지속가능한 하구역 관리 방안 (II)

Abstract

This report presents results of the second year study on development of the national environmental policies and strategies for sustainable estuarine management in Korea. While the first yearstudy focused on defining management area boundaries of 17 major estuaries, classifying estuarine types in management perspective and developing policy directions of the classified management types, this second-year study aims to establish management strategies for three representative estuaries of Han River, Youngsan River and Sumjin River, to investigate the current status of damaged estuarine wetlands, and to evaluate the environmental values of the representative estuaries. In addition, this study provides a basis for the next phase study which aims to develop an estuarine management system and a national estuary management master plan. In order to develop a national estuary management system, historical losses of estuarine wetland habitats and ecosystem values of the remaining wetlands were estimated quantitatively. The analysis of the topographical map shows that while wetlands of Han estuary decreased slightly from 218㎢(4.96% of total estuary area) in 1910s to 191 ㎢(4.35% of total estuary area) in 2000s due to the geopolitical reasons, constructinga river-mouth barrage and extensive reclamations in Youngsan estuary resulted in a significant loss of wetland from 309 ㎢(20.24% of total estuary area) to 73 ㎢((4.78% of total estuary area). Likewise, the area of wetlands of Sumjin estuary decreased from 77㎢(6.55% of total estuary area) in 1910s to 55㎢ (4.7% of total estuary area) in 2000s mainly because of the development of Gwangyang Bay. The environmental value of wetlands in Han estuary, Youngsan estuary and Sumjin estuary are estimated 39.8million, 6.37million and 17.95million Won/ha/yr respectively by benefit-transfer methods using meta-analysis. If the values are recalculated based on Contingent Valuation Method (CVM), it gets lower than them (1.22 million, 3.4 million and 9.57million Won/ha/yr, respectively) however,it still shows that the wetland annually provides 391.1billion, 24.5billion and 48.9billion Won benefit respectively for Han estuary, Youngsan estuary and Sumjin estuary. In addition, environmental value estimated from Emergy Model is 11.85 million, 5.97million and 17.63million Em/ha/yrfor Han estuary, Youngsan estuary and Sumjin estuary, respectively. These results show that well-reserved estuarine wetland and ecosystem provide considerable economic benefits even if the values can be ranged according to the estimation methods. By carrying the comprehensive investigation and analysis on the seventeenmajor estuaries in Korea, the first phase study suggests the vision, "An estuary which is a comfortable living place with vitality, biological and cultural diversity andeconomical prosperity" and twelve policy directions including developing integrated management system, sharing responsibility among stakeholders, inducing participation of local residents, guaranteeing a connection between space and the media, using the ecosystem level approach, supporting various uses, and preserving biological diversity to accomplish the vision. Based on the above policy direction, this study investigates specific environmental issues for each representative estuary and suggests proper management strategies. The management priority of Han estuary should be a protection ofof a natural estuarine ecosystem because of its domestic and international importance: The Han estuary has a huge wetland which is a habitat of 26 endangered species. It is also a center of East Asia and Australia flyway of endangered migrating birds, and for this, it became a core area to be protected for the preservation of Yellow Sea ecosystem. However, a pressure to develop this estuary has been greatly increased, due to the released tension between South and North Korea as well asgovernment support for the local development of an ordered area. Moreover, over fishing and habitat loss have caused depletion of natural resources, and deterioration of environmental quality such as an occurrence of mal-formed fishes, contamination of sediment, eutrophication and marine debris are also going to be serious issues for the Han River estuary management.Thus, it is important to manage Han estuary as "preservation of inherent estuarine ecosystem and restoration of plentiful natural resources". In order to accomplish the above goal, 5 management strategies and 27 core projects are suggested. They include a designation of ’wetland protection area’ (Han River, Ganghwa tidal flat), an application of ’total pollutantload management system’ to improve water quality,tightened land-use regulations in sensitive areas such as riparian zone, habitat quality improvement to protectvaluable natural resources such as yellow puffer, an introduction of ’development right transfer system’ to compensate tighter land-use regulation, financial supports in environmental-friendly agriculture for migratory birds, and development ofan integrated estuary management program. Youngsan estuary is one of the most environmentally-damaged estuaries in Korea due to the ’Comprehensive Youngsan River Watershed Development Project’ which resulted in development of 74,200 ha of watershed including construction of river-mouth barrage. Most of all, river-mouth barrage and accompanied reclamation caused serious negative environmental effects: changes in coastal hydrodynamic regime such asan increase of tidal range and a decrease of tidal current velocity; blocking fish migration path and estuarine circulation; decreasing ecological