| Author: | Chen, Yang |
| Title: | Assessment of the environmental, ecological, and social impacts of river restoration projects in Hong Kong |
| Advisors: | Wang, Yuhong (CEE) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Stream restoration -- China -- Hong Kong Water quality -- China -- Hong Kong Stream ecology -- China -- Hong Kong Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Civil and Environmental Engineering |
| Pages: | xxi, 282 pages : color illustrations |
| Language: | English |
| Abstract: | River restoration is a popular strategy used to enhance the ecological health of urban rivers. In Hong Kong, a total of 26 river restoration projects have been implemented over the past two decades with the aim of improving ecosystems and providing social benefits to communities. With the number of river restoration projects increasing, there arises a pressing need to evaluate the effectiveness of these initiatives in terms of their impacts on the environment, ecology, and society. The lack of post-project evaluation makes it difficult to fully comprehend the outcomes of those existing restoration projects and to improve future projects based on lessons learned. To address this issue, this research aims to conduct a comprehensive evaluation of river restoration projects in Hong Kong from the aspects of environmental, ecological, and social impacts. More specifically, the assessment content includes water quality, hydro-morphology, biodiversity, and social impacts. Four rivers in Hong Kong were used for comprehensive studies, including the Lam Tsuen River (LTR), Ma Wat River (MWR), Tung Chung River (TCR), and Kai Tak River (KTR). The research was conducted over a four-year period from 2018 to 2022 based on a variety of methods, involving laboratory tests to assess water quality, on-site surveys to evaluate hydro-morphology, on-site observations to study biodiversity, and face-to-face questionnaires and interviews to gauge social impacts. The major research components and findings are introduced as follows. (1) Water quality assessment. This study compares water quality between channelized, restored, and natural river sites. It aims to identify differences in the water quality of these sites and gain lessons for future river restoration designs. Water quality was assessed using different physicochemical parameters, including the human implication. The key findings and conclusions from water quality assessment are listed as follows: 1) Rehabilitation features and techniques affect the water quality of the revitalized river sections. 2) The measured water quality parameters are subject to temporal and seasonal variations, with better water quality being found in temperate and dry seasons, and the impacts of river restoration on water quality are also subject to seasonal variations. 3) Certain water quality parameters are closely associated, and dissolved oxygen (DO) can reduce a variety of pollutants. 4) E. coli, generally independent of other water quality parameters, remains at elevated levels at the surveyed sites. 5) Compared to natural rivers, water quality at the restored sections is either similar or worse, largely depending on the surrounding environments of the restored sections. 6) Water quality generally deteriorated from upstream to downstream, likely attributed to urbanization and human activities. (2) Hydro-morphological assessments. The research includes assessing the hydro-morphological characteristics of two restored and two natural river sites. These assessments provide valuable information on the naturalness of habitats that can be utilized to enhance future river restoration projects. The key findings and conclusions from hydro-morphological assessment are listed as follows: 1) The hydro-morphological characteristics of natural sites such as habitat features and substrate types offer valuable references for river restoration. 2) Judged by Habitat Quality Assessment (HQA) and Habitat Modification Score (HMS), the bankside and aquatic features at the natural sites are more intact, richer, and more diverse than those at the restored sites. (3) Biodiversity assessment. A framework for evaluating biodiversity was developed. This framework was subsequently applied to a benchmark study that compared the biodiversity evaluation and conservation efforts of two sets of restored and natural river sites. By utilizing this framework, it becomes possible to comprehend and compare the ecological diversity and conservation outcomes of various restoration approaches. The key findings and conclusions from biodiversity assessment are listed as follows: 1) A methodological framework and a decision table were developed for biodiversity evaluation from the perspective of architectural, engineering, and construction (AEC) practitioners. 2) The restored sites are comparable with, or even better in certain biological groups than their natural benchmarks in species richness, abundance, Shannon-Wiener index (H’), and Simpson’s index of diversity (D). 3) The biological assemblages of the restored sites are generally quite different from their natural counterparts. The natural sites host many more species protected at the national and global levels. 4) The differences between the restored sites and the natural sites are driven by fundamental biological processes and interactions between biotic and abiotic factors of the respective sites. 5) While quantitative biodiversity indices are not well-linked to water quality and habitat quality, the Dragonfly Biotic Index (DBI) can serve as a good indicator of habitat quality. (4) Social impact assessments. The research conducted social impact assessments at three restored river sites. These assessments specifically examined public perception, visitor behaviors, overall evaluations, and recommendations for improvement. The objective was to gain insights into the social implications and effectiveness of river restoration efforts from the perspective of the local community. The key findings and conclusions from social impact assessment are listed as follows: 1) River restoration attracts urban residents to visit the restored sites more often than before, and visits involving recreational activities are higher at the low-population density sites (MWR/LTR) than those at the high-population density site (KTR). 2) The visitors generally found that the visual attractiveness of the river sites is improved after restoration, and their overall perceptions on visual attractiveness, air freshness, and auditory environment are more positive at the low-population density sites. 3) The visitors’ emotional states are significantly affected by biodiversity and the perceived visual attractiveness, air freshness, and auditory environment of the restored sites. 4) According to the feedback of the visitors, the important factors to be considered in river restoration differs between the high-population density site and the low-population density sites, but the expected facilities and features are similar. 5) Visitors from all the sites strongly prefer the involvement of local residents and other representative groups in the development of restoration projects. In this research, a comprehensive analysis was conducted to examine the aspects of water quality, hydro-morphology, biodiversity, and social impacts related to river restoration projects. Although the focus is on river restoration in Hong Kong, the lessons learned, methods employed, and the biodiversity evaluation framework developed have the potential to be applied in other compact cities. By comparing channelized, restored, and natural river sites, this research demonstrates how effectively a restored river moves away from its baseline and how close it comes to the ideal pre-disturbed state. The research findings offer valuable insights and recommendations for optimizing restoration techniques and management strategies in future river restoration projects, not only in Hong Kong but also in other compact cities. |
| Rights: | All rights reserved |
| Access: | open access |
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