Design Rainfall Research Articles

Rainfall–Runoff Analysis for Sustainable Stormwater Drainage for the City of Madinah, Saudi Arabia

Design of urban drainage infrastructure depends on the rainfall pattern and runoff volumes. Under the current impacts of urbanization and industrialization in the Kingdome of Saudi Arabia (KSA), there is a need to review the guidelines for design of drainage infrastructure. In this study, a methodology is developed to investigate the impact of variations in rainfall on the capacity of drainage infrastructure for the city of Madinah (Taibah), KSA. Rainfall data collected from Madinah Municipality was analyzed to determine the normal annual rainfall (average of the annual rainfall for 30 years). Data consistency was checked using double mass curve technique, and the design rainfall (DR) was estimated by Gumbel Extreme Value Distribution. The Mann-Kendall test was run at 5% significance level on rainfall time series over the period 1985–2015; however, no significant trend was observed. Urban drainage schemes are designed for peak flows based on DR. The true values of DR are difficult to estimate due to uncertainties associated with variations in estimation procedures and data limitations. An attempt is made to elaborate the impact of data errors (both systematic and random) on DR to facilitate engineers in selecting safety factor for design of urban drainage infrastructure. The stormwater trunk-sewer was designed to safely convey the runoff for an area around the Masjid-e-Al-Nabawi. Rainfall–runoff modeling was performed by Rational Method to find the peak flow and Nash GIUH. It was found that there is about 20% change in diameter of trunk sewer for change in return period from 2 to 10 years.

A comparison of methods to estimate future sub-daily design rainfall

Abstract Warmer temperatures are expected to increase extreme short-duration rainfall due to the increased moisture-holding capacity of the atmosphere. While attention has been paid to the impacts of climate change on future design rainfalls at daily or longer time scales, the potential changes in short duration design rainfalls have been often overlooked due to the limited availability of sub-daily projections and observations. This study uses a high-resolution regional climate model (RCM) to predict the changes in sub-daily design rainfalls for the Greater Sydney region in Australia. Sixteen methods for predicting changes to sub-daily future extremes are assessed based on different options for bias correction, disaggregation and frequency analysis. A Monte Carlo cross-validation procedure is employed to evaluate the skill of each method in estimating the design rainfall for the current climate. It is found that bias correction significantly improves the accuracy of the design rainfall estimated for the current climate. For 1 h events, bias correcting the hourly annual maximum rainfall simulated by the RCM produces design rainfall closest to observations, whereas for multi-hour events, disaggregating the daily rainfall total is recommended. This suggests that the RCM fails to simulate the observed multi-duration rainfall persistence, which is a common issue for most climate models. Despite the significant differences in the estimated design rainfalls between different methods, all methods lead to an increase in design rainfalls across the majority of the study region.

Probability analysis of seasonal rainfall pattern for Ananthapuramu district of Andhra Pradesh

Rainfall is the major controlling factor in planning of agricultural programmes, design and management of any water resource scheme. India is predominantly an agricultural country with about 60 per cent of the cultivated area under rainfed conditions. The present study was carried for Ananthapuram district which is one among the rainfed areas in the country.The design rainfall is calculated from the probability analysis. It is assigned some probability level of occurrence or exceedance. The daily or monthly rainfall analysis for a wide range of applications extending from real time monitoring and prediction of flood events to initialization and validation of numerical weather prediction (NWP), climate analysis and climate diagnostic study. The study showed there is a large variation in the rainfall received yearly as well as Kharif and Rabi seasons. Similarly the co-efficient of variation is 39.15 per cent for yearly rainfall, 57.35 per cent for Kharif and 65.18 per cent for Rabi seasons this indicates the annual rainfall data are less variable and is more stable or more uniform. The probability analyses were conducted for the year 2001-2012. Probability of getting 2012 year wise as well as season wise the yearly rainfall is 731mm only five per cent and probability of getting 413mm is 94.9 per cent. It indicates that the last 12 years trend shows the yearly rainfall will not cross 400-500 mm which is the bench mark for designing the crops that are to be grown in Ananthapuramu district. Similar trends were noticed in the probability analysis in season wise. When analyzed statistically there was a negative correlation between water requirement and yield and similarly positive correlation between rainfall and yield, the results are reflected. The trend values are shown linearly dependent. There is a perfect linear dependency on the trend values. The actual crop water requirements are progressively decreasing from 2012 to 2020.

