• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.260-260
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• 2016

Soil erosion is a very serious problem from agricultural as well as environmental point of view. Various computer models have been used to estimate soil erosion and assess erosion control practice. Universal Soil loss equation (USLE) is a popular model which has been used in many countries around the world. Erosivity (USLE R-factor) is one of the USLE input parameters to reflect impacts of rainfall in computing soil loss. Value of R factor depends upon Energy (E) and maximum rainfall intensity of specific period ($I30_{max}$) of that rainfall event and thus can be calculated using higher temporal resolution rainfall data such as 10 minute interval. But 10 minute interval rainfall data may not be available in every part of the world. In that case we can use hourly rainfall data to compute this R factor. Maximum 60 minute rainfall ($I60_{max}$) can be used instead of maximum 30 minute rainfall ($I30_{max}$) as suggested by USLE manual. But the value of Average annual R factor computed using hourly rainfall data needs some correction factor so that it can be used in USLE model. The objective of our study are to derive relation between averages annual R factor values using 10 minute interval and hourly rainfall data and to determine correction coefficient for R factor using hourly Rainfall data.75 weather stations of Korea were selected for our study. Ten minute interval rainfall data for these stations were obtained from Korea Meteorological Administration (KMA) and these data were changed to hourly rainfall data. R factor and $I60_{max}$ obtained from hourly rainfall data were compared with R factor and $I30_{max}$ obtained from 10 minute interval data. Linear relation between Average annual R factor obtained from 10 minute interval rainfall and from hourly data was derived with $R^2=0.69$. Correction coefficient was developed for the R factor calculated using hourly rainfall data.. Similarly, the relation was obtained between event wise $I30_{max}$ and $I60_{max}$ with higher $R^2$ value of 0.91. Thus $I30_{max}$ can be estimated from I60max with higher accuracy and thus the hourly rainfall data can be used to determine R factor more precisely by multiplying Energy of each rainfall event with this corrected $I60_{max}$.

• Water for future
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• v.29 no.3
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• pp.187-195
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• 1996

In this study, a methodology for the hourly prediction of rainfall surfaces was applied to the Pyungchang river basin at the upstream of South Han river with meteorological radar and ground rainfall data. The methods for the exclusion of abnormal echoes, and suppression of ground clutter, and the augmentation of attenuation effects associated with rainfall phenomena were reviewed, and the relationship between radar reflectivity (Z) and rainfall rate (R) was analyzed. The transformation of augmented radar reflectivities into the rdar rainfall surfaces was carried out, and afterward they were synthesized with the ground rainfall data generating the hourly rainfall surfaces. For the prediction of hourly rainfall surface, the moving factors of rainfall field estimated by the cross correlation coefficient method and the temporal variation of radar rainfall intensities were considered. The synthesized hourly rainfall surfaces were used to predict the hourly rainfall surfaces up to 3 hours in advance and subsequently the results were compared with the measured and the synthesized. It seems that the prediction method need to be verified with more data and be complemented further to consider the physical characteristics of rainfall field and the topography of the basin.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.12-19
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• 2006

Landslide model experiments considering hourly rainfall were performed to investigate and predict the run out distance induced by landslides. The model flume and the rainfall simulator were designed and produced. The model flume was designed in consideration of the landslide characteristics of Korea. The landslides in Korea were mainly occurred in the interface between soil layer and rock layer. The rainfall simulator was produced for controlling hourly rainfall ranged from 100mm/hr to 1,000mm/hr. Jumnunjin standard sand as slope soils was placed on the model flume. The model experiments were performed with changing the hourly rainfall ranged from 150mm/hr to 250mm/hr. In this experiments, the inclination of slope was 25o and the relative density of slope soils was 35%. As a result of experiments, the pore water pressure is rapidly increased at landslide occurring time, and the scale of landslide is increased with increasing in hourly rainfall. The spreading range of run out distance is occurred with pan type, and the spreading width and length are rapidly increased in its early stage and slowly increased after early stage. Also, The increasing velocity of run out distance of debris is influenced by hourly rainfall.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.501-504
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• 2008

A non-homogeneous markov model which is able to simulate hourly rainfall series is developed for estimating reliable hydrological variables. The proposed approach is applied to simulate hourly rainfall series in Korea. The simulated rainfall is used to estimate the design rainfall and compared to observations in terms of reproducing underlying distributions of the data to assure model's validation. The model shows that the simulated rainfall series reproduce a similar statistical attribute with observations, and expecially maximum value is gradually increased as number of simulation increase.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.73-80
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• 2017

The objective of this study is to investigate whether the daily rainfall depth derived from daily data represents the event rainfall depth derived from hourly data. For analysis, the 85th, 90th, and 95th percentile daily rainfall depths were first computed using daily rainfall data (1986~2015) collected at 63 weather stations. In addition, the storm event was separated by the interevent time definition (IETD) of 6, 12, 18, and 24 hr using hourly rainfall data. Based on the separated storm events, the 85th, 90th, and 95th percentile event rainfall depths were calculated and compared with the using hourly rainfall data with the 85th, 90th, and 95th percentile daily rainfall depths. The event rainfall depths computed using the IETD were greater than the daily rainfall depths. The difference between the event rainfall depth and the daily rainfall depth affects the design and size of the facility for controlling the stormwater. Therefore, the designer and policy decision-maker in designing the stormwater best management practices need to take into account the difference generated by the difference of the used rainfall data and the selected IETD.

