In the Great Flood of 1862 , the Santa Ana River flooded massively , and as a result " captured " several of the streams flowing into Anaheim Bay . Starved of much of its fresh water input , the bay gradually increased in salinity and the wetland area decreased . Between 1854 and 1949 the bay lost 30 percent of its area largely as a result of sedimentation and the decreased fresh water runoff available to flush it out . However , many of these streams were redirected into the bay in 1964 following the construction of the Santa Ana River Mainstem Project , which channelized the part of the Santa Ana in Orange County to prevent flooding . The purpose was to reduce the total amount of water flowing into the Santa Ana , reducing its flood crests , but an unintended benefit was the restoration of the bay 's natural fresh water source
Great Flood of 1862
Great Flood of 1862
Anaheim Bay