A Practical Method to Prevent an Overestimation of Peak Discharge in a Small Watershed

We proposed a practical method which prevents an overestimation of peak discharge in a small watershed. In ‘rainfall intensity-duration’ relationship, as duration value is arbitrarily increased, rainfall intensity is decreased. This design rainfall adjustment deduced peak discharge efficiently without change in the ‘time of concentration’ and ‘storage coefficient’ of watershed. We also suggested guidelines for selecting a correction factor of rainfall duration by comparing to the existing methods. In addition, we developed the alternative way to avoid the discontinuous peak discharge in the upper boundary of area defining a small watershed. Keywords: Small Watershed, Peak Discharge, Unit Hydrograph, Rainfall Intensity, Duration

Modification of a design storm pattern for urban drainage systems considering the impact of climate change

Inundation of urban areas due to heavy rainfall more frequently occurs in many large cities all over the world. This is more evident now due to the impacts of climate change. The design rainfall storm pattern, an input used to design urban drainage systems, plays an important role for developing sufficient drainage capacity for big cities. There are few studies in Thailand focusing on the accuracy of the Chicago Design Storm, which has been widely used for decades, in estimation of the peak intensity of rainfall for drainage systems. This study aims to first examine the accuracy of the Chicago Design Storm using observed data. Second, the impacts of climate change on rainfall intensity and on the Chicago Design Storm were investigated. Bangkok and its vicinity were selected as study area. Rainfall storm data with 1-5 minutes records and 15 minute records were collected from the meteorological station at AIT over the past 21 years and from the rainfall station in Sukhumvit area of Bangkok for 15 years. The Gumbel distribution was used in a Frequency Analysis to establish IDF Curves. The CDS, Yen & Chow and Sifalda methods were used to synthesize a Design Storm Pattern. Comparison of results of these methods with the observed data revealed that the CDS has good agreement in shape, i.e. peak intensity and time to peak. The CDS is still recommended for use in practice. However, MAPE was also used to evaluate accuracy of the synthesized CDS in comparison with the observed data. It was found that the CDS should be modified to reduce its peak intensity. Moreover, the impact of climate was also investigated. The Equidistance Quantile-Matching Method was adopted to compute IDF curves to include the climate change impact. The Global Climate Model (GCM), and HasGEM2-ES with RCP4.5 were used to generate rainfall data for the next 25 years. The changes in IDF curves due to climate change were compared. With the changed IDF curves, the peak intensity of design storms increased by up to 25%. It is therefore recommended to account for the impacts of climate change on design storms.

Bivariate frequency analysis of rainfall intensity and duration for urban stormwater infrastructure design

This study presents a storm-event based bivariate frequency analysis approach to determine design rainfalls in which, the number, intensity and duration of actual rainstorm events were considered. To derive more realistic design storms, the occurrence probability of an individual rainstorm event was determined from the joint distribution of storm intensity and duration through a copula model. Hourly rainfall data were used at three climate stations respectively located in Singapore, South Korea and Canada. It was found that the proposed approach could give a more realistic description of rainfall characteristics of rainstorm events and design rainfalls. As results, the design rainfall quantities from actual rainstorm events at the three studied sites are consistently lower than those obtained from the conventional rainfall depth-duration-frequency (DDF) method, especially for short-duration storms (such as 1-h). It results from occurrence probabilities of each rainstorm event and a different angle for rainfall frequency analysis, and could offer an alternative way of describing extreme rainfall properties and potentially help improve the hydrologic design of stormwater management facilities in urban areas.

