Gallinas Creek Watershed

Gallinas Creek Watershed map

Draft Watershed Workplan

Purpose

The Board of Supervisors authorized the Department of Public Works to begin implementation of a County-wide Watershed Program on May 13, 2008.  The purpose of the Watershed Program is to provide a framework to integrate flood protection and environmental restoration with public and private partners to protect and enhance Marin County’s watersheds.  In the Las Gallinas Creek Watershed, this program would seek to identify opportunities that provide the following benefits:

  • Develop cost effective solutions to reduce flooding damages that threaten communities, local economies, and public services
  • Improve navigational access to lower Las Gallinas Creek
  • Protect, enhance and restore sensitive creek and wetland habitat and water quality
  • Identify multi-benefit type projects that will improve the County’s ability to compete for State and Federal funding
  • Identify projects that are resilient to sea level rise
  • Evaluate the beneficial re-use of dredged material for wetland restoration, levee maintenance and shoreline protection within lower Las Gallinas and Miller Creeks
  • Reduce ecological impacts of flood maintenance activities

The Las Gallinas watershed program would identify and describe the recommended watershed improvement measures and provide details on project feasibility, sequencing, preliminary costs and funding strategies.  It is anticipated that some type of revenue measure will be required to implement the recommended measures.

Background

The 5.6 square mile Gallinas Creek watershed has two main drainage basins.  The north fork is the larger of the two drainages and flows from the ridgeline through Santa Margarita Valley and the community of Terra Linda to its confluence with South Gallinas Creek near McInnis Park.  South Gallinas Creek is fed by several small tributaries that originate in the San Rafael Hills and San Pedro Ridge and flow through the communities of San Rafael Meadows, Los Ranchitos and Santa Venetia.

Las Gallinas Creek – North Fork
During the construction of the Terra Linda housing development in the late 1950s and 60s, portions of Gallinas Creek and its tributaries were channelized and lined with concrete.  Prior to the construction of the concrete channel, the Freitas family reported steelhead using the large pools in the creek. No steelhead have been observed in the upper reaches of Gallinas Creek since the channel was straightened and lined with concrete. The concrete lining of Gallinas Creek generates high water temperatures, which leads to excessive algal growth and poor water quality entering the Gallinas Creek Slough.

Moving downstream of Highway 101, development becomes progressively denser, with the lowland areas east of Highway 101 supporting neighborhoods, industrial and commercial development.  Portions of these lowland areas are within FEMA’s mapped 100 year flood plain.  While these areas may not have been impacted from the floods of 2005/06, sea level rise poses a potential threat to this area.  There have been local efforts to restore wetlands in this area.  Audubon completed a small wetland restoration project on State Lands during the 1990s.  The north fork of Gallinas Creek joins the south fork at McInnis Park.

Las Gallinas Creek – South Fork
There are two designated County Flood Zones that drain to the south fork of Gallinas Creek: Flood Zone #6 and Flood Zone #7.

Flood Zone #6 was established after construction of the San Rafael Meadows subdivision in the 1960s.  This is a very small zone located just west of Highway 101 across from the County Civic Center.  Houses were built in a low-lying area and experienced frequent flooding until improvements were made. In the early 2000s, during the construction of a new subdivision project a majority of the stormwater causing the flooding was rerouted around the community thereby eliminating a significant cause of flooding in the zone.  Moreover, the Flood Zone #6 area was annexed by the City of San Rafael.  The City now owns and is responsible for the maintenance of the Zone’s drainage facilities.

Flood Zone #7 is comprised of the unincorporated community of Santa Venetia, east of 101 along San Pedro Road.  Santa Venetia was one of the first developments in Marin County to be constructed on fill over bay mud and occurred in an era before the County had the authority to regulate or control development.  Due to the low initial elevation of the fill and the compressible nature of the underlying bay mud, the area has subsided and is now below the high tide level.  To protect themselves from tidal flooding of Las Gallinas Creek, the residents of Santa Venetia formed Flood Control Zone #7 in 1962.  The annual maintenance program for facilities includes pump stations and levees, as well as other drainage facilities in the Zone.

