Flood Control Requirements - The Corps of Engineers, specifically Water Management, is responsible for defining and monitoring Flood Control Space within both its own reservoirs, as well as within Section 7 (SEC7) reservoirs. Corps' Water Management is also responsible for the minute by minute operation of the flood control projects which the Corps owns. Part of this monitoring responsibility entails the daily determination of how much of the reservoir's total storage space should be used for Flood Control Space. Therefore, the Corps computes a Top of Conservation Pool value for every reservoir under our jurisdiction which has authorized flood space. The reservoir storage space below the Top of Conservation Pool value may be used for any of the project's non-flood control authorized purposes. Space above the Top of Conservation Pool value is reserved to store flood waters for later release and is monitored (SEC7 projects) or managed (Corps projects) by the Corps. The rate (i.e., how quickly) at which flood water stored in the reserved flood space is released depends upon many factors. Some of these factors are the downstream channel conditions, the stage or flow at downstream control points, the magnitude of the storm which produced the flood water storage, the forecast of the timing and magnitude of future storms, and the current flood season. There are typically two overlapping flood seasons for projects in the West, namely the Rainflood Season and the Snowmelt Flood Season. Briefly, flood waters above the Top of Conservation Pool are managed as follows:
River Stage Definitions
|MONITOR STAGE - The Stage at which initial action must be taken by
concerned interests (livestock warning, removal of equipment from lowest overflow areas,
or simply general surveillance of the situation). This level may produce overbank flows
sufficient to cause minor flooding of low-lying lands and local roads.
FLOOD STAGE - The Stage at which overbank flows are of sufficient magnitude to cause considerable inundation of land and roads and/or threat of significant hazard to life and property.
|MONITOR STAGE - The Stage at which patrol of flood control project
levees becomes mandatory, or the Stage at which flow occurs into bypass areas from project
PROJECT FLOOD STAGE - The Stage at which the flow in a flood control project is at maximum design capacity (U.S. Corps of Engineers "Project Flood Plane"). At this level there is a minimum freeboard of 3 feet to the top of levees.
DANGER STAGE - The Stage at which the flow in a flood control project is greater than maximum design capacity and where there is extreme danger with threat of significant hazard to life and property in the event of levee failure. This is generally 1 foot above project flood stage.
Source: CDEC http://cdec4gov.water.ca.gov/stageInfo.html
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