• Journal of Korea Water Resources Association
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• v.43 no.7
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• pp.635-643
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• 2010

A representative unit hydrograph responding to a small basin is used to calculate the flood discharge in the basin. The peak discharge and the time to peak of the unit hydrograph are dealt with its characteristic values. In this study it is shown and analyzed the fluctuations at peak discharges and times to peak of unit hydrographs by rainfall storms in a small national basin $8.5\;km^2$ wide are no small. And on assumption that a major factor in the fluctuations of the unit hydrographs in a small basin be rainfall intensity of a rainstorm, both relations of peak discharge and time to peak with rainfall intensity are suggested as exponential functions respectively. In this result although it is a limit of the study in which its result is accompanied with not small dispersion in the peak values of unit hydrograph due to a defect in used data it is sure an averaging regression relation between peak discharge and time to peak with rainfall intensity as identified in this study has hydrological worth from the complementary viewpoint of the theory of unit hydrograph.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.1
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• pp.21-26
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• 2013

In recent study, infiltration analysis considering rainfall intensity is more economical and practical than existing analysis method. Revised construction slope design standard is also stated to full-fill infiltration analysis considering rainfall for practical stability review. Infiltration analysis considering rainfall for practical stability review. But, to infiltration analysis, the process is complicated by ground impermeability and rainfall intensity. In this study, we perform infiltration analysis to charge infiltration conditions, soil type and rainfall characteristics, for more pratical stability review. Using the result, we can suggest construable condition on the assumption that soil is saturated up to surface zone.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.97-97
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• 2020

Flooding in urban areas is caused by heavy rains for a short period of time and drains within 1 to 2 hours. It is also characterized by a small flooding area. In addition, flooding is often caused by various and complex causes such as land use, basin slope, pipe, street inlet, drainage pumping station, making it difficult to predict flooding. Therefore, this study analyzes the effect of each basin characteristic on the occurrence of flooding in urban areas by correlating various basin characteristics, whether or not flooding occurred, and rainfall(Limit Rainfall), and intends to use the data for urban flood prediction. As a result of analyzing the relationship between the imperviousness and the urban slope, pipe, threshold rainfall and limit rainfall, the pipe showed a correlation coefficient of 0.32, and the remaining factors showed low correlation. However, the multiple correlation analysis showed the correlation coefficient about 0.81 - 0.96 depending on the combination, indicating that the correlation was relatively high. In the future, I will further analyze various urban characteristics data, such as area by land use, average watershed elevation, river and coastal proximity, and further analyze the relationship between flooding occurrence and urban characteristics. The relationship between the urban characteristics, the occurrence of flooding and the limiting rainfall amount suggested in this study is expected to be used as basic data for the study to predict urban flooding in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.101-110
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• 2017

The National Emergency Management Agency (NEMA) presented the disaster prevention performance target rainfall (DPPTR) for disaster prevention. The estimation criteria for DPPTR is a 10 year cycle. On the other hand, the target rainfall recalculated every 10 years is difficult to reflect the current change in rainfall on climate change. In this study, the probability of precipitation using the recent rainfall data was prepared and the weights according to socio-economic criteria reflecting the urban characteristics and adjusted probability rainfall criteria were applied to the results. The difference between the existing target rainfall and recalculated result was compared. The input data for the estimated probability rainfall was selected from 6 points located in the rainfall observing station of Chungcheongnam-do, Daejeon region. As a result of the estimation, in the case of upward probability precipitation weight, some similar areas were observed. On the other hand, there were a few cases of upward or downward changes within 10 mm. Considering the rainfall variability and uncertainty due to climate change, the existing target rainfall does not present the condition properly. Therefore, hydrological designers need to calculate the target rainfall, reflecting the present condition.

• Journal of Korean Society on Water Environment
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• v.24 no.2
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• pp.169-173
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• 2008

A field monitoring was conducted in order to find out the discharge characteristics of non-point source pollutants in the agricultural area. Event Mean Concentration (EMC) of TSS, $BOD_5$, $COD_{Mn}$, TP, TN was calculated based on the monitoring data of 10 rainfall events at agricultural watersheds. A significant relationship was observed from the correlation between EMCs and rainfall characteristics. The result shows that EMC ranges of 95% confidence intervals were 50.5~203 mg/L for TSS, 0.8~14.2 mg/L for $BOD_5$, 4.2~20.7 mg/L for $COD_{Mn}$, 2.4~4.5 mg/L for TN and 0.2~0.5 mg/L for TP, respectively. The correlation coefficients between TSS and TP and between $BOD_5$ and $COD_{Mn}$ were found to be 0.912 and 0.961. But TN was lower correlated with other EMC factors. It was also found that rainfall characteristics was not correlated with EMCs.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.1-15
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• 2020

