• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1004-1009
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• 2011

Soil erosion in North Korea has been continued to accelerate by deterioration of topographical conditions. However, few studies have been conducted to predict the amount of soil loss in North Korea due to limited data so far. Rainfall erosivity is an important factor to predict the amount of long-term annual soil loss by USLE (universal soil loss equation). The purpose of this study is to investigate rainfall erosivity, which presented the potential risk of soil erosion by water, in North Korea. Annual rainfall erosivities for 27 stations in North Korea for 1983~2010 were calculated using regression models based on modified Institute of Agricultural Sciences (IAS) index in this study. The result showed that annual average rainfall erosivity in North Korea ranged from 2,249 to 7,526 and averaged value was $4,947MJmm\;ha^{-1}\;hr^{-1}\;yr^{-1}$, which corresponded to about 70% of annual average rainfall erosivity in South Korea. The finding was that the potential risk of soil erosion in North Korea has been accelerated by the increase of rainfall erosivity since the late 1990s.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.221-229
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• 2008

This study revised a model for hydrologically analyzing rainwater harvesting facilities considering their rainfall-runoff properties and the data available. This model has only a few parameters, which can be estimated with rather poor measurements available. The model has a non-linear module for rainfall loss, and the remaining rainfall excess (effective rainfall) is assumed to be inflow to the storage tank. This model has been applied for the rainwater harvesting facilities in Seoul National University, Korea Institute of Construction Technology, and the Daejon World Cup Stadium. As a result, the runoff coefficients estimated were about 0.9 for the building roof as a rainwater collecting surface and about 0.18 for the playground. This result is coincident with that for designing the rainwater harvesting facilities to show the accuracy of model and the simulation results.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1101-1106
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• 2004

Rainfall induced landslides are disasters causing sever damage on the human life and the infrastructures. In this paper, a simplified procedure to evaluate the slope stability problems induced by rainfall by modifying the Iverson's pressure head dispersion model. The proposed approach extends the applicability of the Iverson's model in to the cases of higher rainfall intensity than the permeability of the soil by incorporating the existence of overland flow. In addition, the Manning equation is applied to calculated the depth of overland flow. From the calculated depth of overland flow, shear stress acting on the surface is included for the driving component triggering the landslides. From the analysis of a case study, the long term rainfall alters the stability of slope.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.39-52
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• 2020

A high quality, long-term, high-resolution precipitation dataset is an essential in climate analyses and global water cycles. Rainfall data from station observations are inadequate over many parts of the world, especially North Korea, due to non-existent observation networks, or limited reporting of gauge observations. As a result, satellite-based rainfall estimates have been used as an alternative as a supplement to station observations. The Climate Hazards Group Infrared Precipitation (CHIRP) and CHIRP combined with station observations (CHIRPS) are recently produced satellite-based rainfall products with relatively high spatial and temporal resolutions and global coverage. CHIRPS is a global precipitation product and is made available at daily to seasonal time scales with a spatial resolution of 0.05° and a 1981 to near real-time period of record. In this study, we analyze the applicability of CHIRPS data on the Korean Peninsula by supplementing the lack of precipitation data of North Korea. We compared the daily precipitation estimates from CHIRPS with 81 rain gauges across Korea using several statistical metrics in the long-term period of 1981-2017. To summarize the results, the CHIRPS product for the Korean Peninsula was shown an acceptable performance when it is used for hydrological applications based on monthly rainfall amounts. Overall, this study concludes that CHIRPS can be a valuable complement to gauge precipitation data for estimating precipitation and climate, hydrological application, for example, drought monitoring in this region.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1B
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• pp.1-11
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• 2010

In this study, To analyzed the monthly long-term change characteristics of Chukwooki rainfall data set (CWK) and modern rain gage rainfall data set (MRG), tests of trend or variation were performed of each data sets using five statistical trend or variation test method. furthermore, changing characteristics of rainfall was analyzed through the accomplishment of the 2-dimensional LOWESS regression (or smoothing) which can consider both annual time-variation and inter-monthly time-variation. From the trend test, it is difficult to confirm that given data sets have significant trends. From the 2-dimensional LOWESS analysis for four rainfall characteristics, after near A.D. 1980, inter-monthly variation width in addition to quantative increment of rainfall are increased rapidly and persistently.

• Journal of Korea Water Resources Association
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• v.41 no.7
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• pp.747-759
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• 2008

This study, a point rainfall process model, which could represent appropriately observed rainfall data, was to select. The point process models-rectangular pulses Poisson process model(RPPM), Neyman-Scott rectangular pulses Poisson process model(NS-RPPM), and modified Neyman-Scott rectangular pulses Poisson process model(modified NS-RPPM)-all based on Poisson process were considered as possible rainfall models, whose statistical analyses were performed with their simulation rainfall data. As results, simulated rainfall data using the NS-RPPM and the modified NS-RPPM represent appropriately statistics of observed data for several aggregation levels. Also, simulated rainfall data using the modified NS-RPPM shows similar characteristics of rainfall occurrence to the observed rainfall data. Especially, the modified NS-RPPM reproduces high-intensity rainfall events that contribute largely to occurrence of natural harzard such as flood and landslides most similarly. Also, the modified NS-RPPM shows the best results with respect to the total rainfall amount, duration, and inter-event time. In conclusions, the modified NS-RPPM was found to be the most appropriate model for the long-term simulation of rainfall.

