• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.17 no.1
• /
• pp.17-23
• /
• 2009

The purpose of this study is possibility of the heavy rainfall prediction using instability index. The convective instability index using this study is Convective Available Potential Energy(CAPE) concerned the growth energy of the storm, Bulk Richardson Number(BRN) concerned the type and strength of the storm, and Sotrm Relative Helicity(SRH) concerned maintenance of the storm. To verify the instability index, the simulation of heavy rainfall case experiment by Numerical Weather Prediction(NWP) model(MM5) are designed. The results of this study summarized that the heavy rainfall related to the high instability index and the proper combination of one more instability index made the higher heavy rainfall prediction.

• Environmental Engineering Research
• /
• v.22 no.4
• /
• pp.393-400
• /
• 2017

One of the big problems facing municipalities is the management and control of urban flooding where urban drainage systems are under growing pressure due to increases in urbanization, population and changes in the climate. Urban flooding causes environmental and infrastructure damage, especially to roads, this damage increasing maintenance costs. The aim of the present study is to develop a decision support tool to identify the performance of storm networks to address future risks associated with climate change in the Middle East region and specifically, illegal sewer connections in the storm networks of Karbala city, Iraq. The storm water management model has been used to simulate Karbala's storm drainage network using continuous hourly rainfall intensity data from 2008 to 2016. The results indicate that the system is sufficient as designed before consideration of extra sewage due to an illegal sewer connection. Due to climate changes in recent years, rainfall intensity has increased reaching 33.54 mm/h, this change led to flooding in 47% of manholes. Illegal sewage will increase flooding in the storm system at this rainfall intensity from between 39% to 52%.

• Proceedings of the KSRS Conference
• /
• 2003.11a
• /
• pp.804-806
• /
• 2003

Probable Maximum Precipitation (PMP) is essential in the design of hydraulic structures such as dams, weirs and flood control structures. Up to the present, PMP has been derived from any proper single storm which can have a large error. PMP values should be evaluated from many historic heavy storm events from all over the country. Since this can be done at the spots of storm occurring and the calculated PMP from all spots in the country can be correlated. The objectives of this study are therefore to evaluate PMP from historic heavy storm data from 1972 to 2000 by using meteorological method, then to correlate and to present the results using GIS. The maximized rainfall depths can be calculate from depth of heavy rainfall and dew point temperature, and then can be analyzed for each rainfall duration to obtain spatial rainfall distribution by using GIS. The depth-area-duration relationship of maximized rainfall can be obtained and this helps to develop enveloped curves . The results from this study are a set of contour maps of PMP for each rainfall duration for all over the country and the depth-area-duration relationships for the area of 100 to 50,000 km.$^{2}$ at duration of 1, 2 and 3 days.

• Journal of Korea Water Resources Association
• /
• v.37 no.5
• /
• pp.437-448
• /
• 2004

The traditional fixed areal DAD(rainfall Depth-Area-Duration) method, generally quoted in most hydrology texts, is a simple and useful procedure when watersheds are small and storm movement is not an important factor of consideration. However, it is difficult to obtain satisfactory results for the more apparent forms of storm movement such as typhoons, or for large watershed. In the latter case, especially the margin of error for the areal average rainfall increases proportionally to the area of study, causing biased result. To overcome these limitations, this study focuses on the storm-centered DAD analysis(moving area DAD method) developed and programmed by the isohyetal concept to obtain accurate and objective results. By comparing and analyzing the observed rainfall rates through both method, it was proved that the currently Proposed method more accurately reflected the average rainfall rate. In short, through this new method, approximately 130 storm events nationwide from 1969 to 1999 was analyzed and compared with the fixed areal method results.

