• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.4
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• pp.57-68
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• 2001

It is matter of common knowledge to give impetus to the water resources development to cope with increasing demand and supply for the water utilization project including agricultural living and industrial water owing to the economic and civilization development in recent years. Regional design rainfall is necessary or the design of the dam reservoir levee and drainage facilities for the development of various kinds of essential waters including agricultural water. For the estimation of the regional design rainfall classification of the climatologically an geographically homogeneous regions should be preceded preferentially This study was mainly conducted to derive the optimal regionalization of the precipitation data which can be classified by the climatologically and geographically homogeneous regions all over the regions except Cheju and Wulreung islands in Korea. A total of 65 rain gauges were used to regional analysis of precipitation. Annual maximum series for the consecutive durations of 1, 3, 6, 12, 24, 36, 48 and 72hr were used for various statistical analysis. Both K-means clustering and mean annual precipitation methods are used to identify homogeneous regions all over the regions. Nine and five homogeneous regions for the precipitation were classified by the K-means clustering and mean annual methods, respectively. Finally, Five homogeneous regions were established by the trial and error method with homogeneity test using statistics of $\chi$$^2$ distribution.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.795-804
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• 2012

Recently, changes in rainfall intensity and patterns have been causing increasing soil loss worldwide. As a result, the water ecosystem becomes worse and crops yield are reduced with soil loss and nutrient loss with it. Many studies have been proposed to estimate runoff and soil loss to predict or decrease non-point source pollution. Although the USLE has been used for many years in estimating soil losses, the USLE cannot reflect effects on soil loss of changes in rainfall intensity and patterns. The WEPP, physically based model, is capable of predicting soil loss and runoff using various rainfall intensity. In this study, the WEPP model was simulated for sediment yield, runoff and peak runoff using data of 5, 10, 30, 60 minute term rainfall, Huff's method and design rainfall. In case of rainfall interval of 5 minutes and 60 minutes, the sediment and runoff values decreased by 24% and 19%, respectively. The peak rate runoff values decreased by 16% when rainfall interval changed from 5 minutes to 60 minutes, indicating the peak rate runoff values are affected by rainfall intensity to some degrees. As a result of simulating using Huff's method, all values (sediment yield, runoff, peak runoff) were found to be the greatest at third quartile. According to the analysis under various design rainfall conditions (2, 3, 5, 10, 20, 30, 50, 100, 200, 300 years frequency), sediment yield, runoff, and peak runoff of 906.2%, 249.4% and 183.9% were estimated using 2 year to 300 year frequency rainfall data.

• Journal of Korea Water Resources Association
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• v.31 no.6
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• pp.695-708
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• 1998

Recently, it seems increasing trends that the design floods on the middle and small scale of urban regions and natural basins are evaluated with introducing to the concept of the critical storm duration. However the study of the critical storm duration is not sufficient and especially on the natural basins, it rarely performed. therefore in this study, estimated the critical storm duration and peak discharge according to the rainfall distribution type, the position of peak rainfall intensity, and the frequency on the natural basins were evaluated using Clark model and the influence of each factors on the design floods was analyzed with sensitivity analysis on the parameters of the model.

• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.2
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• pp.36-46
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• 2009

The objective of this study is to analyze the effect of artificial soil ground on a structure. When the artificial soil ground is planted, the technical factors to be considered will be the load for buildings and the growth of plants. There are no current studies of the effect of artificial soil ground on a structure and this study will analyze the load effects of artificial soil ground, which mixes both pearlite and natural soil on structures. The load affecting the structures due to artificial soil ground will be maximized when the artificial soil ground becomes saturated, and which would occur when the rainfall intensity exceeds the infiltration capacity of the artificial soil ground. In order to determine whether the artificial soil ground has reached saturation or not, a 10 years frequency and 10 minutes rainfall intensity which is used for in urban drain design, is utilized. The hydraulic conductivity of artificial soil and mixed soil has been changed depending on the proportion of the mix, It has a range of fluctuation in the degree of hardening, in particular, but does not exceed the 10 minutes rainfall intensity over 10 years frequency in the most cases. Therefore, it would be efficient to apply the saturated unit weight of artificial soil ground as the design load of a structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.4
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• pp.537-545
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• 2018

Determination of the time parameters such as the travel time in the design flood is very important. The travel time is mainly used for flood and river management, and the travel time of non flood season is used for maintenance flow and management of the river. Estimation of travel time for natural rivers is mainly based on the geomorphological factors of the basin. In addition to the topographical factors, the travel time is calculated by considering the factors of the runoff curve, velocity and rainfall intensity. However, there is no study on the estimation of travel time considering both the rainfall condition and the soil moisture accounting by the frequency period. Therefore, the travel time calculation is divided into the case of setting the Hwanggang Dam and the Imjin bridge water level station of Imjin river as the natural river considering rainfall condition by the frequency period and the soil moisture accounting, and the case of traveling the Imjin bridge water level station according to the condition of outflow of the Hwanggang Dam. For the sections set as natural rivers, the results were verified by comparing with the newly developed travel time calculation method. Based on the results, the travel times of the Hwanggang Dam outflow conditions were calculated. The time to travel in this study can be secured flood control of the Imjin river basin and time to prepare for danger when outflowing the the Hwanggang Dam.

