Trancas Lagoon

GENERAL

Source

Site Trancas Lagoon

Map Point Dume 7.5' USGS quadrangle

Location Approximately 3 miles west of Point Dume in the City of Malibu.

Contacts Santa Monica Bay Restoration Project, 213-266-7516

City of Malibu, 310-456-2489

Approximate Wetland Acreage 2
1

Approximate Historic Acreage Not specified
1

Ownership Owner Acres Source

Private 10 1

LAND USE

Source

Land Use Designation 1995 City of Malibu General Plan designations for the creek drainage north of Hwy 1 are community commercial west of the creek and rural residential east of the creek, both sides are included in a special plan overlay; south of Hwy 1 both sides of the creek are designated single family medium. The area south of Hwy 1 is an environmentally sensitive habitat area in the Local Coastal Plan
2

Onsite Use Highway 1 bisects the lagoon; the creek bed is channelized through the floodplain for flood control.
2

Historic Use Reference documents summarized changes in the Santa Monica Mountains watershed as a whole since the early 1800s, with uses gradually intensifying from native american homelands to grazing and agriculture under the expansive spanish rancheros, to urban development.
1

Adjacent Use Immediately to the west near the mouth are private homes, and a commercial nursery and shopping center; Zuma State Beach, including a parking lot and boat storage area, lie immediately to the southeast; residential development occupies the eastern portion of the floodplain and lines the bank tops on the west.
1, 6, 7

Historic Adjacent Use Reference documents summarized changes in the Santa Monica Mountains watershed as a whole; since the early 1800's land uses have shifted from native american homelands to vast spanish ranches, with urban development picking up after WWII. The steep mountain terrain slowed urbanization of this area relative to the broader coastal plains of Los Angeles.
1

HYDROLOGY

Source

Tidal Influence The mouth of the creek is often blocked by a sand berm which prevents tidal exchange and causes the creekwater to pond during seasonal high flows. An informal arrangement between County Parks and the Department of Fish and Game allows the County to breach the berm on a restricted basis, to prevent flooding.
1, 6

Watershed Area 10 square miles
1

Tributaries and Flow Tributary Flow Source

Trancas Creek Flow is ephemeral; the peak rate calculated for the lower creek for a 50-yr rainfall was 7,570 cfs (model assumed burn conditions and 53% of the watershed undeveloped). There is a cement and boulder-lined debris basin approximately .8 mile up the canyon; below this the creek is concrete-lined to just east of Hwy. 1. 1, 4, 9

Dams None
4

Other Sources Surface water runoff
1

WATER QUALITY

Source

General Trash and pollutants from the nearby parking lot are reportedly deposited into the lagoon. Designated Beneficial Uses for the Creek are mun, nav, rec1 (except areas channelized in concrete), rec2, warm, wild, and rare. The Creek was not evaluated for inclusion in the 303(d) list. However ocean waters adjacent to the beach exceeded selected criteria for fish consumption, there is an advisory regarding PCBs and DDT, and recreation, coliform counts have led to beach closures.
1, 3, 10, 11

Dissolved Oxygen (DO) Not available

Water Salinity No quantitative data available, however brackish and freshwater plants (not named) grow in the lagoon area.
1

Sedimentation No quantitative data available; a 1993 site visit identified gullies eroding the alluvial bluffs as substantial sources of sediment.
1

SOIL

Source

Soil Diablo-Altamont association described as deep and well-drained.
1

Habitat Acres Vegetation

Riparian 2.1 Not specified 1

ANIMAL USE

Source

Birds No data located

Fish No data located

Benthic Invertebrates No data located

Insect No data located

Other Wildlife No data located

Special Status Species No data located

OUTLOOK

Source

Enhancement Status A conceptual plan for stabilizing the hydrologic regime, providing for tidal circulation and restoring floodplain vegetation at the site was prepared in 1993 as part of the Santa Monica Bay Restoration Project. It had not been implemented as of Fall 1996.
1

