sentences:  It has been calculated that a 100-year flood in the watershed would only affect a roughly wide area for the lower reaches of San Juan Creek inside San Juan Capistrano, while for Arroyo Trabuco, only a wide area would be affected, mainly due to considerable entrenchment of the river bed.However, the U.S. Army Corps of Engineers considers many levees in the San Juan Capistrano area to be inadequate for handling the 100-year flood, and that such a flood would cause $149 million of property damage.The San Juan Creek watershed covers in south Orange County and a very small portion of Riverside County.