Distribution of Arundo donax in coastal watersheds of Southern California

This is a new draft version of a regional distribution map for Arundo donax for southern California (Santa Barbara to Tijuana). There are two versions of the map, one through January 2000 (example shown below) and one through January 2002 that indicates current Arundo control projects. JPEG images of these two maps are provided below, and can be viewed online or downloaded. A GIS coverage will also be available soon for this Arundo distribution data. The accompanying text (see below) describes general dispersal patterns and the distribution for each river along with some information on groups that organized the control effort and/or carried out the work. This information was presented at the CalEPPC Conference in October 2001 and will appear in the conference proceedings sometime in late 2002.

The maps are shown below, but to really view the details, links to larger images and the GIS coverage are provided below that can be downloaded or viewed online.

• ARUNDO DISTRIBUTION MAP through Jan 2000 (645KB JPEG file)
• ARUNDO DISTRIBUTION MAP through Jan 2002 (583 KB JPEG file or 1.4MB EPS file)
• ARUNDO DISTRIBUTION MAP through October 2004 (642KB JPEG file)

ARUNDO DISTRIBUTION MAP GIS COVERAGE (this is a zipped file)

To download right click once and hold down and select "Save Target As". You can then save these images as JPEG files which you can view in Photoshop or other image viewing programs. The image dimensions are quite large, but can be resized if necessary. The resolution of the JPEG file will be 72 dpi. The EPS file can be opened in Adobe Illustrator. If you would like higher resolution images or a printed out version contact us.

To view the text as a Word document, click here

DISTRIBUTION OF ARUNDO DONAX IN COASTAL WATERSHEDS OF SOUTHERN CALIFORNIA

Bill Neill
Riparian Repairs, 4900 Glenview Ave., Anaheim CA 92807
phone: 714-779-2099; email: bgneill@earthlink.net

Jason Giessow
Santa Margarita and San Luis Rey Weed Management Area & DENDRA Inc.
213 La Veta Ave., Encinitas CA 92024
phone: 760-943-6924; email: wma@smslrwma.org


INTRODUCTION

A regional map showing distributions of Arundo donax (giant reed) in southern California's coastal watersheds has been posted at the website of the Santa Margarita and San Luis Rey Weed Management Area (www.smslrwma.org).  Map coverage extends from the Santa Ynez River in Santa Barbara County to the Mexican border.

The Arundo distribution map is based on visual inspection of riparian corridors, viewed from public roads, bridges and roadside overlooks where possible, and to a lesser degree from bike paths and foot trails.  In numerous places, Arundo control proponents with knowledge of local areas provided maps or verbal reports of Arundo distributions that were incorporated into the regional map.

The Arundo survey adopted the reconnaissance mapping protocol developed by Team Arundo del Norte, whereby the abundance of Arundo is classified according to the average number of clumps per mile in a relatively narrow riparian corridor, or the average distance between clumps in a broad floodplain.

Most of the survey was conducted during the second half of 1999 and first half of 2000.  The baseline map shows areas cleared of Arundo before January 2000.  Also posted is an updated version that displays project sites treated by January 2002.

SURVEY PROTOCOL
Lengths of riparian corridor that contain Arundo are divided according to abundance into four classes on the regional map:

Isolated:  1 to 5 clumps per mile; >1000 ft average spacing between clumps
Scattered:  6 to 20 clumps per mile; 250-1000 ft average spacing
Abundant:  20 to 200 clumps per mile; 25-250 ft average spacing
Dominant:  Amalgamated clumps, continuous in places  

This classification of Arundo abundance was adopted from the "windshield" survey protocol of Team Arundo del Norte, posted at: ceres.ca.gov/tadn.

Note that the term "Dominant" refers to aerial abundance, not structural prominence, and can describe a shaded understory of Arundo beneath a canopy of taller native trees or eucalyptus

Arundo is mapped as "Absent" when not observed along distances of one mile or more of riparian corridor, or is inferred to be absent between accessible locations.

