ASDSO Dam Safety Toolbox

Care and Diversion of Water

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Construction of a tunnel for the diversion of water at a construction site.

(Image Source: Wikipedia)

"The design for a dam that is to be constructed across a stream channel must consider diversion of the streamflow around or through the damsite during the construction period. The extent of the diversion problem varies with the size and flood potential of the stream; at some damsites diversion may be costly and time-consuming and may affect the scheduling of construction activities; whereas, at other sites it may not present any great difficulties. Nevertheless, a diversion problem exists to some extent at all sites except those located offstream, and the selection of the most appropriate scheme for diversion during construction is important to the economy of the dam."[1]

"The diversion scheme selected ordinarily represents a compromise between the cost of the diversion facilities and the amount of risk involved. The proper diversion scheme will minimize the potential for serious flood damage to the work in progress at a minimum of expense. The following factors should be considered in a study to determine the best diversion scheme:

  1. Streamflow characteristics;
  2. Size and frequency of diversion flood;
  3. Methods of diversion;
  4. Specifications requirements."[1]

"The method, or scheme, of diverting floods during construction depends on the magnitude of the flood to be diverted; the physical characteristics of the site; the type of dam to be constructed; the nature of the appurtenant works, such as the spillway, penstocks, or outlet works; and the probable sequence of construction operations. The objective is to select the optimum scheme considering practicability, cost, and the risks involved. The diversion works should be capable of being incorporated into the overall construction program with minimal impact and delay."[1]

If a cofferdam is proposed, its hazard potential to the downstream public should be evaluated. Design criteria should be imposed by the regulating agency commensurate with that risk. The regulating agency may consider the anticipated service life of the structure and other risk reduction measures when determining appropriate design criteria for the structure. The dam owner's construction insurance policy may also specify design criteria for temporary conditions during construction.

Best Practices Resources

Design Standards No. 14: Appurtenant Structures for Dams (Ch. 2: Hydrologic Considerations) (Bureau of Reclamation), USBR

Design of Small Dams, USBR


On-Demand Webinar: Stream Management for Dam Construction

On-Demand Webinar: Managing Increased Dam Safety Risk During Reconstruction


Revision ID: 7386
Revision Date: 07/21/2023