THE IMPACTS OF PELOSIKA AND AMERORO DAMS IN THE FLOOD CONTROL PERFORMANCE OF KONAWEEHA RIVER

Konaweeha watershed is the largest watershed in Southeast Sulawesi with Konaweeha River as the main river. The main issues in Konaweeha Watershed is floods that occur caused damage to infrastructure and public facilities, lowering agricultural production, and cause fatalities. One of the government's efforts to cope with the flooding problem in Konaweeha Watershed is planning the construction of multi-purpose dams in the upstream of Konaweeha Watershed that is Pelosika Dam and Ameroso Dam. Necessary to study the flood control performance of the two dams. Analyses were performed with hydrologic-hydraulic modeling using HEC-HMS software (Hydrologic Modelling System) version 4.0 and HEC-RAS (River Analysis System) version 4.1. The design rainfalls that were used as input to the model were 2 year, 5-year, 10-year and 25 year. Scenarios used in this study are: (1) Existing Scenario (2) Pelosika Dam Scenario; (3) Ameroro Dam Scenario; (4) Pelosika and Ameroro Dams Scenario. The results showed the maximum water surface elevation along the downstream of Konaweeha River in Scenario (2) and (4) were almost the same in the 2 and 5 years return period design flood. However, in case of 10 and 25 years return period, the difference of maximum water surface elevation at downstream of Konaweeha River was slightly significant. Furthermore, the damping efficiency of the peak discharge (at Probably Maximum Flood or PMF) was found to be 71.70% and 18.18% for the individual Pelosika Dam and Ameroro Dam respectively. Further discussion suggests the development of Pelosika Dam as the higher priority rather than that of the Ameroro Dam.

Extreme 1-day rainfall distributions: Analysing change in the Western Cape


 
 
 Severe floods in the Western Cape Province of South Africa have caused significant damage to property and infrastructure over the past decade (2003–2014). The hydrological design criteria for exposed structures and design flood calculations are based mostly on the implicit assumption of stationarity, which holds that natural systems vary within an envelope of variability that does not change with time. This assumption was tested by examining the changes in extreme 1-day rainfall high percentiles (95th and 98th) and both the 20- and 50-year return period rainfall, comparing the period 1950–1979 against that of 1980–2009 across the province. A generalised Pareto distribution and a peaks-over-threshold sampling approach was applied to 76 rainfall stations across the province. Of these stations, 48 (63%) showed an increase in the 50-year return period 1-day rainfall and 28 (37%) showed a decrease in the 1980–2009 period at the 95th percentile peaks-over-threshold. At the 98th percentile peaks-over-threshold, 49 stations (64%) observed an increase and 27 (36%) a decrease for the later period. The change in the number of 3-day storms from the first to the second period is negligible, evaluated at 0.9% and 0.5% at the 95th and 98th percentile peaks-over-threshold levels, using cluster analysis. While there is no clear spatial coherency to the results, the general trend indicates an increase in frequency of intense rainfalls in the latter half of the 20th and early 21st centuries. These results bring into question assumptions of stationarity commonly used in design rainfall.
 
 
 
 
 Significance: 
 
 
 
 63% of analysed rainfall stations in the Western Cape display an increase in 20- and 50-year 1-day rainfall extremes.
 The results challenge the current assumptions of climate stationarity made in design rainfall estimations.
 We propose an alternative methodology to rainfall extremes analysis for design flood estimation.
 The methods employed can be replicated by future studies in other regions.
 
 
 

Integrating nonstationary behaviors of typhoon and non-typhoon extreme rainfall events in East Asia

Extreme rainfall events in East Asia can be derived from the two subcomponents of tropical cyclones (TC) and non-TC based rainfall (mostly summer monsoons). Critical natural hazards including floods and landslides occur repeatedly due to the heavy rainfall associated with the two subcomponents, and disaster losses are increasing because global warming has caused changes in the extreme rainfall characteristics of two subcomponents. Subsequently, the frequency and intensity of extreme rainfall have reportedly become nonstationary. The majority of literature on nonstationary frequency analyses do not account for the different behaviors (stationarity or nonstationarity) of annual maximum rainfall (AMR) from the two subcomponents (PMTC and PMNTC). To carry out a nonstationary frequency analysis considering the different behaviors of the PMTC and PMNTC series, this study proposes a novel approach of integrating the fitted PMTC and PMNTC series after modeling the nonstationarity of the PMTC and PMNTC series individually. The presented results conclude that the proposed approach provides more reliable estimates than existing nonstationary approaches by reflecting the different features of the PMTC and PMNTC series. We suggest that the proposed approach provides a reasonable design rainfall in constructing hydraulics to mitigate the different nonstationary effects of two TC and non-TC rainfall extremes.

