제주도 하천에 대한 SWAT 모형의 적용

정우열 ( Woo Yul Jung ),양성기 ( Sung Kee Yang ) 한국환경과학회 2008 한국환경과학회지 Vol.17 No.9

SWAT 모형을 이용한 제주도 하천의 유출량 모의

정우열 ( Woo Yul Jung ),양성기 ( Sung Kee Yang ) 한국환경과학회 2009 한국환경과학회지 Vol.18 No.9

한천유역의 홍수량 산정을 위한 HEC-HMS 모형의 민감도 분석

정우열 ( Woo Yul Jung ),양성기 ( Sung Kee Yang ),김동수 ( Dong Su Kim ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.4

The streams in Jeju Island have very distinctive hydrological and geological properties and there are a lot of limits in applying the general flood estimation method. This study presented parameters dominant in the Hancheon stream of Jeju Island by analyzing the sensitivity of parameters of HEC-HMS model regarding rainfall events in the target basin, and extracted the optimal parameter(Time of Concentration of Clark Unit Hydrograph: KravenⅡ method, Storage Coefficient: Sabol method) by analyzing and comparing it with the flood runoff data observed in the site and Jeju Island`s observation data.

제주도 도심하천 유역의 유출특성 해석

정우열 ( Woo Yul Jung ),양성기 ( Sung Kee Yang ),이준호 ( Jun Ho Lee ) 한국환경과학회 2013 한국환경과학회지 Vol.22 No.5

Jeju Island, the heaviest raining area in Korea, is a volcanic Island located at the southernmost of Korea, but most streams are of the dry due to its hydrological/geological characteristics different from those of inland areas. Therefore, there are limitations in applying the results from the mainland to the studies on stream run-off characteristics analysis and water resource analysis of Jeju Island. In this study, the SWAT(soil & water assessment tool) model is used for the Hwabuk stream watershed located east of the downtown to calculate the long-term stream run-off rate, and WMS(watershed modeling system) and HEC-HMS(hydrologic modeling system) models are used to figure out the stream run-off characteristics due to short-term heavy rainfall. As the result of SWAT modelling for the long-term rainfall-runoff model for Hwabuk stream watershed in 2008, 5.66% of the average precipitation of the entire basin was run off, with 3.47% in 2009, 8.12% in 2010, and root mean square error(RMSE) and determination coefficient(R2) was 496.9 and 0.87, respectively, with model efficient(ME) of 0.72. From the results of WMS and HEC-HMS models which are short-term rainfall-runoff models, unless there was a preceding rainfall, the runoff occurred only for rainfall of 40mm or greater, and the run-off duration averaged 10∼14 hours.

선행강우를 고려한 제주하천 유출특성 분석

양성기 ( Sung Kee Yang ),김동수 ( Dong Su Kim ),정우열 ( Woo Yul Jung ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.4

The rainfall-runoff characteristics in Jeju Island significantly differ from those in inland, due to highly permeable geologic features driven by volcanic island. Streams are usually sustained in the dry conditions and thereby the rainfall-runoff characteristics changes in terms of initiating stream discharge and its types, depending highly on the antecedent precipitation. Among various the rainfall-runoff characteristics, lag time mainly used for flood warning system in river and direct runoff ratio for determining water budget to estimate groundwater recharge quantity are practically crucial. They are expected to vary accordingly with the given antecedent precipitation. This study assessed the lag time in the measured hydrograph and direct runoff ratio, which are especially in the upstream watershed having the outlet as 2nd Dongsan bridge of Han stream, Jeju, based upon several typhoon events such as Khanun, Bolaven, Tembin, Sanba as well as a specific heavy rainfall event in August 23, 2012. As results, considering that the lag time changed a bit over the rainfall events, the averaged lag time without antecedent precipitation was around 1.5 hour, but it became increased with antecedent precipitation. Though the direct run-off ratio showed similar percentages (i.e., 23%) without antecedent precipitation, it was substantially increased up to around 45% when antecedent precipitation existed. In addition, the direct run-off ration without antecedent precipitation was also very high (43.8%), especially when there was extremely heavy rainfall event in the more than five hundreds return period such as typhoon Sanba.

산지하천의 전자파 표면유속 측정에 기반한 유량 및 유속 관측 오차 분석

김동수 ( Dong Su Kim ),양성기 ( Sung Kee Yang ),정우열 ( Woo Yul Jung ) 한국환경과학회 2014 한국환경과학회지 Vol.23 No.4

Fixed Electromagnetic Wave Surface Velocimetry (Fixed EWSV) has been started to be used to measure flood discharge in the mountain stream, since it has various advantages such that it works well to continuously measure stream discharge even in the night time as well as very strong weather. On the contrary, the Fixed EWSV only measures single point surface velocity, thus it does not consider varying feature of the transverse velocity profile in the given stream cross-section. In addition, a conventional value of 0.85 was generally used as the ratio for converting the measured surface velocity into the depth-averaged velocity. These aspects could bring in error for accurately measuring the stream discharge. The capacity of the EWSV for capturing rapid flow velocity was also not properly validated. This study aims at conducting error analysis of using the EWSV by: 1) measuring transverse velocity at multiple points along the cross-section to assess an error driven by the single point measurement; 2) figuring out ratio between surface velocity and the depth-averaged velocity based on the concurrent ADCP measurements; 3) validating the capacity of the EWSV for capturing rapid flow velocity. As results, the velocity measured near the center by the fixed EWSV overestimated about 15% of the cross-sectional mean velocity. The converting ratio from the surface velocity to the depth-averaged velocity was 0.8 rather than 0.85 of a conventional ratio. Finally, the EWSV revealed unstable velocity output when the flow velocity was higher than 2 m/s.

