• Title/Summary/Keyword: Effective rainfall

Search Result 489, Processing Time 0.027 seconds

A Practical Approach Determining an IDF formula with Limited Rainfall-Duration Data Availability (제한적 강우-지속기간 자료를 이용한 실용적 IDF 관계식의 유도)

  • Seong, Kee-Won
    • Journal of Korea Water Resources Association
    • /
    • v.41 no.6
    • /
    • pp.587-595
    • /
    • 2008
  • In order to aid the derivation of the IDF relationship for a station with insufficient duration-rainfall data, an approach to derive a simple and practical IDF formula is presented. The IDF formula is described simply by the term of the two parameters and a design frequency. The model parameters were estimated from a statistical technique based on the normal distribution of transformed rainfall intensities. In order to give the transformed data, both the Kruskal-Wallis statistic and the Manly transformation of duration-rainfall data were adopted. With the methods, the proposed IDF formula becomes a simpler model that compares well with conventional form. In addition, it allows avoiding an exceptional condition of the higher rainfall intensity for longer duration. The performance of the proposed formula was evaluated by using the limited rainfall data for short duration from two gauge stations. The result showed that the IDF formula developed in this work was an effective tool, providing a reliable relationship between the intensity and duration even though insufficient data are only available.

Evaluation for Non-Point Sources Reduction Effect by Vegetated Ridge and Silt Fence (식생밭두렁과 실트펜스를 이용한 밭 비점오염 저감효과 평가)

  • Kim, Dong-Hyeon;Kim, Sang-Min
    • Journal of The Korean Society of Agricultural Engineers
    • /
    • v.57 no.5
    • /
    • pp.129-137
    • /
    • 2015
  • The objective of this study was to test the non-point source pollution (NPS) control by the vegetated ridge and silt fence through field monitoring. The experiment plots were established with three sizes which are 5 m width by 22 m length with 8 %, 3 % slope and 15m width by 15 m length with 6 % slope. Flumes with the floating type stage gages were installed at the outlet of each plot to monitor the runoff. For a rainfall monitoring, tipping bucket rain gage was installed within the experiment site. Water quality samples were monitored during the heavy rainfall occurred. The amount of rainfall from 4 monitored events ranged from 27.6 mm to 130 mm. The runoff reduction rate could vary depending on slope, soil, crop growth condition, rainfall amount, rainfall intensity, antecedent moisture condition, and many other factors. The runoff from vegetated ridge and silt fence treatment plots was 24.05 % and -8.28 % lower than that from control plot, respectively. The monitoring results showed that the average pollution loads reduced by vegetated ridge compared to control were BOD 36.62~53.60 %, SS 40.41~73.71 %, COD 39.34~56.41 %, DOC 49.08~53.67 %, TN 26.74~67.23 %, and TP 52.72~91.80 %; by silt fence compared to control were SS 41.73 %, COD 1.93 %, and TN 2.38 %. The paired t-test result indicated that the vegetated ridge and silt fence were statistically significant effect in SS load reduction, with a 5 % significant level. Monitored results indicated that vegetated ridge and silt fence were both effective to reduce the pollutant from the field surface runoff.

A Characteristic Analysis of Critical Duration of Design Rainfall in Medium Sized Catchment (중규모 하천유역에서 임계지속기간 특성 분석)

