극치호우사상에 기초한 설계강우의 지속기간

박민규,박무종,김형수 한국방재학회 2011 한국방재학회논문집 Vol.11 No.5

Rainfall duration of design storm is one of most important factors of hydrologic design. However the study is rare to investigate the characteristics of rainfall duration, this make it difficult the efficient design procedure. In Korea, the critical storm duration has been used for calculating peak discharge for design. The critical storm duration is defined as the storm duration which produces the biggest flood peak discharge in considering various storm durations. However the suitability of this critical storm duration has not been proved in actual rainfall runoff relationships. In this study, annual maximum storm events and observed maximum rainfall-runoff data at dam stations are evaluated to assess the design rainfall duration, and the results are as follows. The most frequent rainfall duration is about 24 hours as extreme storm events in Korea. There was no significant trend between basin areas and design rainfall durations. The bigger basin area shows wider rainfall durations. The duration of 24 hours is most appropriate for the fixed design storm duration if the rainfall is uniformly distributed throughout the whole basin area. 설계강우의 지속기간은 수공설계에서 고려해야할 가장 중요한 인자 중의 하나이지만 이와 관련해서 연구성과의 부족은 효과적인 설계를 어렵게 하는 요인이 되고 있다. 우리나라의 수공설계에서는 첨두홍수량을 구하기 위해 임계지속기간을 고려하고 있다. 이를 위해 다양한 지속기간별로 유출계산을 실시하고 가장 큰 첨두홍수량이 얻어지는 지속기간을 설계강우의 지속기간으로설정하고 있다. 이와 관련하여 이러한 방법론이 적절한지를 관측극치호우를 기초로 평가한 연구는 찾아보기 어렵다. 본 연구에서는 설계호우의 지속기간을 평가하기 위해 연최대호우사상 계열과 댐유역의 강우유출자료를 평가하였으며 그 결과는 다음과 같다. 우리나라에서 극치호우 사상들이 보여주는 가장 빈번한 지속기간은 24시간 내외였다. 한편, 유역면적과 강우의 지속기간은뚜렷한 경향성을 가지고 있지 않았으며 다만 유역면적이 커질수록 면적강우의 지속기간의 범위가 보다 폭넓게 나타나는 특성이관찰되었다. 유역전체에 강우가 균등하게 내리는 경우를 가정할 수 있을 경우 적절한 설계강우의 지속기간은 대체로 24시간 내외를 가진다고 평가할 수 있었다. 핵심용어 : 설계강우, 지속기간, 연최대

