San Juan Creek


GENERAL

Source
SiteMouth of San Juan Creek

MapDana Point, USGS 7.5' quadrangle

LocationSouthern Orange County, in the City of Dana Point. The area south of Highway 1 is in Doheny State Beach, and most of the biological information in the profile focuses on this area.

ContactsU. S. Army Corps of Engineers, Los Angeles District, (213) 452-3812.


California Department of Parks and Recreation, (714) 848-1566, or (714) 492-0802.

Approximate Wetland Acreage 3
2
Approximate Historic Acreage Approximately 300 acres in the lower 2 miles, in 1948
2
OwnershipOwner Acres
Source

California Department of Parks and Recreation Not specified (the portion of the creek within the park extends 200 linear yards inland from the mouth).
2

Orange County Flood Control District Not specified (The creek channel from Pacific Coast Highway inland).
8
LAND USE

Source
Land Use Designation The flood control channel is unzoned, and the area within Doheny State Beach, though not subject to local land use controls, is zoned recreation.
8
Onsite UseThe lower 2.6 miles of the creek are channelized for flood control, Hwy 1 crosses the creek approximately 0.2 mile upstream of the ocean, and the area south of Hwy 1 is part of Doheny State Beach.
1, 2
Historic UseConversion of the floodplain to residential and commercial uses began soon after the creek was channelized and armored in 1962.
1
Adjacent UseApproximately 80% of the land adjacent to the channel is in residential or commercial use; two water treatment plants, one on each side of the river, lie just upstream of the Hwy 1 bridge (neither discharges into the Creek).
1
Historic Adjacent Use Immediately prior to channelization of the lower creek in 1962, much of the area outside of the floodplain was in agricultural use. Crop production had been a major use in the watershed since the late 1800's.
1
HYDROLOGY

Source
Tidal Influence A beach berm blocks the mouth most of the time, but the subsequent build-up of water causes it to break periodically. No information is available on the degree of tidal exchange that may occur while the mouth is open.
1, 7
Watershed Area 176 square miles
1
Tributaries and Flow Tributary
Flow
Source

San Juan Creek The creek is perennial as it is reported to have been historically, although currently flows are augmented by urban runoff. The 1987 calculated 100-yr peak discharge at the ocean was 59,500 cfs. The channel is braided for most of its length; there are several gradient control structures in the main channel as well as a sand and gravel mining operation; downcutting is occurring along the entire mainstem; the lower 2.6 miles have concrete banks and an earthen bottom.
1, 2
DamsOso Reservoir and Mission Viejo Lake on Oso Creek.
1
Other Sources Groundwater
1
WATER QUALITY

Source
GeneralWater quality during low flow periods is described as poor; the beach was closed for 8 days in 1995 because of water quality concerns. The creek was included in the 1996 draft list of impaired water bodies, selected standards having been exceeded for coliform bacteria. Designated Beneficial Uses are: rec1, rec2, wild, rare, mar, migr.
1, 4, 5
Dissolved Oxygen (DO) 1995 - A single sample taken in January (depth and time of day not reported) at the Pacific Coast Highway measured 8.4 mg/l. Temperature was 13.9 C.
1
Water Salinity 1995 - A single sample taken in January (depth and time of day not reported) at the Pacific Coast Highway measured 398 mmoh/cm.
1
Sedimentation1984 - The volume of sediment yielded by the watershed during a 2-yr storm was calculated at 6,080 tons.
1
SOIL

Source
SoilNo information specific to the mouth; soils in the watershed are very erodible, composed of sandy clay loams with varying overlayers of gravelly or cobbly silty sands.
1
HabitatAcres Vegetation
Riparian (Acreage includes only the area within Doheny State Beach). 3+1996 - Willows, cottonwoods, sycamores, mulefat, bulrush, cattail and giant reed* were among species observed on the banks.
6
ANIMAL USE

Source
Birds1996 - During a qualitative evaluation in April 1987, of a vegetation enhancement project, 5 species were observed, including 1 of special status.
2
FishNo data located

Benthic InvertebratesNo data located

InsectNo data located

Other Wildlife No data located
Special Status Species 1996 - Tri-colored blackbird.
2
OUTLOOK

