COASTAL DATA MONITORING IN SUPPORT OF CLEAN BEACH INITIATIVE,


Cabrillo Beach is a well-used, urban green space popular 
with Los Angeles beachgoers and water-sports 
enthusiasts. A goal of The Clean Beach Initiative (CBI) for 
Inner Cabrillo Beach (ICB) was the achievement of a more 
thorough understanding of hydrodynamic and water quality 
changes that may occur during natural habitat restoration 
beach construction activities in the ICB vicinity. Under a 
contract with the U.S. Army Engineer Research and 
Development Center (ERDC), Evans-Hamilton, Inc. (EHI) 
was tasked with monitoring currents, winds, and water 
properties in the vicinity of ICB to support the CBI. 

SCOPE AND APPROACH 

Tide-Dominated Flood Currents Circulation Pattern. 
The circulation study was designed based on information 
indicating that the shallow ICB area had relatively slow 
circulation, and that bacteria problems were occurring in 
the very shallow nearshore waters (less than 0.5 m); thus, 
the movement of those very shallow waters was also 
important to measure and understand, if possible. EHI 
recommended a combination of measurement techniques, 
including the release and tracking of dye and conducting 
direct measurements of the circulation using profiling 
current meters. Additional meteorological, water 

CABRILLO BEACH, CA 

level (tide height), and water property measurements were 
also collected to document the conditions under which the 
circulation study was performed so that identical or very 
similar conditions could be chosen for the post-construction 
circulation study. 

RESULTS 

The ICB preconstruction monitoring study significantly 
advanced the understanding of the circulation and water 
properties along this important public recreation area. The 
circulation was found to be more complex and energetic 
than anticipated. The study revealed that circulation 
provides more flushing of near-beach waters when strong 
winds prevail than would normally be expected from tidal 
currents alone. EHI determined that four dominant 
circulation patterns occur from these interactions of the tide 
and wind in the ICB area: tide-dominated flood currents, 
tide-dominated ebb currents, wind-affected flood currents, 
and wind-affected ebb currents.