Though the Santa Venetia neighborhood did not flood during the 2005 New Year’s Eve storm, sea level rise, land subsidence and aging infrastructure remain key flood protection challenges.  Stormwater is collected via pipes and discharged into Las Gallinas Creek via a series of five pump stations.  Four million dollars of potential flood protection improvements have been identified within Santa Venetia alone.  The most pressing identified infrastructure need in Santa Venetia is the replacement of Pump Station No.2.  It is recommended that the pump be rebuilt to improve its reliability and to increase its pumping capacity to handle the 100-year storm event (It currently can handle flows up to the 10-year event.)  A special election was held in 2010 to fund flood protection improvements in Flood Control Zone 7 including the replacement of Pump Station No. 2, improvements to Estancia Ditch, and additional levee studies.  The tax measure was not approved.  The District is now investigating the feasibility of pursuing revenue sources for the replacement of Pump Station No. 2.

Las Gallinas Draft Plan map

Homeowners along the tidal reaches of Gallinas Creek also desire creek access and a navigable channel.  The community formed CSA #6 (see figure above) in the 1960s to dredge the channel for navigation and flood protection.  The community is working to raise the funds to perform another round of maintenance dredging.  Preliminary plans and cost estimates have been developed. The estimated dredging construction costs exceed funds available and will require additional funds to implement.

Mouth of Las Gallinas Creek
The mouth of Las Gallinas Creek is bordered by County and State Park lands.  The beneficial re-use of sediment from the dredging of Las Gallinas Creek could be used to restore diked baylands to functional tidal marsh.  The Army Corps of Engineers prepared a preliminary restoration plan for the McInnis Park Wetland Restoration Project in 2001, under Section 206 WRDA 1996 as an element of the San Pablo Bay Watershed Restoration Plan.  Suggested restoration actions include levee breaching, marsh plain and channel grading and invasive species removal.
Tidal marsh restoration in the Gallinas Creek system would restore ecosystem function and processes, as well as provide critical habitat for the endangered California clapper rail and salt marsh harvest mouse.  The opportunity exists to evaluate alternatives that could improve any project’s resiliency to predicted sea level rise scenarios.
Miller Creek – Baylands

The tidal reaches of lower Miller Creek, which shares it outlet to San Pablo Bay with Las Gallinas Creek will be considered as part of the Gallinas Creek Watershed Program study area.  Historically,  Miller Creek discharged out onto a large flood plain without a clear channel connection to the bay.  In the 1920s, Miller Creek was rerouted, channelized, and leveed to provide space for agricultural fields.  The current alignment rerouted the creek to the south and placed it into a narrow, leveed channel with two 90-degree bends before reaching San Pablo Bay.  Las Gallinas Valley Sanitary District uses the creek as their discharge point during winter months at the downstream bend.  Because these two creeks share a floodplain along San Pablo Bay, a concurrent planning effort to evaluate sediment movement, tidal prism and tidal marsh restoration is practical, sensible, and cost-effective.

historical map

Stakeholder Outreach

The watershed program will utilize a collaborative, iterative process to develop an integrated flood protection and habitat restoration program.  The Marin County Board of Supervisors recommended establishing stakeholder committees at three levels to support community outreach and to provide overall program direction (a complete list of recommended committee members is included at end of this document).  A broad community outreach program is also recommended.

Community outreach will be developed around two key messages:

1. The watershed approach is the practical and desired alternative to identifying cost effective solutions for improving flood protection; and

2. Implementation at the watershed scale takes time and does not take precedence over the maintenance and rehabilitation of aged existing infrastructure.

Description of Gallinas Watershed Stakeholder Committees

Policy Advisory Committee - This group of elected officials is comprised of the District County Supervisor, two representatives from the participating city council and the Board of Directors of the participating agencies.  This committee provides policy input on program direction and community issues and will meet 1-2 times per year.

Operations and Finance Committee- The participating District manager and/or city manager and the Marin County Public Works director will use these meetings to evaluate progress and prioritize funding strategies and will meet 3-4 times per year.

Technical Working Group- This group will include staff of participating State, Federal and local regulatory and participating agencies and community members with a science and technical background.  The group will be responsible for the review of watershed products and provide input on issues, needs and watershed priorities.  This group will include conservation and watershed groups, homeowners associations and other technical experts within their respective watersheds.  This group will meet at least quarterly to provide input and to review the development of work products

Community Outreach
Targeted community meetings, presentations at various local boards and homeowners associations and utilization of the watershed program website (www.marinwatersheds.org) will support communication to the community at large.  The program website provides dedicated information about the watershed and is regularly updated with notices about workshops, meetings, proposals and projects.

