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HomeMy WebLinkAbout3338; Agua Hedionda & Calavera Creek Dredging; Rancho Carlsbad Channel Maintenance Agua Hed.; 2002-08-12WETLAND DELINEATION REPORT FOR THE RANCHO CARLSBAD C-L MAXNTIENANa PRUJXCT Prepared for CITY OF CARISBAD 1635 FARADAY AVENUE CARLSBAD, CA 92008 --- GERALD A. scm SENIOR BIOLOGIST TABLE OF CONTENTS Introduction Methods Results A. Vegetation, Soils, ad Hydrology B . Jurisdictional Areas Referents Cited TABLE 1 : Jurisdictional Areas on Agua Hedionda Creek FIGURES 1 : Regional Location 2: Project Location on USGS Map 3: Jurisdictional Wetlands and Waters PHOTOGRAPHS 1 : Agua Hedionda Creek - Low Sandbar 2: Agua Hedionda Creek - High Sandbar Introduction A wetland and jurisdictional determination was conducted on Agua Hdionda Creek within the Rancho Carlsbad community as part of a proposed maintenance project. The study area is located within the City of Carlsbad east of El Carnino Real and north of College Boulevard within the Rancho Carlsbad Mobile Home Park (Figures 1 and 2). The proposed project is the removal of accumulated sediment from Agua Hedionda Creek. Sediment removal will return the 100-year storm flood control capacity of the creek, minimizing the flood prone area within the Rancho Carlsbad community. Agua Hedionda Creek within the study area was converted from a naturaI creek to an earthen trapezoidal flood control channel in the 1970's. Currently, during low flow periods, the creek is comprised of a series of sandbars among the meandering active channel (Photographs 1 and 2). Water temporarily covers the entire channel during flood events: The distribution of sandbars and alignment of the low flow active channel is dynamic, changing with each wet season. The elevation and size of the sandbars varies in time, but typically the channel bed develops a series of lower sandbars (6 to 12 inches above the active channel) and higher sandbars (1 8 to 20 inches above the active channel). Vegetation development within the channel is also dynamic, depending on the intensity and frequency of the flood events in any given wet season. In most years, only a limited amount of herbaceous vegetation grows in the channel; woody vegetation is preventsd from growing due to the scour of flood events. Methods The wetland delineation followed the guidelines set forth by the U.S. Army Corps of Engineers (US ACE 1987) to delineate wetlandi'jurisdictional areas. According to this methodology, three criteria must be fulfilled in order to classify an area as a jurisdictional wetland: (1) a predominance of hydrophytic vegetation, (2) the presence of wetland hydrology, and (3) the presence of hydric soils. Areas meeting all three of these parameters are designated as wetlands. Hydrophytic Vegehtion Characterization. Areas identified as potential wetlands were examined to determine he dominant plant species for each vegetation sh-atum (i.e., tree, shrub, herb, and vine). Dominant species from each stratum were recorded on a summary data sheet along with the associated wetland indicator status of those species. The wedand indicator status of each dominant species was determined using the California list of wetland plants developed by the U.S. Department of the Interior (1 997).