tjce Turkish Journal of Civil Engineering 2822-6836 UCTEA Turkish Chamber of Civil Engineering 10.18400/tjce.1427060 Hydromechanics Numerical Modelization in Civil Engineering Water Resources and Water Structures Hidromekanik İnşaat Mühendisliğinde Sayısal Modelleme Su Kaynakları ve Su Yapıları Determination of Ungated Ogee Spillway Length so as to Pass Design Flood Safely Determination of Ungated Ogee Spillway Length so as to Pass Design Flood Safely https://orcid.org/0000-0002-8111-4557 Haktanır Tefaruk ERCİYES ÜNİVERSİTESİ 01 01 2025 36 1 109 121 01 28 2024 07 24 2024 Copyright © 1990, Turkish Journal of Civil Engineering 1990 Turkish Journal of Civil Engineering

Because the flowrate over an ungated ogee spillway depends on the net head of the water conveyed in the approach channel and because the energy losses depend on the flowrate, computation of the spillway discharge for a given gross head of water in the reservoir entering the approach channel necessitates a trial-and-error scheme. For given information of (a) the elevations of the lake water surface and of the spillway apex, (b) the energy loss coefficient at the entrance, the side wall inclination, the length, and the roughness coefficient of the trapezoidal approach channel, an iterative method for computing the discharge over an ungated ogee spillway is presented. Next, for given information of (a) the (volume) ↔ (water surface elevation) relationship of the reservoir, (b) the spillway apex elevation, (c) the maximum allowed lake water surface elevation, and (d) the design flood hydrograph, an iterative method for computing both the length of the ungated ogee spillway and the outflow hydrograph simultaneously such that the maximum water surface elevation reached during routing of the design flood hydrograph becomes equal to the maximum allowed elevation is presented. Matching of the maximum water surface elevation reached in the reservoir while routing of the design flood hydrograph to the pre-specified maximum lake elevation requires a trial-and-error scheme of reservoir routing computations over many different-length spillways. The iterative method presented in this study which is executed in a single run of the coded computer program is a short-cut alternative to the long approach. The developed method is applied to Catalan Dam, which is one of the large dams in Türkiye from reservoir capacity, flood attenuation, and hydroelectricity production aspects, as a case study. The length of an ungated spillway is computed by the method presented here as an alternative to the existing radial-gated spillway, and the reservoir routing computations are done with the design flood hydrograph given in its final project by both the ungated and the gated spillways, and the maximum lake water surface elevations and the outflow hydrographs are found to be fairly close to each other.

Because the flowrate over an ungated ogee spillway depends on the net head of the water conveyed in the approach channel and because the energy losses depend on the flowrate, computation of the spillway discharge for a given gross head of water in the reservoir entering the approach channel necessitates a trial-and-error scheme. For given information of (a) the elevations of the lake water surface and of the spillway apex, (b) the energy loss coefficient at the entrance, the side wall inclination, the length, and the roughness coefficient of the trapezoidal approach channel, an iterative method for computing the discharge over an ungated ogee spillway is presented. Next, for given information of (a) the (volume) ↔ (water surface elevation) relationship of the reservoir, (b) the spillway apex elevation, (c) the maximum allowed lake water surface elevation, and (d) the design flood hydrograph, an iterative method for computing both the length of the ungated ogee spillway and the outflow hydrograph simultaneously such that the maximum water surface elevation reached during routing of the design flood hydrograph becomes equal to the maximum allowed elevation is presented. Matching of the maximum water surface elevation reached in the reservoir while routing of the design flood hydrograph to the pre-specified maximum lake elevation requires a trial-and-error scheme of reservoir routing computations over many different-length spillways. The iterative method presented in this study which is executed in a single run of the coded computer program is a short-cut alternative to the long approach. The developed method is applied to Catalan Dam, which is one of the large dams in Türkiye from reservoir capacity, flood attenuation, and hydroelectricity production aspects, as a case study. The length of an ungated spillway is computed by the method presented here as an alternative to the existing radial-gated spillway, and the reservoir routing computations are done with the design flood hydrograph given in its final project by both the ungated and the gated spillways, and the maximum lake water surface elevations and the outflow hydrographs are found to be fairly close to each other.

