Enhancing Spillway Efficiency Discharge Coefficients: Insights from Historical Models and Case Studies of Ogee, Lateral, and Non-Linear Structures
type: CreativeWork
description: Accurate estimation of spillway discharge capacity remains fundamental to dam safety and hydraulic design. Classical formulations such as those of USBR (1987), Ven Te Chow (1959), USACE (1990) and DWS Calibration Manual were developed under the idealised geometric and hydraulic assumptions. However, many South African dams were designed and tested under complex three-dimensional approach conditions. Asymmetric basing geometries and non-standard spillway layouts. Although numerous physical model studies and subsequent DWS calibrations records exist, these datasets have not previously been synthesised int a consolidated framework to evaluate the systematic discharge behaviours across configurations. This study analyses historical South African physical model studies and available calibration datasets spanning more than four decades to identify consistent tendencies in spillway discharge performance under practical geometric and hydraulic conditions. Sixty dams were compiled, including ogee, side-channel, and non-linear spillways. The datasets were normalised using dimensionless discharge coefficients and unit head ratios to allow consistent comparison across model scales and prototype conditions. Statistical trend analysis was applied to evaluate how observed discharge behaviour compares with established theoretical formulations under varying geometric scenarios. The results demonstrate that ogee spillways exhibit the most consistent and predictable behaviour, with relatively small systematic deviations between theory and observed performance. Approach-flow asymmetry and non-perpendicular inflow introduce measurable efficiency reductions, primarily associated with non-uniform velocity distribution and contraction effects not fully captured in classical two-dimensional formulations. Curved spillways may exhibit slight efficiency enhancement due to flow concentration effects. Lateral (side-channel) spillways show consistent overprediction when ogee-based formulations ar…
abstract: Accurate estimation of spillway discharge capacity remains fundamental to dam safety and hydraulic design. Classical formulations such as those of USBR (1987), Ven Te Chow (1959), USACE (1990) and DWS Calibration Manual were developed under the idealised geometric and hydraulic assumptions. However, many South African dams were designed and tested under complex three-dimensional approach conditions. Asymmetric basing geometries and non-standard spillway layouts. Although numerous physical model studies and subsequent DWS calibrations records exist, these datasets have not previously been synthesised int a consolidated framework to evaluate the systematic discharge behaviours across configurations. This study analyses historical South African physical model studies and available calibration datasets spanning more than four decades to identify consistent tendencies in spillway discharge performance under practical geometric and hydraulic conditions. Sixty dams were compiled, including ogee, side-channel, and non-linear spillways. The datasets were normalised using dimensionless discharge coefficients and unit head ratios to allow consistent comparison across model scales and prototype conditions. Statistical trend analysis was applied to evaluate how observed discharge behaviour compares with established theoretical formulations under varying geometric scenarios. The results demonstrate that ogee spillways exhibit the most consistent and predictable behaviour, with relatively small systematic deviations between theory and observed performance. Approach-flow asymmetry and non-perpendicular inflow introduce measurable efficiency reductions, primarily associated with non-uniform velocity distribution and contraction effects not fully captured in classical two-dimensional formulations. Curved spillways may exhibit slight efficiency enhancement due to flow concentration effects. Lateral (side-channel) spillways show consistent overprediction when ogee-based formulations ar…
author: Nyflis, Emmanuel
language: en
date published: 2026-03
date modified: 2026-07-24T04:40:09Z
provider: Stellenbosch University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Stellenbosch : Stellenbosch University