River and stream channels are mapped as "Non-riparian" where trees and other riparian vegetation are sparse or absent, due to water diversion or flood control management or natural causes.  Such channels may be lined with rock or concrete, or periodically mowed or graded, or landscaped, or nearly barren of vegetation due to limited water supply or natural flood scour.  "Non-riparian" channels generally lack Arundo, but those that contain minor amounts are not distinguished on the regional map; the absence of riparian habitat is the primary consideration.

Channels labeled as containing "Abundant tamarisk" denote degraded riparian habitat that lacks Arundo but is too dry to support trees other than tamarisk, generally owing to upstream water diversions.

Areas cleared of Arundo by restoration projects are depicted on the regional map only if they encompass the full width of a riparian corridor and a half-mile or more of its length.

In terms of aerial cover, Arundo populations assigned to the "scattered" category occupy not more than one percent of the riparian corridor vegetated area, and the division between "abundant" and "dominant" categories is equivalent to aerial coverage of about ten percent.

ARUNDO DISPERSAL PATTERNS

Typically along riparian corridors the upstream end of an Arundo population is sharply defined and is the site of initial introduction.  These sites usually are residential yards or other developed property where Arundo was planted adjacent to the stream channel.  In several watersheds Arundo was introduced to remote locations by plantings near hot springs; examples include Hot Spring Creek near Montecito in Santa Barbara County, Arrowhead Springs near San Bernardino, and San Juan Hot Springs northeast of San Juan Capistrano in Orange County.

In the simplest cases, the introduction site is marked by the largest Arundo clump in a watershed.  Owing to flood transport of vegetative propagules, derivative clumps extend for miles downstream, becoming smaller and less abundant with increasing distance from the parent source.

Dulzura Creek in southern San Diego County is an example of a simple dispersal pattern:  the largest clump is located next to the creek at the town center; in the upstream direction, Arundo clumps have been planted at several locations but not are not present along the stream channel; in the downstream direction, Arundo abundances are mapped as "abundant" over the first mile from the parent clump, as "scattered" over the second mile, and as small "isolated" clumps over the next 5 miles, ending near Lower Otay Lake.

Other streams showing the downstream-thinning pattern of early invasion include the San Jacinto River east of Hemet in Riverside County; the upper portion of San Juan Creek in Orange County; and in San Diego County, the San Luis Rey River east of I-15, Escondido Creek, the Harbison Creek tributary of the Sweetwater River, and Cottonwood and Potrero Creeks near their confluence.

More complicated dispersal patterns result where, following the initial introduction, (1) Arundo has been transplanted upstream of the parent clump either intentionally or accidentally; or where (2) Arundo has been planted independently on several tributaries of the main channel; or where (3) channel constrictions, barriers and excavations have caused propagules to accumulate irregularly.

Examples of complex dispersal patterns cited above include (1) Matilija Creek in Ventura County, where "scattered" clump density is mapped upstream of "abundant" clump density; (2) the San Luis Rey River west of I-15 in northern San Diego County, where Arundo was planted on three tributaries (Keys Creek, Live Oak Creek, Ostrich Creek) and on the main channel above the confluence of the tributaries; (3) the Santa Ana River in Riverside County where the Prado Basin and Prado Dam mark a sharp discontinuity in Arundo clump density.

Additionally, in watersheds where introduced many decades ago, Arundo does not diminish in abundance downstream but instead becomes the dominant vegetation.  In these systems Arundo appears able to spread into all flood-prone areas, not limited by factors such as lack of perennial moisture or rocky substrate or dense shade.  Examples include the lower portions of rivers such as the Ventura, Santa Clara, Santa Ana, Santa Margarita, San Luis Rey and San Diego Rivers.

The mapped distribution patterns are consistent with earlier recognition that Arundo is spread to new sites by floods or human-assisted transport of plant fragments, rather than by seed dispersal because viable seed has not been reported in California (Bell 1993, Else 1996).  Both rhizomes (root) and stem fragments can grow into new clumps of Arundo, with rhizomes considered to be the more common source of new plants (Else 1996).