강원도 춘천 지역의 산사태 발생 강우 임계치 분석

이원영(Won Young, Lee),성효현(Hyo Hyun, Sung) 대한지리학회 2018 대한지리학회지 Vol.53 No.5

본 연구의 목적은 강원도 춘천 지역에서 산사태를 일으키는 강우강도와 지속시간의 임계치와 누적강우량과 지속시간의 임계치를 구하고, 그에 대한 검증을 통해 최적 임계치를 구하는 것이다. 이를 위해 강우 이벤트의 정의를 주관적 정의, 24시간 무강수 기간 기준의 총 누적강우량을 반영한 강우 이벤트 정의, 24시간 무강수 기간 기준의 시간최대강우량 발생시점까지의 누적강우량을 반영한 강우 이벤트 정의의 3가지로 나누고, 분위회귀분석 방법으로 춘천 지역의 산사태 발생에 대한 2퍼센타일과 10퍼센타일의 임계치 식을 구하였다. 임계치에 대한 검증을 위해 Contingency Table과 Skill Score 값을 분석한 결과, 24시간 무강수 기간의 총 누적강우량에 대한 누적강우량과 지속시간의 2퍼센타일 임계치(E=73.915D<SUP>0.2046</SUP>, 22≤D≤231)가 최적의 임계치로 도출되었다. 그 다음으로 동일한 강우 이벤트 정의에서 구한 강우강도와 지속시간의 2퍼센타일 임계치(I=75.423D<SUP>-0.798</SUP>, 22≤D ≤231)가 2번째로 최적인 임계치로 도출되었다. 따라서 로컬 스케일의 강우 임계치 연구에서 누적강우량과 지속시간의 임계치가 강우강도와 지속시간의 임계치보다 산사태의 발생 가능성에 대한 예측 정확성을 높이고, 산사태 오경보 가능성을 최소화할 수 있는 최적의 판별 조건임을 알 수 있었다. 이는 산사태 발생여부 및 산사태 발생지점수와 강우요소와의 상관분석 결과에서 누적강우량과의 상관계수가 가장 높고, 강우강도와의 상관계수가 가장 낮은 것에서도 누적강우량의 중요성을 보여준다. 또한 산사태 발생유무는 강우지속시간보다 시간최대강우량과의 상관성이 더 높았고, 산사태 발생지점수는 시간최대강우량보다 강우지속시간과의 상관성이 높았다. 춘천지역의 강우 임계치를 대한민국 전역의 임계치와 비교하면 전반적으로 보다 긴 강우지속시간, 더 많은 누적강우량에서 산사태가 발생하기 시작하였다. The objective of this study is to determine intensity-duration thresholds and cumulative rainfall-duration thresholds for triggering landslides in Chuncheon, Korea, and to find the optimal threshold value through verification. For the purpose, we defined the definition of rainfall event as the subjective definition, total cumulative rainfall event after over 24-hour non-rainfall period, and cumulative rainfall until the hourly maximum rainfall after over 24-hour non-rainfall period. And 2 percentile and 10 percentile rainfall thresholds in chuncheon region were established, using quantile regression analysis. As a result of the analysis of the Contingency Table and the Skill Score value for the validation of the threshold value, cumulative rainfall-duration thresholds that reflect total cumulative event rainfall after over 24-hour non-rainfall period (E=73.915D<SUP>0.2046</SUP>, 22≤D≤231) was derived as the most optimal threshold value. Next, the rainfall intensity-duration threshold (I=75.423D<SUP>-0.798</SUP>, 22≤D≤231) obtained from the same rainfall event definition was derived as the second most optimal threshold. Therefore, in the study of the rainfall threshold of the local scale, the cumulative rainfall-duration threshold is the optimum discrimination condition which can increase the prediction accuracy of the possibility of landslide occurrence and minimize the possibility of the landslide false alarm than the rainfall intensity-duration threshold. This shows that cumulative rainfall is the most important factor in the result of correlation analysis between the occurrence of landslides or number of landslides and rainfall factors, and the correlation coefficient of rainfall intensity is the lowest. In addition, the occurrence of landslides was more correlated with the hourly maximum rainfall than rainfall duration, and the number of landslides was more correlated with rainfall duration than the hourly maximum rainfall. Landslides in Chuncheon began to occur in longer rainfall durations and more cumulative rainfall in comparison with the threshold values throughout Korea.