Watershed Management The Creek is within the watershed of Santa Monica Bay, a National Estuary and subject of a comprehensive restoration plan. A major focus of the plan is the reduction of point and nonpoint pollution in the watershed. Also, much of the watershed is in the Santa Monica Mountains National Recreation Area.
8, 1

Pressure Concrete lining of the upstream creek channel, development up to the bank near the mouth and upstream, urban runoff, and gully formation around the lagoon basin.
1, 7

SOURCES

1 Romberg Tiburon Centers and Philip Williams and Associates. 1993. Wetland Inventory and Restoration Potential, Santa Monica Bay Watershed. 111 pp. Report prepared for the Santa Monica Bay Restoration Project identifying potential wetland restoration projects at: the Ballona wetlands complex, Lower Topanga Canyon, Malibu Lagoon, Upper Medea Creek, and Trancas Lagoon. The discussion includes a history of land use in the watershed and the effects on wetlands. It also describes the current extent of wetlands based on mapping of aerial photographs. Conceptual restoration plans for the 5 sites outline existing conditions, identify opportunities and constraints as well as goals and objectives and estimate implementation costs.

2 City of Malibu Planning Department. 1995. City of Malibu general plan. ~200 pp., plus appendices. Elements of the General plan cover landuse, open space and recreation, and conservation among other issues.The purpose of the General Plan is to serve as a guide for future development and conservation, protection, and restoration and management of the City's existing natural resources. A brief description of environmentally sensitive resources is given and rare and endangered species within the City are identified. The EIR for this General Plan and supporting technical reports (not viewed) are available at Malibu City Hall.

3 California Regional Water Quality Control Board, Los Angeles Region. 1994. Water quality control plan Los Angeles Region (4). 187 pp., plus appendices. The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance the water quality and protect the beneficial uses of all regional waters. The plan designates beneficial uses and associated water quality objectives for inland surface waters, ground waters, coastal waters, and wetlands for the Los Angeles and Ventura 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.

4 Rick Morgan, City of Malibu. Personal communication October 3, 1996.

5 Santa Monica Bay Restoration Project. April 27, 1994. Correspondence to the Coastal Conservancy. 1 pp. Letter from the Santa Monica Bay Restoration Project to the Coastal Conservancy, regarding restoration planning at Trancas Lagoon and Lower Zuma Creek.

6 Gregory Woodell, Los Angeles County Department of Beaches and Harbors. Personal communication October 3, 1996.

7 Department of Water Resources. 1993. Aerial Photograph. Section 2, Flight Line 61-1. 1:12,000 aerial photograph of the coast showing lower Trancas Creek, taken April 14, 1993.

8 Santa Monica Bay Resoration Project. 1994. Public summary of the Santa Monica Bay Restoration Plan. 68 pp. Public information document describing the restoration planning effort in the Bay. It explains the values of the aquatic and wetland resources and how they are affected by activities in the watershed. It also provides a summary of current resource conditions and describes both the strategy and specific actions for improving and protecting Bay health.

9 Los Angeles Department of Public Works. 1985. Internal memorandum regarding the capacity of a private drain. 1pp. and map. This memo evaluates the adequacy of a private drainage system given the calculated 50-yr flow rates above and below a private drain and outlet on Topanga Creek.

10 California Regional Water Quality Control Board, Los Angeles Region. 1994. Water quality control plan Los Angeles Region (4). 187 pp., plus appendices. The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance the water quality and protect the beneficial uses of all regional waters. The plan designates beneficial uses and associated water quality objectives for inland surface waters, ground waters, coastal waters, and wetlands for the Los Angeles and Ventura 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.

11 Los Angeles Regional Water Quality Control Board. 1996. Water Quality Assessment and Documentation. 106 pp. A list of waterbodies in the Los Angeles and Ventura County coastal watersheds that do not or are not expected to attain water quality standards after application of required technology-based controls. It includes a description of the methods and criteria used in the assessment. 303(d) lists are prepared as part of the Water Quality Assessment of the State's major waterbodies, and meet a requirement of Section 303(d) of the federal Clean Water Act.