• Journal of Korea Water Resources Association
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• v.52 no.10
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• pp.657-669
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• 2019

To estimate accurate design quantiles considering statistical characteristics of hydrological data is one of the most important procedures in the design of hydraulic structures. While at-site frequency analysis estimates design quantile using observed data at a site of interest, regional frequency analysis (RFA) utilizes a number of sites included in a hydrologically homogeneous region. Therefore, RFA could provide a more accurate design quantile at ungauged site or sites with short observation period. In this review article, RFA is classified into stationary RFA and nonstationary RFA depending on the characteristic of hydrological data, and the basic concept, procedure, and application of each technique are explained in detail focused on the index flood method. Additionally, a review of the state of the art for RFA procedure is presented. This paper is finalized by describing the stationary regional rainfall frequency analysis over South Korea contained in the amendment of "Standard guidelines for design flood estimation" and various future study topics related to nonstationary RFA.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.3
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• pp.263-271
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• 1996

The frequency band above 20GHz is the great radio resource which has not been used. But the attenuation by atmosphere is so large that the radio systems using this frequency band must have shorter hops. There are few studies of optimal hop length for these millimetric wave radio links in Korea. In this paper we analyzed the millimetric wave propagation characteristics in atmosphere and estimated rain attenuation which have a great effect on hop length. Furthermore, we present a rainfall rate(mm/h) of the cities including Seoul and Pusan using the data collected by several rainfall gauges. This paper presents a method of obtaining the optimum hop length for millimer wave radio links based on the rain rate date.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.189-189
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• 2018

확률강우량은 수공구조물 설계, 목표강우량과 같은 방재성능목표 그리고 방재성능평가에 활용되는 기준으로 활용되고 있다. 과거 강우자료계열을 기반으로 통계분석 과정을 걸쳐 산정되는 확률강우량은 재현기간별 발생빈도에서 실제 발생한 강우량보다 과소 산정되는 문제점이 있다. 이에 본 연구에서는 강우자료를 최대치계열과 초과치계열로 구분하여 각각 확률강우량을 산정하고, 확률분포형별 확률강우량과 실제 강우량의 비교분석을 실시하였다. 또한, 실제 강우의 재현기간별 발생빈도를 기반으로 과소 추정되는 확률강우량의 문제점을 보완하는 산정방안을 제시하였다. 본 연구의 결과는 과소 추정되는 확률강우량의 문제점을 보완하여 적정 확률강우량 산정함으로써, 수공구조물 설계 및 방재성능평가에 기여할 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.44 no.10
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• pp.777-786
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• 2011

In the previous researches for storm sewer design, the flow path, pipe diameter and pipe slope were determined to minimize the construction cost. But in the sewer networks, the flows can be changed according to flow path. The current optimal sewer layout models have been focussed on satisfying the design inflow for sewer designs, whereas the models did not consider the occurrences of urban inundation from excessive rainfall events. However, in this research, the sewer networks are determined considering the superposition effect to reduce the inundation risk by controlling and distributing the inflows in sewer pipes. Then, urban inundation can be reduced for excessive rainfall events. An Optimal Sewer Layout Model (OSLM) was developed to control and distribute the inflows in sewer networks and reduce urban inundation. The OSLM uses GA (Genetic Algorithm) to solve the optimal problem for sewer network design and SWMM (Storm Water Management Model) to hydraulic analysis. This model was applied to Hagye basin with 44 ha. As the applied results, in the optimal sewer network, the peak outflow at outlet was reduced to 7.1% for the design rainfall event with 30 minutes rainfall duration versus that of current sewer network, and the inundation occurrence was reduced to 24.2% for the rainfall event with 20 years frequency and 1 hour duration.

• Journal of The Korean Society of Agricultural Engineers
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• v.60 no.1
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• pp.121-131
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• 2018

Past climate change influences multiple environmental aspects, certain of which are specifically related to agricultural water resources such as water supply and demand. Changes on rainfall and hydrologic patterns can increases the occurrence of reservoir water shortage and affect the future availability of agricultural water resources. It is a main concern for sustainable development in agricultural water resources management to evaluate adaptation capability of water supply under the changing climate and farming methods in paddy field. The purpose of this study is an evaluation method of design frequency of drought and water supply safety for agricultural reservoirs to investigate evidence of climate change occurrences at a local scale. Thus, it is a recommended practice in the development of water supply management strategies on reservoir operation under changing climate and farming methods in paddy field.