• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.2
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• pp.91-102
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• 2010

This study analyzed methodologies for determining the representative direction of a storm event. The mean direction, median direction, and modal direction of von Mises distribution were considered as representative directions. In addition, the results with and without considering the storm moving distance were also compared. As results, the modal directions of von Mises distribution were found to explain the directional characteristics of a moving storm much better than other methods. Also, it was found that the storm moving distance has a significant effect on the determination of representative directions of a moving storm, whose uncertainty can also be decreased significantly by considering the moving distance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.15-25
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• 2006

Using kinematic wave equation, the influence of moving storms to runoff was analysised with a focus on watersheds. Watershed shapes used are the oblong, square and elongated shape, and the distribution types of moving storms used are uniform, advanced and intermediate type. The runoff hydrographs according to the rainfall distribution types were simulated and the characteristics were explored for the storms moving down, up and cross the watershed with various velocity. The shape, peak time and peak runoff of a runoff hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed shapes. A rain storm moving in the cross direction of channel flow produces a higher peak runoff than in the downstream direction and upstream direction. A peak runoff from a storm moving downstream exceeds that from a storm moving upstream. For storms moving downstream peak time was more delayed than for other storm direction in the case of elongated watershed. The runoff volume and time base of the hydrograph decreased with the increasing storm speed.

• Journal of Korea Water Resources Association
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• v.37 no.10
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• pp.823-836
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• 2004

Using the simple geometry for the idealized catchment consisting of two plane surfaces and a stream between them, runoff was analysed for the moving storms based on the kinematic wave equation. The storm velocity applied in this study was 0.25∼2.0 m/s moving up, down and cross direction of catchment. Applied rainfall distribution types are uniform, advanced, delayed, intermediate type. The results indicate that the moving storms of cross direction generate the largest peak runoff, and the smallest runoff appears in the case of up stream direction. The sensitivity of runoff to rainfall distribution types decreases as storm velocity increases. It is clear that faster storm velocity generates faster peak time and becomes thin hydrographs rapidly.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.109-117
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• 2010

This study quantified the storm direction for a river basin by applying the von Mises distribution, also determined the representative storm direction. Additionally, the whole procedure was repeated for several storm types such as frontal, typhoon and convective storms for their comparison. From the results derived by analyzing a total of 101 storm events for the Naesung river basin, the von Mises distribution was found to explain the directional characteristics of storms. The representative moving directions derived for three different storm types were significantly different each other, which is coincident with the climate of Korea. The results derived in this study could be helpful to estimate more quantitatively the difference in the runoff response with respect to the moving direction of a storm.

• Korean Journal of Hydrosciences
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• v.5
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• pp.1-16
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• 1994

In this paper distributed models for simulating spatially and temporally varied moving storm in a watershed were developed. The complete simulation in a watershed is achieved through two sequential flow simulations which are overland flow simulation and channel network flow simulation. Two dimensional continuity equation and momentum equation of kinematic approximation were used in the overland flow simulation. On the other hand, in the channel network simulation two types of governing equations which are one dimensional continuity and momentum equations between two adjacent sections in a channel, and continuity and energy equations at a channel junction were applied. The finite difference formulations were used in the channel network model. Macks Creek Experimental Watershed in Idaho, USA was selected as a target watershed and the moving storm on August 23, 1965, which continued from 3:30 P.M. to 5:30 P.M., was utilized. The rainfall intensity fo the moving storm in the watershed was temporally varied and the storm was continuously moved from one place to the other place in a watershed. Furthermore, runoff parameters, which are soil types, vegetation coverages, overland plane slopes, channel bed slopes and so on, are spatially varied. The good agreement between the hydrograph simulated using distributed models and the hydrograph observed by ARS are Shown. Also, the conservations of mass between upstreams and downstreams at channel junctions are well indicated and the wpatial and temporal vaiability in a watershed is well simulated using suggested distributed models.

• Water for future
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• v.26 no.1
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• pp.81-91
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• 1993

In this paper, a moving storm in the real watershed was simulated using a distributed model. Macks Creek Experimental Watershed in Idaho, USA was selected as a target watershed and the moving storm of August 23, 1965, which continued from 3:30 P.M. to 5:30 P.M., was utilized. The rainfall intensity of the moving storm in the watershed was temporally varied and the storm was continuously moved from one place to the other place in a watershed. Furthermore, runoff parameters, which are soil types, vegetative cover percentages, overland plane slopes, channel bed slopes and so on, are spatially varied. The model developed in the previous paper was utilized as a distributed model for simulating the moving storm. In the model, runoff in a watershed was simulated as two parts which are overland flow and channel flow parts. The good agreement was obtained between a simulated hydrograph using a distributed model and an observed hydrograph. Also, the conservations of mass are well indicated between upstream and downstream at channel junctions.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.153-153
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• 2021