In this study, the characteristics of crop damage area by flooding for 113 middle range watersheds during 2000-2016 were analyzed and future crop damage area by flooding were analyzed using 13 GCM outputs such as hourly maximum rainfall, 10-min maximum rainfall, number of days of 80 mm/day, daily rainfall maximum, annual rainfall amount associated with RCP 4.5 and RCP 8.5 scenarios and watershed characteristic data such as DEM, urbanization ratio, population density, asset density, road improvement ratio, river improvement ratio, drainage system improvement ratio, pumping capacity, detention basin capacity, and crop damage area by flooding. A constrained multiple linear regression model was used to construct the relationships between the crop damage area by flooding and other variables. Future flood index related to crop damage may mainly increase in the Mankyung watershed, Southwest part of Youngsan and Sumjin river basin and Southern part of Nackdong river basin. Results are useful to identify watersheds which need to establish strategies for responding to future flood damage.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1029-1037
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• 2008

The finite element analysis of transient water flow through unsaturated soils was used to investigate effects of hydraulic characteristics, initial relative degree of saturation, methods to consider boundary condition, and rainfall intensity and duration on water pressure in slopes. The finite element method with shear strength reduction technique was used to evaluate the stability of slopes under rainfall. The slope-related disasters in Korea usually occur between July and September during the typhoon and localized heavy rain. This means that the rainfall is the most important factor that leads to the slope-related disasters. The slope-related disasters can happen at very short time and lead to big damage. To forecast the change of the heave of the groundwater in slope the Seep/w program was used.

• Journal of Wetlands Research
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• v.15 no.2
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• pp.233-250
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• 2013

Gradually or radically change how the characteristics of the climate characteristic using change point analysis for the precipitation indicators were investigated. Significantly the amount, extreme and frequency were separated by precipitation indicators, each indicator RIA(Rainfall Index for Amount), RIE(Rainfall Index for Extremes) and RIF(Rainfall Index for Frequency) was defined. Bayesian Change Point was applied to investigate changing over time of precipitation indicators calculated. As the result of analysis, precipitation indicators in South Korea was found to recently increase all indicators except for the annual precipitation days and 200-yr precipitation. RIA revealed that there was a very clear point of significance for the change in Ulleungdo, Relatively significant results for RIE were identified in Gumi, Jecheon and Seogwipo. Also, since the 1990s, an increase in the number of variation points, and the horizontal width of the fluctuation point was being relatively wider. Based on these results, rethink the precipitation on the assumption of stationarity was judged necessary.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.3
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• pp.109-121
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• 2020

Converting the agricultural land-use of rice field to upland has been increasingly conducted as farmers encourages themselves to grow higher value-added crops on rice fields under the policy support. Comparing to rice field, Upland shows different characteristic of discharge due to the slope, scale, and shape of field and characteristics of rainfall event. In this study, we designed the experiment fields reflecting flat-upland characteristics with different land scale, and tried to collect the discharge and load data. Soybeans and corn were selected as target crops considering the possibility of large-scale cultivation and crop demand. The cultivation was conducted during the growth period in 2019 with 3 different field scales. Hence, we have collected the discharge data from 17 rainfall events and the load data for 8 rainfall events. As a result, the magnitude of rainfall events and the discharge duration were found to have a strong positive correlation and field discharge occurred during the period by 55% to 83% of rainfall duration. Besides we found other relationships and characteristics of rainfall event, discharge, and pollutant load and also pointed out that continuous monitoring and more data are required to derive statistically significant results. Compared with slope-field monitoring data obtained from the precedent research, the runoff ratio of the flat-fields was significantly lower than slope-fields. Overall the discharge in the slop and flat-fields shows appreciably different characteristics so that the related researches need to be further conducted to reasonably assess environmental impact of agricultural activities at flat-field.

• Journal of the Korean GEO-environmental Society
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• v.18 no.1
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• pp.13-21
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• 2017

In this study, the behavior characteristics and triggering rainfall of debris flow were investigated on the basis of DB constructed by performing field investigation and collecting the rainfall data at the sites where debris flow occurred around the west of Gangwon and adjacent areas during the last 10 years. For hill slope and channelized type of debris flow, its behavior characteristic was analyzed through runout channel of debris flow divided into zone of initiation, transportation and deposition and its magnitude was estimated by considering erosion at zones of initiation and transportation. Some considerations related to establishment of landslide forecasting criterion were raised by comparing the analyzed results of analysis of rainfall at the time of debris-flow occurrence with the previous researches about the triggering rainfall of debris flow. In addition, an ID curve of inducing debris flow adequate to the investigated site was proposed and compared with results of previous study.