Probabilistic modeling of dam failure scenarios: a case study of Kanlikoy Dam in Cyprus

One of the most perilous natural hazards is flooding resulting from dam failure, which can devastate downstream infrastructure and lead to significant human casualties. In recent years, the frequency of flash floods in the northern part of Nicosia, Cyprus, has increased. This area faces increased risk as it lies downstream of the Kanlikoy Dam, an aging earth-fill dam constructed over 70 years ago. In this study, we aim to assess potential flood hazards stemming from three distinct failure scenarios: piping, 100-year rainfall, and probable maximum precipitation (PMP). To achieve this, HEC-HMS hydrologic model findings were integrated into 2D HEC-RAS hydraulic models to simulate flood hydrographs and generate flood inundation and hazard maps. For each scenario, Monte Carlo simulations using McBreach software produced four hydrographs corresponding to exceedance probabilities of 90%, 50%, 10%, and 1%. The results indicate that all dam breach scenarios pose a significant threat to agricultural and residential areas, leading to the destruction of numerous buildings, roads, and infrastructures. Particularly, Scenario 3, which includes PMP, was identified as the most destructive, resulting in prevailing flood hazard levels of H5 and H6 in the inundated areas. The proportion of inundated areas in these high hazard levels varied between 52.8% and 57.4%, with the number of vulnerable structures increasing from 248 to 321 for exceedance probabilities of 90% and 1%, respectively. Additionally, the number of flooded buildings ranged from 842 to 935, and 26 to 34 km of roads were found to be inundated in this scenario. These findings revealed the need for authorities to develop comprehensive evacuation plans and establish an efficient warning system to mitigate the flood risks associated with dam failure

Lefkoşa için bir taşkın yönetim sistemi geliştirilmesi.

The implementation of effective flood management particularly in ungauged basins requires regional frequency analysis (RFA) to determine the occurrence probabilities of extreme precipitation events. In this context, the quality control and homogeneity analysis of daily precipitation series of 37 stations in Northern Cyprus are carried out and trend analyses are employed to assess the variability of extreme precipitation indices. The increasing trends especially in winter period are dominated the northern part of the island. Then, identification of homogeneous regions is performed by utilizing the time series clustering approaches as a new perspective in RFA and the quantile estimates for different return periods are obtained. The flood hydrographs generated from the SCS Unit Hydrograph approach are provided to the outlet of Kanlıköy and Gönyeli ponds which are the boundary conditions for the river model. Moreover, 1D model MIKE 11 for the Kanlıdere River’s tributaries is developed to simulate the flow in main channel. Besides, the flow depths, velocities, and flood inundation extent on floodplain is detected by 2D MIKE 21 model. MIKE FLOOD coupling of MIKE 11 and MIKE 21 is used to simulate the flood event in 2010 and the flood inundation maps are generated based on the different scenarios. Flood mitigation alternatives, such as dredging and increasing crest elevations of dam and spillway for Gönyeli Pond, and implementation of a new upstream detention facility for Kanlıköy Pond were proposed. The proposed structural measure shows that Nicosia can be protected from flooding up to approximately 500-year return period.Ph.D. - Doctoral Progra

Baseflow Separation Model Based On Topografhical And Hydrometeorological Data For Euphrates River Basin