지역별 방재성능 달성을 위한 목표강우량에서 강우지속기간의 적용성에 관한 연구

안태진 한국방재학회 2014 한국방재학회논문집 Vol.14 No.6

소방방재청(2012)은 도시방재성능의 달성을 위하여 1시간, 2시간 및 3시간 강우지속기간을 갖는 목표강우량을 전국 지자체별로 제시한 바 있다. 지자체별로 제시된 목표강우량은 각 지역에서 확보하여야 할 최소한의 방재성능에 대응되는 강우량으로 정의하였으며 유하시설의 설계는 1시간 지속기간 목표강우량을 추천하였고 저류시설 및 유역대책은 2시간 및 3시간 지속기간 목표강우량을 추천하였으나, 목표강우량의 강우지속기간에 관한 많은 의문이 제기되었다. 이에 따라 본 연구는 먼저 우수관거 지구인 유하시설의 설계를 위하여 제시된 목표강우량의 강우지속기간의 적정성을 판단하고자, 대표적 도시유출 모형인 SWMM을 이용하여 10개 표본지구에 관하여 강우-유출 모의를 실시하고, 1시간 강우지속기간과 임계지속기간의 최대유출량을 비교하였다. 한편 저류지 및 펌프장 시설 경우에도 2시간 및 3시간 강우지속기간에 해당하는 최고수위와 임계지속기간의 최대수위를 비교하였으며, 이에 더불어 저류시설의 설계를위한 목표강우량의 적정한 강우지속기간을 검토하기 위하여 기수립된 114개소 사전재해 영향성 검토에서 결정된 방재조절지의 임계지속기간인 설계강우지속기간을 수집하였다. 이를 통하여 소방방재청에서 제시한 1시간, 2시간 및 3시간 강우지속기간 목표강우량을이용하여 도시방재성능을 평가하고 개선함에 있어서의 적용성을 보여 주었으며 공간적인 범위는 유역면적이 5.0 km2이내인 경우가 적정한 것으로 분석되었다. The National Emergency Management Agency, the NEMA(2012) in Korea has proposed regional target rainfall with 1, 2 and 3 hourrainfall duration for all 168 counties of our country to enhance regional disaster prevention performance. The proposed regional targetrainfall may be defined as the amount of rainfall corresponding a minimum of disaster prevention performance. Target rainfall with1 hour duration has been suggested for the conveyance facilities and 2 and 3 hour target rainfall for storage facilities and watershedmeasures. However, some question for applying duration of target rainfall has been raised. Thus, in this study rainfall - runoff simulationsby the SWMM for selected 10 sample municipal districts have been conducted to determine applicability of rainfall durationproposed by the NEMA in Korea. Since the peak flow by 1 hour rainfall may be almost same as the peak flow by critical rainfallduration for 10 sample basins, 1 hour rainfall duration in stormwater sewer districts may be selected as design rainfall duration. Furthermore,water level of stormwater storage and detention pond of drainage pumping system by 2 hour or 3 hour rainfall might bealmost same as the water level by critical rainfall duration. In addition the critical rainfall durations from the designed 114 projectshave been collected with the size of watershed and the durations of design rainfall. According to the analysis of watershed area andcritical duration, 2 hour or 3 hour rainfall duration may be used as design rainfall duration for 5 km2below watershed area. It has beenshown that 1, 2 and 3 hour target rainfall including rainfall distribution proposed by the NEMA in Korea may be used to estimate andto improve the integrated disaster prevention performance in urban area of interest.

연최대치 계열과 연최대치 독립 호우사상 계열의 비교

유철상,박철순 한국수자원학회 2012 한국수자원학회논문집 Vol.45 No.5

본 연구에서는 강우 지속기간이 짧은 경우와 긴 경우에 대한 연최대치 계열과 연최대치 독립 호우사상 계열의 차이를 살펴보았다. 연최대치 독립호우사상은 1961년부터 2010년까지의 서울지점 시강우 자료에 다양한 IETD와 절단값을 적용하여 추출하였다. 결정된 연최대치 독립호우사상 계열은 기존의 연최대치 계열과 비교하였다. 그 결과를 요약하면 다음과 같다. 첫째, IETD와 절단값의 영향은 예상할 수 있는 수준을 벗어나지 않았다. 예를 들어, IETD의 증가에 따라 짧은 지속기간 및 긴 지속기간을 갖는 독립 호우사상의 발생 빈도는 유사한 감소비율을 갖으나, 절단값의 증가에 따라서는 특히 지속기간이 긴 호우사상의 발생 빈도가 급격히 감소하는 것으로 나타났다. 둘째, 추출된 독립 호우사상의 평균 강우강도는 강우 지속기간에 관계없이 거의 일정한 것으로 나타났다. 이는 연 최대치 강우강도가 주로 지속기간이 긴 호우사상에서 결정될 가능성이 크다는 것을 의미한다. 마지막으로, 강우 지속기간이 짧은 경우, 연 최대치 계열과 연 최대치 독립 호우사상 계열의 차이가 매우 큰 것으로 확인되었다. 그러나 이러한 차이는 강우 지속기간이 증가함에 따라 현저히 줄어들었다. 이러한 결과는 특히 매우 짧은 집중시간을 고려하는 작은 유역의 경우, 전통적인 자료분석 방법을 통해 결정된 설계강우가 실제 발생 가능성이 없는 비현실적인 경우가 될 가능성이 매우 큼을 의미한다. This study investigated the differences between annual maximum series and annual maximum independent rainfall event series with relatively short and long rainfall durations. Annual maximum independent rainfall events were selected by applying various IETDs and thresholds to the hourly rainfall data in Seoul for the duration from 1961 to 2010. Annual maximum independent rainfall event series decided were then compared with the conventional annual maximum series. Summarizing the results is as follows. First, the effect of IETD and threshold was not beyond the expected level. For example, as the IETD increases, the frequencies of independent rainfall events decreased similarly in their rate for both with short and long durations. However, as the threshold increases, the frequency of those with rather long durations decreased much higher. Second, The mean rainfall intensity of the independent rainfall events was found to remain constant regardless of their duration. This indicates that the annual maximum rainfall intensity could be found in a rainfall event with longer durations. Lastly, the difference between the annual maximum rainfall series and the annual maximum independent rainfall event series with rather short rainfall durations was found significantly large, which decreases with longer durations. This result indicates that the conventional data analysis method, especially for small basins with short concentration time, could lead an unrealistic design rainfall with little possibility of occurrence.