Arundo is highly adapted to the flood regime characteristic of southern California riparian systems.  Periodic high flow events "re-set' the riparian system, removing mature stands of vegetation and depositing new substrate of sand and gravel.  Native vegetation can re-seed these depositional bars and sprout from plant fragments.  Similarly, floods dislodge and break up clumps of Arundo and spread them downstream, with each plant fragment growing to a new Arundo clump or stand.  Urbanization has altered flow regimes for many systems, either directly by channelization or elimination of floodplains or indirectly by reducing water retention of uplands through development.  This has resulted in 'flashier' flood regimes that may promote the spread of Arundo.  Additionally many seasonal streams and creeks have been turned into perennial systems fed by agricultural and urban run-off

In coastal watersheds Arundo is not confined to riparian areas with high water tables, but is able to survive on rainfall at upland sites.  Consequently, isolated clumps can be found growing on hillsides and next to roads where rhizome fragments have been transported by road construction or soil dumping.  Compared to those nourished by riparian groundwater, Arundo clumps at mesic locations have shorter growing seasons, and are shorter and less robust -- with stalks generally less than 15 ft tall.  These upland clumps expand slowly and do not spread without assistance to riparian areas

One general observation is that Arundo is relatively rare in the national forests of southern California.  In most occurrences Arundo has been introduced at private inholdings within several miles upstream of the national forest boundary.  Exceptions are limited to Angeles National Forest, where Arundo was introduced along roads that traverse the National Forest (San Francisquito Canyon and Bouquet Canyon) and at a mine located high in the watershed of Big Tujunga Canyon.  

WATERSHED SUMMARIES

1.  Southern Santa Barbara County:
1.1  Santa Ynez Valley:  Arundo is rare in the Santa Ynez watershed and only 4 clumps are known along the main stem of Santa Ynez River from Juncal Dam to Vandenburg Air Force Base, separated by an air distance of about 55 miles

In the upper portion of the watershed, Arundo is not present at Big Caliente and Little Caliente Hot Springs northeast of Gibraltar Reservoir, nor is it evident from Paradise Road between Gibraltar Reservoir and Lake Cachuma.  In the middle portion of the watershed, starting in 1994, county flood control staff cleared scattered, mostly small Arundo clumps along a 4-mile reach of Alamo Pintado Creek between Los Olivos and Solvang.

Near the river channel 6 miles west of Buellton, in 2001 county staff discovered populations of 1 and 3 clumps adjacent to vineyards accessed from Santa Rosa Road.  In the Lompoc area, several Arundo clumps are present at Mission La Purissima Concepcion and one grows in a rural yard at the lower end of San Miguelito Canyon, but adjacent tributaries are not invaded.   

1.2  Coastal canyons near Santa Barbara:  An Arundo infestation extends down Hot Springs Canyon and Montecito Creek, starting at abandoned gardens near ruins of Hot Springs Hotel, initially constructed in the 1880's and burned in 1920 and 1964.  In other canyons near Santa Barbara, Arundo appears to be absent in Los Padres National Forest and rarely present in urbanized areas, with the exception of the lower portions of Arroyo Burro and Mission Creek in the City of Santa Barbara.  West of Goleta, the lower 1.2 miles of Refugio Canyon harbors dense Arundo on private land below the National Forest boundary.

2.  Ventura River and tributaries:

On Matilija Creek above Matilija Dam, Arundo presumably was first planted behind vacation cabins or along the access road, then later was transplanted upstream to the highest inholding in the national forest.  Two miles below Matilija Dam, the abundance of Arundo in the Ventura River channel drops sharply where water is diverted to Lake Casitas.  The town of Ojai was another early introduction site, from where abundant Arundo extends down San Antonio Creek and then down the Ventura River to the ocean.  Removal efforts are limited currently to a demonstration project on the Ventura River near the San Antonio Creek confluence, sponsored by the Ventura Co. Flood Control District and Ventura Co. Resource Conservation District.

