Start Date
4-29-2025 3:45 PM
Description
A contemporary activity in dam engineering is the raising of embankments to increase reservoir storage or flood level in a channel. For embankment dams, the raised position of the spillway must be located on a native soil/rock shoulder of the dam, to avoid geotechnical problems associated with possible embankment settlement. Consequently, for many sites, the approach flow entering a spillway likely will not be acceptably uniform, as the approach flow becomes increasingly skewed to reach the spillway’s entrance with the raised embankment. This concern raises the question of where to position the spillway’s ogee crest within the spillway entrance and has general implications for the overflow protection of all earthen embankments for which the approach flow is skewed, whether an ogee crest is used or not. This paper uses Los Vaqueros Dam in California as a case-study example of these issues. A skewed distribution of flow at the spillway’s entrance required the ogee crest location to be significantly modified so that flow distribution across it was acceptably uniform. The flow field between the spillway entrance and the ogee crest was complex, containing several flow-separation zones: flow separated from the spillway entrance’s two vertical walls, and at the vertical face of the ogee crest. Experiments conducted with a hydraulic model of the spillway show that changing the ogee crest location significantly affects the flow field and consequent uniformity of flow over the ogee crest.
Included in
Skewed Approach Flow to the Spillway of an Embankment Dam
A contemporary activity in dam engineering is the raising of embankments to increase reservoir storage or flood level in a channel. For embankment dams, the raised position of the spillway must be located on a native soil/rock shoulder of the dam, to avoid geotechnical problems associated with possible embankment settlement. Consequently, for many sites, the approach flow entering a spillway likely will not be acceptably uniform, as the approach flow becomes increasingly skewed to reach the spillway’s entrance with the raised embankment. This concern raises the question of where to position the spillway’s ogee crest within the spillway entrance and has general implications for the overflow protection of all earthen embankments for which the approach flow is skewed, whether an ogee crest is used or not. This paper uses Los Vaqueros Dam in California as a case-study example of these issues. A skewed distribution of flow at the spillway’s entrance required the ogee crest location to be significantly modified so that flow distribution across it was acceptably uniform. The flow field between the spillway entrance and the ogee crest was complex, containing several flow-separation zones: flow separated from the spillway entrance’s two vertical walls, and at the vertical face of the ogee crest. Experiments conducted with a hydraulic model of the spillway show that changing the ogee crest location significantly affects the flow field and consequent uniformity of flow over the ogee crest.