Resources by Topic

Resources by Topic: Hydraulics


Hydraulics is the branch of engineering related to the behavior of fluids and for dams, the parameters of interest include discharge (or flow) rate, velocity, pressure, duration, and depth of flowing water and how these parameters impact the performance of the structures of the dam. Hydraulics for dams is often considered complimentary to hydrology.

Hydraulic structures at dams can be divided into spillways and outlet works. Spillways are typically designed to pass normal and flood flows while outlet works are used to discharge water to supply lines for drinking water or to facilities used to produce hydropower. Outlet works are also often used to lower or drain the impoundment.

The spillway or system of spillways at a dam should be designed to safely pass the required Spillway Design Flood (SDF) or Inflow Design Flood (IDF). Types of spillways include:

  • Riser (tower) and conduits
  • Channels excavated into earth or rock
  • Straight overflow weirs of various shapes (broad and sharp crested, ogee)
  • Overflow weirs with more complex plan forms (box spillways, duckbill weirs, labyrinth weirs)
  • Side channel spillways
  • Gated overflow spillways

Spillways and outlet works are divided into several components, listed below in order of the direction of flow:

  • Entrance channel
  • Intake structure
  • Control section (may be part of intake structure)
  • Conveyance structure
  • Energy dissipator
  • Exit channel

The analysis and design for each of these components involves estimating the hydraulic properties of water as it passes over and through the element. The performance of hydraulic structures can be evaluated using physical and/or numerical models (i.e. computational fluid dynamics). Numerous methods for the analysis of hydraulic structures have been developed, primarily based extensive modeling performed by agencies such as the US Army Corps of Engineers, Bureau of Reclamation, and Natural Resources Conservation Service.

Hydraulic analysis required for dams also includes the modeling of a failure (or breach) of the structure and resulting downstream flooding. Dam breach and downstream inundation analyses and mapping are used to assign hazard category, develop the SDF/IDF, and estimate flooding for use in development of emergency action plans (EAPs). This analysis requires knowledge of the mechanics of dam failures and open channel flow.

Individuals interested in hydraulic analysis for dams should develop a strong understanding of fluid mechanics and open channel flow.


To be proficient in this area one needs to understand and/or have experience in the following areas:

  • Basic Hydraulics for Dams
  • Floodplain Hydraulics: Hydraulics of Open Channel Flow; Computer Modeling of Open Channel Flow; GIS-based Methods Applications
  • Spillway Hydraulics: Hydraulic Design of Outlet Works; Hydraulics of Stepped Spillways; Hydraulics of Labrynth Spillways;Hydraulics, Stability, and Integrity of Earthen and Rock Spillways
  • Hydraulic Design of Stilling Basins and Energy Dissipators
  • Hydraulic Design of Erosion Protection for Channels (Wave Protection, etc)
  • Hydraulic Design of Overtopping Systems
  • Numerical and Physical Modeling of Spillways
  • Hydraulics for Conduits, Valves and Gates
  • Reservoir and Channel Routing: Level-pool Routing Theory; Dynamic Routing Theory; Computer Modeling of Routing Through Channels and Reservoirs
  • Dam Break Modeling: Methodologies – Steady flow theory and overview of unsteady flow theory; Incremental Dam Breach Analysis;Simplified Inundation Mapping for Emergency Action Plans

Classroom and Web-Based Training

ASDSO Technical Seminars: Classroom
  • Hydraulic Analysis of Spillways (basic) Held in 2005-2007
  • Conduits, Valves and Gates (basic) Held in 2008-2009
  • Dam Failure Analysis (advanced) Held in 2005-2006.
ASDSO Webinars:
  • Hydraulics 101 for Dam Safety

For additional training opportunities, search the ASDSO Training Directory.

Guidelines, Resources, & Suggested References

Some of the most highly recommended resources in this area are listed below. For additional resources, search the ASDSO Bibliography. Suggested search terms: conduits, fuse plugs, gates, hydraulics, models, outlet works, spillways

  • E. F. Brater, H. W. King, J. E. Lindell and C. Y. Wei. Handbook of hydraulics for the solution of hydraulic engineering problems (1996). McGraw-Hill.
  • V. T. Chow. Open-Channel Hydraulics (1988). McGraw-Hill.
  • C. V. Davis and K. E. Sorensen. Handbook of Applied Hydraulics (1969). McGraw-Hill.
  • E. A. Elevatorski. Hydraulic energy dissipators (1959). McGraw-Hill.
  • Khatsuria, R.M. Hydraulics of Spillways and Energy Dissipators, Chapter 12: "Fuse plugs and fuse gate spillways" (2004). Marcel Dekker.
Federal Publications

Federal Emergency Management Agency

Federal Energy Regulatory Commission

Federal Highway Administration

U.S. Army Corps of Engineers

U.S. Bureau of Reclamation

U.S. Department of Agriculture, Soil Conservation Service


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