Source
Enhancement Status State Parks carried out a project in the late 1980's to eradicate giant reed in the channel and re-establish native riparian vegetation. In 1996, this project was judged to have been substantially successful, although the potential remained for giant reed to return to dominance.
2, 3
Watershed Management The U.S. Army Corps of Engineers is conducting a study of San Juan and Aliso Creek watersheds to describe existing conditions, recommend solutions to a range of environmental problems, and determine the level of federal involvement needed to implement those solutions. By fall 1996, the Corps had completed a comprehensive summary of existing information and held a number of public workshops. In addition, 37,000 acres of the watershed are slated for preservation through the County Natural Communities Conservation Planning effort.
1
PressurePressure to improve the channel capacity of the lower creek which is currently inadequate for large flood events; downstream impacts caused by an unstable channel, intensified land use in the watershed, and in-stream sand and gravel mining.
1
SOURCES


1U. S. Army Corps of Engineers. 1996. Draft San Juan Creek and Aliso Creek Watershed Management Study, Orange County, California: existing conditions data collection summary. 234 pp. plus appendices. This report summarizes existing information on geomorphology, geology and soils, land use, biological resources, hydrology, hydraulics, sediment transport, groundwater, and water quality in the San Juan and Aliso Creek watersheds. The study was conducted to establish a baseline of data and identify information gaps as part of an effort to address damage to environmental and water resources, and to economies in the watersheds, as a result of land use changes. Two appendices are bound with this report: 1) a general description of biological communities, air and water quality conditions, and cultural and recreational resources and 2) an analysis of the economic effects of both correcting and ignoring selected problems in the watershed. Additional technical appendices are bound separately.

2California Department of Parks and Recreation. 1987. Doheny State Beach Riparian Habitat Restoration. 6 pp. Description of a proposed project to remove exotic vegetation (predominantly giant reed) from levee banks and islands within the channel, and replant with native riparian species. It provides brief descriptions of both the historic coverage of riparian habitat and the current distribution of plant species. The species to be planted are identified along with the methods and materials, and an estimated budget.

3California Coastal Commission. 1988. Staff report on permit 5-88-157 application. 6 pp. Text of a staff recommendation that the Coastal Commission approve without special conditions, the Department of Parks and Recreation's application for a permit to remove exotic vegetation and replant the Creek channel and banks with native species. The report contains a brief description of the proposed project and it's consistency with the Coastal Act and the approved Local Coastal Program.

4San Diego Regional Water Quality Control Board. 1994. Water quality control plan for the San Diego basin. ~225 pp. plus appendices. The plan designates beneficial uses and associated water quality objectives for inland surface waters, coastal waters, reservoirs and lakes and ground water in San Diego County and parts of Orange and Riverside counties. It includes a discussion of applicable policies and statutory requirements, and identifies measures for achieving water quality objectives. It also describes ongoing monitoring and assessment programs. Appendices contain summaries of regional growth forecasts and water quality criteria for organic and inorganic constituents.

5San Diego Regional Water Quality Control Board. 1996. Draft 303(d) list for the San Diego Basin. 27 pp. A proposed list of waterbodies in the San Diego Basin that do not or are not expected to attain water quality standards after application of required technology-based controls. Specifies selected beneficial uses and criteria assessed, and the percentage of samples in which criteria were exceeded. It also identifies waterbodies for which previous assessments are no longer applicable.

6California Coastal Commission. 1996. Untitled compliance evaluation for permit 5-88-157. 5 pp. A qualitative evaluation by Commission staff, of the success of the Department of Parks and Recreation's riparian enhancement project at the mouth of San Juan Creek. The evaluation is based on a visual site inspection 8 years after the permit was issued. Project success is judged according to stated project objectives and to an assessment of ecological value characterized by hydrology, morpholgy, substrate, water quality, and plant and animal use.

7Gatwood, Elden, U. S. Army Corps of Engineers. January 21, 1997. Personal communication.

8Swaneck, Jim, Orange County Public Facility and Resources Department. January 22, 1997. Personal communication.


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