Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Developing Flood Mitigation Measures for Baledwayne City, Somalia, by Using the Hec-Ras Model(Izmir Institute of Technology, 2022) Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis study covers the investigation of the flood mitigation measures required to protect the city of Baledwayne, which is located in the Hiran region of Somalia and has been subject to frequent floods recently. In the HEC-HMS model, the precipitation data measured in 2019 and DEM at the Baledwayne and Bulo-Burti stations of the Hiran region were used as input. The observed discharge in the Shabelle river in 2019 of both stations was imported into the model to compare the simulated rainfall-runoff hydrographs. The rainfall-runoff hydrographs of 2019 were simulated with the HEC-HMS model using these parameters, SCS Curve Number for analyzing runoff volume, Snyder Unit Hydrograph for estimating direct runoffs, and Constant Monthly for calculating the baseflow and Muskingum for channel routing. The outflow hydrographs at both stations were successfully simulated. With the 1D&2D HEC-RAS model, flood maps were generated using various alternatives to protect the study area from floods of Q500 flow rate with a return interval of 500 years. The Deyr 2019 flood event was used for the calibration of the model. The model determined the flood extent and depth of this flood event by changing the roughness coefficient at specific intervals. Various flood mitigation measures have been investigated after calibration. It has been found that the best protection can be achieved by the combination of these four flood mitigation measures: (1) rehabilitation of the Warabole diversion channel, (2) construction of detention ponds at the upstream of the floodplain, (3) levees along both sides of the river and (4) improvement of the river.Master Thesis Trend and Drought Analysis of Three Stations in the Puntland State of Somalia(Izmir Institute of Technology, 2022) Muse, Nur Mohamed; Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyLong-term rainfall and temperature records were used to analyze drought features as well as temperature and precipitation trends in Somalia's north area from 1980 to 2020. Monthly records are being used at three locations (Bossaso (station 1), Qardho (station 2), and Garowe (station 3).Deciles, Discrepancy precipitation index, percent normal, Gamma, log normal, and normal-SPI were used to examine the Drought. The past extreme and severe droughts that occurred in the early 1980s and throughout the course of the last two decades are being detected using the log-SPI, gamma-SPI, PN, and Deciles The Mann Kendall (MK) test, Spearman's rho (SR test), and the Şen trend test were used in the trend analysis to identify trends in time series, and the Pettitt test to detect change points in time series. In contrast, the Thiel-sen Approach was used to estimate the magnitude of the slope in the precipitation and temperature time series. The average temperature and annual precipitation are increasing by about 0.3C per decade and 3 mm per year, according to the trend analysis results.Master Thesis Experimental and Numerical Investigation of Piping in Uniform Embankment Dam With Weak Layer at the Upper Region(Izmir Institute of Technology, 2022) Tayfur, Gökmen; Tayfur, Gökmen; Bor Türkben, Aslı; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFrom the past to nowadays, earth-fill dams have been built thanks to their advantages, however, piping is a problem that earth-fill dams can experience and then fail. While there are many studies about the overtopping failures of the dams, there are not too many surveys about dam failures due to piping. Dams having a height of 0.6 m, a bottom width of 2 m, and a crest width of 0.20 m were built in a channel of 1 m wide, 0.81 m high and 6.14 m long. 3 different scenarios have been created and the evolution of dam failure resulting from seepage at the dam was recorded by six cameras located at different locations. In the closed system, water was pumped from the lower reservoir to the upper channel. The dam was constructed by using a mixture consisting of 85 % sand and 15 % clay. A circular tunnel with a diameter of 2 cm was created at the middle or corner of the dam according to the scenario and at 6 cm below the dam crest. The breach areas at different time instants at upstream and downstream sides are determined by using the Gauss Area calculation method and by image processing, and then it has been found that methods give close values to each other. Breach discharge and time-varied velocity values were determined by using the continuity equation. Empirical relations were intended to be derived for the breach flow rate and empirical relations represented in the literature were trialed by using experimental findings.Master Thesis Design of Coanda Intakes for Optimum Sediment Release Efficiencies and Water Capture Performances(Izmir Institute of Technology, 2020) Hazar, Oğuz; Elçi, Şebnem; Tayfur, Gökmen; Tayfur, Gökmen; Elçi, Şebnem; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyBottom type water intake structures are frequently preferred in the case of flows containing high levels of sediment in case where it is not possible to construct settling pool or if their construction costs are high. Coanda and Tyrolean type water intake structures are the most commonly used bottom type intake structures. It has been observed in a limited number of studies that Coanda type water intakes are superior to the Tyrolean type water intakes both in terms of withdrawing the design amount of