Seung Jin Hong

Regional Frequency Analysis for Future Precipitation from RCP Scenarios

(Received: 2 February 2015, Revised: 4 February 2015, Accepted: 13 February 2015)요 약기후변화로 인해 강우 패턴과 강우강도의 변동성이 커지고 있으며, 도시화 및 산업화에 따른 불투수면적의 증가로 인해, 집중호우에 따른 도시침수와 홍수피해가 심화될 것으로 예상하고 있다. 따라서 본 연구에서는 홍수방어 대안 설정을 위한 설계 강수량(design rainfall) 또는 확률강수량에도 변화가 예상되므로 지역빈도해석을 통해 미래 확률강수량을 산정 및 분석하고자 한다. 기상청 산하 30년 이상의 관측치를 갖고 있는 58개 지점을 대상으로 과거 관측자료를 수집하고, 기후변화를 고려한 미래 확률강수량 추정을 위해 대표농도경로(RCP) 시나리오에 의한 강수량 자료를 이용하여 지역빈도해석을 실시하였다. 기후변화에 따른 강수량 자료의 편의를 제거하기 위하여 분위사상법(Quantile Mapping) 및 이상치 검정을 실시하였다. Hosking and Wallis(1997)가 제시한 L-moment방법을 이용하여 지역빈도해석을 실시하였으며, 80년, 100년, 200년 빈도에 대한 미래 목표기간별 확률강수량을 산정하였다. 그 결과 21세기 말에 전국의 확률강수량이 현재의 관측 확률강수량에 비해 25 ∼ 27% 상승하는 것으로 예측되며, 특히, 제주도 지역이 가장 크게 증가하는 것으로 분석되었다. 따라서 미래 기후변화로 인한 강수량의 증가와 도시화에 따른 유출특성 변화로 자연재해 발생 및 피해는 더욱 증가할 것으로 예상되며, 미래 홍수안전도를 위한 대비책 마련이 필요할 것으로 판단된다.핵심용어: 기후변화, 대표농도경로(RCP) 시나리오, 지역빈도해석, 확률강수량AbstractVariability of precipitation pattern and intensity are increasing due to the urbanization and industrialization which induce increasing impervious area and the climate change. Therefore, more severe urban inundation and flood damage will be occurred by localized heavy precipitation event in the future. In this study, we analyze the future frequency based precipitation under climate change based on the regional frequency analysis. The observed precipitation data from 58 stations provided by Korea Meteorological Administration(KMA) are collected and the data period is more than 30 years. Then the frequency based precipitation for the observed data by regional frequency analysis are estimated. In order to remove the bias from the simulated precipitation by RCP scenarios, the quantile mapping method and outlier test are used. The regional frequency analysis using L-moment method(Hosking and Wallis, 1997) is performed and the future frequency based precipitation for 80, 100, and 200 years of return period are estimated. As a result, future frequency based precipitation in South Korea will be increased by 25 to 27 percent. Especially the result for Jeju Island shows that the increasing rate will be higher than other areas. Severe heavy precipitation could be more and more frequently occurred in the future due to the climate change and the runoff characteristics will be also changed by urbanization, industrialization, and climate change. Therefore, we need prepare flood prevention measures for our flood safety in the future.Key words:Climate Change, RCP Scenarios, regional frequency analysis, frequency based precipitation

Impact of Climate Change on Habitat of the Rhynchocypris Kumgangensis in Pyungchang River

Abstract This study tried to analyze the impact of climate change on ecological habitat. In this regard, the Rhynchocypris Kumgangensis was selected among the CBIS(Climate-sensitive Biologocal Indicator Species) suggested by the Ministry of Environment. And ecological habitat and restrictive conditions for its survival was surveyed. Future runoff and water quality in the upstream of Pyungchang river were simulated by appling climate change scenarios to SWAT model which is able to simulate water quality. The estimated results explained characteristics on the increase of runoff, BOD, and water temperature and the decrease of DO in the future. The restrictive condition on ecological habitat of the Rhynchocypris Kumgangensis was used water quality during the April to May spawning season since BOD and DO were satisfactory as the first grade of water criteria in the estimated result of future water quality. As a result, it was analyzed that habitat of the Rhynchocypris Kumgangensis in the present was possible about 50~60% of the river. But the habitat would be decreased gradually in the future and would be possible in a very small part of the river in the long term.

