Orange County Flood
Local Flood Hazard
The major flooding threat in Orange County is the Santa Ana River. In 1938, the
Santa Ana River flooded parts of Anaheim, Santa Ana, and Garden Grove, reportedly
killing more than 50 people. Although the Prado Dam helped to substantially reduce
the flood damage, the 1969 storm caused the largest dollar loss in Orange County
history. Santa Ana River is owned by the U.S. Army Corps of Engineers, and operated
by U.S. Army Corps of Engineers Los Angeles District and Orange County Flood Control
District. Despite the corps extensive efforts at flood control protection, it appears
that portions of the County, which would not be inundated by the river overflow
during the 100-year event, could be subject to flooding from overflow of storm water
drainage facilities that are presently inadequate for carrying the 100-year discharge.
East Garden Grove-Wintersburg Channel and Ocean View Channel system is one of the
underlying channel systems of the Santa Ana River floodplain. This drainage system
does not have the capacity to contain the 100-year flood because the channel banks
and levees are overtopped at several locations.
In addition to the Santa Ana River, other areas subject to flooding during severe
storms include the area adjacent to Atwood Channel, Brea Creek Channel, Carbon Canyon
Channel, Capistrano Beach Storm Channel, El Modena Irvine Channel, Fullerton creek
Channel, Hickey Canyon Storm Channel, Houston Storm Channel, Horno Creek Channel,
Modjeska Canyon, Silverado Canyon, Niguel Storm Drain, Oso Creek Channel, San Juan
Creek Channel, Santiago Creek Channel, and Trabuco Creek Channel. In the central
portion of the County areas adjacent to Santiago Creek and Collins Channel may be
inundated. Large portions of the San Diego Creek watershed in the City of Irvine
and unincorporated area of the County are also subject to inundation. In the southern
part of the County, the flooding is mostly confined to the canyon areas; however,
these areas are also of concern since their development is expanding.
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