Modeling the probability distribution of peak discharge for infiltrating hillslopes

AbstractHillslope response plays a fundamental role in the prediction of peak discharge at the basin outlet. The peak discharge for the critical duration of rainfall and its probability distribution are needed for designing urban infrastructure facilities. This study derives the probability distribution, denoted as GABS model, by coupling three models: (1) the Green‐Ampt model for computing infiltration, (2) the kinematic wave model for computing discharge hydrograph from the hillslope, and (3) the intensity‐duration‐frequency (IDF) model for computing design rainfall intensity. The Hortonian mechanism for runoff generation is employed for computing the surface runoff hydrograph. Since the antecedent soil moisture condition (ASMC) significantly affects the rate of infiltration, its effect on the probability distribution of peak discharge is investigated. Application to a watershed in Sicily, Italy, shows that with the increase of probability, the expected effect of ASMC to increase the maximum discharge diminishes. Only for low values of probability, the critical duration of rainfall is influenced by ASMC, whereas its effect on the peak discharge seems to be less for any probability. For a set of parameters, the derived probability distribution of peak discharge seems to be fitted by the gamma distribution well. Finally, an application to a small watershed, with the aim to test the possibility to arrange in advance the rational runoff coefficient tables to be used for the rational method, and a comparison between peak discharges obtained by the GABS model with those measured in an experimental flume for a loamy‐sand soil were carried out.

Zero increase in peak discharge for sustainable development

For urban land development, some or all natural land uses (primarily pervious) are converted into impervious areas which lead to increases of runoff volume and peak discharge. Most of the developed countries require a zero increase in peak discharge for any land development, and the policy has been implemented for several decades. The policy of zero increase in peak discharge can be considered as historical and early stage for the low impact development (LID) and sustainable development, which is to maintain natural hydrological conditions by storing a part or all of additional runoff due to the development on site. The paper will discuss the policy, the policy implementation for individual projects and their impact on regional hydrology. The design rainfalls for sizing LID facilities that are determined in 206 weather stations in USA are smaller than design rainfalls for sizing detention basins. The zero-increase policy links to financial responsibility and sustainability for construction of urban stormwater infrastructures and for reducing urban flooding. The policy was compared with current practices of urban development in China to shine the light for solving urban stormwater problems. The connections and differences among LID practices, the zero-increase policy, and the flood control infrastructure were discussed.We promote and advocate the zero-increase policy on peak discharge for comprehensive stormwater management in China in addition to LID.

Climate change effects and extreme rainfall non-stationarity

It is necessary to perform analysis to confirm stationarity or detect non-stationarity of extreme rainfall data in order to derive accurate design rainfall estimates for hydraulic structure design. In this study, non-stationarity of extreme rainfalls in the Antalya region in Turkey was investigated through statistical non-stationarity tests and stationary and non-stationary generalised extreme value distribution models. After determination of stationarity of extreme rainfalls in the Antalya region, a frequency analysis was conducted in a stationary context to derive design rainfall intensities. Future (2080–2099) design rainfall intensities were then estimated and bias corrected, and current and future design rainfall intensities were compared and discussed. Non-stationarity analysis showed no evidence of non-stationarity in Antalya. Bias-corrected future design rainfall intensity estimates showed that design rainfall intensities in the future are expected to be larger than current design rainfall intensities for return periods of 5, 10, 20, 50 and 100 years. This study is expected to contribute to a better understanding of the relationship between global warming and extreme rainfall in one of the most climate change sensitive parts of Turkey.

A comparison of methods for estimating climate change impact on design rainfall using a high-resolution RCM

Design rainfall is used to analyse and size water infrastructure and is generally derived from historical rainfall records. Given the expected changes in extreme rainfall due to anthropogenic climate change, future hydrologic design based on historical data may not be appropriate. While a number of studies have assessed the impact of climate change on design rainfall using different methods, to date there has been no comprehensive comparison or examination of the implications of alternative methods on future design rainfall estimates. This study compares the nine methods for estimating the design rainfall for the current climate and the potential changes in the future for the Greater Sydney region. A Monte Carlo cross-validation procedure was employed to evaluate the skill of each method in estimating the design rainfall for the current climate. It was found that bias correcting the annual maximum rainfall based on the empirical distribution combined with regional frequency analysis produces the design rainfall closest to the observations. While regional frequency analysis was found to have limited impact on the design rainfall estimation for the current climate, it provides much more spatially coherent patterns of future change and it is recommended that regionalisation be used in all design rainfall impact assessments. Despite the variations between different methods, a 20–35% increase in design rainfall over the coastal region is consistently projected. This will pose significant challenges for existing infrastructure in that area.

