2007 Annual Monitoring Report (pdf 16MB) - Bolsa Chica Lowlands ...

Bolsa Chica Lowlands Restoration Monitoring2007 Annual ReportIf left unchecked and unmanaged, the primary implication of a substantial reduction of thelongshore sediment supply is shoreline erosion downdrift of the entrance channel. The BolsaChica project, however, incorporates two sand management measures to actively address thepotential for downdrift erosion by eliminating or substantially reducing the net long-term loss ofsand downcoast. To compensate for anticipated short-term sediment losses from the littoral budgetdue to the natural formation of an ebb bar, initial lagoon shoaling, and fillet formation along thejetties, the ebb bar located offshore of the entrance channel was pre-filled, and supplemental sandwas placed as beach nourishment adjacent to the channel at the time of construction. These prefillswere intended to minimize littoral sand loss to ebb bar formation and provide supplementalsand for early inlet stabilization. In addition, the long-term project sediment management planprovides for periodic down-coast beach nourishment using sediment derived from the FTB duringmaintenance dredging operations. This bypassing operation essentially restores the sediment lostfrom the littoral budget to the downdrift beaches over the long-term. The first such maintenancedredging is planned for Fall 2008. Taken together, these measures are anticipated to maintain thehistorical supply of sediment to the beaches located south of the entrance channel.Figure 2-20. Shoreline Changes at Upcoast Transects, October 2005 to October 2007.Merkel & Associates, Inc. 91