Jingul Joo

Extreme Storm Estimation by Climate Change Using Precipitable Water

In this study, probable maximum precipitation change was predicted using RCP 8.5 IPCC climate change scenario as extreme storm change. The modelling results based on average have the restriction on extreme rainfall value representation and future behavior prediction. To overcome these problems, this study uses air temperature change and precipitable water relationship in order to calculate the magnitude of probable maximum precipitation. The results showed about 40% increase in probable maximum precipitation. These were expected to use as reference of extreme storm increase such as IDF changes.

GIUH Variation by Estimating Locations

RV-GIUH must be applied at an outlet or a junction of highest order stream of a subbasin because the model was derived for basins following Horton`s ordering system. However hydrograph is calculated at various locations which does not fit to the desirable points. Therefore, some guideline is required for RV-GIUH application in practice. This study would like to suggest the outlet location criteria for appling RV-GIUH at un-gauged basin. Locations were selected by moving to upstream from outlet of Sanganmi basin and unit hydrograph using derived and simple RV-GIUH were estimated at each location. As the results, the peaks of RV-GIUH in upstream were exaggerated because of distortion of length ratio and total stream length. To avoid this error, the location must be selected at 60% downstream of highest stream length. To apply RV-GIUH at various places, equations correcting distortion of total stream length were suggested. With the correcting equations, it can be possible that RV-GIUH is applied at 20% downstream of highest stream length. Application and precision of RV-GIUH will be improved through this research.

Analysis of drought characteristics depending on RCP scenarios at Korea

This study implemented a comparison of SPI characteristics in terms of quantitative and spatial analysis depending on four RCP scenarios. For this purpose, we compared quantitative characteristics of drought using standard precipitation index resulted from daily precipitation data reflecting future green gas concentration scenarios, and spatial distribution field of seasonal drought occurrence frequency and its duration, was analyzed to compare drought trends depending on the RCP scenarios. As a result, we found that SPI time series was quite different from each other and correlation coefficients were lower than 0.08. Depending on the RCP scenarios, spatial distribution results showed different trends in drought severity, frequency, and duration. The biggest reason of the difference is daily precipitation data based on the different greenhouse gas concentrations, but we could not find the effect of the concentration extent on drought occurrence projection. In addition, according to the results from this study, drought analysis results using single RCP scenario may have considerable uncertainty.

Evaluation of Problems to Apply Runoff Curve Number to Mountain Area in Korea

This study examined problems in application process of SCS curve number method and its effect on estimating effective rainfall in mountain area. First, it was found that the mountainous area in South Korea, which has a high percentage rate of rocky surface, needs to be categorized as an area for independent land-use. When the rocky area was considered for independent land-use, SCS curve num- ber was higher than 5.75%. Thus, there is a possibility that it affects the estimate effective rainfall. Second, it is crucial to make accu- rate match for the same cover type between South Koreas and USAs employing cover type table from National Resources Conservation Service. Moreover, it is a challenge to ascertain which cover type from NRCS is suitable with Korea because most of the previous studies conducted have not provided reasons why the studies use such kind of cover type. The results on this study are useful when SCS curve number method is applied to estimate the amount of flood discharged.

Effect of Changes in Soil Maps on the Effective Rainfall Based on SCS CN Method

This study was conducted to compare characteristics of various soil maps and difference criteria of hydrologic soil group in detail. As a result, it was found that hydrologic soil groups between reconnaissance and detailed soil map has a large difference. There are also differences in the three different detailed soil maps. Likewise, the difference of hydrologic soil group is the result of a huge difference in the runoff curve number. Three soil maps were studied to examine the effect of changes in soil maps on effective rainfall calculation for Pyeongchang river basin. It was found that the runoff curve number is varied depending on the detailed soil map, even though it was in the same basin. The difference between maximum and minimum runoff curve number was higher than 13 depending on the detailed soil map. Consequently, a change of soil map has a decisive effect on the runoff curve number, so it is possible that the changes affect the estimates of flood runoff discharge.

