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Arana Gulch Enhancement Plan  -   Creekside Restoration Project

Sediment Basin Clearing Project at Harbor High School
 
Informal Fish Survey

Creekside Restoration
Project

Background
Watershed Description
Restoration Site Description
Proposed Land Use
Objective
Location
Project Description
Bank Stabilization & Revegetation
Rehabilitation of Riparian Corridor
Permits
Scheduling

Background

Watershed Description

Arana Creek is located within the County of Santa Cruz and partially within the city limits of the City of Santa Cruz. The watershed drains a 3.3 square mile drainage and includes approximately six miles of streams. The watershed drains into the Santa Cruz Small Craft Harbor approximately 1 mile from Monterey Bay. Land ownership within the watershed is approximately 61% private and 29% public. Peak flood discharges for Arana Creek range from 790 cfs for a 10-year event to 1650 cfs for a 100-year event (FEMA, 1986).

Arana Creek includes the main stem and two unnamed tributaries, which enter the main stem at approximately 3 miles from the mouth of the creek. Highway 1 is the major transportation corridor, which divides the watershed. In the headwaters above Highway 1, Arana Creek is characterized by a steep, narrow, relatively straight channel, which is deeply incised into a wide alluvial floodplain and confined by steep bedrock-valley side slopes. Bed and bank materials are predominantly sand, which is generally well rooted with riparian vegetation. Relatively little development has occurred within in the upper reaches of the watershed, but some flood plain alterations (road fill, drainage improvement, and vegetation removal) are present. Most of the upper watershed is occupied by mixed willow or willow-alder riparian forest. Upland tree species, notably coast live oak and California Bay, are scattered in this forest and are most abundant around the margins. Tree canopy cover over the creek generally exceeds 80 percent in the upper reaches of the watershed.

The lower portion of the watershed (below Highway 1) has been heavily urbanized and the stream channel has been altered. Channelization is common and removal of the riparian zone has occurred in several places. The lower portion of the watershed is characterized by two place areas through which the creek travels. These areas are the Santa Cruz Greenbelt property adjacent to the Santa Cruz Small Craft Harbor and Harbor High School just upstream of the greenbelt area.

Aquatic species known to be present in the creek include the steelhead trout and the California Redlegged Frog. Habitat conditions are also suitable for the Western Pond Turtle. Antidotal reports of steelhead sitings have been recorded for the creek near the Harbor High School site and the Greenbelt property during the last five years. The last recorded spawning by a female steelhead was observed March 1, 1984 (Titus & Erman, 1993). Limiting factors associated with steelhead decline include riparian dysfunction including lack of canopy cover and nutrients, excessive sediment yield resulting from bank instability, and lack of adequate spawning gravels and resting/pool areas due to siltation. The riparian community on the project site has been highly impacted by exotics, although communities of willow-dominant and alder-dominant riparian forest are present as well as a remnant of oak woodland. A vegetation map created for the project site identified 42 native species present and 43 exotics present.

Community involvement within the watershed is high. A Coordinated Resources Management Program, the Arana Gulch Watershed Alliance (AGWA), is active in the watershed and is assisting in the prioritization of watershed management planning and restoration. AGWA is submitting a grant application for preparation of a Watershed Enhancement Plan for Arana Creek. The Coastal Watershed Council is supportive of this proposal. A volunteer monitoring program has been ongoing in the watershed since September 1996, managed by the Coastal Watershed Council. Water quality data collected through the volunteer program demonstrates that water quality is not the primary limiting factor to salmonid populations. Water quality conditions are supportive for both spawning and rearing of salmonids, although problems with temperature and dissolved oxygen levels are present at the Harbor High School site.

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Restoration Site Description

In June 1997, the Arana Gulch Watershed Alliance established a volunteer restoration subcommittee to evaluate potential restoration sites within the watershed. The Coastal Watershed Council was a member of the committee. Four priority sites were identified by the committee and ranked according to land ownership, contribution to habitat decline and potential for funding and/or community involvement. The committee informally agreed that the first restoration focus would be a site at Harbor High School.

Over the last several years this area has been experiencing severe channel cutting and streambank failure due to channelization and increased flows from impervious surfaces (see photos). The channel is attempting to increase its width with accelerated erosion. The channel has become entrenched and is eroding the streambank vertically. The heavy sediment deposition in this area has resulted in an important loss of stream habitat in the project site and downstream. A 1993 survey by an independent fisheries biologist identified this reach of the creek as having the poorest fish rearing conditions do to lack of in-stream and canopy cover and sedimentation of the streambed.