 Ogee profile ungated spillway reservoir flood routing reservoir flood Ogee profile ungated spillway reservoir flood routing reservoir flood USBR (1987) Design of Small Dams, Chapter 9 Spillways, C. Hydraulics of Control Structures, 3rdedition, U.S. Department of the Interior, Bureau of Reclamation, U.S. Government Printing Office, Washington DC. Sanko (2007) Final Feasibility Report of Yedigöze Dam ve Hydro-Power Plant (in Turkish), Appendix-4: Hydraulic Design of the Flood Spillway. Sanko Engineering and Consulting Company, Çetin Emeç Boulevard, 6th Street, No: 61/7, 06520 Balgat, Ankara, Turkey. Temelsu (2007) Final Design Project of the Bayramhacılı Dam (Civil Engineering Works), Chapter 3.1 Hydraulic Computations, 4. Flood Spillway (in Turkish). Temelsu International Engineering Services Company, Çankaya, Ankara, Turkey. DSİ (2006) Circular 2006/1 Criteria for Determining Design Flood for Spillways of Dams (In Turkish). General Directorate of State Water Works, Department of Dams and Hydropower Plants, Ankara, Türkiye. Savage B M and Johnson M C (2001) Flow over Ogee Spillway: Physical and Numerical Model Case Study. Journal of Hydraulic Engineering - ASCE, 127(8), 640–649. https://doi.org/10.1061/(ASCE)0733-9429(2001)127:8(640) Chatila J G and Tabbara M (2004) Computational modeling of flow over an ogee spillway. Computers & Structures, 82(22), 1805–1812. https://doi.org/10.1016/j.compstruc.2004.04.007 Alhashimi S A (2013) CFD Modeling of Flow over Ogee Spillway by Using Different Turbulence Models. International Journal of Scientific Engineering and Technology Research, 02(15), 1682–1687. Goharrizi F Z and Moghadam M A (2010) Evaluation of a Numerical Modeling for Flow over an OGEE Spillway. 8th International River Engineering Conference, Shahid Chamran University, 26–28 January 2010, Ahwaz, Iran, 1–10. Salmasi F and Abraham J (2022) Discharge coefficients for ogee spillways. Water Supply, 22(5), 5376–5392. doi: 10.2166/ws.2022.129 Kocaer Ö and Yarar A (2020) Experimental and numerical investigation of flow over ogee spillway. Water Resources Management, 34(13), 3949–3965. https://doi.org/10.1007/s11269-020-02558-9 Fadafan M A and Kermani M-R H (2015) Modeling of flow over an ogee spillway using moving particle semi-implicit method. E-proceedings of the 36th IAHR World Congress, 28 June – 3 July 2015, The Hauge, The Netherlands. Yildiz A, Yarar A, Kumcu S Y, Marti A I (2020) Modeling of flow over an ogee spillway using moving particle semi-implicit method. Applied Water Science, 10:90. https://doi.org/10.1007/s13201-020-1177-4 Kumcu Ş Y, Kocabeyler M F, Özaydın V, Kökpınar M A (2010) Physical Modeling Test Report of the Flood Spillway of Kavşak Dam (In Turkish). Publication number: 1005, Research and Quality Control Department, General Directorate of State Water Works, Ankara, Türkiye. Daneshfaraz R, Ghaderi A, Abraham J, Torabi M (2021) Effect of Different Channels on Discharge Coefficient of Labyrinth Weirs. Teknik Dergi, 32(4), 11081–11096. https://doi.org/10.18400/tekderg.629128 Şentürk F (1994) Hydraulics of Dams and Reservoirs. Water Resources Publications, PO Box 260026, Highlands Ranch, Colorado, 80126-0026, USA. Haktanir T, Citakoglu H, Acanal N (2013) Fifteen-stage operation of gated spillways for flood routing management through artificial reservoirs. Hydrological Sciences Journal, 58(5), 1013–1031. http://dx.doi.org/10.1080/02626667.2013.796431 DSİ (1987) Final Project of Catalan Dam (In Turkish). General Directorate of State Water Works, Department of Dams and Hydropower Plants, Ankara, Türkiye.