A local-regional scaling-invariant Bayesian GEV model for estimating rainfall IDF curves in a future climate

Lima, Carlos H.R.,Kwon, Hyun-Han,Kim, Yong-Tak Elsevier 2018 Journal of hydrology Vol.566 No.-

<P><B>Abstract</B></P> <P>Future changes in rainfall patterns induced by climate changes will affect society and ecosystems, and quantifying these changes is of utmost importance for the management of hydroclimate risk. In particular, the estimation of intensity-duration-frequency (IDF) curves for rainfall data is a routine procedure in urban hydrology and hydraulic studies and should be revisited to reflect future changes in rainfall variability. In this work, we propose a novel methodology based on the scaling-invariant property of rainfall duration versus intensity to estimate parameters of a generalized extreme value (GEV) distribution at sub-daily scales. A Bayesian inference framework is developed so that uncertainties are reduced and can be easily propagated to IDF curves. The proposed model can be employed to: (i) improve local (at-site) GEV estimates for sites with limited rainfall records; (ii) estimate GEV parameters at sub-daily scales and construct IDF curves for sites where only daily rainfall records are available (partially gauged sites); (iii) construct regional IDF curves for homogeneous hydrologic regions; and (iv) update local and regional IDF curves from simulations of future daily rainfall. The model is tested using historical rainfall data from 18 gauges located in the Han River Watershed in South Korea, and projected climate change scenarios RCP 6 and RCP 8.5 from the Met Office Hadley Centre HadGEM2-AO model. When considering historical data, the results show that the model satisfactorily estimate IDF curves for both gauged and partially gauged sites. In future scenarios, the model reveals a substantial increase in rainfall events of rare intensity (large return periods), mostly due to changes in the rainfall variability rather than changes in the average rainfall. Particularly, for a 100-year return period event, we expect an increase of about 23% in scenario RCP 6 and about 30% under scenario RCP 8.5 when projected using regional IDF curves. To the best of our knowledge, this is the first statistical approach in the literature to assess future changes in regional IDF curves, which in our opinion is more suitable than evaluating local estimates only.</P>

선행강우를 고려한 산사태 유발 강우기준(ID curve) 분석

홍문현,김정환,정경자,정상섬 한국지반공학회 2016 한국지반공학회논문집 Vol.32 No.4

This study was conducted to suggest a landslide triggering rainfall threshold (ID curve) for landslide prediction byconsidering the effect of antecedent rainfall. 202 rainfall data including domestic landslide and rainfall records wereused in this study. In order to consider the effect of antecedent rainfall, rainfall data were analyzed by changing InterEvent Time Definition (IETD) and IETD based ID curve were presented by regression analysis. Compared to the findingsof the previous studies, the presented ID curve has a tendency to predict the landslides occurring at a relatively lowrainfall intensity. It is shown that the proposed ID curve is appropriate and realistic for predicting landslides throughthe validation of proposed ID curve using records of landslides in 2014. Based on this analysis, it is found that thelonger IETD, the greater the effect of antecedent rainfall, and the steeper the gradient of ID curve. It is also foundthat the rainfall threshold (intensity) is higher for the short period rainfall and lower for the long period rainfall.

