• Journal of Korea Water Resources Association
• /
• v.30 no.1
• /
• pp.75-82
• /
• 1997

The stream morphologic characteristics of Wonju stream with small watershed are developed with a regular correlation referred to the Horton-Strahler's lows of stream order. Using Manning's formula and the discharges simulated by NWS-PC rainfallrunoff model that has been applied to the adjacent basin for model calibration and verification, the hydraulic characteristics at Wonju bridge are investigated. The peak discharge and the time to peak of unit hydrograph are analyzed by the calculated geomorphologic parameters. Rather primitive as this study is, these results are provided to be used for geomorphologic instantaneous unit hydropraph of ungaged basins including this study area. Through the reestablishment of rating curve and hydrograph with continuous field observations, the hydrologic and hydraulic characteristics of Wonju stream must be presented.

• Water for future
• /
• v.28 no.4
• /
• pp.171-183
• /
• 1995

The Snyder's Unit Hydrograph Method is applied to simulate the November 1985 Flood of the Cheat River Basin, which is located in the North-East region of West Virginia in United States. The entire basin is divided into many subareas according to the hydrologic and geologic characteristics. The overland flows are computed on each subarea and combined together along the streams. The flows are also routed by the Normal Depth Storage and Outflow Method in Modified Pulse option. The several structural flood control alternatives are examined. The study shows the OPTION III which has the three moderately sized dam is ultimately suitable to control the flood. The HEC-1 computer model is used to analyze the flood.

• Water Engineering Research
• /
• v.6 no.2
• /
• pp.91-99
• /
• 2005

One of the most important factors for estimating a flood runoff from streams is the lag time. It is well known that the lag time is affected by the morphometric properties of basin which can be expressed by catchment shape descriptors. In this paper, the notion of the geometric characteristics of an equivalent ellipse proposed by Moussa(2003) was applied for calculating the lag time of geomorphologic instantaneous unit hydrograph(GIUH) at a basin outlet. The lag time was obtained from the observed data of rainfall and runoff by using the method of moments and the procedure based on geomorphology was used for GIUH. The relationships between the basin morphometric properties and the hydrological response were discussed based on application to 3 catchments in Korea. Additionally, the shapes of equivalent ellipse were examined how they are transformed from upstream area to downstream one. As a result, the relationship between the lag time and descriptors was shown to be close, and the shape of ellipse was presented to approach a circle along the river downwards. These results may be expanded to the estimation of hydrological response of ungauged catchment.

• Journal of Wetlands Research
• /
• v.12 no.3
• /
• pp.99-106
• /
• 2010

In this study unit hydrograph and infiltration capacity curves have been determined based on rainfall-runoff data for the upper Ansung stream basin. Infiltration capacity curve also has been computed based on measurements of accumulated infiltration. Accumulated infiltration curve which has close relationship with unit hydrograph has been found in adopting the following two approach methods. In the first method the mean infiltration capacity with infiltration index method and the Kostiakov accumulation infiltration curves have been computed based on hydrological data for the GongDo gauging station of the upper Ansung stream basin. In the second method the accumulation curve has been determined through directly observed infiltration data for four points in the upper basin and has been compared with the infiltration capacity curves by three observed rainfall-runoff event.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.46 no.6
• /
• pp.3-10
• /
• 2004

The fundamental study of hydrologic redesign of Donghwa area located in a sccond tributary of Seomjin river was performed. The amounts of hydrologic design were estimated using the available cumulated hydrology data provided by Korea Agricultural and Rural Infrastructure Corporation (KARICO). The management status of The water resources in Donghwa area was also widely surveyed. The probability rainfalls, probable maximum precipitation (PMP) and probability floods were estimated and subsequently their changes analyzed. The amount of 200 year frequency rainfall with l day duration was 351.1 mm, 2.5 % increased from the original design value, and The PMP was 780.2 mm. The concentration time was reestimated as 2.5 hours from existing 2.4 hours. Soil Conservation Service(SCS) method was used to estimate effective rainfall- The runoff curve number was changed from 90 to 78, therefore the maximum potential retention was 71.6 mm, 154 % increased from the original value. The Hood estimates using SCS unit hydrograph showed 8 % increase from original value 623 $m^3$/s to 674 $m^3$/s and The probable maximum Hood was 1,637 $m^3$/s. Although the Row rate at the dam site was increased, the Hood risk at the downstream river was decreased by the Hood control of the Donghwa dam.