Program Description and Outcomes

The Watershed Program will build upon existing studies and develop new analytical tools to evaluate and quantify the extent of flooding and to evaluate the range of proposed solutions.  This process will be summarized in a final report.  The final report will also include recommendations on how to leverage local funds to attract State and Federal grant funds.  The final report will provide an assessment of and describe the type of local revenue measures that could support project implementation.

The following is a description of the proposed tools and outcomes.  An excellent overview of existing conditions and relevant studies is available at www.marinwatersheds.org.

Analytical Tool Development
The District has identified the general causes of flooding within the watershed but focused modeling and analysis will provide the ability to refine the engineering analysis required to develop conceptual designs for improvements and to get a better idea of the costs associated with implementation.

The following tools will assist with the identification and review of a range of alternatives:

Hydrology and hydraulics models - An understanding of how much water is moving through the watershed (hydrology), how fast it moving and where it is going (hydraulics) is critical to quantifying flooding impacts and identifying solutions.  The development and use of computer models to quantify stormwater runoff and channel flow are the industry standard used to describe flooding.  These modeling tools will allow us to identify areas that need increased flood protection and to understand how channel and floodplain modifications will influence the ability of the channel to carry flood flows.

Flood Zone 7 is actively engaged in a process with the Army Corps of Engineers (ACOE) to evaluate the levees that protect Santa Venetia.  As part of this evaluation, the ACOE developed the following types of models:

  • A hydrology model that develops flood flows from the watershed into the north and south forks of Las Gallinas Creek.
  • A hydraulics model for the south fork of Las Gallinas Creek that evaluates both tidal and creek water surface elevations under flood flow conditions
  • In addition, the Corps performed an evaluation of direct coastal flooding impacts under current and 50-year sea level rise conditions

Additional model refinements may be driven by the alternatives analysis.

In addition to the creek channel models described above, there are also specific stormwater models to evaluate flow in low-lying developed areas where the majority of flow is routed via roads and a storm drain system to stormwater pump stations.  This type of model could be useful for evaluating storm flows in Santa Venetia because flood control practices rely on an underground storm drain system, pump stations and three direct stormwater bypasses to deliver runoff to Las Gallinas Creek.  A stormwater drainage system model for Flood Zone #7-Santa Venetia could improve the efficiency of pump operations by providing information on pumping capacity and to evaluate the optimal distribution of flows to the five pump stations.  This type of modeling would also evaluate stormwater pipe capacity and identify constriction points.

At the end of this phase, we will have a watershed based hydrology and hydraulics models of Las Gallinas Creek and limited tributaries that will allow us to review conceptual project alternatives for their benefits including an evaluation of sea-level rise scenarios.

Geomorphic and Sediment Assessment in Tidal Areas - Levees bordering lower Las Gallinas and Miller Creeks have greatly reduced the tidal prism (volume of water that moves in and out on each tide cycle) thereby reducing the ability of the channels to transport sediment out of the system.  This has resulted in sediment deposition in the tidal reaches of the creek and a loss of depth for boating access.  This assessment will seek to identify a channel width and alignment that maximizes the creek’s ability to transport sediment to the Bay based upon geomorphic analysis of similar systems in the Bay.  This information will used to inform future creek dredging needs and extent of dredging.  It will also benefit management of sediment flow to better protect sewer plant infrastructure and outfalls.

GIS-based mapping and database development- A geographic information system database will be developed to evaluate opportunities to restore creeks and wetlands.  Existing data will be used to develop a watershed-scale database and maps to assist with project prioritization.

Conceptual Alternatives Development

One of the primary goals of this watershed program is to identify cost effective alternatives for maintaining or improving the level of flood protection.  Utilizing the tools developed through the watershed program the District and the community will be able to evaluate a range of alternatives to identify practical and sustainable projects.  The models will be used to analyze and develop the full range of feasible measures consistent with the program goals.  Preliminary costs, flood protection benefits and habitat impacts and/or enhancements will be clearly identified through this process.