  • Lee, Jung-Sik;Park, Jong-Young;Kim, Seok-Dong
    • Journal of the Korean Society of Hazard Mitigation
    • /
    • v.9 no.1
    • /
    • pp.135-144
    • /
    • 2009
  • The objective of this study is to examine the effect of hydrological factors on critical durations, and to analyze the relationship between the watershed characteristics and the critical duration of design rainfall in the medium sized catchments. Hydrological factors are used to return period, probable intensity formula, hydrograph method, effective rainfall and temporal pattern of design rainfall. Hydrologic analysis has done over the 44 medium sized catchments with $50{\sim}5,000{\beta}{\yen}$. Watershed characteristics such as catchment area, channel length, channel slope, catchment slope, time to peak, concentration of time and curve number were used to simulate correlation analysis. All of hydrological factors except return period influence to the critical duration of design rainfall. Also, it is revealed that critical duration is influenced by the watershed characteristics such as area, channel length, channel slope and catchment slope. Multiple regression analysis using watershed characteristics is carried out for the estimation of relationship among these. And the 7 type equations are proposed by the multiple regression using watershed characteristics and critical duration of design rainfall. The determination coefficient of multiple regression equations shows $0.96{\sim}0.97$.

Integration of top-down and bottom-up approaches for a complementary high spatial resolution satellite rainfall product in South Korea

  • Nguyen, Hoang Hai;Han, Byungjoo;Oh, Yeontaek;Jung, Woosung;Shin, Daeyun
    • Proceedings of the Korea Water Resources Association Conference
    • /
    • 2022.05a
    • /
    • pp.153-153
    • /
    • 2022
  • Large-scale and accurate observations at fine spatial resolution through a means of remote sensing offer an effective tool for capturing rainfall variability over the traditional rain gauges and weather radars. Although satellite rainfall products (SRPs) derived using two major estimation approaches were evaluated worldwide, their practical applications suffered from limitations. In particular, the traditional top-down SRPs (e.g., IMERG), which are based on direct estimation of rain rate from microwave satellite observations, are mainly restricted with their coarse spatial resolution, while applications of the bottom-up approach, which allows backward estimation of rainfall from soil moisture signals, to novel high spatial resolution soil moisture satellite sensors over South Korea are not introduced. Thus, this study aims to evaluate the performances of a state-of-the-art bottom-up SRP (the self-calibrated SM2RAIN model) applied to the C-band SAR Sentinel-1, a statistically downscaled version of the conventional top-down IMERG SRP, and their integration for a targeted high spatial resolution of 0.01° (~ 1-km) over central South Korea, where the differences in climate zones (coastal region vs. mainland region) and vegetation covers (croplands vs. mixed forests) are highlighted. The results indicated that each single SRP can provide plus points in distinct climatic and vegetated conditions, while their drawbacks have existed. Superior performance was obtained by merging these individual SRPs, providing preliminary results on a complementary high spatial resolution SRP over central South Korea. This study results shed light on the further development of integration framework and a complementary high spatial resolution rainfall product from multi-satellite sensors as well as multi-observing systems (integrated gauge-radar-satellite) extending for entire South Korea, toward the demands for urban hydrology and microscale agriculture.

  • PDF

Evaluation of Probability Rainfalls Estimated from Non-Stationary Rainfall Frequency Analysis (비정상성 강우빈도해석법에 의한 확률강우량의 평가)

  • Lee, Chang-Hwan;Ahn, Jae-Hyun;Kim, Tae-Woong
    • Journal of Korea Water Resources Association
    • /
    • v.43 no.2
    • /
    • pp.187-199
    • /
    • 2010
  • This study evaluated applicability and confidence of probability rainfalls estimated by the non-stationary rainfall frequency analysis which was recently developed. Using rainfall data at 4 sites which have an obvious increasing trend in observations, we estimated 3 type probability rainfalls; probability rainfalls from stationary rainfall frequency analysis using data from 1973-1997, probability rainfalls from stationary rainfall frequency analysis using data from 1973-2006, probability rainfalls from non-stationary rainfall frequency analysis assuming that the current year is 1997 and the target year is 2006. Based on the comparison of residuals from 3 probability rainfalls, the non-stationary rainfall frequency analysis provided more effective and well-directed estimates of probability rainfalls in the target year. Using Bootstrap resampling, this study also evaluated the parameter estimation methods for the non-stationary rainfall frequency analysis based on confidence intervals. The confidence interval length estimated by the maximum likelihood estimation (MLE) is narrower than the probability weighted moments (PWM). The results indicated that MLE provides more proper confidence than PWM for non-stationary probability rainfalls.