Webmaster: wetlands@resources.ca.gov

GENERAL			Source
Site	Trancas Lagoon
Map	Point Dume 7.5' USGS quadrangle
Location	Approximately 3 miles west of Point Dume in the City of Malibu.
Contacts	Santa Monica Bay Restoration Project, 213-266-7516
	City of Malibu, 310-456-2489
Approximate Wetland Acreage	2		1
Approximate Historic Acreage	Not specified		1
Ownership	Owner	Acres	Source
	Private	10	1


LAND USE			Source
Land Use Designation	1995 City of Malibu General Plan designations for the creek drainage north of Hwy 1 are community commercial west of the creek and rural residential east of the creek, both sides are included in a special plan overlay; south of Hwy 1 both sides of the creek are designated single family medium. The area south of Hwy 1 is an environmentally sensitive habitat area in the Local Coastal Plan		2
Onsite Use	Highway 1 bisects the lagoon; the creek bed is channelized through the floodplain for flood control.		2
Historic Use	Reference documents summarized changes in the Santa Monica Mountains watershed as a whole since the early 1800s, with uses gradually intensifying from native american homelands to grazing and agriculture under the expansive spanish rancheros, to urban development.		1
Adjacent Use	Immediately to the west near the mouth are private homes, and a commercial nursery and shopping center; Zuma State Beach, including a parking lot and boat storage area, lie immediately to the southeast; residential development occupies the eastern portion of the floodplain and lines the bank tops on the west.		1, 6, 7
Historic Adjacent Use	Reference documents summarized changes in the Santa Monica Mountains watershed as a whole; since the early 1800's land uses have shifted from native american homelands to vast spanish ranches, with urban development picking up after WWII. The steep mountain terrain slowed urbanization of this area relative to the broader coastal plains of Los Angeles.		1


HYDROLOGY			Source
Tidal Influence	The mouth of the creek is often blocked by a sand berm which prevents tidal exchange and causes the creekwater to pond during seasonal high flows. An informal arrangement between County Parks and the Department of Fish and Game allows the County to breach the berm on a restricted basis, to prevent flooding.		1, 6
Watershed Area	10 square miles		1
Tributaries and Flow	Tributary	Flow	Source
	Trancas Creek	Flow is ephemeral; the peak rate calculated for the lower creek for a 50-yr rainfall was 7,570 cfs (model assumed burn conditions and 53% of the watershed undeveloped). There is a cement and boulder-lined debris basin approximately .8 mile up the canyon; below this the creek is concrete-lined to just east of Hwy. 1.	1, 4, 9
Dams	None		4
Other Sources	Surface water runoff		1


WATER QUALITY			Source
General	Trash and pollutants from the nearby parking lot are reportedly deposited into the lagoon. Designated Beneficial Uses for the Creek are mun, nav, rec1 (except areas channelized in concrete), rec2, warm, wild, and rare. The Creek was not evaluated for inclusion in the 303(d) list. However ocean waters adjacent to the beach exceeded selected criteria for fish consumption, there is an advisory regarding PCBs and DDT, and recreation, coliform counts have led to beach closures.		1, 3, 10, 11
Dissolved Oxygen (DO)	Not available
Water Salinity	No quantitative data available, however brackish and freshwater plants (not named) grow in the lagoon area.		1
Sedimentation	No quantitative data available; a 1993 site visit identified gullies eroding the alluvial bluffs as substantial sources of sediment.		1


SOIL			Source
Soil	Diablo-Altamont association described as deep and well-drained.		1
Habitat	Acres	Vegetation
Riparian	2.1	Not specified	1


ANIMAL USE			Source
Birds	No data located
Fish	No data located
Benthic Invertebrates	No data located
Insect	No data located
Other Wildlife	No data located
Special Status Species	No data located


OUTLOOK			Source
Enhancement Status	A conceptual plan for stabilizing the hydrologic regime, providing for tidal circulation and restoring floodplain vegetation at the site was prepared in 1993 as part of the Santa Monica Bay Restoration Project. It had not been implemented as of Fall 1996.		1
Watershed Management	The Creek is within the watershed of Santa Monica Bay, a National Estuary and subject of a comprehensive restoration plan. A major focus of the plan is the reduction of point and nonpoint pollution in the watershed. Also, much of the watershed is in the Santa Monica Mountains National Recreation Area.		8, 1
Pressure	Concrete lining of the upstream creek channel, development up to the bank near the mouth and upstream, urban runoff, and gully formation around the lagoon basin.		1, 7