The watershed approach considers the development of multi-benefit projects as a basic tenet to ensure that project priorities are eligible for the broadest range of funding at the State and Federal levels.

Final Report

This document will describe the identified alternatives and documentation for each.  Maps and graphics will support this analysis and the report will include recommendations and process for pursuing implementation, establishing priorities and funding.

Proposed Budget

Expenditures

 

Calibration of USACE Hydrology Model 

$20,000

Surveying    

$45,000

GIS Mapping   

$10,000

Hydraulic modeling   

$40,000

Stormdrain modeling (Santa Venetia only)       

$60,000

Geomorphic/Sediment Study             

$40,000

Alternatives analysis

$60,000

Final Report   

$45,000

Project Management    

$25,000

Stakeholder Outreach  

$27,500

Total

$392,500

Revenue

 

County of Marin  

$80,000

City of San Rafael (proposed

$80,000

Flood Control Zone 6    

$12,500

Flood Control Zone 7        

$80,000

CSA 6    

$60,000

Las Gallinas Valley Sanitary District         

$80,000

Total

$392,500

 

Status of Local Agency Participation

To date we have received commitment and financial support from the following agencies:

  • County of Marin
  • Las Gallinas Sanitary District
  • County Service Area 6
  • Flood Zone 6
  • Flood Zone 7

We are still pursuing commitment and financial participation from the following agencies:

  • City of San Rafael

 

Gallinas Creek Flood Protection and Watershed Program

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Watershed Overview

 

The Gallinas Creek watershed is located the eastern side of Marin County between the Miller and San Rafael watersheds.  The 5.6 square mile basin has two main drainage areas.  The north fork is the larger of the two drainages and flows from the ridgeline through Santa Margarita Valley and the community of Terra Linda to its confluence with South Gallinas Slough near McInnis Park.  South Gallinas Slough is fed by several small tributaries that originate in the San Rafael Hills and San Pedro Ridge and flow through the highly urbanized communities of San Rafael Meadows and Santa Venetia.

Watershed History

Human Settlement

Coast Miwok lived throughout the Santa Margarita valley.  The first rancho in the watershed was established in 1844 as a land grant to Timothy Murphy.  The grant included three ranchos, San Pedro, Santa Margarita and y Las Gallinas, with the Santa Margarita rancho roughly corresponding to the Gallinas Creek watershed.

With the establishment of the ranchos, grazing began in earnest.  Heavy grazing eventually led to loss of riparian vegetation and incising of the creeks.  In 1853, John Lucas inherited the 7,600-acre Santa Margarita Rancho, built a home, and continued grazing cattle.  He sold about 1,200 acres of the Rancho to Manuel Freitas in 1898, who continued to graze dairy cattle on the rich grasslands but also planted oat hay.  Dairy cattle grazing continued through most of the watershed into the 1900s.

In the early 1900s, the tidal marshes along the bayfront were diked and drained to create additional agricultural land.  In 1914, Mabry McMahan attempted to establish a Venetian-style city complete with gondolas in the area now known as Santa Venetia.  He got as far as building landfill, canals, and levees and establishing several structures, but wasn’t able to fulfill his vision; Santa Venetia and Santa Margarita Island Open Space Preserves retain part of that effort.  The first housing development in the watershed was established in the area and the Santa Venetia neighborhood remains an active inhabited area in the watershed. 

Further development in the valley areas west of Highway 101 began around 1950 and has continued as a mix of residential and commercial facilities.  By the mid-1960s most of the lower watershed was filled with urban development; by the mid-1970s the urban nature of the area was much like the present day.  The establishment of open space preserves along the ridge tops gave rise to a regrowth of riparian vegetation and many creeks in the upper watershed now have thick riparian growth.

Aerial photo looking northeast towards the bay from above Hwy 101.  January 16, 1973.

Aerial photo looking northeast towards the bay from above Hwy 101. January 16, 1973. DPW file photo.

 

Watershed Today

Changes to Watershed Processes

Prior to urbanization and the tidal wetland reclamation practices of the early 1900s, Gallinas Creek was an extensive tidal slough system fed by intermittent streams originating above Santa Margarita Valley and the headlands surrounding South Gallinas slough.  By the 1940s the main tidal sloughs were leveed and the smaller channels and interior tidal marshes drained and filled for agricultural land (Kamman Hydrology and Engineering, Inc. 2004 ) creating the channel configuration present today.