LSTM Prediction of Streamflow during Peak Rainfall of Piney River (LSTM을 이용한 Piney River유역의 최대강우시 유량예측)

  • Kareem, Kola Yusuff;Seong, Yeonjeong;Jung, Younghun
    • Journal of Korean Society of Disaster and Security
    • /
    • v.14 no.4
    • /
    • pp.17-27
    • /
    • 2021
  • Streamflow prediction is a very vital disaster mitigation approach for effective flood management and water resources planning. Lately, torrential rainfall caused by climate change has been reported to have increased globally, thereby causing enormous infrastructural loss, properties and lives. This study evaluates the contribution of rainfall to streamflow prediction in normal and peak rainfall scenarios, typical of the recent flood at Piney Resort in Vernon, Hickman County, Tennessee, United States. Daily streamflow, water level, and rainfall data for 20 years (2000-2019) from two USGS gage stations (03602500 upstream and 03599500 downstream) of the Piney River watershed were obtained, preprocesssed and fitted with Long short term memory (LSTM) model. Tensorflow and Keras machine learning frameworks were used with Python to predict streamflow values with a sequence size of 14 days, to determine whether the model could have predicted the flooding event in August 21, 2021. Model skill analysis showed that LSTM model with full data (water level, streamflow and rainfall) performed better than the Naive Model except some rainfall models, indicating that only rainfall is insufficient for streamflow prediction. The final LSTM model recorded optimal NSE and RMSE values of 0.68 and 13.84 m3/s and predicted peak flow with the lowest prediction error of 11.6%, indicating that the final model could have predicted the flood on August 24, 2021 given a peak rainfall scenario. Adequate knowledge of rainfall patterns will guide hydrologists and disaster prevention managers in designing efficient early warning systems and policies aimed at mitigating flood risks.

Re-establishing the Antecedent Moisture Condition of NRCS-CN Method Considering Rainfall-Runoff Characteristics in Watershed Based on Antecedent 5-Day Rainfall (유역의 강우-유출 특성을 고려한 NRCS-CN 방법의 선행토양함수조건의 재설정: 선행5일강우량을 기준으로)

  • Yoo, Ji-Young;Moon, Geon-Woo;Ahn, Jae-Hyun;Kim, Tae-Woong
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.34 no.3
    • /
    • pp.849-858
    • /
    • 2014
  • The mount of antecedent 5-day rainfall (P5) is usually used to determine the antecedent soil moisture condition for estimating effective rainfall using the NRCS-CN method. In order to re-establish the threshold of P5 considering basin characteristics, this study investigated the sensitivity of the threshold of P5 to effective rainfall by comparing the corresponding observed direct runoff. The overall results indicate that the direct runoff estimated using the re-establihed threshold of P5 has smaller mean error (RMSE of 27.3 mm) than those using the conventional threshold (RMSE of 35.2 mm). In addition, after evaluating the effectiveness of threshold of P5 using the improvement index, the threshold re-established in this study improved the ability to estimate the direct runoff by 30% on average. This study also suggested to employ regression models using topographic indices to re-establish the threshold for ungauged basins. When using the re-established threshold from the regression model, the RMSE decreased ranging from 0.4 mm to 15.1 mm and the efficiency index of Nash and Sutcliffe increased up to 0.33.