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2013Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2013Su, yüzyıllar boyunca insanoğlunun günümüzdeki medeniyetler seviyesine gelmesinde çok önemli bir rol oynamıştır. Tarihe bakıldığında bütün büyük uygarlıkların su kenarında kuruldukları görülmektedir. Günümüzde ise gelişen teknolojiyle birlikte sudan içme ve kullanma suyu, sulama, enerji üretimi gibi daha geniş alanlarda faydalanılmaktadır. Buna paralel olarak akarsulardan daha fazla ve daha etkin yararlanma ihtiyacı doğmuştur. Bu yüzden araştırmacılar akarsulardaki toplam akışı ve akışın bileşenlerini inceleme sürecine girmişlerdir. Bir akarsudaki toplam akış, dolaysız akış ve dolaylı akış (taban akışı) olarak iki kısma ayrılarak incelenebilir. Dolaysız akış, yüzeysel akış ve gecikmeye uğramamış yüzeyaltı akışı, dolaylı akış ise yeraltı akışı ve gecikmeye uğramış yüzeyaltı akışıdır. Taban akışı özellikle kurak mevsimlerde akarsu yatağındaki akışın büyük bir kısmını, bazen de tamamını oluşturmaktadır. Hızı yavaş olduğundan akarsuya erişimi uzun bir süre alır ve akarsuyu sürekli besleyen bir kaynak niteliğindedir. Taban akışı akarsudaki akımın önemli bir kısmını oluşturduğundan kuraklık tahminlerinde, su yönetimi ve planlama çalışmalarında, su temini, hidroelektrik projeleri, akarsu taşımacılığı, atıksu seyreltilmesi, akarsulardan tarım ve enerji üretimi amaçlı su çekilmesi gibi çok sayıda farklı çalışma alanı için kullanılmaktadır. Bu nedenle taban akışını toplam akıştan ayırmak veya tahmin etmek önemlidir. Bu çalışmada literatürde genel kabul görmüş hidrograf analizine dayanan birtakım yöntemler özetlendikten sonra çok değişkenli regresyon denklemlerini geliştirmede kullanılan regresyon analizi yöntemi anlatılmıştır. Taban akışı ayırma yöntemleri içerisinde yaygın olarak kullanılan İngiliz Hidroloji Enstitüsü’nün yumuşatılmış minimumlar yöntemi (İHEY) günlük ortalama akım verilerine uygulanarak taban akışı indeksi hesaplanmış ve regresyon denklemleriyle yapılan taban akışı tahminleriyle karşılaştırmada kullanılmıştır. Ayrıca akarsu havzasının topoğrafik ve hidrometeorolojik verileri ile model serbest değişkenleri oluşturulmuştur. Bu çalışmada çoklu regresyon analizi yapılarak önce taban akışı indeksi, ardından taban akışını havzanın topoğrafik ve hidrometeorolojik özelliklerinden tahmin etmek için kullanılabilecek iki denklem geliştirilmiştir. Bu denklemler çoklu regresyon analizini pratikleştiren PASW İstatistik 18 programı yardımıyla oluşturulmuştur. Uygulama alanı olarak Türkiye’nin en büyük su potansiyeline sahip Fırat nehri havzası seçilmiştir. Havzadaki Elektrik İşleri Etüt İdaresi’ne (EİEİ) ait 15 akım gözlem istasyonunun günlük ortalama akım verileri kullanılmış ve yukarıda bahsedilen yöntemler kullanılarak taban akışı indeksi ve taban akışı debileri tahmin edilmiştir. Sonuç olarak elde edilen tahminler İHEY yöntemi ile karşılaştırılarak değerlendirilmiştir. Geliştirilen denklemlerin İHEY yöntemine benzer sonuçlar verdiği, bu nedenle kullanılabilir olduğu anlaşılmıştır.Baseflow is an important component of streamflow which is generated from groundwater and delayed shallow subsurface flows. Especially in rainless seasons, approximately total flow in the stream channel is the result of baseflow from the groundwater. Therefore separation of baseflow from the total flow has become an important issue for the planning and effective management of water resources. It is also important for determination of water availability and water quality and improving the strategies to protect the environment and the other living biota. The majority of the methods used to seperate baseflow are based on graphical, analytical and digital filtering techniques which all these techniques have the same sense of calculating the baseflow from streamflow hydrograph. In this study, the well-known smoothed minima method of UKIH (United Kingdom Institute of Hydrology) is used for calculating baseflow. In addition to this, regression analysis is built with some properties of catchment to estimate the baseflow index and baseflow discharge. Daily stream flow data are provided from the Electrical Power Resources, Survey and Development Administration from Turkey which operates gauging stations for streamflow observations. In Turkey, there are 25 hydrological basins with different topographical, morphological and meteorological conditions. In this study, 15 gauging stations from Euphrates basin are used for baseflow analysis. Furthermore, the topographical and hydrometeorological data are obtained from internet-based geographic program (geodata) in the websites of the Ministry of Forest and Water Affairs and the General Directorate of State Meteorological Works, respectively. In this study, first the UKIH method is used to separate baseflow. The method is based on dividing daily stream flow data into non-overlapping 5-day blocks. Once the baseflow is separated, baseflow index (BFI) is calculated as the ratio of baseflow to total streamflow. The non-dimensional BFI changes between 0 and 1. BFI approaches 1 if the groundwater contribution to stream flow is high. Another approach employed in this study is based on multiple regression for estimating BFI and baseflow discharge. Topographical and hydrometeorological data are used as predictor variables in the regression. Preliminary results show that BFI and baseflow discharge are correlated with hydrometeorological and topographical variables of watershed. The regression models are validated by comparing its results with UKIH method. Two methods give similar results.Yüksek LisansM.Sc