During the construction of the Terra Linda housing development in the 1950s Gallinas Creek and its tributaries in Santa Margarita Valley were channelized along Del Ganado Road and Freitas Parkway, following the historic creek alignment.  Tributaries to South Gallinas Slough were also channelized in the 1950s and 60s during the construction of Los Ranchitos and San Rafael Meadows.  From aerial photos it appears that channels in the upper watershed were incised and lacked riparian vegetation; characteristics of a heavily grazed watershed (Kamman Hydrology and Engineering, Inc. 2004).

Today the main Gallinas Creek channel in Santa Margarita Valley is a concrete-lined, trapezoidal flood control channel fed by storm drain outlets along its length.  Flow in the Gallinas Creek has become perennial due to residential irrigation runoff and the non-permeable concrete channel bed.

Although the creeks that drain the southern portion of the Gallinas watershed have not been turned into trapezoidal concrete flood channels, they have been realigned and their banks heavily armored.

Habitat Types

Vegetation

Vegetation

Historically, the Gallinas Creek watershed supported extensive native forests, healthy riparian systems, and expansive wetlands in the lower watershed. Currently, the watershed is highly urbanized and native communities have been fragmented and altered from their original condition.  The upper watershed is composed primarily of annual grasslands interspersed with mixed evergreen forest (including oak-bay woodland), coastal scrub, and small outcroppings of serpentine habitat.  The upper slopes are largely Marin County Open Space ridge lands.  In the upper watershed, where the channel is open and not restricted to underground culverts, the banks are typically dominated by non-native plants.

Along the southern watershed boundary, upslope of Santa Venetia, there is a large tract of oak-bay woodland which is continuous with China Camp State Park.  While not technically part of the Gallinas Creek watershed, China Camp State Park at the southeastern corner of the watershed supports a number of intact communities including extensive woodlands, grassy meadows, and pristine wetlands and special-status species, providing habitat connectivity between the two watersheds.

Upstream of Highway 101 (upper watershed), the stream channel and tributaries are restricted to rectangular and trapezoidal channels and underground storm drains, respectively.  The upper slopes of the watershed are county-owned open space (Terra Linda – Sleepy Hollow Divide Open Space Preserve) and in these areas native uplands dominate.  Downstream of Highway 101 where the creek is tidally influenced, it is channelized.  Marshes adjacent to San Pablo Bay are leveed.  The lower creek-slough provides the most important biological resources within the watershed. The lower marsh habitats represent some of the largest remaining tidally influenced habitats in the bay region (Goals Project 1999 1).

Fish and Wildlife

The lower watershed supports a number of special-status plants and animals.  Of particular interest are the occurrences of wetland-adapted species along the baylands.  Noteworthy species include San Pablo song sparrow, California black rail, salt marsh harvest mouse, and California clapper rail.  

Downstream of Highway 101, the creek is tidally influenced and forms a network of sloughs contained within man-made levees.  The north fork slough is adjacent to McInnis County Park.  The south fork slough originates downstream of the Marin County Civic Center, wraps around Santa Margarita Island Open Space Preserve, and then the community of Santa Venetia.  The two channels connect at Santa Venetia Open Space Preserve.  In this area, the tidal channels and adjacent salt water and brackish-water marshes support a number of animals.  Birdlife is abundant and waterfowl frequent the tidal sloughs. Rails and shorebirds are common along the edges in marsh habitat.  River otters are also known to frequent the area (Kamman Hydrology and Engineering, Inc. 2004 2).  The north mouth of Gallinas Creek, supports one of the largest populations of California clapper rail within San Pablo Bay (Herzog, et al., 2005 3).  Overall, the watershed is known to support 86 breeding bird species (Kamman Hydrology and Engineering, Inc. 2004).

Historically, the Gallinas Creek watershed may have supported steelhead and other fish.  Kamman Hydrology and Engineering, Inc. (2004) noted observations by Walter Freitas of steelhead swimming up main Gallinas Creek during the winter months.  Historical observations occurred at least as far as St. Isabella’s Church, upstream of Las Gallinas Avenue, at Trinity Avenue.  Currently, the upper Gallinas Creek watershed is not known to support fish due to a lack of habitat and perennial water.  The lower tidal sloughs likely support estuarine fish; however, there are no reports documenting their occurrence. 