flow and excluding the sediment as much as possible. However, the biggest obstacle to the widespread usage of Coanda type water intake is their complex design and difficulties of the analysis. It has been observed that there are no formula or numerical studies that calculate the water Capture Performance (WCP) and Sediment Release Efficiency (SRE) of the Coanda screens. In order to overcome this gap in the literature, six different Coanda screens have been tested for both WCP and SRE using various incoming flows and sediment compositions. The data obtained as a result of the experimental studies were analyzed using statistical analysis method and two different equations were obtained that enable to find the WCP and SRE. In a situation where the incoming flow conditions and screen parameters are known, someone can gain a preliminary knowledge about the screen performance by using these equations. As a result of this study, adding new data to the literature and eliminating the mentioned lack in the literature was aimed.Master Thesis Hec Hms Hydrological Model Application Using Scs Curve Number and Soil Moisture Accounting: Case Study of Alaşehir Basin(Izmir Institute of Technology, 2019) Akdeğirmen, Özgün; Baba, Alper; Tayfur, Gökmen; Baba, Alper; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyWater is known as source of life throughout mankind’s history. According to first records of written history; Sumerians and Akkadians used water for their inland transportation and irrigation systems. With first settlements, mankind’s dependency to water has been increased and became one of the most substantial natural resource in our modern age. Importance of this resource even more solidifies when we consider its property of being limited. With realization of global climate change in early 19th century; treat to this limited resource has been revealed. Approximately 68% of the freshwater on earth reserved in glaciers and icecaps and 30% is reserved in groundwater systems according to United States Geological Survey’s (USGS) studies. Owing to the quantity and less compromised to contaminants nature, majority of our freshwater needs met from groundwater. Although the importance of groundwater, its management have always been a challenge due to hard to quantify volumetric changings in aquifers. This study focused on creating a hydrological basin model to investigate volumetric recharge changings in groundwater system. Under scope of this study in an attempt to acquire groundwater recharge amounts; practicality of HEC-HMS hydrological modeling software has been investigated. A SCS Curve Number and Soil Moisture Accounting (SMA) loss methods has been chosen for HEC-HMS modeling application due to availability and accessibility of data that required for loss methods. After data collection from meteorological stations, core drill samples; both methods have been used in HEC-HMS simulation environment and their predictions have been compared. In the comparisons, it was determined that the SCS Curve Number method predicts higher flow potentials and groundwater infiltration amounts compared to the SMA method. Models foresee an average of 33.4 % of precipitation infiltrates into groundwater system.Master Thesis Numerical Modeling the Flood Wave as a Result of Ürkmez Dam(Izmir Institute of Technology, 2018) Şahin, Gül Sümeyra; Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyDams are constructed to provide benefits to society, hydropower generation, including water supply management and flood control. However, floods caused by failure of a dam is quite catastrophic for lives, properties and environment. Flow models for dam break scenarios ensures crucial information about land use planning and risk managment to minimize flood losses. In this study, estimation of flood innundated areas caused by flood triggered by failure of Urkmez Dam in Izmir is carried out by using HEC-RAS onedimensional (1D) unsteady flow routing model (full Saint Venant equations) and two dimensional model (2D) (full Saint Venant equations or Diffusion wave equations). The experimental distorted physical model provides controlling to simulations. The aim of the paper is to assess the risk of a dam failure potential by comparing performances of 1D and 2D simulations. Two models were compared considering the required data, data preparation, inundated area, flood velocity, flood depth, and flood waves.Master Thesis Numerical Investigation of Flood Induced Seepage Under Levees(Izmir Institute of Technology, 2018) Semerci, Aykut; Tayfur, Gökmen; Tayfur, Gökmen; Pulat, Hasan Fırat; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFlood creates the most complex problems of engineering hydrology and extreme flood contains the crucial risk for urban areas, infrastructure, industry and agriculture. The aim of this paper is to study the transient flow caused by flood for levee of Filyos River. Numerical modeling based on finite element method was performed in the analyses. Plaxflow is an add-on module to Plaxis 2-D, is used for the time variation of seepage in several points of interest within the levee. Transient exit velocity at several points of interest within the levee and degree of saturation of levee and hydraulic gradient were investigated based on whether the levee contained covered materials (riprap, filter and geocomposite materials) along upstream face of levee or not. In addition, under seepage of water through different soil types underneath Filyos levee was examined. Moreover, the results of transient flow analyses when piping occurred and sand boil formed were presented for different