Cevza Melek Kazezyılmaz-Alhan

On numerical modeling of overland flow

The reliability of several finite difference numerical formulations for solving one-dimensional kinematic and diffusion wave equations that describe overland flow is investigated. Particular emphasis is placed on two numerical schemes which are second order accurate in space and time, one each from the explicit and implicit families, respectively: the MacCormack and the 4-point implicit schemes. The end numerical solutions are compared to analytical solutions used as benchmark data, and to implicit and explicit schemes widely used to solve the overland flow governing equations. The magnitude of the time step was selected from the CFL stability condition. The algorithms are used to solve two examples, and the results are compared in terms of accuracy and required computational time. In both cases, the results indicate that the MacCormack and 4-point implicit methods are superior in terms of accuracy to the other widely used schemes. The MacCormack and 4-point implicit methods are comparable in accuracy, but the MacCormack algorithm is computationally more efficient.

Calibrated Hydrodynamic Model for Sazlıdere Watershed in Istanbul and Investigation of Urbanization Effects

AbstractProtecting and improving water resources play an important role for meeting the future demand for drinking water and preventing flood events. Increasing population tends to cause a shift from rural to urban areas, which results in the alteration of concentration time, water quantity, and flow rate. Because of these changes, specific solutions need to be investigated to prevent flood and overflow. For this purpose, calibrated hydrodynamic models should be developed to understand the hydrodynamic behavior of the catchment. Sazlidere Watershed, which provides an average of 55  million m3 of water per year, is one of the most important watersheds of Istanbul, Turkey. There is a tremendous population increase in the area, and moderate flood events are frequently observed. Therefore, in this study, a calibrated hydrodynamic model for Sazlidere Watershed was developed by using the Environmental Protection Agency Storm Water Management Model (EPA SWMM). The model is calibrated by using the rainfall and fl...

Experimental Investigation on Hydrologic Performance of LID with Rainfall-Watershed-Bioretention System

AbstractRapid development in a watershed affects both surface water and groundwater resources. Urbanization results in an increase in surface runoff and volume of water collected downstream of the watershed. Low-impact development (LID) best management practices (BMPs) such as bioretentions, vegetated rooftops, rain barrels, vegetative swales, permeable pavements, and stormwater wetlands have been implemented to diminish adverse effects of urbanization such as flood by reducing peak flows on the surface and thus managing stormwater runoff. The objective of this study is to investigate the hydrological performance of bioretentions, which may also be considered as a small-size local constructed wetland, by conducting experimental analyses under various rainfall intensities and durations. For this purpose, an experimental setup called a rainfall-watershed-bioretention (RWB) system is constructed, which involves an artificial rainfall system, drainage area, and four bioretention columns with different soil te...

Hydrological Model of LID with Rainfall-Watershed-Bioretention System

Sustainable water management is crucial in the reduction of water pollution and floods. New techniques should be investigated in order to avoid present and future problems such as flood, drought, and water contamination. For this purpose, Low Impact Development-Best Management Practice (LID-BMP) has recently come into the stage in storm water management. Vegetative swales, green roofs, bioretentions, storm water wetlands, rain barrels, permeable asphalts and pavements are among LID-BMPs. Bioretention type of LID is implemented to diminish adverse effects of urbanization such as flood by reducing peak flows on surface and thus managing storm water runoff. The aim of this study is to investigate the hydrological performance of bioretentions by developing a hydrological model based on the data obtained using experimental setup called Rainfall-Watershed-Bioretention (RWB). The hydrological model of RWB (HM-RWB) consists of two main components: (i) rainfall-runoff model in which kinematic wave theory is used for simulation of surface runoff generated over the drainage area that reaches the bioretention as inflow; (ii) runoff-bioretention flow model in which Green-Ampt method under unsteady rainfall is employed and further improved by incorporating the effect of ponding depth on bioretention for the simulation of outflow at the exit of the bioretention. It is observed that the results of the hydrological model developed herein are in good agreement with the measured data obtained in the RWB experimental setup.