There are no reported occurrences of federally-listed as threatened and California Species of Special Concern California red-legged frog within the watershed (CDFG 2008 4).  A U.S. Fish and Wildlife Service protocol site assessment for red-legged frogs was conducted at St. Vincent’s School in 2001 by LSA in adjacent Miller Creek (LSA 2001 5).  The assessment found only marginal habitat for this species and no historical or recent records of California red-legged frogs in this area.

There are no reported occurrences of California Species of Special Concern northwestern pond turtle within the watershed (CDFG 2008).

Heron and egret nesting colonies have been monitored by Audubon Canyon Ranch since the early 1990s (Kelly, et al., 2006 6).  Up until recently, a colony of approximately 18 great blue herons nests occupied oak woodland habitat and a small redwood grove on private property off of North San Pedro Road.  The colony was abandoned after the 1996 breeding season.  A second colony on private property on North San Pedro Road has been monitored since 2002. It currently supports 1 to 3 great blue heron nests.  There is a single record of a great egret in 2002 at this location.  Mature eucalyptus trees are currently being utilized (Condenso, personal communication, May 15, 2008; Kelly, et al., 2006).

PRBO Conservation Science has been actively monitoring tidal marsh bird populations throughout the San Francisco Bay region since 1996.  The goal of the monitoring is to assess population status and trends of special-status birds and “model and predict the relative abundance and distribution of tidal marsh birds with respect to local habitat features, configuration, and surrounding landscapes patterns” (PRBO Conservation Science 2008 7).  Focal species include California clapper rail, California black rail, San Pablo song sparrow, salt marsh common yellowthroat, and marsh wren.  The study area for this work includes the tidal marshes of China Camp State Park (Liu, et al., 2007 8).

In 2005 and 2006, an estuary-wide study to determine temporal and spatial patterns in the California clapper rail population was conducted by PRBO Conservation Science and Avocet Research Associates (Herzog, et al., 2005).  This study was correlated with previous work completed in 1992 and 1993 within the San Pablo and Suisun Bays and population trends were evaluated.  Rails were monitored on north fork, south fork, and the mouth of Gallinas Creek.  Between initial observation in 1992 and the 2005 field season, clapper rail populations increased within the Gallinas Creek watershed 9

Human Habitation and Land Use

Land UseImperviousness

Land Use                                        Imperviousness

The Gallinas watershed is largely within the North San Rafael planning area.  The western ridge tops separating the watershed from the Miller Creek watershed to the north and San Rafael Creek watershed to the south are protected as County open space.  Moving downhill through the watershed, development becomes progressively denser, with the lowland areas east of Highway 101 supporting fully developed neighborhoods, shopping, schools, and hospital facilities.

Land protection and restoration efforts in the watershed include wetland restoration by the Marin Audubon Society and Marin Community Foundation, in partnership with other funders, that began in 1972 and were completed in 1977 restoring about three acres of filled land to tidal marsh.

The Friends of Gallinas Creek, San Pablo Watershed Restoration Program Partners, The Bay Institute and Marin County Stormwater Pollution Prevention Program (MCSTOPPP) are planning extensive restoration in the upper and lower watershed to improve riparian cover, provide habitat, reduce erosion, and restore wetlands.


1 Gallinas Creek Restoration Feasibilty Study and Conceptual Design Report Marin County, CA

2 Baylands Ecosystem Habitat Goals: A Report of Habitat Recommendations

3 Gallinas Creek Restoration Feasibilty Study and Conceptual Design Report Marin County, CA

4 Temporal and Spatial Patterns in Population Trends in California Clapper Rail (Rallus longirostris obsoletus) 2005 Progress Report

5 California Department of Fish and Game (CDFG). 2008. California Natural Diversity Database. California Department of Fish and Game, Sacramento, CA.

6 California Red-legged Frog Site Assessment: St. Vincents's School Property San Rafael, Marin County

7 Annotated Atlas and Implications for the Conservation of Heron and Egret Nesting Colonies in the San Francisco Bay Area

8 http://www.prbo.org/cms/135

9 2007 Annual Report: California Clapper Rail (Rallus longirostris obsoletus)