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Typical diversion methods for working in the dry and their applicability

Typical diversion methods for working in the dry and their applicability.

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Diversion practice Applicability Limitations
Partial stream diversion
  • Suitable when work area is on one side of the stream channel or stream bank.
  • Appropriate stream size and duration of use depends on materials.
  • Structures are placed in the stream to confine flow to one side while work progresses on the “dry” side.
  • Sand bags, stone, or similar diversions are appropriate for smaller streams and work areas, while coffer dams, portable dams, or other similar barriers are necessary for larger water bodies.
  • Not easily moved or adjusted after installation.
  • Sand bag or stone in-channel diversions are typically not appropriate for larger streams.
  • May be subject to failure or erosion during storm events.
  • Results in a smaller area of stream access compared to other diversion methods.
  • See Diversion barrier controls (cofferdams/ temporary dikes) for more information
Diversion channels/ditches
  • Most appropriate for short duration projects with low baseflows.
  • Requires sufficient area in the stream corridor to construct the diversion channel.
  • Requires a positive slope to allow flow through the channel.
  • Not easily moved or adjusted after installation.
  • Insufficient flow capacity in pipe can cause diversion failure and severe erosion.
Piped diversions/ culverts (bypass pipe)
  • Most appropriate for short duration projects with low baseflows.
  • Appropriate when the required flow diversion can be accomplished without pumping.
  • Construction equipment cannot be driven over pipes.
  • Insufficient flow capacity in pipe can cause diversion failure and severe erosion.
Pumped diversions (“pump-arounds”)
  • Most appropriate for short duration projects with low baseflows.
  • Typically used when there is limited space for a diversion.
  • Pump(s) must be sized to accommodate stream baseflow.
  • Limited by pump capacity, and continuous pumping can be costly.
  • Pump failure can result in delays and additional costs.