Studies on Biodiversity of Fishes at Gyeongan streams in the Applications of Landscape Indices and Impervious Cover Model

Abstract

본 연구에서는 경안천 유역의 5개 소유역을 대상으로 1) 원격탐사 및 지리정보시스템 기법을 이용하여 시공간적 불투수면 변화를 조사하였고, 2) 경관 분석 프로그램인 FRAGSTATS를 이용하여 불투수면 변화에 따른 경관 지수를 산정하였으며, 3) 대상유역의 불투수면 모델 적용성을 평가하였으며, 4) 불투수면이 수환경과 수생태계에 미치는 영향을 분석하였다. 본 연구를 통해 유역의 토지이용계획에 경관생태학적 불투수면 관리를 위한 기초정보를 제공하며, 향후 하천 개발 전, 후의 효과 평가나 각종 도시개발사업 계획 시 수생태적 지표를 개발하여 이를 유역관리에 활용해야 한다는 인식을 새롭게 한 점에서 그 의의가 있다고 하겠다. 또한, 국내 유역 특성을 고려한 불투수면 지표 모델 연구를 통하여 불투수면 저감방안 수립 및 유역관리 등에 효과적으로 활용할 수 있을 것으로 기대된다.;Impervious cover has been used as an effective indicator in basin management, and the impervious cover model is a tool to evaluate the soundness of rivers in line with the ratio of impervious cover to manage sub-watersheds within a basin. Also, landscape indices such as the number of pieces (patches), the total length of the perimeter and the density of the perimeter of impervious cover in a basin are tools to evaluate the impact on the runoff and water quality of the basin. In addition, the soundness of the aquatic ecosystem is used as an environmental indicator that shows the quality of a basin. Therefore, for basin management, it is necessary to study impervious cover and to apply the impervious cover model, and it is also urgently needed to analyze its impacts on the aquatic environment and ecosystem in a diversified and comprehensive manner. This study conducted on five sub-watersheds in the Gyeongan Stream watershed 1) studied the changes of impervious cover in terms of time and space using the remote sensing and the geographical information system techniques, 2) calculated landscape indices in line with the changes of impervious cover using FRAGSTATS, a landscape analysis program, 3) evaluated the applicability of the impervious cover model in the basin studied, and 4) analyzed the impact of impervious cover on the aquatic environment and ecosystem. To analysis the changes of impervious cover in the basin, the image data from 1975 to 2000 provided by WAMIS, a national water resource information system, was used and analyzed with the cycle of five years. The ratio of the impervious area in the Gyeongan Stream watershed increased by more than eight times from 0.87% in 1975 to 7.0% in 2000 and again increased to 11.23% in 2006, which shows urbanization progressed rapidly in the region. According to the FRAGSTATS analysis that quantified the landscape structure, the fragmentation index of impervious cover increased by around 4.5 times from 647 in 1975 to 2,916 in 2000, which showed that due to the changes in land use with rapid urbanization and land development in the 1980S, fragmentation progressed significantly. The landscape form analysis quantifies the form of the landscape based on the complexity of the form of patches, which increased by more than 2.3 times from 1975 to 2000, showing that the form of the landscape is changing more non-structurally. Among sub-watersheds in the Gyeongan Stream watershed, the upper reaches and the middle reaches showed higher fragmentation than other sub-watersheds, and thus it is judged that they have significantly undergone urbanization. In application of the impervious cover model, Biochemical Oxygen Demand (BOD) was used as the indicator of water quality among the water quality data of the Gyeongan Stream watershed. And Total Core Area (TCA) was used as the indicator of biodiversity and was compared to the number of fish species actually appearing in the Gyeongan Stream watershed. As a result, it was found that if the impervious ratio covers around 6% even in the sensitive state (the ratio of impervious cover being less than 10%), the condition worsens. TCA (Total Core Area) and the number of appearing fish species tended to decrease in line with the impervious ratio, and the result of monitoring the types of species inhabiting the basin showed that the species that live in clean water more frequently appeared in the area with less impervious ratio. Since it will negatively impact water quality and landscape ecological changes if the urbanization ratio exceeds 25% and the quality of the river worsens to the state of ‘impacted’, it is judged that continued management and countermeasures are required. As such, the impervious cover model and the landscape index are useful tools to diagnose the overall state of the water body in line with the changes of impervious cover and to evaluate the performance of basin management. This study is meaningful in that it provides the basic information for landscape ecological management of impervious cover to the land use planning in the basin, and it renewed the recognition that aquatic ecological indicators should be developed for the assessment of the impact before and after development of rivers and for planning of various urban development projects and be utilized for basin management. Also, the study of the impervious cover indicator model that took into consideration the characteristics of domestic basins is expected to be effectively utilized for establishment of measures to reduce impervious cover and basin management.