극치자료계열의 Scaling 특성과 Bayesian GLM Model을 이용한 지역빈도해석

확률강수량 산정은 하천관리, 수공구조물 설계 및 위험도 분석에 있어 중요한 기초적인 자료 중 하나이다. 실무에서는 대표지속시간에 대해서 지점빈도해석을 통해 확률강수량을 추정하고 이를 지속시간에 대해서 회귀분석을 실시하여 IDF (intensity-duration-frequency) 곡선을 작성한다. 이들 IDF곡선을 활용하여 기타 지속시간에 대해서는 내삽 또는 외삽으로 보간 하여 확률강수량 추정이 이루어지고 있다. 우리나라의 경우 상대적으로 자료 연한이 짧은 점을 고려한다면, 보다 정확하고 신뢰성 있는 확률강수량 산정 기법의 필요성이 대두되고 있다. 이러한 이유로 본 연구에서는 Bayesian GLM 모형을 통하여 자료의 확률분포 매개변수의 Scaling 특성을 고려할 수 있는 지역빈도해석 모형을 개발하였다. 모형 적용결과 개별지점에서 효과적인 매개변수 추정뿐만 아니라, 유역전체의 특성을 대표하는 매개변수 추정이 가능하였다. 본 연구결과를 통해 도출된 IDF 곡선은 향후 다양한 수자원분야의 기초자료로 활용될 수 있을 것으로 기대되며, 미계측유역 또는 지속시간별 자료가 불충분한 지역에 대해서도 활용이 가능할 것으로 판단된다. Design rainfalls are one of the most important hydrologic data for river management, hydraulic structure design and risk analysis. The design rainfalls are first estimated by a point frequency analysis and the IDF (intensity-duration-frequency) curve is then constructed by a nonlinear regression to either interpolate or extrapolate the design rainfalls for other durations which are not used in the frequency analysis. It has been widely recognised that the more reliable approaches are required to better account for uncertainties associated with the model parameters under circumstances where limited hydrologic data are available for the watershed of interest. For these reasons, this study developed a hierarchical Bayesian based GLM (generalized linear model) for a regional frequency analysis in conjunction with a scaling function of the parameters in probability distribution. The proposed model provided a reliable estimation of a set of parameters for each individual station, as well as offered a regional estimate of the parameters, which allow us to have a regional IDF curve. Overall, we expected the proposed model can be used for different aspects of water resources planning at various stages and in addition for the ungaged basin.

Extreme Precipitation Frequency Analysis Using a Minimum Density Power Divergence Estimator

The recently observed hydrologic extremes are unlike what has been experienced so far. Both the magnitude and frequency of extremes are important indicators that determine the flood safety design criteria. Therefore, how are design criteria updated faced with these extremes? Both a sudden increase of design rainfall by the inclusion of these extremes and complete ignorance are inappropriate. In this study, the changes in extremes were examined and an alternative way to estimate the design rainfall amounts was developed using the data from 60 stations in South Korea. The minimum density power divergence estimator (MDPDE) with the optimal value of a tuning parameter, α, was suggested as an alternative estimator instead of the maximum likelihood estimator (MLE); its performance was evaluated using the Gumbel (GUM) and the generalized extreme value (GEV) distribution. The results revealed an increase in both the frequency and magnitude of extreme events over the last two decades, which imply that the extremes are already occurring. The performance of the MDPDE was evaluated. The results revealed decreased and adjusted values of the design rainfall compared to MLE. On the other hand, the MDPDE of the GEV distribution with a positive shape parameter, ξ, does not show its advantage conditionally because the GEV distribution has a heavier right tail than the GUM distribution (ξ = 0). In contrast, the results showed the high sensitivity of the MLE to the extremes compared to MDPDE.

Application of Linear Moments and Uncertainty Analysis to Extreme Rainfall Events in Sabah

Linear moments (LM) has been applied in extreme rainfall study for several countries, including China, United States of America, and Peninsular Malaysia. In this study, the LM procedures were applied to extreme rainfall data corresponding to locations provided in Malaysia Urban Stromwater Manual (MSMA) to derive new design rainfalls. Different record lengths were considered to assess the changes in design rainfall, and Monte Carlo simulations were carried out to compute confidence interval of the derived design rainfalls. Based on the Goodness-of-Fit (GoF) test results, the Generalized Extreme Value (GEV) probability distribution was chosen to derive the design rainfalls. The updated design rainfalls at all four locations showed significant reduction at design rainfalls of 50-year ARI and above. The difference of the design rainfalls from shorter record lengths with respect to the full record length and the confidence intervals do not necessarily reduce with a longer record. In hypothetical cases where 100-yr ARI rainfall was added, the increase in design rainfalls did not exceed the upper bound of the confidence intervals. The derived confidence intervals hence allow for better risk assessment, and should be considered in the design of critical structures, i.e. dams.

