• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.299-304
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• 2005

Geoid undulation and gravity anomaly were calculated from GRACE satellite data on the eastern Asia including Korean peninsula. Geoid undulation varies from -60m in the China to 60m toward the Pacific Ocean across the Korean Peninsula. Calculated gravity anomalies are in the range of -60 and 60 mgal except the subduction zone showing -100 mgal. High positive values are observed at Mt. Baekdu, Kaema highland and Taebaek mountains, and low values at Ulleung, Japan and Yamato basins in the East sea. We removed regional components below the spherical harmonic degree of 10 from gravity anomaly to get the residual anomaly for crust components. Residual gravity anomaly shows high anomalies at the northern mountainous area and Kyungsang basin in the Korean Peninsula. And low anomalies appears at the western Korea bay basin, Kunsan basin, Cheju basin, and Ulleung basin in the marine. Anomalies separated by the spherical harmonic degree as well as the residual anomalies are useful for the study of large crustal structure about geologic scale and depth distribution and for the survey of natural resources.

• Spatial Information Research
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• v.15 no.2
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• pp.159-167
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• 2007

In this study, we investigated the application of extending the Huff's method to design discharge being used at present up to the event of concentrated rainfall. As our field study site, we selected Odae Cheon basin in Pheongchang, which was affected by concentrated rainfall in July 2006. Actual concentrated rainfall and design rainfall derived from the Huff's method were used to calculate the discharge and storm water levels, which were compared with the directly measured water-level marks of storm discharges. The results showed that the peak storm discharge from the torrential rainfall was twice higher than the design rainfall. The short term discharges from concentrated rainfall closely corresponded to the rainfall discharges of 150 years storm frequency.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.89-94
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• 2003

The formation of a severe snow storm occurred in the mountainous coastal region near Mt. Taegualyang and Kangnung city in the eastern part of Korea was investigate from 0900LST, December 7 through 9, 2002, using MM5 model. As synoptic scale easterly wind induced a great amount of moisture from the East Sea into the inland coastal region and sea-breeze further induced more moisture from the basin toward the top of the mountain side. The lifted moisture toward the mountain top was cooled down along the eastern slope of the mountain and near the mid of the mountain the moisture was much cooled down with relative humidity of 100％ under the air temperature below $O^{\circ}C$, resulting in the formation of snow. Relative humidity of 100％ generally occurred at the 5km away from the coast toward the inland mountain and the band of 100％ RH was parallel to the coastal line. The 100％ band coincided with minimum air temperature band and line.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.245-253
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• 2019

The objectives of this study are to estimate the return period of flash flood and evaluate its appropriateness based on the actual observation events for small mountainous watersheds in the Han River basin. For these goals, Flash Flood Guidance (FFG) was estimated from 1-hr duration Threshold Runoff (TR) and Saturation Deficit (SD) of soil moisture which was derived from Sejong University Rainfall Runoff (SURR) model. Then, the return period of flash flood was calculated by comparing the rainfall quantile to the 1-hr duration rainfall that exceeded the FFG during the past period (2002-2010). Moreover, the appropriateness of the estimated return period of flash flood was evaluated by using the observation events from 2011 to 2016. The results of the return period of flash flood ranged from 1.1 to 19.9 years with a mean and a standard deviation of 1.6 and 1.1 years, respectively. Also, the result of the appropriateness indicated that 83% of the return periods derived from observation events were within the return period of flash flood range. Therefore, the estimated return period of flash flood could be considered as highly appropriate.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.233-233
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• 2015

