projects in the form of dams, reservoirs, dykes, and irrigation infrastructure focused on the social and economic benefits and disregarded the adverse effects on the physical, chemical, and biological characteristics of the affected rivers. Since the 2000s, the comprehension of river remolding has transformed so decisions are more socially and ecologically beneficial. However, restoration actions are often implemented aimlessly, without a detailed plan or sufficient communication, leading to the failure of accomplishing objectives for a variety of ecologic, financial, and social reasons. Thus, a pre-assessment framework is proposed in this paper, to determine river restoration priorities, emphasizing both social and ecological aspects. The vague notion of river health is evaluated using the Variable Fuzzy Assessment Model (VFAM) and expressed by modified Nightingale Rose Diagrams (NRDs). The river social ecosystem was subsequently analysed using this framework in the Ashihe River near Harbin City, Northeast China. The application of VFAM demonstrated that the health status of the upper, middle, and lower sections of the river could be classified as sub-healthy, degraded, or sick in terms of ecosystem structures, and sub-healthy, degraded, or degraded in terms of social functions, respectively. The health status of the lower section was the poorest and should be restored first. Using NRDs, we found that water quality deterioration and irrigation works are the two key factors in river degradation, which must be improved throughout the entire watershed. Aesthetics and recreation should also be given priority to restore the lower section due to the demands of nearby residents. Several measures are also suggested for decision makers who need a more detailed design to implement. This framework potentially assists with communicating with stakeholders, avoids aimless restoration actions, and contributes to comparing with the measuring after restorations.