Assessment of urban stream morphology: an integrated index and modelling system.

Physical morphology is an important attribute of a stream system. The morphological state of a natural pristine stream often reflects its biological condition because of their close links. In contrast, the morphology of an urban stream may exhibit different behaviours due to serious human disturbances. For an urban stream system, the morphological condition not only determines the in-stream habitat quality but also provides the physical basis for the stream's municipal functionalities. By comparing the morphological characters of urban and natural streams, this paper develops an integrated index system and model for the assessment of urban stream morphology. The model is applied to the Ancient Canal (Zhenjiang, China) with the aim of comparing the morphological conditions of reaches with and without ongoing restoration programs and further of assessing the effectiveness of the restoration methods and techniques. The results indicate that the water security and the landscape functionality of the canal have been upgraded. However, the quality of the in-stream habitat has been degraded as a result of the restoration. Based on the modelled results, recommendations are given for improving the effects of the next-phase restoration. The assessment system and findings from the application presented here are expected to have important implications for the restoration of disturbed urban streams in many other cities in China and elsewhere in the world.