A Study on the application of Critical Rainfall Duration for the Estimation of Design Flood (설계홍수량 산정에 따른 임계지속시간의 적용성에 관한 연구)

  • Chang, Seong Mo;Kang, In Joo;Lee, Eun Tae
    • Journal of Wetlands Research
    • /
    • v.6 no.3
    • /
    • pp.119-126
    • /
    • 2004
  • In recent, the critical rainfall duration concept is widely used but we do not have understandable criteria yet. However, the critical rainfall duration is usually calculated considering concentration time, runoff model using effective rainfall, and unit hydrograph for the estimation of design flood. This study is to derive the regression equations between the critical rainfall duration and hydrologic components such as the basin area, slope, length, CN, and so on. We use a GIS tool which is called the ArcView for the estimation of hydrologic components and the HEC-1 module which is provided in WMS model is used for the runoff computation. As the results, the basin area, basin slope, and basin length had a great influence on the estimations of peak runoff and critical rainfall duration. We also investigated the sensitivities for the peak runoff and critical duration of rainfall from the correlation analysis for the involved components in the runoff estimation.

  • PDF

Sensitivity Analysis of the SWMM Model Parameters Based on Design Rainfall Condition (설계강우조건에 따른 SWMM모형 매개변수의 민감도 분석)

  • Lee, Jong-Tae;Hur, Sung-Chul;Kim, Tae-Hwa
    • Journal of Korea Water Resources Association
    • /
    • v.38 no.3 s.152
    • /
    • pp.213-222
    • /
    • 2005
  • This study is a sensitivity analysis of the parameters which affect the simulation results under various design rainfall conditions, using the SWMM model, for three selected basins in urban areas. The sensitivity of the peak flow rate is defined by $S_Q$ (=1.0 - (min. ratio of peak flow rate/max. ratio of peak flow rate)), and the rainfall conditions are classified in terms of design rainfall frequency, duration, and distribution. The simulation results show that in most conditions the parameters - the impermeable area ratio, the sewer slope, and the initial infiltration capacity - have more significant effects on the results than other parameters. As the design rainfall frequency increases, the sensitivity of the sewer slope and sewer roughness increases, while the parameters related with the surface runoff decrease. When the rainfall duration increases, the sensitivities of most parameters of surface runoff and sewer flow decrease. Also, at the 1st quarterly Huff rainfall distribution condition, the impermeable area ratio has high sensitivity, but at the 4th quarterly condition the parameters related with sewer flow show higher sensitivities. These tendencies can be explained by considering the procedure for computing the effective rainfall and kinematic wave on the surface and sewer flow.

Runoff analysis according to LID facilities in climate change scenario - focusing on Cheonggyecheon basin (기후변화 시나리오에서의 LID 요소기술 적용에 따른 유출량 분석 - 청계천 유역을 대상으로)

  • Yoon, EuiHyeok;Jang, Chang-Lae;Lee, KyungSu
    • Journal of Korea Water Resources Association
    • /
    • v.53 no.8
    • /
    • pp.583-595
    • /
    • 2020
  • In this study, using the RCP scenario for Hyoja Drainage subbasin of Cheonggyecheon, we analyzed the change with the Historical and Future rainfall calculated from five GCMs models. As a result of analyzing the average rainfall by each GCMs model, the future rainfall increased by 35.30 to 208.65 mm from the historical rainfall. Future rainfall increased 1.73~16.84% than historical rainfall. In addition, the applicability of LID element technologies such as porous pavement, infiltration trench and green roof was analyzed using the SWMM model. And the applied weight and runoff for each LID element technology are analyzed. As a result of the analysis, although there was a difference for each GCMs model, the runoff increased by 2.58 to 28.78%. However, when single porous pavement and Infiltration trench were applied, Future rainfall decreased by 3.48% and 2.74%, 8.04% and 7.16% in INM-CM4 and MRI-CGCM3 models, respectively. Also, when the two types of LID element technologies were combined, the rainfall decreased by 2.74% and 2.89%, 7.16% and 7.31%, respectively. This is less than or similar to the historical rainfall runoff. As a result of applying the LID elemental technology, it was found that applying a green roof area of about 1/3 of the urban area is the most effective to secure the lag time of runoff. Moreover, when applying the LID method to the old downtown area, it is desirable to consider the priority order in the order of economic cost, maintenance, and cityscape.