Estimating design floods in ungauged watersheds through regressive adjustment of flood quantiles from the design rainfall - runoff analysis method

It is required to estimate reliable design floods for hydraulic structures in order to respond more effectively to recent climate change. In this study, differences of design floods that were estimated the flood frequency analysis (FFA) and the design rainfall-runoff analysis (DRRA) were analyzed. In Korea, due to lack of measured flood data, the DRRA method is used in practice to determine the design floods. However, assuming the design floods estimated by the FFA as true values, the DRRA method over estimated the design floods by 79%. Thus, this study proposed a practical method to estimated design flood in ungauaged watersheds through regressive adjustment of flood quantiles estimated from the DRRA method. To this end, after investigating the differences between design floods acquired from the FFA and the DRRA method, nonlinear regression analyses were performed to develop the adjustment formulas for 8 large-dam watersheds. Applying the adjustment formula, the accuracy was improved by 65.0% on average over the DRRA method. In addition, when considering the watershed size, the adjustment formula increases the accuracy by 2.1%p on average over when not considering the watershed size.

Consideration of documentary records in the Annals of the Choson Dynasty for the frequency analysis of rainfall in Seoul, Korea

ABSTRACTIn this study, flood records in the Annals of the Choson Dynasty (1392–1910) were considered for the frequency analysis of rainfall in Seoul, Korea. The old Korean rain gauge (Chukwooki) data (1777–1907) were also used to evaluate major flood records in the Annals of the Choson Dynasty. The design rainfalls were estimated using the binomial censored data maximum likelihood estimator. The results can be summarized as follows. (1) The frequency analysis was done for 24 h rainfall amounts as this was assumed to represent the three different rainfall records well: the documentary records in the Annals of the Choson Dynasty, the Chukwooki data and the modern data. Also, given the possible uncertainty level of the classification results of the documentary records, only 19 catastrophic events (the highest level of flood) were considered in the frequency analysis. The threshold value was decided to be 388 mm by comparing the documentary records with the Chukwooki data. (2) The sensitivity analysis shows that the effects of the threshold value, the number of catastrophic records, and the accuracy level of the flood records in the Annals of the Choson Dynasty on the frequency analysis results are very limited. That is, the length of the flood records in the Annals of the Choson Dynasty was found to be long enough to overcome the possible uncertainty of the flood records. (3) The design rainfalls estimated by taking into account the flood records in the Annals of the Choson Dynasty were found to be very similar to those for the modern data. However, the confidence intervals estimated by considering all the records available were found to be just one third of those of the modern data.

Simulation on the Time Progress of the Non-Point Source Pollution Load in Initial Stage Runoff for Small Watershed

Taking a reservoir in South China as an example, we use rainfall-runoff unit hydrograph method to analyze the time changing process of surface runoff inflow, which generated by typical design rainfall. On the basis of time series data of flow and water quality in control section of the main rivers in Xili Reservoir, we establish mathematical response relation between non-point source pollutants flux, such as flux of COD, flux of NH3-H, in catchment area of control section and runoff. Then we simulate the time dynamic change progress of non-point source pollution load which generate with the initial stage runoff that generated by design rainfall and flow into reservoir. It can provide technical parameters for the design of non-point source which generate from early runoff treatment project.

Analyzing trend and developing an empirical formula for estimating rainfall intensity: a case study Eskisehir city, Turkey

Trend and stationarity analysis conducted for the city center of Eskisehir province, Turkey. The Intensity- Duration – Frequency (IDF) curves and formulas for the estimation of the design rainfall intensity have been developed. Through the application of four different frequency methods, the IDF has been developed for a record of 64 years. The functions employed are; Normal, Log – Normal, Gumbel, and Log –Pearson Type III. A formula for each function developed by determining the parameters with the help of a non-linear regression method. The most appropriate fit of probability distribution determined by goodness of fit test i.e. Chi – Square. The results of the study revealed no evidence of significant trend or nonstationarity in any duration. With an exception to the Normal function which exceeded the critical region in several durations, all the functions found to show high fitting. LPT III identified as the best fit. The coefficient of correlation for the developed formulas found high in all the functions except for LPT III. The study endorsed that the estimation of rainfall intensity for any storm duration and return period can be done for Eskisehir using LPT III and Gumbel formulas as they are evaluated as best fitting.