Hydraulic Performance of Outlet Works

---

Outlet Works Hydraulics

“The hydraulic analysis of the flow through a flood control conduit or sluice usually involves consideration of two conditions of low. When the upper pool is at low stages, for example during diversion, open-channel flow may occur in the conduit. As the reservoir level is raised, the depth of flow in the conduit increases until the conduit flows full. In the design of outlet works, the number and size of the conduits and the elevations of their grade line are determined with consideration of overall costs. The conduits are usually designed to provide the required discharge capacity at a specified reservoir operating level, although adequate capacity during diversion may govern in some cases. Conduits should normally slope downstream to ensure drainage. The elevation of good foundation materials may govern the invert elevation of conduits for an embankment dam.”

Reservoir Drawdown

“Where practicable, reservoir release facilities should be provided to lower the pool to a safe level adequate to correct conditions that might threaten the integrity f the dam.”

“Low level outlets are provided to maintain downstream flows for all levels of the reservoirs operational pool. The outlets may also serve to empty the reservoir to permit inspection, to make needed repairs, or to maintain the upstream face of the dam or other structures normally inundated.”

Examples

Best Practices Resources

Federal Guidelines for Dam Safety (FEMA P-93)

Hydraulic Design of Reservoir Outlet Works (EM 1110-2-1602)

Hydrologic Engineering Requirements for Reservoirs (EM 1110-2-1420)

Trainings

Citations:

Revision ID: 3231
Revision Date: 09/15/2022