지속가능한 하구역 관리방안Ⅰ

Abstract

This report presents the results from the first year of the ongoing three-years study on development of the national environment management policies and strategies to support sustainable estuarine development in Korea. Objectives of the first year study are - to define management area boundaries of 17 major estuaries, to classify estuarine types in the management perspective, and to develop policy directions of the individual management types. Diverse approaches including field survey, existing data review, case analysis, workshops, interviews and questionnaires were employed to collect a wide range of data and stakeholder’s opinions. Management boundaries were delineated mainly by the physical, geographical, and land use characteristics of the estuaries. Landward boundaries were commonly determined by the tidal head, but seaward boundaries were defined case by case based on the geographical characteristics and land use patterns of the individual estuaries. It was also included in the management area to support watershed- based management of the main and tributary watersheds lying between the tidal head and seaward boundary. Among the 17 major estuaries, we defined 15 management areas because Ansung and Sapgeu estuaries, Mangeong and Dongjin esturies could be respectively treated as one estuarine system as Asanman estuary and Saemangeum estuary according to their common reponses on the river-mouth barrages. Socio-economic data indicates that estuaries have been excessively used and developed without considerations on the environment. Top seven largest estuaries, except for the Han Estuary which has been protected by the Demilitarized Zone ever since the Korean War, already lost their natural integrity because of the river-mouth barrage construction. About 329km2 of estuarine wetlands have been reclaimed during the last 20 years and according to the National Reclamation Plan, more than 30% of the current estuarine wetlands will be further reclaimed by the year 2011. There are 77 industrial complexes which produce about US$ 4billion/year export goods, more than 300,000 companies which comprise about 40% of national level, and 7 major national trading ports which are responsible for 46% of national capacity in the estuaries. These economic and development activities are also clearly reflected in much higher population increase rate (average 3.6%) in the estuaries than the national average (0.98%) during the last five years. A few estuaries, which are protected by the DMZ (lower part of the Han Estuary) or designated conservation area (a part of the Nakdong estuary), still have extensive wetlands and are well known as both nationally and internationally protected birds habitats. However, other estuaries were severely damaged, and thus show a very low geo-biodiversity and poor environmental quality. Most estuaries show less than 0.5 geodiversity evaluation ratio (=number of observed geomorphological features/ number of reference geomorphological features), and have lower biodiversity evaluation ratio (=number of important flora and fauna species/number of total flora and fauna species) than 0.15. Water quality (in term of BOD) ranges Grade III~IV, except for the small estuaries located on east coast, and temporal data indicate that water qualities of Sapgeu, Donjin, and Tamjin estuaries have been consistently deteriorated. Particularly, the estuaries with river-mouth barrage showed more serious environmental problems such as decrease of biodiversity and fish stock, deterioration of water quality, destruction of wetland, as well as sediment contamination. Despite the tremendous development pressure and degraded environmental quality, government efforts to protect and improve estuarine environment have remained at nominal level mainly because of the fragmented management structure and policy barriers between the responsible government agencies. So far, no integrated laws, regulations, comprehensive management plans, or partnership programs directly applicable for the estuaries have been developed at this point to overcome the problem. In addition, existing environmental management schemes and tools could not be effectively applied to estuaries because of internal constrains and poor management concepts. For example, only minor parts of estuaries are designated as protected areas, and can be covered by the mandated environment management plans. Lack of survey and research on esturine environment is one of the fundamental issues which should be resolved before developing the estuary management system. In order to develop general policy directions, firstly the 15 targeted estuaries were grouped into artificial estuaries which have river-mouth barrages and natural estuaries. The natural estuaries were further classified into tide-dominated deltaic estuary, tide-dominated estuary, and wave-dominated estuary, according to their physical settings and geomorphological characteristics. The artificial estuaries include Asanman(Ansung, Sapgeu), Geum, Saemangeum (Mangeong, Dongjin), Youngsan, and Nakdong estuaries. Except for the Han estuary which is a tide-dominated deltaic estuary, all the natural estuaries located in south coast (Tamjin, Gawha, Sumjin) and east coast (Heongsan, Taewha, Younduk, Samcuk, Gangneong, Yangyang) belong to tide-dominated and wave-dominated estuaries, respectively. Since each estuarine type has its own unique natural conditions and development circumstances, we could suggest different policy options as follows. (a) Artificial estuaries: reassessment of economic benefit and environmental cost of the existing river-mouth barrage, improvement of barrage operations, restoration of natural estuarine circulation with a modifying barrage structure, dredging of excessively accumulated or contaminated sediments, minimization of agricultural land into other higher density land use purposes, environmentally friendly development of riverside open spaces for the local residence, and development of site specific outreach and education programs. (b) Tide-dominated deltaic estuary: designation of ecosystem conservation (or wetland protection) areas, designation of riparian buffer zones(500~1,000m) along downstream of Singok submerged weir, development of estuarine management program and comprehensive management plan, planning and implementation of joint researches with the North Korean Government in DMZ, formation of special resident support funds for the protected area designation, and development of environmentally sound eco-tourism model. (c) Tide-dominated estuary: Implementation of no net-loss wetland policy, introduction of total natural coastline management system, development and application of practical management tools for the existing protected areas, development of estuary management programs, and strengthening of central government support for research and survey. (d) Wave-dominated estuary: strengthening of environmental impact assessment for the construction of coastal protection facilities, implementation of cleanup projects for the contaminated hot spots, development of a specific landmark or environmental symbol, and development watershed-based estuary management program.