Date of Award:

8-2026

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Brian M. Crookston

Committee

Brian M. Crookston

Committee

John Rice

Committee

Blake P. Tullis

Committee

Som Dutta

Committee

Sébastien Erpicum

Abstract

Dams play a critical role in protecting communities from flooding and providing reliable water supplies. When large amounts of water pass through a dam’s spillway during floods, the discharge can travel at high speeds and carry potentially destructive kinetic energy that can damage the dam or erode downstream channels if that energy is not properly controlled. To reduce this risk, engineers commonly use hydraulic structures called energy dissipators that slow spillway discharge and safely release it downstream.

Commonly used energy dissipators at embankment dams include stilling basins that rely on a hydraulic jump – a sudden rise in water depth that converts fast-moving water into slower, safer conditions. The standardized design guidance of hydraulic jump stilling basins was developed under specific hydraulic conditions; however, advancements in dam construction (e.g., stepped spillways) or the presence of site-specific constraints are not well represented in such design guidance. Therefore, this research investigates the performance of two hydraulic jump stilling basins tested downstream of a stepped spillway and a real-world case study of a stilling basin with non-uniform inflow conditions. The results of the investigations improve understanding of how these systems work under conditions that are frequently encountered in practice but not well represented in existing design guidance.

Laboratory experiments were performed on two types of stilling basins downstream of stepped spillways, which are increasingly constructed because of their reduced expense and natural ability to dissipate some energy along the chute. One of the stilling basin types studied, the St. Anthony Falls stilling basin, had not been previously evaluated with a stepped spillway, making the results a new contribution to the field. Measurements focused on water surfaces, pressures, and their temporal fluctuations.

The case study examined a spillway design where site constraints, non-uniform flow conditions, and limited tailwater required departure from standard design guidance. Physical modeling was used to test alternative stilling basin configurations and refine the final design to improve performance while reducing construction costs.

This research provides engineers with additional guidance for designing energy dissipators at embankment dams, especially when stepped spillways or site constraints are involved. By better understanding how these systems behave in realistic conditions, dam engineers can make safer, more reliable, and most cost-effective decisions that help protect infrastructure and downstream communities.

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