• Journal of Korea Water Resources Association
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• v.53 no.4
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• pp.237-247
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• 2020

The purpose of this study is to analyze whether design rainfall and hyetograph, which are the main elements of design rainfall, can properly reflect the those of observed rainfalls through inundated rainfall events. The target areas were selected at seven large cities with high damages regarding to the flooding. Comparative analysis between probability and observed rainfall shows that 57% of the cases, in which rainfall amount through the IDF curve is estimated lower than the observed rainfall, do not properly reflect the observed rainfalls. In particular, this trend is exacerbated by the cases in low return period and the rain type of typhoon or frontal rain. The comparative results of rainfall intensity formula showed that the Talbot and Japanese formula were stable in the short- and long-term return periods, respectively. The comparison of hyetograph results also showed that the Mononobe method properly reflects the maximum rainfall intensity and the Huff method properly reflects the shape of rainfall pattern.

• Water for future
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• v.9 no.2
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• pp.76-86
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• 1976

The 30-year design flood hydrograph for the Musim Representative Basin, one of the study basins of the International Hydrological Program, is synthesized by the method of unit hydrograph. The theory of unit hydrograph has been well known for a long time. However, the synthesis of flood hydrograph by this method for a basin with insufficient hydrologic data is not an easy task and hence, assumptions and engineering judgement must be exercized. In this paper, the problems often encountered in applying the unit hydrograph method are exposed and solved in detail based on the theory and rational judgement. The probability rainfall for Cheonju Station is transposed to the Musim Basin since it has not been analyzed due to short period of rainfall record. The duration of design rainfall was estimated based on the time of concentration for the watershed. The effective rainfall was determined from the design rainfall using the SCS method which is commonly used for a small basin. The spatial distribution of significant storms was expressed as a dimensionless rainfall mass curve and hence, it was possible to determine the hyetograph of effective design storm. To synthesize the direct runoff hydrograph the 15-min. unit hydrograph was derived by the S-Curve method from the 1-hr unit hydrograph which was obtained from the observed rainfall and runoff data, and then it was applied to the design hyetograph. The exsisting maximum groundwater depletion curve was derived by the base flow seperation. Hence, the design flood hydrograph was obtained by superimposing the groundwater depletion curve to the computed direct runoff hydrograph resulting from the design storm.

• Environmental Engineering Research
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• v.18 no.1
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• pp.9-20
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• 2013

In this paper, the rainfall elasticity of streamflow was estimated to quantify the effects of climate change on 5 river basins. Rainfall elasticity denotes the sensitivity of annual streamflow for the variations of potential annual rainfall. This is a simple, useful method that evaluates how the balance of a water cycle on river basins changes due to long-term climate change and offers information to manage water resources and environment systems. The elasticity method was first used by Schaake in 1990 and is commonly used in the United States and Australia. A semi-distributed hydrological model (SLURP, semi-distributed land use-based runoff processes) was used to simulate the variations of area streamflow, and potential evapotranspiration. A nonparametric method was then used to estimate the rainfall elasticity on five river basins of Korea. In addition, the A2 (SRES IPCC AR4, Special Report on Emission Scenarios IPCC Fourth Assessment Report) climate change scenario and stochastic downscaling technique were used to create a high-resolution weather change scenario in river basins, and the effects of climate change on the rainfall elasticity of each basin were then analyzed.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.59-72
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• 1987

Although long-term runoff analysis is important as much as flood analysis in the design of water works, the technological level of the former is relatively lower than that of the latter. In this respect, the precise estimation model for the volume of successive runoff should he developed as soon as possible. Up to now, in Korea, Gajiyama's formula has been widely used in long-term runoff analysis, which has many problems in applying in real situation. On the other hand, in flood analysis, unit hydrograph method has been exclusively used. Therefore, this study aims at trying to apply unit hydrograph method in long-term runoff analysis for the betterment of its estimation. Four test catchment areas were selected ; Maesan area in Namlum river as a representative area of Han river system, Cheongju area in Musim river as one of Geum river system, Hwasun area in Hwasun river as one of Yongsan river system, and Supyung area in Geum river as one of Nakdong river system. In the analysis of unit hydrograph, seperation of effective rainfall was carried out firstly. Considering that effective rainfall and moisture condition of catchrnent area are inside and outside of a phenomenon respectively and the latter is not considered in the analysis, Initial base flow(qb)was selected as an index of moisture condition. At the same time, basic equation(Eq.7) was established, in which qb can take a role as a parameter in relating between cumulative rainfall(P) and cumulative loss of rainfall(Ld). Based on the above equation, computer program for estimation model of qbwas seperately developed according to the range of qb, Developed model was applied to measured hydrographs and hyetographs for total 10 years in 4 test areas and effective rainfall was estimated. Estimation precision of model was checked as shown in Tab- 6 and Fig.8. In the next stage, based on the estimated effective rainfall(R) and runoff(Qd), a runoff distribution ratio was calculated for each teat area using by computerised least square method and used in making unit hydrographs in each test area. Significance of induced hydrographs was tested by checking the relative errors between estimated and measured runoff volume(Tab-9, 10). According to the results, runoff estimation error by unit hydrograph itself was merely 2 or 3 %, but other 2 or 3 % of error proved to be transferred error in the seperation of effective rainfall. In this study, special attentioning point is that, in spite of different river systems and forest conditions of test areas, standardized unit hydrographs for them have very similar curve shape, which can be explained by having similar catchinent characteristics such as stream length, catchinent area, slope, and vegetation intensity. That fact should be treated as important factor ingeneralization of unit hydrograph method.