Flooding is a natural process that occurs to varying degrees on a somewhat regular basis and typically only presents a problem when larger events present public health and safety concerns or threaten public infrastructure or private property. The relatively small size of the Rose Creek watershed and the fact that most of the upper watershed within MCAS Miramar is still undeveloped has allowed most of the Rose Creek stream network to remain in a natural state with limited areas protected by structural flood control facilities. Most of the structural ‘improvements’ are limited to the western third of the watershed and mainly occur within the upper and lower Rose Canyon. The improvements are primarily comprised of flood channels with concrete sides and natural bottoms, but fully concrete-lined channels near major transportation routes, such as I-805, SR-52, I-5, and West Mission Bay Drive.
As a result of the risk to public infrastructure and private property, the US Army Corps of Engineers and California Department of Water Resources conducted a hydrologic study of Rose and San Clemente drainages in 1972 that mapped 100-year and 500-year floodplains. These floodplains have been incorporated into the Federal Emergency Management Agency (FEMA) Flood Insurance Rate Map (FIRM) for the area and depict 288 acres of land within the 100 year floodplain and another 325 acres of land with undetermined flooding potential.
The 1972 study and resultant mapping products did not delineate the 100-year or 500-year floodplains within MCAS Miramar. The US Army Corps of Engineers did complete a Planning Level Delineation of Aquatic Resources, Floodplain Mapping, and Functional Assessment of Riparian Ecosystems at MCAS Miramar in 2001 that identified a little over 900 acres within the Base boundary in Rose Canyon and a little less than 2,200 acres within San Clemente Canyon as being within the 100 year floodplain. The US Army Corps of Engineers has recently completed a more detailed floodplain assessment for MCAS Miramar.