٨١ Gonbad Kavous University Journal of New Approaches in Water Engineering and Environment Volume 2, Issue 1 Laboratory Study of Energy Losses in Simple and Toothed Triangular Spillway Mohammad Ali Namavi Zadeh 1 , Aslan Egdernezhad 2*1 , Ali Reza Masjedi 3 1 M.Sc. Student, Department of Water Sciences and Engineering,, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran. 2 Assistant professor, Department of Water Sciences and Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.. 3 Associate professor, Department of Water Sciences and Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran. Received:11.03.2023; Accepted:12.06.2023 Abstract: With the construction of high dams along rivers, excess floods are discharged through overflows when the dam reservoir capacity is exceeded. As the flow in these overflows is supercritical, the kinetic energy of the flow at the end of the overflow is very high and can cause erosion downstream. Therefore, an overflow requires an energy-consuming structure at the end to reduce excess energy output and minimize erosion and scouring downstream. In this study, experiments were performed to investigate the relative energy losses in two models of simple triangular and toothed overflow made of fiberglass in four different landings at three depths of 100%, 90%, and 80%. The effective variables in this study were the landing number and the bottom depth at the end of the hydraulic jump. The results of this study showed that at three downstream depths, energy losses decrease with increasing landing number. Also, energy losses in the free projectile mode are higher than in the other two modes due to the full development of the hydraulic jump. In the general comparison mode, the performance of a toothed triangular overflow is better in energy dissipation than in the toothed mode, due to the fracture and compression of the flow lines in contact with the teeth at the end of the overflow projectile. In general, the use of teeth at the end of the overflow projectile causes energy loss in the conditions of 100% of the bottom depth in the toothed triangular overflow compared to the simple triangular overflow by an average of 7%, and in the conditions of 90% and 80% of the bottom depth by about 8% and 10%, respectively. Keywords: Triangular overflow, bottom depth, energy dissipation, indentation * . Corresponding author, Email: a_eigder@ymail.com