• Journal of Environmental Science International
• /
• v.24 no.4
• /
• pp.425-435
• /
• 2015

A number of projects for development have been done continuously due to the increase of tourist in Jeju Island. However flood disaster countermeasure due to urbanization is not considered during this development projects. This study is to make basic process for the flood estimation in Han stream of Jeju Island. The variation of stream discharge due the every 5 years' land use change from 1980 to 2005. Data for flood events (rainfall and discharge) were collected for HEC-HMS model. Clark method was used for unit hydrograph analysis. For the estimation of Clark unit hydrograph parameters, Kraven II and Sabol's empirical equations were applied. The peak discharge increased 9.9~33.67% and total discharge amount increased 12.53~30.21%. Also, time of concentration for peak discharge was reduced by 10 minutes for each event.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2002.05b
• /
• pp.1334-1339
• /
• 2002

The objective of this study is to help practicing engineers easily use the Clark model which is used for estimating the magnitude of design flood for small stream. A representative unit hydrograph was derived on the basis of the past rainfall-runoff data and unit hydrographs, and the storage coefficient of Clark model was estimated by using hydrograph recession analysis. Since the storage coefficient(K) is a dominating factor among the parameters of Clark method, a mulitple regression formula, which has the drainage area, main channel length and slope as parameters, is propsed to estimate K value of a basin where measured data are missing. The result of regression analysis showed that there is a correlation between a storage coefficient(K) and aforemetioned three parameters in homogenious basins. A regression formular for K was derived using these correlations in a basin of Han River, Nakdong River, Young River, Kum River and Sumjin River

• Water for future
• /
• v.25 no.4
• /
• pp.97-107
• /
• 1992

The purpose of this study is to estimate the flood hydrograph and runoff at ungaged small watershed by using interactive program with geomorphologic and climatic data obtained from the topographic maps following the law of stream classification and ordering by Horton and Strahler. The present model is modified from Allam's interactive program which derives the geomorphologic instantaneous unit hydrograph(GIUH). This program uses the results of Laplace transformation and convolution integral of probability density function in travel time at each station, This program is used to estimate the time to peak, the flood discharge and the direct runoff at San seong station in Bocheong Stream.

• Water for future
• /
• v.12 no.2
• /
• pp.56-62
• /
• 1979

Many methods of estimating design floods from rainfall data involve a trial and error procedure to determine the duration of the design rainfall, which is very complicated and time-consuming. In this study, an effort was given to derive an analytical expression for estimating the appropriate duration for use with a particular unit hydrograph. According to the so-derived analytical expression the coordinateds of hvdrograph curve and rainfall curve for the Musim Representative Basin were computed and then plotted on a same scal graph paper on which the critical durations of design rainfall excess of various recurrence intervals were determined by the point of intersection of the tow curves.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1454-1458
• /
• 2007

The determination of feasible design flood is the most important to control flood damage in river management. Model parameters should be calibrated using observed discharge but due to deficiency of observed data the parameters have been adopted by engineer's empirical sense. Storage constant in the Clark unit hydrograph method mainly affects magnitude of peak flood. This study is to estimate the storage constant based on the observed rainfall-runoff data at the three stage stations in the Imjin river basin and the three stage stations in the Ansung river basin. In this study four methods have been proposed to estimate the storage constant from observed rainfall-runoff data. The HEC-HMS model has been adopted to execute the sensitivity of storage constant. A criteria has been proposed to determine storage constant based on the results of the observed hydrograph and the HEC-HMS model.