• Journal of Korean Society of Water and Wastewater
• /
• v.33 no.3
• /
• pp.177-190
• /
• 2019

The purpose of this study was to analyze the effects of sewerage facilities through I/I analysis by rainfall by selecting areas where storm overflow diverging chamber is remained due to the non-maintenance drainage equipment when the sewerage system was reconstructed as a separate sewer system. Research has shown that wet weather flow(WWF) increased from 106.2% to 154.8% compared to dry weather flow(DWF) in intercepting sewers, and that the WWF increased from 122.4% to 257.6% in comparison to DWF in storm overflow diverging chamber. As a result, owing to storm overflow diverging chamber of partially separate sewer system with untreated tributary of sewage treatment plant, rainfall-derived infiltration/inflow(RDII) has been analyzed 2.7 times higher than the areas without storm overflow diverging chamber. Meanwhile, infiltration quantity of this study area was relatively higher than that of other study areas. Therefore, it is necessary to reduce infiltration quantity through sewer pipe maintenance nearby river. Drainage equipment maintenance should be performed not to operate storm overflow diverging chamber in order to handle the appropriate sewage treatment plant capacity for rainfall because it is also expected that RDII due to rain will occur after maintenance. In conclusion, it is necessary to recognize aRDII(allowance of rainfall-derived infiltration/inflow) and to be reflected it on sewage treatment plant capacity because aRDII can occur even after maintenance to the complete separate sewer system.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.26 no.5
• /
• pp.292-299
• /
• 2014

Since most of the researches on the coastal inundation due to typhoons have considered only storm surges, an additional inundation due to rainfall has been neglected. In general, typhoons are natural disasters being accompanied by the rainfall. Thus, it is essential to consider the effect of rainfall in the numerical simulation of coastal inundation due to storm surges. Because the rainwater is discharged to the sea through the storm sewer system, it should be included in the numerical simulation of storm surges to obtain reasonable results. In this study an algorithm that can deal with the effects of rainfall and sewer system is developed and combined with a conventional storm surge numerical model. To test the present numerical model various numerical simulations are conducted using the simplified topography for the cases including the inundation due to rainfall, the drainage of rainwater, the backflow of sea water, and the increase of sea water level due to drainage of rainwater. As a result, it is confirmed that the basic performance of the present model is satisfactory for various flow situations.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.5
• /
• pp.619-624
• /
• 2005

This work is for examining a simplified equation based on the rational formula, which can easily decide storm-water detention volume in small urban catchments. The storm-water detention volume is determined by the inflow hydrograph flowing to detention basin and the outflow hydrograph discharged from the detention basin. The ratio of average outflow over the period of rainfall duration against allowable discharge was 0.5 in former simplified equation. But this research has found that the average outflow ratio depends on the storage methodology. In the case of the on-line storage method, the average outflow ratio is a function of the time of concentration of the catchments and rainfall duration, which ranged from 0.5~1.0. In the case of the off-line storage method, the average ratio is a function of peak discharge and allowable discharge except above time of concentration and rainfall duration, where its function value ranged from 1.0~2.0. When applying this equation to small catchment in Mokpo city, South Korea, we could easily calculate the relation curve between the storm-water detention volume and allowable discharge.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.26 no.2
• /
• pp.69-84
• /
• 1984