diversity; water quality deterioration due to the stagnation; a decrease of estuary-based socio-cultural activities. Recently, there has beena pressing demand to improve the water quality of Youngsan reservoirs from the agriculturally usable level to the level for intact water recreations and tourism. In addition, there have been efforts to restore estuarine cultures by restoring shipping channelsand associated historical sites. In these respects, this study concludes "improvement of water quality of Youngsan reservoir and restorations of ecosystem and culture" as a management goal for Youngsan estuary. In order to accomplish this goal, 28 core projects, based on 5 management strategies,are provided. Major core projects areredefining of designated water use of Youngsan reservoir, implementing of watershed and in-reservoir water quality improvement measures, modifyingriver-mouth barrage structure for restoring estuarine circulation, introducing’no net loss of natural shoreline’ policy to establish coastal eco-belt for tourism,restoration of wetlands to restore estuarine ecosystem; designation of environmental management zone for systematic land-use regulations for environmental purpose andrevival of ’Hwangpo Sailboat Festiva’l linked with the modification of river-mouth barrage as one of the local cultural arrangements. Sumjin estuary is one of the few natural estuaries still keeping a typical estuarineThe major environmental issue in thisarea is the increasing upstream seawater intrusion and associated problems of destruction of naturalcorbicula habitat and salination of ground water. Several causes of the extension of seawater intrusion were identified as decreased stream flow because of upstream dam construction, lowered stream bottom level because of the extraction of sand and gravel, and decreased Gwangyang bay volume due to the extensive coastal reclamation, but no consensus has reached between stakeholders yet.Considering this unique characteristics of Sumjin estuary, its management goal is suggested as "keeping sound estuary circulation and improvement of health of ecosystem". Like other estuaries, 27 core projects based on 5 management strategies are suggested. Examples of the core projects include removing unused stream weirsto restore stream continuity, installation of fish passages in the weirs, redefiningstream water flow in dry season, adjustment of the amount of effluent water in the upstream dam, anintroduction of ’total pollutant load management system’ in Gwangyang Bay, reconsideration of development demands arising competitively between ministries and offices, reconsideration of validity of a reclamation plan for the environmentally-friendly development in the Galsa Bay and development of integrated estuary management modeling systeme for estuary management. Although each estuary has different local conditions and environmental issues and this has led their countermeasures to be different, all estuaries have common problems in a management system. In other words, development-oriented government policy, fragmented management systems according to the media and functions, a mechanically divided environment management system (Ministry of Environment, MOE for land and Ministry of Maritime Affairs and Fisheries, MOMAF for sea), and lack of knowledge-base management. Based on the analysis of the three representative estuaries and exemplary cases of other countries, this second phase study suggests a basic structure of the estuary management system to solve those management problems that will take a concrete shape in the third phase(2006) study. Main objectives of developing estuary management system are to secure integration in estuary management, to harmonize development pressure with environment preservation, to take different characteristics of each region and category into consideration, to preserve function and value of ecosystem and to strengthen knowledge-bases for estuary management. In order to meet these objectives, this study gives following suggestions: 1) develop and implement ’Comprehensive Estuary Management Plan (CEMP)’ for major estuaries, 2) develop a formal system to solve conflicts and to facilitate negotiation between stakeholder in estuary, 3) launchjoint research projects to solve interest-conflicting estuarine issues, 4) establish ’Estuary Management Program (EMP)’ responsible for preparation of CEMP, facilitating above 2) and 3) items, estuary research, monitoring, education and outreach activities and 5) enact ’Estuary Management Act (tentatively named)’ to support development CEMP and EMP legally. This report particularly introduces three possible EMP structures in which MOE, MOMAF, or neutral agencies takes a leading role in other stakeholder’s participation. Each one has distinctive advantagesand shortfallson the connection with existing management structures, stability of fund raising, and possibility of participation of stakeholder. In addition, its practical results depend on the interest of related ministries and offices. Considering these factors, this study defers selecting final suggestion. Therefore, applicability and validity of the suggested EMP structure will be refined through several estuary forums and policy consultations with stakeholders, which are planned for the third phase study (2006). Once proper EMP structure is determined, more detail suggestions on development and operation of EMP and associated issues such as enactment of Estuary Management Act, modification of related existing laws and regulations, identification of funding sources and roles and responsibilities of participants will come naturally.