Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Determination of Flood Risk Areas and Development of Mitigation Strategies in Kabul River Basin, Afghanistan(01. Izmir Institute of Technology, 2023) Barez, Esmayel; Tayfur, GökmenFlooding is a devastating and natural catastrophe to population, environment, and socioeconomic development globally. Floods occur frequently in Afghanistan, especially in Kabul River Basin. Many geographical techniques have been established in recent years to map, predict and model flood risks. This research investigates identification of flood-prone zones and development of mitigation measures in Kabul River Basin. First, in this research, GIS and MCDA methodology was applied to generate flood risk map. Also, AHP method was applied to determine the best weights to be assigned to the factors that influence risk of flooding. A flood risk map of KRB was produced using 10 conditioning criteria; soil, rainfall, lithology, LULC, TWI, NDVI, distance to stream channels, curvature, elevation, and slope. Based on the weighted overlay integration of GIS-AHP technique, KRB was grouped into four flood vulnerability zones; very low, low, high, and very high. Generated flood risk map indicates a good match with the flood risk areas and location of past floods in the basin over recent years. Second, 2D HEC-RAS model and flood frequency analysis were developed for different scenarios to simulate the flow of river and to develope mitigation measures with a 500- year return period in the main river of Kunar and the lower Kabul sub-basin. Manning's n values were used to calibrate HEC-RAS model, and past flood events applied for validation. Flood mitigation strategies, including river restoration, construction of dam, and reservoir improvement were proposed on the Kunar and lower Kabul sub-basin. Keywords: Flood Inundation Map, Hydraulic Modelling, ArcGIS-MCDA.Master Thesis Experimental and Numerical Investigation of the Evolution of Piping and Resulting Breach in Earth-Fill Dams(01. Izmir Institute of Technology, 2022) Dumlu, Emre; Tayfur, GökmenEarth-fill dams have been constructed for decades by compacting natural soil materials near the dam site. Piping is of the most important causes of their failure. In the scope of this thesis, 2 m in length homogenous earth-fill dams were constructed in a rectangular flume in the laboratory of the Izmir University of Economics. The experimental and numerical investigations on a breach by generating piping were realized with different weak zone scenarios. Three experiments were performed by placing a weak layer cross-section 5x5 cm2 at the dam bottom center. One scenario was performed by locating a weak layer of 2x2 cm2, 28 cm above the bottom. Temporal breach areas and the breach-wetted areas are evaluated on scaled screenshots by using Gauss’s area formulation. The Temporal breach discharges were calculated from the continuity equation. Furthermore, finite element analyses on the breaching of homogenous earth-fill dams in different scenarios were performed by comparing the hydraulic gradient with the critical value. In addition to the bottom and middle scenarios, two upper scenarios were also modeled. The water depths were used for each scenario to represent the experimental conditions, and some approaches were made for the weak zones. To simulate the breach mechanism with different loops, a python algorithm was integrated with the Jupyter console. As a result of the simulations, it has been observed that the findings obtained by simulations were in accord with the experimental studies, and the dams were exposed to backward piping starting from downstream towards upstream.Master Thesis Drought Assessment in Aydın and İzmir Districts in Turkey(01. Izmir Institute of Technology, 2022) Mersin, Denizhan; Safari, Mir Jafar Sadegh; Tayfur, GökmenDrought indices are widely used in order to track the severity, duration, and frequency of droughts, drought indices are frequently utilized. Turkey's Aegean region, which is expanding, has a range of water resources, including lakes, streams, lakes, and groundwater aquifers. In this study, the drought features in the Büyük Menderes, Küçük Menderes, and Gediz basins in the Aegean area of Turkey are investigated using long-term total precipitation and temperature records from 14 meteorological stations between 1973 and 2020 (47 years). For this, the Standardized Precipitation Index (SPI) and the Standardized Precipitation and Evapotranspiration Index (SPEI), and Discrepancy Precipitation Index (DPI) are used to investigate drought patterns, monthly and over 3-, 6-, and 12-month (annual) periods. The results reveal that the monthly indices show almost the same results for the whole study area, but the different indices differ in the severity of drought. As a common belief, moderate, severe, and extreme drought is observed at the end of the 1980s and around 2020, which is the closest year to the present. In addition, the trend analysis of the annual temperature (daily average) and total precipitation time series data collected from these 14 stations is examined. Sen test, Mann-Kendall test, and Spearman's rho test are used for trend detection. The Pettitt test is used to estimate the magnitude of the slope in the series and the Theil-Sen approach is used to detect the change point of the series. For precipitation, all stations showed a statistically significant increase in trends. In the temperature analysis, on the other hand, all stations show statistically significant increasing trends in daily average temperatures. The amount of precipitation increase determined by the Theil-Sen test is found to be between 4.2 and 7.9 mm/year.Master Thesis Developing Flood Mitigation Measures for Baledwayne City, Somalia, by Using the Hec-Ras Model(Izmir Institute of Technology, 2022) İbrahim, Abdullahi Abdulwahid; Tayfur, GökmenThis 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, GökmenLong-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) Okan, Merve; Tayfur, Gökmen; Bor Türkben, AslıFrom 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 Modelling Rainfall-Runoff Processes in Kabul River Basin Using Arc Swat Model(01. Izmir Institute of Technology, 2020) Tanı, Hamidullah; Tayfur, GökmenSWAT model is applied to Kabul River Basin (KRB) located in Afghanistan to assess the runoff. KRB is located between latitudes 33 ﾟN and 37 ﾟ N, and longitudes 67 ﾟE and 74 ﾟE, with a drainage area of 72000 km2. This study (1) determines the most sensitive parameters that affect the catchment flow, (2) estimates monthly and daily flows of the basin from the available meteorological stations data, (3) calibrates and validates the simulated and observed flow data for different hydrological stations located in the basin, and (4) determines the total amount of surface runoff and water yield in the basin. SWAT-CUP is applied for the sensitivity analysis. Initially 27 different sensitive parameters effecting the runoff are tasted and 20 most sensitive ones are found. Among these, GWQMN.gw (Treshold depth of water in the shallow aquifer required for return flow to occur ), SMTMP.bsn (Snow melt base temperature), CN2.mgt (SCS runoff curve number II), PLAPS.sub (Precipitation lapse rate), and HRU_SLP.hru (Average slope steepness) are found to be the most sensitive parameters. The predicted flow is calibrated and validated against the measured flow for seven different Hydrological Stations both on a monthly and daily time scales. The performance of the model is checked by applying R2, NSE, and the RSR. Overall, the model's monthly simulation flow is superior to the daily simulation.Master Thesis Design of Coanda Intakes for Optimum Sediment Release Efficiencies and Water Capture Performances(Izmir Institute of Technology, 2020) Hazar, Oğuz; Tayfur, Gökmen; Elçi, ŞebnemBottom 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, GökmenWater 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, GökmenDams 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.