Effectiveness Analysis of Artificial Wetland for Flood Reduction

Wetlands have various functions such as water purification, disaster management, habitat of creature, climate change management, etc. Constructed wetland has been introduced as an alternative especially for flood control in the river basin, because it can reduce flood stage as well as improve water quality. However, the previous studies only focused on the function of water quality improvement and ecological function of biodiversity, and the studies on the flood control effects according to artificial wetlands including channel-type wetlands have not yet been carried out. In this study, we compared and analyzed the flood inundation by doing comparative analysis on flood level change before and after creation of constructed wetlands. For this study, outflow of study area were calculated using HEC-HMS model, and we investigated the change in flood stage before and after creation of constructed wetlands using HEC-RAS model by modeling artificial wetland. The results showed that flood stage after wetland construction was decreased and the reduced stages were maximum 0.81 m, average 0.11 m when we compared with flood stage before wetland construction. Also, flood inundation mapping results showed that the total area of inundation was also decreased in about 1,994,000 m 2 after wetland construction, and so this study has shown that the artificial wetland can reduce flood stage in Mokgamcheon basin.

Future Climate Data from RCP 4.5 and Occurrence of Malaria in Korea

Since its reappearance at the Military Demarcation Line in 1993, malaria has been occurring annually in Korea. Malaria is regarded as a third grade nationally notifiable disease susceptible to climate change. The objective of this study is to quantify the effect of climatic factors on the occurrence of malaria in Korea and construct a malaria occurrence model for predicting the future trend of malaria under the influence of climate change. Using data from 2001–2011, the effect of time lag between malaria occurrence and mean temperature, relative humidity and total precipitation was investigated using spectral analysis. Also, a principal component regression model was constructed, considering multicollinearity. Future climate data, generated from RCP 4.5 climate change scenario and CNCM3 climate model, was applied to the constructed regression model to simulate future malaria occurrence and analyze the trend of occurrence. Results show an increase in the occurrence of malaria and the shortening of annual time of occurrence in the future.

Water Quality Analysis of Hongcheon River Basin Under Climate Change

Impacts of climate change are being observed in the globe as well as the Korean peninsula. In the past 100 years, the average temperature of the earth rose about 0.75 degree in celsius, while that of Korean peninsula rose about 1.5 degree in celsius. The fifth Assessment Report of IPCC(Intergovermental Panel on Climate Change) predicts that the water pollution will be aggravated by change of hydrologic extremes such as floods and droughts and increase of water temperature (KMA and MOLIT, 2009). In this study, future runoff was calculated by applying climate change scenario to analyze the future water quality for each targe period (Obs : 2001 ∼ 2010, TargetI: 2011 ∼ 2040, Target II: 2041 ∼ 2070, TargetIII : 2071 ∼ 2100) in Hongcheon river basin, Korea. In addition, The future water quality was analyzed by using multiple linear regression analysis and artificial neural networks after flow-duration curve analysis. As the results of future water quality prediction in Hongcheon river basin, we have known that BOD, COD and SS will be increased at the end of 21 century. Therefore, we need consider long-term water and water quality management planning and monitoring for the improvement of water quality in the future. For the prediction of more reliable future water quality, we may need consider various social factors with climate components.