Quality and Homogeneity Analysis of Precipitation Data in North Cyprus

This study aims to reveal procedures for testing and creating a set of complete, quality-controlled, and homogeneous precipitation data sets in North Cyprus. Database involves 37 daily precipitation series which are uniformly distributed throughout the study area with observation periods ranging from 1976 to 2015. As a first step of the procedures, the estimation of the missing values is carried out considering a range of distances with various estimation methods based on neighboring stations. Secondly, the quality assessment of the complete series is performed in terms of detection of unreasonable values and outliers. Thirdly, the two-step approach including the computation of four homogeneity methods and classification of the results is used to check the presence of inhomogeneities in series. As a result of applied procedures, the outliers exceeding the threshold value at monthly scale are observed as expected particularly in summer and early autumn covering the hot and dry periods. Additionally, some stations named as Mehmetçik and Boğaz are flagged as discordant according to the discordancy measures relying on L-moment ratios. In homogeneity analysis, daily precipitation series are analyzed through the testing variables such as, total annual precipitation, monthly maximum precipitation, annual wet days, and seasonal total precipitation. Tatlısu, Yeşilırmak, and Çayönü stations are found as inhomogeneous based on the four absolute homogeneity tests and in conclusion, 33 out of 37 precipitation stations are assessed and proven to be reliable

Regional frequency analysis of precipitation using time series clustering approaches

A regional frequency analysis using L-moments was performed with time series clustering approaches to identify homogeneous regions using dynamic data sets in Northern Cyprus. In this context, the conventional approach, based on station characteristics and different time series clustering approaches, classified as shape-based, feature-based, and model-based, were compared. Hierarchical Ward's method with the correlation-based similarity measure of the feature-based approach was determined as the best method regarding the results of the jackknife validation procedure, which was performed for assessment of clustering approach uncertainty. Therefore, the cluster analysis ended up with five homogeneous subregions, and according to the goodness-of-fit measure, the Pearson Type III, generalized logistic, and generalized normal distributions were chosen as the best fit for different subregions. The accuracy of the estimated quantiles was evaluated through Monte Carlo simulations and, consequently, the quantiles for different return periods were estimated, which demonstrated spatial consistency in terms of increasing trend from the low-lying Mesaoria Plain toward the north coastal strip, including the Kyrenia Mountains and the Karpass Peninsula

Quality control, homogeneity analysis, and trends of extreme precipitation indices in Northern Cyprus

In this study, the annual and seasonal changes in extreme precipitation indices were investigated in Northern Cyprus by using the non-parametric Mann–Kendal trend test and Sen’s slope estimator. To this end, quality control of data procedure including estimation of missing data, detection of unreasonable values, and outliers were applied to 36 daily precipitation series to identify different errors. In order to test the homogeneity of the daily series, a two-step approach with four homogeneity tests and overall classification were used. The investigation of trends for extreme precipitation indices indicated that the trends were mostly nonsignificant and increasing in scale annually. On seasonal scale, the percentage of stations with increasing trend was almost the same with the percentage of stations with decreasing trend in autumn and spring. Besides, the upward trend was observed at more than 77% of the stations in winter with 11% having significantly increasing trends. Generally, there was no spatial coherence as well as a mixed pattern of trends changing from station to station