This study investigates the effects of rainfall, discharge, wave, and alongshore transport on coastal fecal indicator bacteria (FIB) concentrations at adjacent beaches in Orange County, California over three year period from October 2001 to September 2004. In order to identify the dominant temporal and spatial patterns of fecal pollutions along the coastal beaches, Empirical Orthogonal Function analysis was utilized for the three-year measurements (n = 39,525) of fecal indicator bacteria concentration data from 17 sampling stations. Through the data analysis and the Empirical Orthogonal Function analysis, it was found that the dominant factor effecting coastal fecal indicator bacteria concentration is precipitation event and consequent water discharge from Santa Ana River in the area. The Empirical Orthogonal Function analysis revealed the potential non-point fecal indicator bacteria sources around northern part of Orange County beaches.