Browsing by Author "Yilmaz, Kutay"
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Article Citation Count: 5Assessment of flood hazards due to overtopping and piping in Dalaman Akkopru Dam, employing both shallow water flow and diffusive wave equations(Springer, 2023) Darama, Yakup; Darama, Yakup; Melek, Abiddin Berhan; Melek, A. Berhan; Civil Engineering; Department of Civil EngineeringThis study was carried out to determine flood propagation using shallow water equations (SWEs) and diffusive wave equations (DWEs) to reveal how the flood modeling results differ in terms of flow depth, flow velocity, and hazard level. The solution methods were tested based on the hypothetical failure of the Dalaman Akkopru Dam resulting from two failure mechanisms: overtopping (OT) and piping (PP). A 2D hydraulic model was constructed using HEC-RAS to determine the propagation of flood waves due to the failure of the dam by the mechanisms selected. Froehlich equations were applied to predict the breaching parameters of the dam. After calibration, the hydraulic model was run to determine the possible flooding magnitude in the towns of Ortaca, Dalaman, and Dalyan. The flood arrival times, maximum flow depths, flow velocities, and hazard classes were obtained for the Dalaman, Ortaca, and Dalyan city centers, and the Dalaman International Airport from the hydraulic model results. The modeling results showed that the inundated area is similar for both the SWEs and DWEs solutions, while the flow depth and velocity results are significantly different due to the neglected convective acceleration terms of the SWEs when deriving the DWEs. Considering the modeling results, even though the DWEs provide a computational cost advantage, the reliability of the solutions should be examined against the SWEs. Hazard maps were generated for both solution methods and failure mechanisms. The results revealed that most of the settlements in the basin have H5 and H6 hazard classes with a high risk of structural damage. Therefore, the installation of early warning systems and evacuation of district centers were suggested as mitigation measures. A feasible evacuation plan for the neighborhoods, taking into account the flood arrival time of the failure scenarios, is needed.Article Citation Count: 7Land degradation by erosion occurred after irrigation development in the Harran plain, Southeastern Turkey(Springer, 2021) Darama, Yakup; Yilmaz, Kutay; Melek, Abiddin Berhan; Civil Engineering; Department of Civil EngineeringA study was made to determine the erosion problem and determine the amount of suspended sediment transport in the drainage channels of the Harran Plain by conducting periodic suspended sediment sampling and discharge measurements in the field between 1997 and 2017. When irrigation in the Harran Plain started in 1990, the production of the agricultural goods quadrupled within a few years. Unfortunately, excessive amounts of irrigation water supplied to irrigate crops also led to the erosion of the soil in the fields by surface runoff. Furthermore, the mixture of clay, silt, and fine sand in the topsoil from certain areas accumulated in the tertiary and secondary drainage systems and reduced the effectiveness of the drainage system. Analysis of the suspended sediment measurements between 1997 and 2017 showed that the yearly averaged sediment transported to Syria by the main drainage canal of the Harran Plain varied between 128 ton.day(-1) to 1268 ton.day(-1), and the average of the 21-year measurement is about 682 ton.day(-1). The logarithmic plot of the suspended sediment rating curve showed that as the discharge of the Cullap Creek increases, the sediment transport rate also increases linearly. It means excess furrow irrigation could cause substantial topsoil loss. Sediment erosion resulting from rainfall events in the Harran Plain is also computed using Revised Universal Soil Loss Equation (RUSLE). The results showed that rainfall erosion from the Harran Plain is 131.5 ton.day(-1). A comparison of this value with the 21-year value of average sediment erosion by irrigation shows that approximately 20% of sediment erosion from the Harran Plain was caused by rainfall events, and the remaining 80% was caused by excess irrigation water in the area. A 2D numerical model was constructed with MIKE 21 software applying Van Rijn Method to calculate suspended sediment load due to irrigation, and it allowed to calculate the load with a 6.47% error. Grouping the irrigated and non-irrigated periods and applying independent t test, a statistical approach constituted and resulted in 79.2% of suspended sediment load is caused by irrigation. The numerical model and statistical analysis supported the findings of field data and RUSLE Model results. The study showed that the main reason of the topsoil loss in the Harran Plain is the excess furrow irrigation.