Bike Forums - Erosion Study in East Bay Park

Joaquin Miller park in Oakland is a very popular park with both hikers and Mountain bikers which of course leads to trail conflict. For some time now, several groups have been trying to get the trails closed to mountain bikers claiming that they cause too much trail erosion. An outside consulting firm was hired to study the impact of users on the Park.

But one of the best finding is this one:
„h Surface runoff was determined to be dominant erosion mechanism acting on the park trails. Erosion generated by horses, bicycles, and hikers was determined to be a minor erosion mechanism on established park trails.

Basically, mountain biking was not a major cause of erosion on the established trail parks.

Of course, not everything is perfect.
One of the findings was that recreational use was a major source of erosion on "bootleg" trails. Many of these "illegal" trails point straight downhill facilitating the flow of water causing deep tracks.

This is something that mountain bikers need to keep in mind before they decide to poach trails. The use of illegal trails can be used against us as ammunition to keep us out.

I couldn't attach the study so I copied it and pasted it on here.

CITY OF OAKLAND
COUNCIL AGENDA REPORT

TO: Office of the City Manager
ATTN: Robert C. Bobb
FROM: Life Enrichment Agency
DATE: July 10, 2001

RE: AN INFORMATIONAL REPORT ON THE JOAQUIN MILLER PARK TRAILS WORKING GROUP

This is an informational report on the status of the Trails Working Group (TWG), an ad-hoc committee of citizens interested in the use and management of Joaquin Miller Park, its trail system and redwood forest. It provides information on the findings and recommendations of a consultant study of Joaquin Miller Park and provides a timeline for the work of the Trails Working Group. This report follows an initial report regarding Joaquin Miller Park trails to City Council on January 11, 2000 and a status report presented on October 24, 2000.

No action is requested from City Council at this time.

SUMMARY

The Trails Working Group met from January to April, 2000 with a goal of drafting a trails management plan for Joaquin Miller Park and other City open space parks managed by OPR. Due to the need for more scientific information on physical and environmental conditions in the park, the TWG suspended its meetings while a consultant study was prepared by William Lettis & Associates (WLA). WLA¡¦s report entitled ¡§An Assessment of Trails, Watercourses, Soils, and Redwood Forest Health in Joaquin Miller Park, Oakland, California, with Recommendations for Management¡¨ was completed in early 2001.

The TWG met on June 14, 2001 to review the WLA report and will meet throughout July to identify recommendations and actions needed to accomplish the goals outlined in the report. The TWG will also consider changes to the Oakland Municipal Code Section 12.60.070 regulating the use of bicycles in parks. If there is no consensus reached by the TWG, OPR will present alternatives and recommendations for the City Council to consider in Fall 2001.

The findings of the WLA report are as follows:

„h Joaquin Miller Park trails that were constructed with adequate grade, alignment, and width characteristics using sound construction techniques are relatively resistant to erosion.
„h Trails that were constructed with poor grade and alignment on soft soils have developed rills, and in some cases gullies.
„h Surface runoff was determined to be the dominant erosion mechanism acting on the park trails and represents only 7% of the total past volume of erosion in the study area.
„h Naturally occurring bank failures and landslides observed along watercourses account for approximately 59% of the total past erosion.
„h Recreational use was determined to be a major source of soil erosion on ¡§bootleg¡¨ or informal trails.
„h The redwood forest overstory is in good condition with respect to tree vigor, pathogens, rot, and insect infestation. No significant differences in growth were noted between trees near trails and trees away from trails.
„h The redwood forest understory suffers from off-trail use and trampling of vegetation, soil compaction, invasive weed infestation, and a loss of species diversity and native plant components.

WLA recommendations to reduce erosion and restore the health of the redwood forest include:

„h Develop a trail management plan.
„h Secure adequate funding.
„h Realign trails that are too steep.
„h Remove outside berms and install water bars to remove water from trails.
„h Improve watercourse crossings.
„h Block all ¡§bootleg¡¨ trails.
„h Install additional barriers and signs to divert off-trail traffic.

FISCAL IMPACTS

There is no fiscal impact associated with this informational report. The total cost of implementing the recommendations in the WLA report is unknown at this time. OPR will present a cost analysis in the Fall 2001 report pending further discussion through the TWG process. OPR will implement the WLA report mitigation measures that are small in scale using volunteer labor and existing baseline budget staffing and funds.

BACKGROUND

OPR presented an action plan for enforcing regulations concerning biking in City of Oakland parks, particularly Joaquin Miller Park and Dimond Canyon, to City Council on January 11, 2000. The action plan included the following elements:

„h Increase enforcement of existing OMC regulations by the Oakland Police Ranger Section.
„h Block off and repair informal trails and eroded tracks being used as mountain bike tracks by installing split rail fence and covering bare ground with wood chips and brush.
„h Establish a Volunteer Trail Patrol under the supervision of the Oakland Police Ranger Unit.
„h Install signage to clearly identify trails where bikes cannot be ridden and post park rules at major trailheads.
„h Form an ad hoc Trails Working Group (TWG) consisting of cyclists, local residents, concerned citizens and staff to draft a trails management plan for Joaquin Miller Park and other open space parks managed by the OPR.

While all of the above measures were initiated in January 2000, the TWG process was suspended by the mutual consent of TWG participants and OPR in April, 2000 because of the need to base further discussion on scientific, impartial information. With input from the TWG, OPR hired William Lettis & Associates (WLA) to conduct an impartial, professional assessment of the condition of the Joaquin Miller Park watershed and the health of the Redwood forest.