Vu Gia - Thu Bon basin is located in central Vietnam between Truong Son mountain range on the border with Lao in the west and the East Sea in the east. The basin occupies about 10,350 km2 or roughly 90% of the Quang Nam Province and includes Da Nang, a very large city with about 876,000 inhabitants. Total annual rainfall ranges from about 2,000 mm in central and downstream areas to more than 4,000 mm in southern mountainous areas. Rainfall during the monsoon season accounts for 65 to 80% of total annual rainfall. The highest amount of rainfall occurs in October and November which accounts for 40 to 50% of the annual rainfall. Rainfall in the dry season represents about 20 to 35% of the total annual rainfall. The low rainfall season usually occurs from February to April, accounting for only 3 to 5% of the total annual rainfall. The mean annual flow volume in the basin is $19.1{\times}109m 3$. Similar to the distribution of rainfall, annual flows are distinguished by two distinct seasons (the flood season and the low-flow season). The flood season commonly starts in the mid-September and ends in early January. Flows during the flood season account for 62 to 69% of the total annual water volume, while flows in the dry season comprise 22 to 38% of total annual run-off. The water volume gauged in November, the highest flow month, accounts for 26 to 31% of the total annual run-off while the driest period is April with flows of 2 to 3% of the total annual run-off. There are some hydropower projects in the Vu Gia - Thu Bon basin as the cascade of Song Bung 2, Song Bung 4, and Song Bung 5, the A Vuong project currently under construction, the Dak Mi 1 and Dak Mi 4 projects on the Khai tributary, and the Song Con project on the Con River. Both the Khai tributary and the Song Con join the Bung River downstream of SB5, although the Dak Mi 4 project involves an inter-basin diversion to Thu Bon. Much attention has recently been focused on the effects that climate variability and human activities have had on runoff. In this study, data from the Vu Gia - Thu Bon River Basin in the central of Viet Nam were analyzed to investigate changes in annual runoff during the period of 1977-2010. The nonparametric Mann-Kendall test and the Mann-Kendall-Sneyers test were used to identify trend and step change point in the annual runoff. It was found that the basin had a significant increasing trend in annual runoff. The hydrologic sensitivity analysis method was employed to evaluate the effects of climate variability and human activities on mean annual runoff for the human-induced period based on precipitation and potential evapotranspiration. This study quantitatively distinguishes the effects between climate variability and human activities on runoff, which can do duty for a reference for regional water resources assessment and management.

• Journal of Korea Water Resources Association
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• v.37 no.5
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• pp.407-424
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• 2004

Using geomorphoclimatic unit hydrograph(GCUH), we estimated the fitness to calculate the mountainous area discharge and flash flood trigger rainfall(FFTR). First, we compared the GCUH peak discharge with the existing report using the design storm at the Dukcheon basin. Second, we compared the HEC-HMS(Hydrologic Engineering Center-Hydrologic Modeling System) model and GCUH with the observed discharge using the real rainfall events at the Taesu stage gage. Third, GCUH and NRCS(Natural Resources Conservation Service) were used for calculating FFTR and proper calculation method was shown. At the Dukcheon basin, the comparison result of using design storm was shown in Table 11, and it was not in excess of 1.1, except for the 30 year return period. In case of real rainfall events, the result was shown in Table 12, and GCUH discharges were all larger than the HEC-HMS model discharges, and they were very similar to the observed data at the Taesu stage gage. In this study, we found that GCUH was a very proper method in the calculation of mountainous discharge. At the Dukcheon basin, FFTR was 12.96 mm in the first 10 minutes when the threshold discharge was 95.59 $m^3$/sec.

• Journal of Korean Society of Forest Science
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• v.99 no.4
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• pp.559-567
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• 2010

This study was conducted to investigate the hydrological characteristics of groundwater level change and rainfall hydrological runoff processes caused by tunnel construction at Milbot bog located in Mt. Cheonseong. Data were collected from July 2004 to May 2008. The results were summarized as follows: The occurrence time of the direct runoff caused by unit rainfall at the Milbot bog were tended to be slower than those at general mountainous basin. Also, runoff did not sensitively respond to amount of rainfall at the most of the long and short term hydrograph. The annual runoff rates from 2004 to 2008 were 0.26, 0.13, 0.16, 0.25 and 0.27, respectively, slightly increased after 2005 regardless of the tunnel construction. Thus, the function of Milbot bog will be weakened, and it supposed to be changed to land in the future because of increasing annual runoff. The annual runoff rate for 4 years was 0.19, which is greatly lower than that of general mountainous basin. The recession coefficient of the direct runoff in short term hydrograph was ranged to 0.89~0.97, which is much larger than that of the general mountainous basin, 0.2~0.8. The recession coefficient of base flow ranged from 0.93 to 0.99, which are similar to general mountainous watershed's values. Groundwater level of Milbot bog increased or decreased in proportion to rainfall intensity, and in the descending time after the groundwater level was reached at peak point, it tends to be decreased very slowly. Also, groundwater level increased or decreased maintaining relatively high value after precedent rainfall. Groundwater level was highest during summer with heavy rainfall, but was lowest during winter. Average groundwater levels decreased annually from 2004 to 2008, -8.48 cm, -14.60 cm, -20.46 cm, -20.11 cm, -28.59 cm, respectively. Therefore, it seems that the Milbot bog is becoming dry and losing its function as a bog.