Differential Quadrature Method in Open Channel Flows: Aksu River, Turkey

AbstractA diffusion wave equation, which is derived from the Saint-Venant equations for one-dimensional, gradually varied, unsteady open-channel flow, describes the wave propagation in open channels. Therefore, it is important to solve the diffusion wave equation accurately and efficiently. In this paper, a numerical solution for a diffusion wave equation is developed by using the Differential Quadrature Method (DQM). The performance of DQM is tested against two other numerical solution methods, the finite difference method (FDM) and finite volume method (FVM). In order to demonstrate the applicability of DQM, first a hypothetical example is solved with both DQM and the two other numerical methods. Then, the DQM is applied to a real flooding event that occurred in Aksu River, Sutculer Basin, located in Mediterranean Region, Turkey. The measured flow rates are routed through the Aksu River by the diffusion wave equation and the outflow is obtained by DQM. Finally, this flood event is also solved by explici...

An evaluation of hydrologic modeling performance of EPA SWMM for bioretention

Recent techniques should be investigated in detail to avoid present and future problems of urbanization like flood, drought and water pollution. Low Impact Development (LID) Best Management Practices (BMPs) such as bioretentions, green roofs, rain barrels, vegetative swales, and permeable pavements have been implemented to diminish the adverse effects of urbanization. In this study, a hydrological model for a Rainfall-Watershed-Bioretention (RWB) system is developed by using the Environmental Protection Agency Storm Water Management Model (EPA SWMM). RWB system is an experimental setup which consists of an artificial rainfall system, a drainage area and four bioretention columns with different soil mixtures. The hydrological modeling capability of SWMM for bioretentions is presented using the experimental data obtained from the experiments conducted in the RWB system under different rainfall events and for bioretentions with different designs. Finally, the modeling results of SWMM are compared with the results of the Hydrological Model of RWB (HM-RWB) system. Results show that EPA SWMM performs well in modeling bioretentions whereas the results of HM-RWB are in better agreement with the experimental data.

A Water Quality-Quantity Model for Avcilar Campus of Istanbul University Incorporating LID Implementation

Rainwater management practices are implementations for improvement of storm water quality and quantity. Implementation of these practices in urban areas is vital because urbanization results in low percentage of permeable soil and cuts off the ground water recharge. Over impermeable surfaces, rain quickly turns into surface runoff and causes flooding. With urbanization, contaminants, which accumulate over the surface, increase and therefore, the contamination of the surface runoff also increases. A number of precautions and control mechanisms are needed to remove these contaminants from the surface runoff which are called as Low Impact Development (LID) Best Management Practices (BMP). LID-BMPs serve for protection of the hydrologic cycle, ecological balance, reduction of the flood risk and improvement of surface water quality. In this study, first, a hydrological model for Avcilar Campus of Istanbul University is developed by using Environmental Protection Agency Storm Water Management Model (EPA SWMM). Then, the water quality model is integrated into the hydrological model by defining various land use types such as low-density residential, high-density residential, highway commercial and highway, and pollution parameters such as total suspended solid (TSS) and lead (Pb). Finally, several LID implementations such as green roof, permeable pavement, bioretention, rain garden, and rain barrel, are defined into the model according to the settlement type on the campus. The impact of the LID implementations on the water quality and quantity are observed. Model results show that the LID implementations greatly reduce the peak discharge. Moreover, LID implementations also decrease pollutant concentrations in surface runoff.

Impact of LID Implementation on Water Quality in Alibeyköy Watershed in Istanbul, Turkey

In this study, the impact of low-impact development (LID) methods implementation on total suspended solids (TSS) is investigated by developing a hydrologic-water quality model for Alibeyköy Watershed located in Istanbul, Turkey. For this purpose, the US Environmental Protection Agency Storm Water Management Model (EPA SWMM) was used, which was calibrated in this watershed. Then, several LID types, such as bioretention, vegetative swales, infiltration trenches and permeable pavements were incorporated into the model, in an effort to evaluate the impacts of distinct and combined LIDs on TSS removal in the Alibeyköy Watershed for different scenarios. Both distinct and combined impacts of LID-BMPs on the reduction of TSS concentration in Alibeyköy Watershed are observed. It is found that bioretention, vegetative swales, permeable pavements, and infiltration trenches have significant effects on TSS removal both in case of distinct and combined implementations. Moreover, it is seen that bioretention and vegetative swales are slightly more effective on TSS removal under a strong rainfall.