The Impact Assessment of Climate Change on the Long-Term Runoff on the Han River in South Korea Based on RCP Climate Change Scenarios

The 2007 World Economic Forum (WEF) referred to climate change as the overriding problem we face. Concerns have been raised about how global warming would accelerate future climate change and its consequences. Many climate change studies expect the possible occurrence of extreme high temperature and increase in heavy rains and strong typhoons in the near future. Currently, climate change scenarios are used to prepare an appropriate plan for these phenomena under climate change. The main purpose of this paper is to suggest and evaluate an operational method of assessing the potential impact of climate change on hydrologic components and water resources at the regional scale. Future runoff was simulated using high resolution RCM (12.5 km X 12.5 km) RCP scenario operated by the Korea Meteorological Administration (KMA) and a semi-distribution model or SLURP. The study was carried out on the Han River including its nine dams. The study found that runoff characteristics, especially annual distribution, could change. The discharge in July tends to decrease while runoff can increase in August and September. The flow duration curve was estimated and compared with observed data and simulated daily runoff data for Paldang-dam to evaluate the effect of climate change. The analysis of the flow duration curve shows that the mean average low flow increased while the average wet and normal flow decreased under the climate change scenario.

Impact of Climate Change on Flood Discharge and Flood Stage in the River Basin

In the recent years, extreme weather events due to the climate change has been frequently occurred over the world. Meanwhile, Korean peninsula has been suffered from the natural disasters such as floods and droughts. Especially, in Korea, the flood damage tends to be increasing rapidly. Therefore, it is necessary to estimate the flood discharge and flood stage under climate change for the purpose of the reduction of flood damage. This study is to assess the impact of climate change on flood discharge and flood stage in Sumjin river basin, Korea. Sumjin, Yochun, and Bosung rivers are selected for this study, and these are the areas in which the model is constructed and applied. SRES A1B climate change scenarios, provided by the IPCC for the simulation of future climate data, were applied for the four different targets periods (Target I : 1971∼2010, Target II : 2011∼2040, Target III : 2041∼2070, Target IV : 2071~2100) and HEC-GeoHMS and HEC-HMS models are used to estimate flood discharge for each target period. Then HEC-RAS model is served for investigating the variation of flood stage due to the climate change at Songjung station which is located in the basin outlet. The results are compared and examined with the previous studies that climate change was not considered. Those results could be used as the basic information for the future disaster prevention planning under climate change.

A comparative study on the simple Two-parameter monthly water balance model and Kajiyama formula for monthly runoff estimation

ABSTRACT A two-parameter monthly water balance model to simulate runoff can be used for a water resources planning programme and climate impact studies. However, the model estimates two parameters of transformation of time scale (c) and of the field capacity (SC) by a trial-and-error method. This study suggests a modified methodology to estimate the parameters c and SC using the meteorological and geological conditions. The modified model is compared with the Kajiyama formula to simulate the runoff in the Han River and International Hydrological Programme representative basins in South Korea. We show that the estimated c and SC can be used as the initial or optimal values for the monthly runoff simulation study in the model. EDITOR M.C. Acreman; ASSOCIATE EDITOR S. Kanae

A Regionalization of Downscaled GCM Data Considering Geographical Features in a Mountainous Area

This study establishes a methodology for the application of downscaled GCM data in a mountainous area having large spatial variations of rainfall and attempts to estimate the change of rainfall characteristics in the future under climate change. The Namhan river basin, which is in the mountainous area of the Korean peninsula, has been chosen as the study area. neural network-simple kriging with varying local means (ANN-SKlm) has been built by combining the artificial neural network, which is one of the general downscaling techniques, with the SKlm regionalization technique, which can reflect the geomorphologic characteristics. The ANN-SKlm technique was compared with the Thiessen technique and the ordinary kriging (OK) technique in the study area and the SKlm technique showed the best results. Future rainfall levels have been predicted by downscaling the data from CNRM-CM3 climate model, which was simulated under the A1B scenario. According to the results of future annual average rainfall by each regionalization technique, the Thiessen and OK techniques underestimated the future rainfall when compared to the ANN-SKlm technique. Therefore this methodology will be very useful for the prediction of future rainfall levels under climate change, most notably in a mountainous area.