Studies On Habitat Assessment Of Urban River In China's Plain Water Network Region

Deterioration of ecological system of urban river has been one of the most urgent problems in economically high-developing regions across the world. River assessment serves as an important method to protect ecological river system and an effective support for river rehabilitation and management. In this context, it is of significance to explore river assessment method in urban area and to facilitate development and enrichment of theory and practice in urban river management.Contradiction between natural and social values of urban river is more obvious than that of natural ones. And it requires coordinating during river rehabilitation and management. However, relevant studies on urban river do not have a long history and outstanding rewarding. As an effective method universally used across the world recently to check health of rivers, monitor deterioration and to facilitate rehabilitation, river habitat assessment is used in this paper to enrich theory and practice in urban river management.Overseas studies and practices on river habitat assessment in urban area have been collected and selected. The concept of urban river habitat and its assessment ideas are identified. The importance of river habitat assessment for river health evaluation and river classification is addressed. Practices on river habitat assessment in countries such as Australia, England, USA and North Africa are summarized to facilitate relevant research in China's plain water network region.A comprehensive three-scale framework is established to assess urban river habitat in China's plain water network. The framework is composed of sixteen indices covering four aspects, namely river bank, channel, embankment and pollution. Meanwhile, a framework for assessing accessibility of urban river habitat has also been established with spatial, visual, continuity and comfort indices. Research on urban river habitat and its relation with accessibility are carried out.Eighteen representative stretches are surveyed in a case study in Shanghai, a symbol city in China's plain water network region. These stretches are located at seven administrative districts in central and suburban Shanghai and can be divided into four functions according to Shanghai's Water Functional Allocation. According to the analytic results of survey data, the surveyed stretches are classified into four kinds concerning bank habitat condition, into three kinds concerning channel habitat, into four kinds concerning embankment and into four kinds concerning human pollution. Different scores are attached to different stretch kinds. The addition of scores for bank habitat, channel habitat, embankment and human pollution are the final score for comprehensive habitat assessment. Based on the final score, habitat condition of surveyed urban river is analyzed, existing problems are discovered and suggestions are given to improve the habitat and accessibility condition there.Results of the case study are as follows: 1) the assessment results are related with location and function of surveyed stretches. Stretches in central urban area have a better habitat condition while river habitat in remote suburban area is not very well. Water habitat in the water resource region in upper Huangpujiang River and its buffer region has potential risk. Moreover, rivers for industrial use have worse habitat condition.2) the accessibility of habitat of surveyed stretches is not satisfying and requires being improved. The improvement of channel habitat and the process of bank development should be in harmony. Coherent planning and management should be carried out to prevent problems such as shattered habitat.3) habitat and its accessibility is contradictory in some surveyed stretches. Stretches with worse habitat condition has fluctuated accessibility.Suggestions are given as follows: 1) survey on river habitat should be carried out before rehabilitation and management of urban river to facilitate the protection of origin habitat and the creation of diversified habitat styles. Consideration should be given to achieve continuity of river habitat both along channel and across channel. Coverage of plants on river bank and diversity of aquatic plants should be increased while concrete buildings along river should be reduced. 2) harmony should be pursued between improvement of channel habitat and of bank habitat to prevent habitat discontinuity. Roads along river should be more available for river access. Buffer belt should be planted along river. Particular passageway should be built for the disable and the young. 3) both sound habitat condition and accessibility of urban river should be achieved. The step-by-step increase of accessibility should be supported by the improvement of habitat condition. At the beginning of river rehabilitation and management, more attention should be paid to the improvement of visual factors and habitat continuity, while spatial factors and habitat comfort should be emphasized at latter stage.