Low impact development implementation: Investigation on the hydrologic performance of bioretention via experimental models

Su kaynaklarının ekonomik, sosyal ve çevresel açıdan en verimli şekilde kullanılması, canlı hayatın sürdürülebilmesi için kaçınılmazdır. Özellikle kentleşme ile birlikte betonlaşma ve buna paralel olarak topraktaki geçirimsiz yüzey artmakta, toprakta meydana gelen sızma azalmakta ve yağış sonucu yüzeyde toplanan fazla su hızlı bir şekilde akışa geçerek taşkına neden olmaktadır. Kentleşme ile beraber toprağa sızamayan su, doğal arıtım olan topraktan mahrum kalmakta ve yüzeyde biriken kirliliği doğrudan su kaynaklarına taşımaktadır. Bu durum su kalitesini olumsuz yönde etkilemekte ve su kirliliğine neden olmaktadır. Bu çerçevede, çevresel sürdürülebilirliğin sağlanması, su kaynaklarının korunması ve kentleşmenin çevre ve su kaynakları üzerindeki olumsuz etkilerinin azaltılması için yeni hidrolojik yöntemlere ihtiyaç duyulmaktadır. Bu çalışma kapsamında, kentleşme sonucu arazi kullanımında meydana gelen değişimler ile artan yüzeysel akış ve su kirliliğini önlemek için Düşük Etkili Kentleşme (DEK) tipi En İyi Yönetim Uygulamaları (EİYU) incelenmiştir. Yüksek yüzeysel akış ve yayılı kirlilik kaynaklarının olumsuz etkilerini azaltmak için kullanılan bir yağmur suyu yönetimi uygulaması ve DEK çeşidi olan “biyotutma” araştırılmıştır. Bu amaçla kurulmuş olan bir deney düzeneği ile biyotutmanın hidrolojik verimliliği ve performansı gözlemlenmiştir. Yapılan deney sonuçları değerlendirilerek biyotutmanın pik debinin azalması üzerine etkisi incelenmiştir. Biyotutma kolonlarında kullanılan malzemelerin mekanik özellikleri incelenmiştir. Elde edilen sonuçlar değerlendirildiğinde malzeme tipi ve özelliklerinin biyotutma kolonlarında suyun tutulmasında etkili olduğu görülmüştür. Kum içeriğinin fazla olması ile kolonlardaki çıkış debisinin arttığı ve ince taneli malzemelerin artması ile azaldığı gözlemlenmiştir. Efficient use of water is vital for economic, social and environmental sustainability of water resources. Especially, urbanization and thus high imperviousness results in a decrease in infiltration and percolation. Consequently, surface runoff generated over the surface increases tremendously and results in floods. Surface runoff also washes off the pollutants that are built up on the surface during dry days which results in poor water quality. Therefore, new methods in hydrology are necessary for environmental sustainability, protection of water resources, and mitigation of impacts of urbanization on environment and water resources. In this study, Low Impact Development (LID) Best Management Practices (BMP) are investigated in order to prevent high surface runoff and water pollution due to land use change caused by urbanization. Bioretention, which is a LID type of storm water management practice, is investigated to mitigate impacts of high surface runoff and nonpoint source pollution. For this purpose, an experimental set-up is developed to observe the hydrologic efficiency and performance of bioretention. Performance of bioretention on peak flow decrease is observed by evaluating experimental results. The mechanical properties of materials used in bioretention columns are investigated. It is observed that the material type and properties are effective in retaining water in bioretention. As the sand content increases, the outflow at the exit of the column also increases and if the fine grained material increases, the outflow at the exit of the column decreases.

Analytical Solutions for Contaminant Transport in Wetlands Incorporating Surface Water and Groundwater Interactions

AbstractWetlands are the transitional zones between uplands and downstream flooded systems; they play an important role in controlling storm water peak flow and downstream water quality. Since surface water/subsurface water interactions affect solute transport within wetlands significantly, contaminant transport models incorporating these interactions need to be investigated for wetland areas. Wetland solute transport dynamics (WETSAND) is a comprehensive wetland model, which has both surface flow and solute transport components. In WETSAND, water quality components are solved by advection-dispersion-reaction equations, which incorporate surface water/groundwater interactions by including the incoming/outgoing mass due to the groundwater recharge/discharge. In this study, analytical solutions for the contaminant transport equations of WETSAND are developed and compared to the numerical solutions obtained by WETSAND. These analytical solutions provide a physical insight to wetland water quality. Results sh...