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

Bolsa Chica Lowlands Restoration Monitoring2007 Annual Reportillustrated in Figure 2-1. Investigations were completed to assess the true rate of shoal accretion anddistribution pattern of flood shoal development.Full TidalBasin (Phase I)Modeled Shoal AreaTidal InletScale 1’’= 1,800’Figure 2-1. Predicted Flood Shoal Area (cited from M&N 1999).MethodologyThe rate and distribution of sand accretion in the FTB inlet was assessed during three surveys in thefirst year: January 19 and June 27, 2007 and January 10, 2008. The results of the 2008 survey areincluded in the present report as they document the bathymetric changes that occurred in the latter halfof 2007. The survey area was presented in Figure 1-1.The surveys were conducted from a small survey vessel with sub-meter accurate differential globalpositioning system (dGPS) and a survey-grade SyQuest Hydrobox ® fathometer. The first surveyextended from the PCH bridge into the FTB, within the maintenance basin and beyond any evidence offlood shoaling. The survey area was expanded in the latter surveys after field observations indicatedthe shoaling extended to the north of the maintenance basin. The expanded survey area extended fromthe PCH bridge north to the Freeman Creek outlet to the FTB. All future surveys will include thislarger area.During the July 2007 and January 2008 surveys, large areas of the shoals were not accessible by boatdue to their high elevation. To determine the elevation of these areas, additional survey work wasconducted using a total station for land-based survey.Merkel & Associates, Inc. 60