HYDRAULIC-HYDROLOGIC STUDIES AND DRAINAGE DESIGN
At Sunko Proje, we are dedicated to creating sustainable, safe, and long-lasting structures in our engineering projects. To achieve this, we apply the most current and advanced engineering techniques in our hydraulic-hydrologic studies and drainage design processes. Below, you will find detailed information about the steps and methods we follow in our projects.
Hydraulic and Hydrologic Studies
Evaluation of Meteorological Data: The first step in our hydraulic and hydrologic studies is the careful evaluation of meteorological data. At Sunko Proje, for watersheds smaller than 10 km², we obtain Rainfall-Intensity-Duration-Frequency curves through the “Meteorological Data Information Presentation and Sales System.” For larger watersheds, we select appropriate flow observation stations close to the watershed from the Meteorology General Directorate’s Station Information Database. These stations are then mapped onto the watershed plan, and their effects are analyzed using the Thiessen polygon method. Additionally, the “Annual Maximum Rainfall Extreme Distribution Calculation” is performed to determine the most suitable rainfall distribution type.
Determination of Watershed Characteristics: The surface runoff coefficients (C) used in the Rational method and the flow curve numbers (SN) used in the Synthetic-Mocus methods are determined by considering the vegetation cover, soil type, and shape of the watershed area. At Sunko Proje, this meticulous evaluation of watershed characteristics is crucial for ensuring maximum efficiency and safety in our projects. The average calculation for each watershed is carefully adapted to the specific conditions of the region.
Hydraulic Calculation Methods
Rational Method: The Rational formula (Q = 0.278 * C * I * A) is used to calculate the runoff from the rainfall area. This formula considers factors such as the surface runoff coefficient (C), rainfall intensity (I), and the area of the rainfall basin (A). At Sunko Proje, we frequently use this method, especially in highway design projects, as it aligns with the highway design manual.
DSİ Synthetic Unit Hydrograph Method: This method is ideal for watersheds larger than 5 or 10 km². However, using this method for smaller watersheds may prolong the design process and lead to less conservative results in flow determination. Sunko Proje employs this method, utilizing Thiessen polygon distribution and other techniques to ensure accurate determination of rainfall frequency values, which allows for the precise calculation of flood discharges.
Mockus (Without Superposition) Method: In this method, the unit hydrograph is considered triangular. The Mockus method is preferred due to its practicality and the generally slightly higher discharge values obtained compared to the synthetic unit hydrograph. By using this method, Sunko Proje ensures the accurate determination of rainfall frequency values and the reliable calculation of flood discharges.
Factors for Safe Design
Climate Change Predictions: Climate change, resulting in shorter rainfall durations and increased rainfall intensities, is one of the critical factors considered in Sunko Proje’s designs. Therefore, the sizes of hydraulic structures selected for watersheds are optimized based on climate change projections.
Sediment Accumulation Prediction: At Sunko Proje, when the frequency of cleaning sediment accumulated within hydraulic structures is unknown, we design these structures with larger dimensions. This approach reduces the risk of clogging and contributes to preventing flood disasters.
Coastal Strip (Wave Effect) Risk Factor: Protecting hydraulic structures against wave effects in coastal areas is crucial for the success of our projects. These structures are carefully designed and placed based on data provided by relevant institutions.
Landslide Area and Altitude Factor: Sunko Proje carefully selects the sizes of hydraulic structures in landslide-prone areas and high-altitude regions. In particular, large structures are preferred in areas where landslides are frequent, and factors such as avalanche risks in snowy areas are considered.
Culvert Design Criteria
Inlet-Outlet Conditions: Providing protection at culvert inlets and outlets is essential to maintaining the hydrodynamics of the culvert and preventing erosion. At Sunko Proje, we take the necessary protective measures at culvert inlets and outlets in accordance with the “Project and Engineering Services Criteria Reports” published by the Highways Department in 2006.
Cross-Section Features and Slope: Using box sections makes it easier to model water behavior and helps achieve more accurate results. At Sunko Proje, we consider the 10% slope limit for culverts and recommend increasing this limit to 15-20% in some apical areas and adding energy dissipators.
Material and Roughness Coefficient: The roughness coefficient used in reinforced concrete hydraulic structures must be selected at higher values using the Cowan method due to material accumulation that increases over time. Sunko Proje considers the values recommended by DSİ in these calculations.
Drainage Design
Review of Road Cross-Sections in Terms of Drainage Design: For drainage design, we work in accordance with the standards set by the KGM-Survey Project and Environmental Department. We recommend implementing ditch systems to increase drainage capacity in central medians.
Concrete Quality and Material Properties: The class of concrete used in drainage design, material properties, and pipe types are determined in a way that aligns with hydraulic calculations. At Sunko Proje, we use calculation methods such as the Chezy formula and Kutter coefficient to ensure maximum efficiency in selecting these materials.
Underground Water Drainage Design: Accurate determination of groundwater level and discharge is critical to the success of our drainage systems. Sunko Proje evaluates the drainage requirement in mixed cross-sections during underground drainage designs and reduces the risk of clogging by selecting larger-diameter tunnel-type pipes.
Ditches and Special Protective Structures: We design ditches and diversion channels in accordance with the highway design manual, adapting them to the natural terrain. The use of trapezoidal geometry and sizing based on Q100 + Air Allowance and Q500-Q1000 discharges is essential for the success of our projects.
Special Protective Structures
Diversion Channels: Diversion channels are designed to match the horizontal and vertical geometries of the route. At Sunko Proje, we prefer concrete-lined channels to ensure that open channels harmonize with the natural terrain.
River Improvement: Sunko Proje employs brit structures to reduce the energy of the water during river improvement works, protecting the channels against slope and bed erosion.
Watershed Protection Structures and Filtration: At Sunko Proje, we integrate stabilization ponds and lagoons, commonly seen in international projects, into watershed protection structures. The purpose of these structures is to temporarily hold water discharged from drainage systems, allowing foreign materials to settle and purify the water before it is returned to nature or transferred to another system. It is important to note that these systems must be cleaned at regular intervals.
Related Circulars and Technical Specifications
Sunko Proje adheres strictly to existing circulars and technical specifications in every project related to bridge and road engineering. These documents include critical resources such as the Highway Design Manual, DSİ’s Irrigation and Drainage Books, and the Project and Engineering Services Criteria Reports. Additionally, we apply advanced engineering calculations and methods such as the Cowan Roughness Coefficient Determination Method in our work.
Conclusion
Sunko Proje’s comprehensive approach to hydraulic-hydrologic studies and drainage design focuses on producing safe and sustainable solutions in engineering projects. Every project is carried out using the most current scientific data, engineering standards, and detailed analyses. This not only ensures the long-term durability of the structures but also minimizes environmental impacts, enabling the creation of robust infrastructures for the future.
If you are interested in taking advantage of these comprehensive drainage design services for your projects, you can contact Sunko Proje and explore the most suitable engineering solutions with our expert team.
Drainage Design- Sunko Proje