• Journal of Korea Water Resources Association
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• v.49 no.4
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• pp.283-291
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• 2016

As the infrastructures and populations are the condensed in the mega city, urban flood management becomes very important due to the severe loss of lives and properties. For the more accurate calculation of runoff from the urban catchment, hourly or even minute rainfall data have been utilized. However, the time steps of the measured or forecasted data under climate change scenarios are longer than hourly, which causes the difficulty on the application. In this study, daily rainfall data was disaggregated into hourly using the stochastic method. Based on the historical hourly precipitation data, Gram Schmidt orthonormalization process and K-Nearest Neighbor Resampling (KNNR) method were applied to disaggregate daily precipitation into hourly. This method was originally developed to disaggregate yearly runoff data into monthly. Precipitation data has smaller probability density than runoff data, therefore, rainfall patterns considering the previous and next days were proposed as 7 different types. Disaggregated rainfall was resampled from the only same rainfall patterns to improve applicability. The proposed method was applied rainfall data observed at Seoul weather station where has 52 years hourly rainfall data and the disaggregated hourly data were compared to the measured data. The proposed method might be applied to disaggregate the climate change scenarios.

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.437-442
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• 2001

In Korea, collapse of railway slopes is frequently occurred due to tycoon or heavy rainfall doling rainy season and has been made personal and social damage greatly. In order to evaluate the stability of railway slopes under rainfall, explanatory variables and subordinate variables were selected for multivariate analysis. The sites which failure had occurred due to rainfall were investigated and critical rainfall was defined by the case that had high value of correlation factor after multivariate analyses for 121 cases had been executed. The maximum hourly rainfall during 24 hours before failure caused the collapse of railway embankment and the 0.3 square value of maximum hourly rainfall during 24 hours before failure caused the collapse of railway cut-slope, From the application to collapse examples, it is judged that critical rainfall curve will be used to estimate the stability of slopes.

• Journal of Korea Water Resources Association
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• v.49 no.11
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• pp.913-922
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• 2016

A long-term precipitation record is typically required for establishing the reliable water resources plan in the watershed. However, the observations in the hourly precipitation data are not always consistent and there are missing values within the time series. This study aims to develop a hourly rainfall simulator for extending rainfall data, based on the well-known Neyman-Scott Rectangular Pulse Model (NSRPM). Moreover, this study further suggests a multisite hourly rainfall simulator to better reproduce areal rainfalls for the watershed. The proposed model was validated with a network of five weather stations in the Uee-stream watershed in Seoul. The proposed model appeared a reasonable result in terms of reproducing most of the statistics (i.e. mean, variance and lag-1 autocovariance) of the rainfall time series at various aggregation levels and the spatial coherence over the weather stations.

• The Journal of Engineering Geology
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• v.15 no.4 s.42
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• pp.435-445
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• 2005

Landslides induced by heavy rainfall from typhoon 'Rusa' in 2002 and typhoon 'Meami' in 2003 were investigated at Samcheok area, and the relationship between landslides and rainfall on that area was analyzed. The average annual rainfall at Samcheok area is generally $1,200mm\~1,300mm$. However, the average annual rainfall at samcheok for 2003 and ton was increased more than 2,000mm because of typhoon 'Rusa' and typhoon 'Meami'. The number of landslides and the landslides area are largely occurred in a area of the relatively high maximum hourly rainfall and 2days cumulative rainfall. Therefore, it confirmed that landslides are directly depended on the hourly rainfall and the cumulative rainfall. The landslides at Samcheok area induced by heavy rainfall due to typhoon are more influenced by the maximum hourly rainfall at the landslide occurrence day. In order to predict a rational landslide size, a new method included the maximum hourly rainfall and the landslide area in a traditional way was proposed. As the result of applying the new proposed method, the landslide size at Samcheok area is involved in the large scale landslide.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.4 no.1
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• pp.24-31
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• 2001

Most of the natural calamities occurred in South Korea are due to rainfall, which are occurred during rainy season, June to September. The life-calamity reported in those seasons were over 75%, and the dead rate by the rainfall was about 98%. Especially, the disasters occurred in Pusan and Kyongsang-Namdo were highest of the whole country. The capability of landslide in this area was very high, which is included to Class 3 or Class 4 of disastrous risk grade suggested by the GIS system(Lee Su-Gon,1999). Those are based on the characteristics of topographical and meteorological data. In this study, the rainfall characteristics in Pusan were analyzed through the relationship between the cumulative rainfall and the maximum hourly rainfall. The landslide in this area depends on the elapsed time after maximum hourly rainfall intensity, and the most of landslide in Pusan recorded during within 3 hours after pick-time of rainfall intensity.