OPR staff and TWG participants identified 11 areas of concern (Areas A through K of Figure 1 in the report). After conducting field assessments in all of the identified areas WLA documented its findings in the report entitled ¡§An Assessment of Trails, Watercourses, Soils, and Redwood Forest Health in Joaquin Miller Park, Oakland, California, with Recommendations for Management¡¨ which was completed in February, 2001.

KEY ISSUES AND IMPACTS

Findings of the WLA Report

WLA concluded the following after conducting field assessments of areas A-K:

Soil Erosion:
„h Approximately 59% of the total past erosion is attributed to naturally occurring bank failures and landslides observed along watercourses.
„h The most common erosion feature in Joaquin Miller Park is rills created by surface runoff. A high outside berm prevents water from leaving the trail forming rills and, if not limited by shallow bedrock, gullies. This erosion, however, represents only 7% of the total past volume of erosion.
„h The creek channel at the junction of the Sunset Trail and the Cinderella Trail is considered a major problem because the combined effects of culvert plugging, stream flow across the trail, and past fill failures has resulted in a major sediment contribution to the creek and a recreation safety hazard.
„h Surface runoff was determined to be dominant erosion mechanism acting on the park trails. Erosion generated by horses, bicycles, and hikers was determined to be a minor erosion mechanism on established park trails.
„h Recreational use was determined to be a major source of soil erosion on ¡§bootleg¡¨ trails. WLA noted many off trail hiking and biking tracks throughout the park. Many of these trails are oriented directly downhill, facilitating the rapid flow of water that deepens the tracks.

WLA trail recommendations:
„h Install water bars or repair existing water bars to direct runoff away from trails.
„h Redirect ephemeral streams to natural channels.
„h Install in-board ditches and ditch relief culverts to help drain trails.
„h Clean and replace old culverts.
„h Replace fill crossings with bridges or rolling dip crossings.
„h Regrade trails where deep gullying has taken place.
„h Rebuild trails that have excessively steep gradients and poor alignment by incorporating switchbacks and/or steps to reduce grade.
„h Block off and sign all ¡§bootleg¡¨ trails at both ends of the trail.
„h Develop a trail management plan to set goals, procedures, and mileposts for improving and maintaining the trail system.
„h Secure adequate funding and the participation of user groups.

Watercourses:
„h WLA found the watercourses in Joaquin Miller Park to be in excellent condition. No major effect of recreational land use was noted in channels.

Redwood Forest Soils:
„h Soil sampling in the redwood forest revealed that with the fine texture and friable nature of these soils they might be highly susceptible to erosion , if exposed. At present, the organic (O) soil horizon, with its dense root mat provides a protective skin for the soft soil underneath. Every precaution should be taken to preserve the O horizon of these soils.

Redwood Forest Overstory:
„h No areas showed signs of declining vigor. One area showed slower growth and lower vigor because it is a harsher growing site and not because of any land use.
„h Very little mechanical damage except scuffed bark on a few trees at two to six feet above ground level, which could ****** growth. Animals may have caused this.
„h The redwood trees in Joaquin Miller Park appear more resistant than average to the effects of rot. Even where the base of a tree was observed to have damage that may expose the tree to a fungal infection, very little or no rot was observed.
„h No problems with pathogens were observed.
„h No significant differences were observed in growth rates between redwood trees growing immediately adjacent to trails and with exposed roots in the trails, and trees not adjacent to trails and not affected by trail use compaction and disturbance.

Redwood Forest Understory:
„h The understory impacts and health problems identified were trampling of vegetation, soil compaction, invasive weed infestation, and a loss of species diversity and native plant components.
„h The vegetation trampling results from all types of off-trail traffic with no distinct differences between the types of off-trail traffic.
„h Off-trail use was noted throughout the trail system, particularly on the flat and gentle slope areas associated with the Fern Ravine and Big Trees Trails.
„h Two of the invasive plants, English ivy and English holly, are shade-tolerant species that aggressively displace native plants in the closed-canopied portions of the redwood forest.

WLA Redwood Forest recommendations:
„h Install additional barriers to divert off-trail traffic, protect areas of intact native vegetation, and limit traffic impacts to the established trails.
„h Initiate an invasive weed control program.
„h Initiate revegetation and/or native plant enhancement projects for poorly vegetated areas, weed eradicated areas, and any recently disturbed areas.
„h Restore the subsurface portion of Palo Seco Creek in the Lower Meadow area. This headwater area of the creek within the park is one of the few semi-intact natural functioning watersheds in the East Bay and is a valuable environmental resource for both flora and fauna.

Ongoing Efforts to Reduce Erosion, Off-Trail Riding and Hiking, and Foreign Plant Invasion Impacts

Efforts are ongoing to accomplish key objectives identified in the consultant¡¦s report. OPR and volunteers will continue to install split rail fencing to reduce off trail riding and hiking, and to implement mitigation measures contained in Appendix A of the WLA report.

The Friends of Sausal Creek (FOSC) with the support of OPR have started a Native Plant Nursery in Joaquin Miller Park which will eventually produce plants to help restore the redwood understory. FOSC and OPR are planning to stage a ¡§Creeks to Bay Day¡¨ volunteer project in Joaquin Miller Park this Fall to remove English ivy that has invaded the redwood forest understory, as recommended by the WLA report.

Alternative Sources of Funding

OPR is considering the submission of grant requests to the California Department of Parks and Recreation Recreational Trails Program (RTP) and the Non-Motorized Trails Program to rebuild the creek crossing at the intersection of the Sunset and Cinderella Trails and for other qualifying projects recommended by WLA. Preliminary estimates of costs for the creek crossing are $75,000 to $100,000.

ENVIRONMENTAL OPPORTUNITIES

The WLA report recommends numerous ways for park users and staff to join together to restore and protect the trail system and the redwood forest understory.