ADCP 다중빔 수심계측자료의 위상학적 보정 알고리즘 개발

김동수 ( Dong Su Kim ),양성기 ( Sung Kee Yang ),김수정 ( Soo Jeong Kim ),정우열 ( Woo Yul Jung ) 한국환경과학회 2013 한국환경과학회지 Vol.22 No.5

Acoustic Doppler Current Profilers (ADCPs) are increasingly popular in the river research and management communities being primarily used for estimation of stream flows. ADCPs capabilities, however, entail additional features that are not fully explored, such as morphological representation of river or reservoir bed based upon multi-beam depth measurements. In addition to flow velocity, ADCP measurements include river bathymetry information through the depth measurements acquired in individual 4 or 5 beams with a given oblique angle. Such sounding capability indicates that multi-beam ADCPs can be utilized as an efficient depth-sounder to be more capable than the conventional single-beam eco-sounders. The paper introduces the post-processing algorithms required to deal with raw ADCP bathymetry measurements including the following aspects: a) correcting the individual beam depths for tilt(pitch and roll); b) filtering outliers using SMART filters; d) transforming the corrected depths into geographical coordinates by UTM conversion; and, e) tag the beam detecting locations with the concurrent GPS information; f) spatial representation in a GIS package. The developed algorithms are applied for the ADCP bathymetric dataset acquired from Han-Cheon in Jeju Island to validate themselves applicability.

다양한 첨단 유량 계측기기를 활용한 제주도 하천 유출 비교 분석

양성기 ( Sung Kee Yang ),김동수 ( Dong Su Kim ),정우열 ( Woo Yul Jung ),류권규 ( Kwon Kyu Yu ) 한국환경과학회 2011 한국환경과학회지 Vol.20 No.6

Different from the main land of South Korea, Jeju Island has been in difficulties for measuring discharge. Due to high infiltration rate, most of streams in Jeju Island are usually in the dried state except six streams with the steady base flow, and the unique geological characteristics such as steep slope and short traveling distance of runoff have forced rainfall runoff usually to occur during very short period of time like one or two days. While discharge observations in Jeju Island have been conducted only for 16 sites with fixed electromagnetic surface velocimetry, effective analysis and validation of observed discharge data and operation of the monitoring sites still have been limited due to very few professions to maintain such jobs. This research is sponsored by Ministry of Land, Transport and Maritime Affairs to build water cycle monitoring and management system of Jeju Island. Specifically, the research focuses on optimizing discharge measurement techniques adjusted for Jeju Island, expanding the monitoring sites, and validating the existing discharge data. First of all, we attempted to conduct discharge measurements in streams with steady base flow, by utilizing various recent discharge monitoring techniques, such as ADCP, LSPIV, Magnetic Velocimetry, and Electromagnetic Wave Surface Velocimetry. ADCP has been known to be the most accurate in terms of discharge measurement compared with other techniques, thus that the discharge measurement taken by ADCP could be used as a benchmark data for validation of others. However, there are still concerns of using ADCP in flood seasons; thereby LSPIV would be able to be applied for replacing ADCP in such flooded situation in the stream. In addition, sort of practical approaches such as Magnetic Velocimetry, and Electromagnetic Wave Surface Velocimetry would also be validated, which usually measure velocity in the designated parts of stream and assume the measured velocity to be representative for whole cross-section or profile at any specified location. The result of the comparison and analysis will be used for correcting existing discharge measurement by Electromagnetic Wave Surface Velocimetry and finding the most optimized discharge techniques in the future.

토지이용변화에 따른 한천유역의 홍수유출 변동 분석

양세창 ( Se Chang Yang ),양성기 ( Sung Kee Yang ),이준호 ( Jun Ho Lee ),정우열 ( Woo Yul Jung ),고광효 ( Kwang Hyo Ko ) 한국환경과학회 2015 한국환경과학회지 Vol.24 No.4

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.

통계적 기법을 적용한 외도천의 단위유량도 제안

이준호 ( Jun Ho Lee ),양성기 ( Sung Kee Yang ),정우열 ( Woo Yul Jung ) 한국환경과학회 2015 한국환경과학회지 Vol.24 No.4

Rainfall-runoff model of Jeju Oedo Stream was used to compute the optimal unit hydrograph by HEC-HMS model that reflecting on watershed characteristics. Each rainfall event was comparatively analyzed with the actual flow measurement using Clark, Snyder and SCS synthetic methods for derived unit hydrograph. Subsequently, the null hypothesis was established as p-value for peak flow and peak time of each unit hydrograph by one-way ANOVA(Analysis of variance) was larger than significance level of 0.05. There was no significant difference in peak flow and peak time between different methods of unit hydrograph. As a result of comparing error rate with actual flow measurement data, Clark synthetic unit graph best reflected in Oedo Stream as compared to other methods, and error rate of Clark unit hydrograph was 0.02~1.93% and error rate at peak time was 0∼2.74%.