A Study on Heavy Rain Forecast Evaluation and Improvement Method

우리나라의 호우특성은 단기간에 발생하는 국지성 집중호 우가 주를 이루고 있으며 이에 따른 피해가 매년 증가하고 있 다. 현재 기상청에서는 호우발생으로 인한 피해를 최소화 하 고, 예상되는 호우에 대응, 대비하기 위해 호우특보 기준을 호 우주의보(Heavy Rain Watch)와 호우경보(Heavy Rain Warning) 로 구분하여 운영하고 있다. WMO(1992)의 호우주의보는 호 우로 인한 피해가 예상될 때 일반 국민이나 관계기관에 주의 를 상기시키며, 호우경보는 호우로 인한 대규모 피해가 예상 될 경우 일반 국민이나 관계기관에 경고하기 위하여 기상청 에서 발표하는 기상특보이다. 그러나 우리나라의 호우특보는 예측강우량의 산정을 위한 레이더의 중요성만을 강조하고 있 을 뿐 기상청의 호우특보 발령기준에 대한 정확도 검토등의 연구는 미비한 실정이다. Kim et al.(2009)은 우리나라의 재산 피해액과 기상청 호우 특보 기준에 따른 관계를 조사하여 지역별 강우강도의 연관 성을 분석하고 재해피해발생 강우량을 제시하였으며 Takahashi Abstract

Evaluation and Calibration Method Proposal of RCP Daily Precipitation Data

This study evaluated RCP scenarios daily precipitation data from the regional climate model and proposed the calibration method ofRCP data for hazard mitigation field. Three data, observed daily precipitation in 2001~2013, RCP scenarios daily precipitation insame period with observed data, and RCP scenarios daily precipitation in 2014~2100, was applied to examine the statistical char-acteristics of each data. As a result, it found that RCP scenarios data properly reflected climate characteristics in the Korean Pen-insula for annual precipitation and monthly precipitation distribution, except number of days with precipitation overestimated. Tocalibrate the problem, this study proposed the method which daily precipitation less than a threshold (0.6~1.7 mm) is considered as norain. The result after calibration has shown that calibrated RCP scenarios data properly reflected climate characteristics in the KoreanPeninsula for annual average number of days with precipitation and the distribution of monthly number of days with precipitation.Key words : Climate change, RCP, Daily precipitation, Number of days with precipitation

A Study on Urban Flood Vulnerability Assessment

Urban flood inundation by poor interior drainage systems causes annually the significant loss of life and properties in Korea. The inundation vulnerability assessment is important for policy establishment and priority decision of disaster management policy. In this study, an assessment model was developed for urban vulnerable areas. An assessment model was applied to arithmetic Urban flood vulnerability assessment and Urban flood vulnerability assessment using Promehtee(Preference Ranking Organization Method for Enrichment Evaluation). Assessment factors that directly affect urban flood were selected to lowland area, length of poor drainage sewer, and curve number. The results of assessment, inundation records are in concordance with arithmetic urban flood vulnerability assessment method about 75% and urban flood vulnerability assessment using Promehtee about 58.3%. In this study, arithmetic urban flood vulnerability assessment method using assessment factors that directly affect urban flood was confirmed by accuracy.

Standard-Rainfall and Capacity of Intercepting Sewer to Control CSOs

The combined sewer overflows(COSs) which enters to river are involved with water pollution of rivers. Therefore, the standard capacity should be decided in proper standard considering water pollution density and characteristic of outflow. But in domestic, the standard capacity is not considered the characteristics of rainfall-outflows and is applied uniformly in all areas. The standard is triple of a maximum amount of sewage per one hour ; 3Q. The outflow of 3Q enters to sewage treatment plant and the overflows enter to river. In this study, a standard rainfall is estimated to determine the capacity of intercepting sewer by statistical analysis of rainfall data and it is considered about the regional characteristic of the rainfall-outflow. The standard rainfall is analyzed through the data of Seoul. In the result the standard rainfall was 6.76mm of 4hr duration. The rainfall-outflows and CSOs are analyzed using SWMM(Storm Water Management Model).

Analysis of quality improvement effects by construction of sewer systems in Nam River Basin

Effects of establishments of more sewer systems on water quality in Nam River, Deokchun River, and Jinyang Lake were analyzed for various scenarios using QUAL2E, WASP 7 water quality model. Three different scenarios were tested: 1) 20.8% of sewer diffusion rate which is same to the existing condition. 2) Expansion of sewer system to 65.2% which would emit less pollutants, BOD 2350.5 kg/d, TN 216.0 kg/d, TP 44.0kg/d. 3) Pollutants emission to maintain first grade water quality in Nam River, Jinyang Lake, BOD and TN in the case 2 were 7.69%, 2.10% lower than those in the case 1 in the Nam River. And in the Jinyang Lake, BOD, TN, and TP in the case 2 were 10.25%, 1.37%, 2.94% lower than those in the case 1. However the simulations showed that water quality could not hold down first grade water quality standard level with the establishments of more sewer systems. To satisfy the criteria in the Nam River and Jinyang Lake, BOD emission must be reduced 27.2%, 37.05% compared to those in the case 1.