This study was carried out to investigate the time distribution of single storms and to establish the model of storm patterns in korea. Rainfall recording charts collected from 42 metheorological stations covering the Korean peninsula were analyzed. A single storm was defined as a rain period seperated from preceding and succeeding rainfall by 6 hours and more. Among the defined single storms, 1199 storms exceeding total rainfall of 80 mm were qualified for the study. Storm patterns were cklassified by quartile classification method and the relationship between cummulative percent of rainfalls and cummulative storm time was established for each quartile storm group. Time distribution models for each stations were prepared through the various analytical and inferential procedures. Obtained results are summarized as follows: 1. The percentile frequency of quartile storms for the first to the fourth quartile were 22.0%, 26.5%, 28.9% and 22.6%, respectively. The large variation of percentile frequency was show between the same quartile storms. The advanced type storm pattern was predominant in the west coastal type storm patterns predominantly when compared to the single storms with small total rainfalls. 3. The single storms with long storm durations tended to show delayed type storm patterns predominantly when compared to the single storms with short storm durations. 4. The percentile time distribution of quartile storms for 42 rin gaging stations was estimated. Large variations were observed between the percentiles of time distributions of different stations. 5. No significant differences were generally found between the time distribution of rainfalls with greater total rainfall and with less total rainfall. This fact suggests that the size of the total rainfall of single storms was not the main factor affecting the time distribution of heavy storms. 6. Also, no significant difference were found between the time distribution of rainfalls with long duration and with short duration. The fact indicates that the storm duration was no the main factor affecting the time distribution of heavy storms. 7. In Korea, among all single storms, 39.0% show 80 to 100mm of total rainfall which stands for the mode of the frequency distribution of total rainfalls. The median value of rainfalls for all single storms from the 42 stations was 108mm. The shape of the frequency distribution of total rainfalls showed right skewed features. No significant differences were shown in the shape of distribution histograms for total rainfall of quartile storms. The mode of rainfalls for the advanced type quartile storms was 80~100mm and their frequencies were 39~43% for respective quartiles. For the delayed type quartile storms, the mode was 80~100mm and their frequencies were 36!38%. 8. In Korea, 29% of all single storms show 720 to 1080 minutes of storm durations which was the highest frequency in the frequency distribution of storm durations. The median of the storm duration for all single storms form 42 stations was 1026 minutes. The shape of the frequency distribution was right skewed feature. For the advanced type storms, the higher frequency of occurrence was shown by the single storms with short durations, whereas for the delayed type quartile storms, the higher frequency was shown gy the long duration single storms. 9. The total rainfall of single storms was positively correlated to storm durations in all the stations throughout the nation. This fact was also true for most of the quartile storms. 10. The third order polynomial regression models were established for estimating the time distribution of quartile storms at different stations. The model test by relative error method resulted good agreements between estimated and observed values with the relative error of less than 0.10 in average.

• Water for future
• /
• v.26 no.2
• /
• pp.49-57
• /
• 1993

A hydrological method is performed to determine the critical duration of design rainfall for the design of storm sewer in Seoul. To seize the effect of the duration and the temporal distribution of the rainfall to the peak discharge of the storm sewer, the Huff's quartile method is used as a temporal pattern for the design rainfall of any durations (9 cases for 20-240 min.) with 10 years return period. The critical duration of design rainfall is determined as the duration which maximizes the peak discharge. This study is applied to 18 urban drainage systems in Seoul. The ILLUDAS model is applied to runoff analysis, and the result shows that the duration which maximizes peak discharge is 30, 60 minutes generally. The relation diagram between peak discharge for the critical duration and watershed area is prepared for the design of storm sewer.

• Journal of Korean Society of Water and Wastewater
• /
• v.19 no.5
• /
• pp.647-654
• /
• 2005

Recently, the economic losses caused by inundation are increasing due to the urbanization and industrialization, i.e., intensive land utilization and concentration of population and properties. It is regarded that the role of the storm sewer systems in urban areas becomes more important as one of the effective countermeasures for reducing the inundation losses. In this study, the effects of rainfall design frequency enhancement on the construction cost of the storm sewer systems were analyzed by increasing the design frequency from the present design frequency of the sewer systems, which is 5~10 years, to 15 years, 20 years and 30 years. The change rate functions of the design discharge and construction cost based on the various design frequencies were derived by regression analysis. According to the analysis, change the rate of design discharge at 15, 20, 30 years rainfall design frequencies were increased by 10%, 17.1%, and 27.2%, respectively, when compared to that at 10 year frequency. Furthermore, it was found that by increasing the design frequency from 10 years to 15 years, 20 years and 30 years, the construction costs were increased by 5.0%, 8.0% and 12.4%, respectively. Finally, their reliabilities need to be tested by applying the rate functions to the real storm sewer districts.