SOURCES
1	Romberg Tiburon Centers and Philip Williams and Associates. 1993. Wetland Inventory and Restoration Potential, Santa Monica Bay Watershed. 111 pp. Report prepared for the Santa Monica Bay Restoration Project identifying potential wetland restoration projects at: the Ballona wetlands complex, Lower Topanga Canyon, Malibu Lagoon, Upper Medea Creek, and Trancas Lagoon. The discussion includes a history of land use in the watershed and the effects on wetlands. It also describes the current extent of wetlands based on mapping of aerial photographs. Conceptual restoration plans for the 5 sites outline existing conditions, identify opportunities and constraints as well as goals and objectives and estimate implementation costs.
2	City of Malibu Planning Department. 1995. City of Malibu general plan. ~200 pp., plus appendices. Elements of the General plan cover landuse, open space and recreation, and conservation among other issues.The purpose of the General Plan is to serve as a guide for future development and conservation, protection, and restoration and management of the City's existing natural resources. A brief description of environmentally sensitive resources is given and rare and endangered species within the City are identified. The EIR for this General Plan and supporting technical reports (not viewed) are available at Malibu City Hall.
3	California Regional Water Quality Control Board, Los Angeles Region. 1994. Water quality control plan Los Angeles Region (4). 187 pp., plus appendices. The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance the water quality and protect the beneficial uses of all regional waters. The plan designates beneficial uses and associated water quality objectives for inland surface waters, ground waters, coastal waters, and wetlands for the Los Angeles and Ventura 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.
4	Rick Morgan, City of Malibu. Personal communication October 3, 1996.
5	Santa Monica Bay Restoration Project. April 27, 1994. Correspondence to the Coastal Conservancy. 1 pp. Letter from the Santa Monica Bay Restoration Project to the Coastal Conservancy, regarding restoration planning at Trancas Lagoon and Lower Zuma Creek.
6	Gregory Woodell, Los Angeles County Department of Beaches and Harbors. Personal communication October 3, 1996.
7	Department of Water Resources. 1993. Aerial Photograph. Section 2, Flight Line 61-1. 1:12,000 aerial photograph of the coast showing lower Trancas Creek, taken April 14, 1993.
8	Santa Monica Bay Resoration Project. 1994. Public summary of the Santa Monica Bay Restoration Plan. 68 pp. Public information document describing the restoration planning effort in the Bay. It explains the values of the aquatic and wetland resources and how they are affected by activities in the watershed. It also provides a summary of current resource conditions and describes both the strategy and specific actions for improving and protecting Bay health.
9	Los Angeles Department of Public Works. 1985. Internal memorandum regarding the capacity of a private drain. 1pp. and map. This memo evaluates the adequacy of a private drainage system given the calculated 50-yr flow rates above and below a private drain and outlet on Topanga Creek.
10	California Regional Water Quality Control Board, Los Angeles Region. 1994. Water quality control plan Los Angeles Region (4). 187 pp., plus appendices. The Los Angeles Regional Board's Basin Plan is designed to preserve and enhance the water quality and protect the beneficial uses of all regional waters. The plan designates beneficial uses and associated water quality objectives for inland surface waters, ground waters, coastal waters, and wetlands for the Los Angeles and Ventura 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.
11	Los Angeles Regional Water Quality Control Board. 1996. Water Quality Assessment and Documentation. 106 pp. A list of waterbodies in the Los Angeles and Ventura County coastal watersheds that do not or are not expected to attain water quality standards after application of required technology-based controls. It includes a description of the methods and criteria used in the assessment. 303(d) lists are prepared as part of the Water Quality Assessment of the State's major waterbodies, and meet a requirement of Section 303(d) of the federal Clean Water Act.