설계강우의 지속시간 및 시간분포에 따른 배수개선 농경지 침수 영향 분석

전상민,강문성,김귀훈,이현지,강기호,유승환,최진용 한국농공학회 2022 한국농공학회논문집 Vol.64 No.2

The objective of this study was to analyze the effect of the duration and time distribution of probability rainfall on farmland inundation for the paddyfields in the drainage improvement project site. In this study, eight drainage improvement project sites were selected for inundation modeling. Hourlyrainfall data were collected, and 20- and 30-year frequency probability rainfalls were estimated for 14 different durations. Probability rainfalls weredistributed using Intensity-Duration-Frequency (IDF) and Huff time distribution methods. Design floods were calculated for 48 hr and critical duration,and IDF time distribution and Huff time distribution were used for 48 hr duration and critical duration, respectively. Inundation modeling was carriedout for each study district using 48 hr and critical duration rainfalls. The result showed that six of the eight districts had a larger flood discharge usingthe method of applying critical duration and Huff distribution. The results of inundation depth analysis showed similar trends to those of design floodcalculations. However, the inundation durations showed different tendencies from the inundation depth. The IDF time distribution is a distribution inwhich most of the rainfall is concentrated at the beginning of rainfall, and the theoretical background is unclear. It is considered desirable to applycritical duration and Huff time distribution to agricultural production infrastructure design standards in consideration of uniformity with other designstandards such as flood calculation standard guidelines.

춘천시에서 발생한 산사태 유발강우의 특성 분석

김상욱,백경오 한국안전학회 2022 한국안전학회지 Vol.37 No.6

Every year, particularly during the monsoon rainy season, landslides at the Chuncheon province of South Korea cause tremendous damage to lives, properties, and infrastructures. More so, the high rainfall intensity and long rainfall days that occurred in 2020 have increased the water content in the soil, thereby increasing the chances of landslide occurrences. Besides this, the rainfall thresholds and characteristics responsible for the initiation of landslides in this region have not been properly identified. Therefore, this paper addresses the rainfall thresholds responsible for the initiation of landslides at Chuncheon from a regional perspective. Using data obtained from rainfall measurements taken from 2002 to 2011, we identify a threshold relationship between rainfall intensity and rainfall duration for the initiation of landslides. In addition, we identify the relationship between the rainfall intensity using a 3-day, 7-day, and 10-day antecedent rainfall observation. Specifically, we estimate the rainfall data at 8 sites where debris flow occurred in 2011 by kriging. Following this, the estimated data are used to construct the relationship between the intensity (I), duration (D), and frequency (F) of rainfall. The results of the intensity-durationfrequency (IDF) analysis show that landslides will occur under a rainfall frequency below a 2-year return period at two areas in Chuncheon. These results will be effectively used to design structures that can prevent the occurrence of landslides in the future. -

Characteristics of Andong Dam Inflow during Non-rainfall Seaso

( Gey-hwan Park ),( Ki-bum Park ),( In-soo Chang ) 한국환경과학회 2018 한국환경과학회지 Vol.27 No.10

In this study, the runoff characteristics of the non-rainfall period were examined using daily rainfall data from 1977 to 2017 and the data of runoff into the dam. Results showed that, the mean runoff decreases with longer non-rainfall periods in the Andong dam basin. The correlation coefficient between non-rainfall days and average runoff reaches 0.85. The results of the analysis of the runoff characteristics during the non-rainfall period, based on the preceding rainfall of Andong dam are as follows. The runoff characteristics of the entire non-rainfall period, shows that, for a rainfall of 1.0 mm or less, the runoff height was larger than the rainfall size and the base runoff larger. The correlation between the antecedent rainfall and runoff height was reached as high as 0.9864 in the 30 ~ 50 mm interval of the antecedent rainfall period, and this is the interval where the linearity of rainfall and runoff was at its maximum in the Andong dam basin. The correlation between the antecedent rainfall and the runoff height reached 0.92 for rainfalls of 100.0 mm. However, for rainfalls of 100.0 mm greater, the correlation between the antecedent rainfall and runoff height during the rainfall period was 0.64, which is relatively small. In this study, we investigated the runoff characteristics of the rainfall period in the Andong dam watershed. As a result, it was confirmed that the mean runoff decreased with rainfall duration. The linearity was found to be weak for rainfall events greater than 100.0 mm. The results of this study can be used as data for water balance analysis and for formulating a water supply plan to establish water resource management of Andong dam.