• Korean Journal of Environment and Ecology
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• v.26 no.4
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• pp.498-511
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• 2012

Mountainous wetland have many species such as II grade endangered species of wild flora and fauna(Drosera rotundifolia) and environmental indicator species(Utricularia racemosa, Habenaria linearifolia, Parnassia palustris, Molinia japonica, etc.). Accordingly, the mountainous wetlands is very important. However, most mountainous wetlands will disappear by natural or artificial aridness processes. Thus, it needs to manage mountainous wetland for protecting from aridness. This study has found out the wetland status of the environmental ecology and aridness processes moreover, it has suggested ways of improving wetland conservation plan and wetland aridness management plan. According to the results of topography structure survey, Hwaeom wetland's altitude is ranged within 750~810m(87.4%), and slope is less than $10^{\circ}$. There was ideally suited mountainous wetland. However, the water supply(1.6 meters depth and 0.8 meters wide) was built on under the wetland. For that reason, there was concerned about the aridness processes by sweeping away peat layer and dropping the water level. The distribution area of hygrophyte was narrowed to 6.7% whereas, woody plants and xerophytic plants was achieved a dominant position. If it leaves the situation as it is, the mountainous wetland will be developed next succession as forest ecosystem. Therefore, in order to sustain the mountainous wetland from aridness, it is set to the base direction of conservation and management as main schemes. Moreover, we have suggested that setting the vegetation conservation and management area which considering a ecological vegetation characteristics, managing the ecotone vegetation, setting the buffer zone for protection of ecological core areas, protecting the mountainous wetland indicator species and designating the management vegetation. In conclusion, in order to sustain and maintain a soundly wetland ecosystem, it needs to several management of wetlands damage factors. 1) suppression of the excessive groundwater to basin, 2) stabilization of wetland via hydrologic storage, 3) suppression of changing and transforming wetland into forest by succession via management of xerophytic plants.

• Journal of Korean Society for Geospatial Information Science
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• v.12 no.1 s.28
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• pp.39-44
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• 2004

The SCS-CN method was known to have difficulties to the applied to the mountainous area like Korean river basins. This study focused to develop a distributed SCS-CN method considering river basin slopes from GIS data. For the purpose, the method was applied to Sulma river and compared with area weighted average method and distributed SCS-CN method using GIS. According to the results, SCS-CN method considering river basin slopes provided better effects on the estimating effective rainfall on the other methods. The necessity of the generalization of the results to the other rivers was discussed.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.146-146
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• 2022

A flash flood is one of the most hazardous natural events caused by heavy rainfall in a short period of time in mountainous areas with steep slopes. Early warning of flash flood is vital to minimize damage, but challenges remain in the enhancing accuracy and reliability of flash flood forecasts. The forecasters can easily determine whether flash flood is occurred using the flash flood guidance (FFG) comparing to rainfall volume of the same duration. In terms of this, the hydrological model that can consider the basin characteristics in real time can increase the accuracy of flash flood forecasting. Also, the predicted radar rainfall has a strength for short-lead time can be useful for flash flood forecasting. Therefore, using both hydrological models and radar rainfall forecasts can improve the accuracy of flash flood forecasts. In this study, FFG was applied to simulate some flash flood events in the Taehwa river basin by using of SURR model to consider soil moisture, and applied to the flash flood forecasting using predicted radar rainfall. The hydrometeorological data are gathered from 2011 to 2021. Furthermore, radar rainfall is forecasted up to 6-hours has been used to forecast flash flood during heavy rain in August 2021, Wulsan area. The accuracy of the predicted rainfall is evaluated and the correlation between observed and predicted rainfall is analyzed for quantitative evaluation. The results show that with a short lead time (1-3hr) the result of forecast flash flood events was very close to collected information, but with a larger lead time big difference was observed. The results obtained from this study are expected to use for set up the emergency planning to prevent the damage of flash flood.