soil types.Master Thesis B and Se Transport Modeling in Saturated/Unsaturated Zones(Izmir Institute of Technology, 2002) Yüreklitürk, O. Emin; Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThere has been renewed interest in the application of models to the transport of non-point source pollutants. However, very little work has been done to evaluate the performance of a functional transient-state model for the transport of a reactive solute over an extensive study period. This research consists of mathematical modeling to simulate water flow, boron and selenium transport through soil in tile-drained croplands.For Boron part a mathematical model was developed to simulate non-conservative boron transport. The dynamic two-dimensional finite element model simulates water flow and boron transport in saturated-unsaturated soil system, including boron sorption and boron uptake by root-water extraction. Two different models have been employed for the sorption of boron. Similarly, for selenium part a finite element model is developed to simulate species of selenium transport in two dimensions in saturated/unsaturated zones. The model considers water, selenate, selenite and selenomethionine uptake by plants. It also considers oxidation/reduction, volatilization, and chemical and biological transformations of selenate, selenite, and selenomethionine. Comparison of boron transport model results with observed data is satisfactory. The model employed with Langmuir isotherm was found to give slightly better simulation results when compared with the model employed with Freundlich. The sensitivity analysis results indicate that the irrigation scheduling and the irrigation water quality are very important parameters for boron accumulation in the soil. Also the adsorption isotherm parameters, which reflect us the soil properties, are found to be important for the boron movement in the soil. Comparison of selenium transport model with observed data is not quite satisfactory in accuracy when compared with the model for boron transport. This may be the result of the complexity of the mechanisms affecting the selenium transport in soil. There are too many parameters, and due to the errors depending on the parameters, the total error for the estimation of the total selenium increases.Master Thesis Drought and Trend Analysis in Trarza Region Im Mauritania(Izmir Institute of Technology, 2016) Traore, Ely Yacoub; Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyLong-term precipitation and temperature historical records (monthly recorded for 44 years) in three stations (Boutilimit (station 1), Nouakchott (station 2), and Rosso (station 3)) are employed to investigate the drought characteristics and to investigate the temperature and precipitation trends during the period of 1970 to 2013 in Trarza region in Mauritania. Six Drought Indices (DIs), namely normal Standardized Precipitation Index (normal-SPI), log normal Standardized Precipitation Index (log-SPI), Standardized Precipitation Index using Gamma distribution (Gamma-SPI), Percent of Normal (PN), the China-Z index (CZI), and Deciles are used for the drought analysis. These methods are based on 1-, 3-, 6-, and 12 month time periods. The results showed that the log-SPI, the gamma-SPI, PN and Deciles were able to capture the historical extreme and severe droughts observed in early 1970s and early 1980s. In the trend analysis, The Mann Kendall (MK test), Spearman’s rho (SR test), Şen trend test were used for the trend identification in the time series and the Pettitt test for detecting the change point at the time series while the Thiel-sen Approach was used to estimate the magnitude of the slope in the precipitation and temperature time series. The results of trend analysis showed that the average temperature and the annual precipitation are both increasing by about 0.3oC per decade and 3 mm per year, respectively.Master Thesis Computation of the Convection Diffusion Equation by the Fourth Order Compact Finite Difference Method(Izmir Institute of Technology, 2015) Bajellan, Asan Ali Akbar Fatah; Tayfur, Gökmen; Tayfur, Gökmen; 03.03. Department of Civil Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThis dissertation aims to develop various numerical techniques for solving the one dimensional convection–diffusion equation with constant coefficient. These techniques are based on the explicit finite difference approximations using second, third and fourth-order compact difference schemes in space and a first-order explicit scheme in time. The suggested scheme has been seen to be very accurate and a relatively flexible solution approach in solving the contaminant transport equation for Pe ≤ 5. For the solution, the combined technique has been used instead of conventional solution techniques. The accuracy and validity of the numerical model are verified. The computed results showed that the use of the current method in the simulation is very applicable for the solution of the convection-diffusion equation. The technique is seen to be alternative to existing techniques. This dissertation is divided into six chapters: The derivation of the convective diffusion equation is given in Chapter 2. The main idea behind the higher order finite difference technique is given in Chapter 3. The numerical approximations to CDE described with ten different explicit schemes are introduced in Chapter 4. The results of numerical experiments using second, third and fourth-order compact difference schemes are presented in Chapter 5. Chapter 6 is devoted to a brief conclusion. Finally the references are introduced at the end.