• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.2
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• pp.3438-3453
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• 1974

Unmeasured value of water for human lives is widely approved, but the water as one of natural resources cannot be evaluated with ease since it changes itself ceaselessly by flowing-out or transforming the phase. Major objectives of the study concerned consequently with investigating its potentiality and evaluating its time seriesly availabity in a volumatic unit. And the study was performed to give the accurate original data to the planners concerned. Some developed rational methods of predicting runoff related to hydrological factors as precipitation, were to be discusseed for their theorical background and to be introduced whether they needed some corrections or not, comparing their estimation with actual runoff from synthetic unit-hydrograph methods. To do so, the study was performed to select Kongju Station, located at the watershed of the Keum River, and to collect such hydrological data from 1962 to 1972 as runoff, water level, precipitation, and so on. On the other hand, the hydrological characteristics of runoff were concluded more reasonably in numerical values, with calculating the the ratio of daily runoff to annual discharge of the flow in percentage, as. the distribution ratio of runoff. The results of the study can be summarized as follows; (1) There needed some consideration to apply the Kajiyama's Formula for predicting monthly runoff of rivers in Korea.(2) The rational methods of predicting runoff might be recommended to become less theorical and reliable than the unique analyzation of data concerned in each given water basin. The results from the Keum River prepared above would be available to any programms concerned. (3) The most accurate estimation for runoff could be suggested to synthetic unithydrograph methods calculated from the relation between each storm and runoff. However it was not contained in the study. (4) The relations between rainfall and runoff at KongJu Station were as following table. The table showed some intersting implications about the characteristics of runoff at site, which indicated that the runoff during three months from July to September approached total of 60% of quantity while precipitation concentrated on the other three from June to August. And there were some months which had more amount of runoff than expected values calculated from the precipitation, such as Febrary, March, August, September, Octover, and December, shown in the table. Such implications should be suggested to meet any correction factors in the future formulation concerned with the subjects, if any rational methods would be required.

• Water for future
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• v.19 no.1
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• pp.75-86
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• 1986

This study aims at the analysis and application of PMP(Probable Maximum Precipitation)for the determination of design flood in the river basin planning and design of major hydraulic structures. PMP was estimated by hydro-meterological method statistical method and envelope curve method. PMF(Probable Maximum Flood)was then estimated from this PMP by synthetic unit hydrograph method and chow method. From the comparison of three methods for PMP estimation of magnitude of PMP in order of statistical, hydro-metrological, envelope curve method. Among PMP results estimated by each method it is believed that the hydro-meteorological method gave the best proper value in comparison with historical maximum rainfall because of this method reflected upon all meterological factor. From the comparison of PMP with probable rainfall and flood, it was shown that estimated value by statistical method and hydro-metrological method were nearly equivalent to the value of return period 100 years and its value of envelope curve method was equivalent to return period 200 to 500 year. It was found that PMF estimated from would be more safe for the design of major hydraulic structures in the consideration.

• Proceedings of the Korea Water Resources Association Conference
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• 1986.07a
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• pp.93-101
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• 1986

This study aims at analysis and application of PMP(Probable Maximum Precipitation) for the determination of design of major hydraulic structures. PMP was estimated by hydro-meteorolgical method and envelope curve method. PMF(Probable Maximum Flood) was then estimated from this PMP by synthetic unit hydrograph method and chow method. From the comparison of three methods for PMP estimation of magnitude of PMP in order of statistical, hydro-meteorlogical, envelope curve method. Amon PMP results estimated by each method it is believed that the hydro-meteorological method gave the best proper value in comparison with historical maximum rainfall because of this method reflected upon all meteorological factor. From the comparison of PMP with probable rainfall and flood, it was shown that estimated value by statistical method and hydro-metelogical method were nearly equivalent to the value of return period 200 to 500 year. It was found that PMF estimated from would be more safe for the design of major hydraulic structures in the consinderation.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.3
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• pp.363-373
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• 2010

"Curve number" (CN) indicates the runoff potential of an area. The US Soil Conservation Service (SCS)'s CN method is a simple, widely used, and efficient method for estimating the runoff from a rainfall event in a particular area, especially in ungauged basins. The use of soil maps requested from end-users was dominant up to about 80% of total use for estimating CN based rainfall-runoff. This study introduce the use of soil maps with respect to hydrologic and watershed management focused on hydrologic soil group and a case study resulted in assessing effective rainfall and runoff hydrograph based on SCS-CN method in a small watershed. The ratio of distribution areas for hydrologic soil group based on detailed soil map (1:25,000) of Korea were 42.2% (A), 29.4% (B), 18.5% (C), and 9.9% (D) for HSG 1995, and 35.1% (A), 15.7% (B), 5.5% (C), and 43.7% (D) for HSG 2006, respectively. The ratio of D group in HSG 2006 accounted for 43.7% of the total and 34.1% reclassified from A, B, and C groups of HSG 1995. Similarity between HSG 1995 and 2006 was about 55%. Our study area was located in Sosu-myeon, Goesan-gun including an approx. 44 $km^2$-catchment, Chungchungbuk-do. We used a digital elevation model (DEM) to delineate the catchments. The soils were classified into 4 hydrologic soil groups on the basis of measured infiltration rate and a model of the representative soils of the study area reported by Jung et al. 2006. Digital soil maps (1:5,000) were used for classifying hydrologic soil groups on the basis of soil series unit. Using high resolution satellite images, we delineated the boundary of each field or other parcel on computer screen, then surveyed the land use and cover in each. We calculated CN for each and used those data and a land use and cover map and a hydrologic soil map to estimate runoff. CN values, which are ranged from 0 (no runoff) to 100 (all precipitation runs off), of the catchment were 73 by HSG 1995 and 79 by HSG 2006, respectively. Each runoff response, peak runoff and time-to-peak, was examined using the SCS triangular synthetic unit hydrograph, and the results of HSG 2006 showed better agreement with the field observed data than those with use of HSG 1995.

• Water for future
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• v.19 no.1
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• pp.65-74
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• 1986

The purpose of this study was to investigate the applicability of Single Linear Reservoir (SLR) model for runoff computations of small river basins in Korea. In the existing watershed flood routing methods the storage coefficient(K), which is the dominant parameter in the model, has been proposed to be computed in terms of the wqtershed characteristics. However, in the prsent study, the rainfall characteristics in addition to the watershed characteristics were taken into account in the multiple regression analysis for more accurate estimation of storage coefficient. The parameters finally adopted for the regressions were the drainge are, mean stream slope of the watershed, and the duration and total dffective amount of rainfalls. To verify the applicability of SLR model the computed results by SLR model with K determined by the regression equation were compared with the observed gydrographs, and also with those by other runoff computation methods; namely, the Clark method, nakayasu's synthetic unit hydrograph method and Nash model. The results showed that the present zSLR model gave the best results among these methods in the case of small river basins, but for the whatersheds with significant draingage area the Clark method gave the best results. However, it was speculated that the SLR model could also be accurately applied for flood compuatation in large wagersheds provided that the regression for storage coefficients were made with the actual data obtained in the large river basins.