Storm Storm event is one of major issues in South Korea due to devastating damage at its landfall. A series of statistical study on the historical typhoon records consistently insist that the typhoon translation speed (TS) is on slowdown trend annually, and thus provides an urgent topic in assessing the extreme storm surge under future climate change. Even though TS has been regarded as a principal contributor in storm surge dynamics, only a few studies have considered its impact on the storm surge. The landfall angle (LA), another key physical factor of storm surge also needs to be further investigated along with TS. This study aims to elucidate the interaction mechanism among TS, LA, coastal geometry, and storm surge synthetically by performing a series of simulations on the idealized geometries using Delft3D FM. In the simulation, various typhoons are set up according to different combinations of TS and LA, while their trajectories are assumed to be straight with the constant wind speed and the central pressure. Then, typhoons are subjected to make landfall over a set of idealized geometries that have different depth profiles and layouts (i.e., open coasts or bays). The simulation results show that: (i) For the open coasts, the maximum surge height (MSH) increases with increasing TS. (ii) For the constant bed level, a typhoon normal to the coastline resulted in peak MSH due to the lowest effect of the coastal wave. (iii) For the continental shelf with different widths, the slow-moving typhoon will generate the peak MSH around a small LA as the shelf width becomes narrow. (iv) For the bay, MSH enlarges with the ratio of L/E (the length of main-bay axis /gate size) dropping, while the greatest MSH is at L/E=1. These findings suggest that a fast-moving typhoon perpendicular to the coastline over a broad continental shelf will likely generate the extreme storm surge hazard in the future, as well as the slow-moving typhoon will make an acute landfall over a narrow continental shelf.

• Journal of Korea Water Resources Association
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• v.33 no.6
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• pp.793-804
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• 2000

Even thought the distribution of the rainfall in the watershed is spatially and temporally vareid, the simulation of the runoff from the watershed is frequently conducted with the constant rainfall distribution assumption. However, the runoff simulated with this assumption indicates over the certain accuracy limitation and the difference by this assumption is bigger in the case of the moving storm which can be frequently indicated with the typhoon, cyclone and hurricane and so on. In this paper, the runoff characteristics of the moving storm are investigated using GIS technique and the isohyetal map observed from 16:00 to 23:00 on August 2, 1999 to the Chun Yang rain gage. The runoff simulated by the moving storms moving to the eight different directions is compared with the others and indicates the big difference with the maximum runoff in the SE direction in the Bokha experimental watershed. Also, the runoff by the moving storm having different moving velocities is compared with the others and indicates the big difference with the bigger discharge in the slowly moving storm. Through the simulation using GIS technique in the watershed, the advantages of the easy preparation of the data and the short computational time can be obtained.

• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.167-185
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• 2010

One of the most difficult problems in estimating design floods is how to determine design storms. More specifically, the design storm problems turn into how to determine temporal and spatial distribution of the storm. In this study, Thiessen-Weighted BlocKing-type(TWBK) moving storms are suggested to resolve the design storm problems and their applicability is investigated. These moving storms are applied for 100-year 48-hour design flood estimation in Han river basin using a physics-based distributed rainfall-runoff model. Simulated floods from moving storms are compared with frequency-based ones estimated from observed floods.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.5
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• pp.64-73
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• 1996

When typhoon occurs, the meteorological conditions get worse and can cause a large damage from storm and flood . This damage, however, can be minimized if a precise analysis of the runoff characteristics by typhoon tracks is used in the flood contorl This paper aims at the analysis of storm occurrence and runoff characteristics by typhoon tracks in Nakdong river basin. Therefore, the data of 14 typhoons which invaded Nakdong river basin during the period from 1975 to 1991 were collected, analyzed, and studied. The major results of this study are as followings; 1) The frequency of the typhoon occurrence here in Korea was affected by the storms three times a year on the average. The highest-recorded frequency was during the months of July to September. 2) The survey of the track characteristics depending on the forms of the storm in the Nakdong river basin showed that typhoon storm advanced from the south of the basin to the north, while the frontal type storm was most likely to advanced from the west to the north. 3) Typhoon tracks are classified into three categories, 6 predictors with high correlation coefficient are finally selected, and stepwise multiple regression method are used to establish typhoon strom forecasting models. 4) The riview on the directions of progress of the storm made it clear that the storm moving downstream from upstream of the basin could develop into peak discharge for ca short time and lead to more flood damage than in any other direction.