Additionally, this section of creek is overrun with nonnative tree and shrub species which further the instability of the stream banks and do not provide necessary habitat for associated native avian, fish, and amphibian species found in the watershed. Over 40 species of exotics have been identified on the project site. The project site is approximately 350 linear feet and includes both sides of creek for a total project area of 700 linear feet. Streambank stabilization and revegetation will occur in an approximate 300-foot section on the southern side of the bank. Non-natives removal and native replanting will occur in the entire project area.

The Coastal Watershed Council conducted a habitat assessment on the 668 foot section of the creek adjacent to Harbor High School in the summer and fall of 1998 using protocols from the DFG Restoration Manual. A DFG fisheries biologist assisted with field observations to ensure quality data. The assessment focused on stream channel morphology, habitat characteristics, and the presence of large woody debris. Results showed the channel was rated "B-5" according to Rosgen stream type classification. There were 21 habitat units identified within the reach and included 10 pools, 8 glides, and 3 low gradient riffles. The primary shelter present were undercut banks with root mass, although some units contained boulders and large/small woody debris. A lack of large woody debris was also noted due to the dominance of normative vegetation and lack or recruitment.

A visit by a DFG Fisheries Biologist in August 1998 resulted in the recommendation that stabilizing the stream bank failure near the high school and providing increased canopy cover and in-stream cover and resting areas would be beneficial to efforts to restore the steelhead population within Arana Creek. Removal of normative species and replacement by natives will also improve nutrient input into the aquatic system.

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Proposed Land Use

The proposed project is located at Harbor High School within the Santa Cruz City School District. The project site is currently a natural area with no plans for construction of any facilities in the future. An informal pedestrian pathway along the creek will remain following restoration.

The proposed project is not required as mitigation in a CEQA approval process, Timber harvest Plan process or otherwise required as mitigation for other activities.

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Objective

The project will improve instream and upslope habitat for spawning and rearing steelhead by removing existing sediment sources, providing native plant cover, and increasing channel capacity for sediment transport. An eroding streambank will be stabilized and revegetated and existing nonnative species will be eradicated and replaced by native riparian species.

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Location

The project site is located in the County of Santa Cruz adjacent to Soquel Drive and LaFonda Avenue. The project site is located on Santa Cruz City School District property south of the football field at Harbor High School. Bank stabilization and revegetation will occur along a 300-foot linear section of the southern bank of the creek. Nonnative removal will occur along 700 linear feet of streambank and upland area. See project maps enclosed.

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Project Description

The project will include:

1. Bank stabilization and revegetation along a 300-foot section of the streambank, and
2. Rehabilitation of the riparian corridor with native vegetation.

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1. Bank Stabilization and Revegetation:

The project will involve the grading and re-sloping of 300-feet of the south bank of the creek to stabilize the existing vertical bank. An estimated 100 cf of material will be removed and disposed of. The bank will be re-sloped and the toe of the bank will be stabilized with rootwads and vortex rocks. Brush layering and live post revetments and live cuttings will then be used to stabilize and re-vegetate the bank slopes. Branch packing will be used at five sites where slumping/gullying is occurring. These sites are upstream of the 300-foot section of bank erosion. A consulting engineer will manage this portion of the project with guidance from the Executive Director of the Coastal Watershed Council.

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2. Rehabilitation of Riparian Corridor with Native Vegetation

The project will also involve the rehabilitation of the riparian corridor with native vegetation to increase canopy cover, provide shade and cover and improve nutrient load to the system. This will be done on both sides of the streambank and upslope areas for a total of 700 feet. A Revegetation Management Plan has been prepared for the project site which includes a complete map of all native and nonnative plants, recommended eradication methods, recommended natives for propagation and cuttings, and long term weeding and management of planted natives. Much of this work will be completed with the help of high school students and community volunteers. A Coastal Watershed Council staff botanist will manage this portion of the project.

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Permits

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Scheduling

Work on the project has already begun with regards to pre-project monitoring, seed collection and native plant propagation and non-natives removal. The local high school is helping with nonnative removal and propagation.

Funding for initiating the project has been provided through a grant provided by the National Fish and Wildlife Foundation in the amount of $17,000. An additional $7,000 has been raised from involved agencies and non-profits. In-kind services have been provided by professional biologists, hydrologists, and engineers. Total amount of match funds raised for the project is estimated at $40,000.

The proposed schedule for the project is as follows:

• Bank re-sloping and stabilization - August 1999

• Removal of non-natives - August - November 1999

• Revegetation of bank area - October 1999

• Replanting with natives in bank and upslope areas - October - February 1999/2000