불포화토 칼럼시험을 통한 연속강우와 반복강우의 강우침투속도 분석

박규보 ( Kyu Bo Park ),채병곤 ( Byung Gon Chae ),박혁진 ( Hyuck Jin Park ) 대한지질공학회 2011 지질공학 Vol.21 No.2

본 연구는 불포화 풍화토별 강우지속시간 및 비강우시간에 따른 강우침투속도 관계를 파악하기 위하여 국내에서 산사태 발생빈도가 높은 선캠브리아기 편마암 풍화토와 백악기 화강암 풍화토를 대상으로 불포화 풍화토 칼럼시험을 하였다. 본 연구에서는 일정시간 간격으로 체적함수비를 측정하기 위하여 함수비 측정 TDR센서를 이용하였다. 강우강도 조건은 20 mm/h로 선정하여 연속강우와 반복강우를 재현하였으며, 반복강우의 경우 강우시간과 비강우시간을 조절하였다. 그리고 흙의 단위중량조건은 편마암 풍화토의 경우 현장 건조단위중량보다 낮고 칼럼상부유출이 일어나지 않는 1.35 g/cm3, 화강암 풍화토의 경우 현장 건조단위중량인 1.21 g/cm3로 선정하였다. 편마암 풍화토와 화강암 풍화토 총 강우량 200 mm인 조건에서 2.090 × 10(-3)~2.854 × 10(-3) cm/s와 1.692 × 10(-3)~2.012 × 10(-3) cm/s로 총 강우량 100 mm에서의 1.309 × 10(-3)~1.871 × 10(-3) cm/s와 1.175 × 10(-3)~1.581 × 10(-3) cm/s보다 강우침투속도가 빠르게 나타났다. 이는 동일 시간당 토층 내 주입되는 물의 양이 200 mm조건에서 100 mm조건보다 많기 때문이다. 완전 건조 상태의 강우침투속도와 강우가 반복되어 물을 함유하고 있는 상태의 강우 재침투속도를 비교해 보면, 편마암 풍화토와 화강암 풍화토의 최초 강우침투속도인 1.309 × 10(-3)~2.854 × 10(-3) cm/s와 1.175 × 10(-3)~2.012 × 10(-3) cm/s보다 강우 재침투속도가 1.307 × 10(-2)~1.718 × 10(-2) cm/s와 1.789 × 10(-2)~2.070 × 10(-2) cm/s로 높게 나타났다. 이는 토층 내 공기의 함입량이 줄어들어서 불포화 투수계수에 영향을 미치는 흡입력(matric suction)이 감소한 것이 원인으로 생각된다. Unsaturated soil column tests were performed for weathered gneiss soil and weathered granite soil to assess the relationship between infiltration velocity and rainfall condition for different rainfall durations and for multiple rainfall events separated by dry periods of various lengths (herein, ``rainfall break duration``). The volumetric water content was measured using TDR (Time Domain Reflectometry) sensors at regular time intervals. For the column tests, rainfall intensity was 20 mm/h and we varied the rainfall duration and rainfall break duration. The unit weight of weathered gneiss soil was designed 1.21 g/cm3, which is lower than the in situ unit weight without overflow in the column. The in situ unit weight for weathered granite soil was designed 1.35 g/cm3. The initial infiltration velocity of precipitation for the two weathered soils under total amount of rainfall as much as 200 mm conditions was 2.090 × 10(-3) to 2.854 × 10(-3) cm/s and 1.692 × 10(-3) to 2.012 × 10(-3) cm/s, respectively. These rates are higher than the repeated-infiltration velocities of precipitation under total amount of rainfall as much as 100 mm conditions (1.309 × 10(-3) to 1.871 × 10(-3) cm/s and 1.175 × 10(-3) to 1.581 × 10(-3) cm/s, respectively), because the amount of precipitation under 200 mm conditions is more than that under 100 mm conditions. The repeated-infiltration velocities of weathered gneiss soil and weathered granite soil were 1.309 × 10(-3) to 2.854 × 10(-3) cm/s and 1.175 × 10(-3) to 2.012 × 10(-3) cm/s, respectively, being higher than the first-infiltration velocities (1.307 × 10(-2) to 1.718 × 10(-2) cm/s and 1.789 × 10(-2) to 2.070 × 10(-2) cm/s, respectively). The results reflect the effect of reduced matric suction due to a reduction in the amount of air in the soil.