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Strategic environmental assessment (SEA), with its most important contribution of promoting integrated decision-making towards sustainability, is increasingly accepted as a decision support tool all over the world. Some problems in SEA, however, are still found including environmental impact identification, quantitative assessment and prediction of cumulative effect in SEA practice, and are the obstruction for SEA’s research, practice and implementation considerably. Many attempts have been taken in order to improve SEA’s approach as well as its instrument. But most of which are still of limited contribution to SEA, and can not ensure SEA’s integrity and validity scientifically. In this context, retrospective assessment in SEA was proposed.Based on the principles of sustainable development, ecosystem-based management and the support of decision-making as well as the review of SEA approaches and retrospective assessment, this thesis initially developed the theoretical framework and approaches of retrospective assessment in SEA. The main results were as follows:Firstly, the definition and theoretical system of retrospective assessment in SEA were proposed for the first time. After examining its scope, content and emphasis, a framework and corresponding characteristics of retrospective assessment in SEA were developed. The retrospective assessment in SEA could resolve the problems of environmental impact identification, quantitative prediction and cumulative effect assessment in SEA because it conformed effectively to SEA’s inherent essences and characteristics of comprehensiveness, regionality, sustainability and uncertainty.Secondly, the framework of retrospective assessment proposed was applied into two SEA case studies. One was SEA for reclamation planning of bays, and the other was SEA for hydrological engineering planning of watershed. The results of retrospective assessment in the first case showed significant cumulative effects including that tidal flux and current velocity decreased considerably which resulted in the reduction of environmental capacity; and the changes of current pattern, sedimentation rate and sediment environment caused the deposition of main channel, 73% decrease of yield of Chinese limulus, and disappearance of lancelet fishery. The probability and loss of risks such as disasters of typhoon, storm surge, oil spill and red tide in history were summarized by the retrospective assessment in the first case study for the risk assessment. While the results of retrospective assessment in the second case showed that the flow velocity and self-purification capacity decreased due to the construction of hundreds of dams in recent ten years; the rate of sand transportation dropped which caused estuarine erosion; natural aquatic ecosystem and fishery in the watershed were destroyed completely, and migrating species disappeared. It was concluded that these remarkable results and effects could be found only by applying retrospective assessment.Finally, based on theoretical and practical study, the thesis demonstrated comprehensively and systematically the advantages and roles of retrospective assessment in SEA, including impact source analysis, environmental impact identification, environmental trend analysis, environmental effect assessment, cause-effect mechanism study, cumulative effect assessment, social and economic effect study, environmental risk assessment, public participation, quantitative prediction, as well as the support for decision-making and management. As a result, the technical framework containing approach and methodology of retrospective assessment in SEA was set up. It would improve the SEA system scientifically.
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