3.  Tributaries of Santa Clara River:    
3.1  Sespe Creek:  Arundo appears to be absent from Sespe Creek except near the outlet in Fillmore.  

3.2  Piru Creek:  The entire watershed is probably Arundo-free, judging from its absence in the rural communities of Gorman and Lockwood Valley, and at widely spaced vantage points elsewhere along Piru Creek.

3.3  San Francisquito Creek:  Arundo was introduced along the Los Angeles Aqueduct right-of-way with highest -- in elevation -- but not densest occurrences at Power Plant No. 1.   Angeles National Forest started a removal program in 1995, employing Pestmaster Services (Bishop) to operate a tractor-size hammer-flail mower.  The program was expanded in 1999 to include Los Angeles Dept. Water & Power property.  During 2000-2001, Pestmaster Services mowed and treated Arundo along the lowest 2.5 miles of San Francisquito Creek as a mitigation project for Valencia Co. bridge construction and bank stabilization.

3.4  Soledad Canyon:  The riparian corridor is free of Arundo through Acton and downstream for a distance of 7 miles, although Arundo is present in some of Acton's residential yards.  In Soledad Canyon the primary introduction site is a rural residence next to the stream channel, 1 mile west of the conservation camp.  Below the introduction site, Angeles National Forest hired Pestmaster Services to clear a one-mile length of the channel starting in 1995.

4. Calleguas Creek watershed:

Calleguas Creek and its tributaries are mostly channelized but in places Arroyo Canejo, Arroyo Simi and Arroyo Las Posas retain riparian character.  Affecting Arroyo Canejo, Arundo probably was introduced to the Thousand Oaks area before urbanization.  Below Simi Valley, Arundo density increases downstream in Arroyo Simi, so the history of introduction is not apparent.  Removal work has been limited to Arroyo Las Posas downstream of Moorpark, when in 1998 the Ventura Co. Flood Control District hired a contractor to clear two-thirds of a mile to mitigate bank stabilization elsewhere.

5.  Santa Monica Mountains:  
5.1  Malibu Creek:  Isolated Arundo clumps are present below Lake Malibu through Malibu Creek State Park.  Below Tapia Park, before treatment, Arundo clumps became abundant at the filled reservoir and extended below the dam to the ocean.  In the lower canyon below Piuma Road, more than 200 Arundo clumps on park land were foliar sprayed in late 2000 by a contractor crew from Agri Chemical & Supply (Oceanside), funded by state and federal grants to the Mountains Restoration Trust.

5.2  Topanga Canyon:  The highest occurrences of Arundo are in oak woodlands and residential yards in the community of Glenview, above the zone of typical riparian vegetation.  Where the riparian corridor starts, Arundo is present and extends to the ocean.

6.  Los Angeles River watershed.
6.1  San Fernando Valley:  Upstream of paved storm drains that cross the valley floor, in canyons of hills bordering San Fernando Valley, Arundo is present in the following approximate amounts:  Dry Canyon/Arroyo Calabasas -- 0.6 acre; Devil/Brown's Canyons -- 0.7 acre; Limekiln Canyon -- none; Aliso Canyon -- 3 clumps.

6.2  Sepulveda Basin:  During Fall 2001, Army Corps of Engineers contractor Reyes & Sons used bulldozers to clear 10-15 acres of Arundo from 1.4 miles of Los Angeles River channel between Balboa and Burbank Blvds., with debris trucked to landfills.  Less than an acre remains in the soft-bottom channel west of Balboa.

6.3  Pacoima Canyon:  Isolated Arundo clumps are present downstream of the bridge crossing southeast of Bear Divide and presumably down to Pacoima Reservoir; above the bridge crossing, none are visible on private land for a distance of one-quarter mile.

6.4  Little Tujunga Canyon:  The highest occurrence of Arundo is a half-mile downstream of Gold Creek Road, near the boundary between Angeles National Forest and private inholdings; approximately 12 net acres are present above Hansen Dam basin. 

6.5  Big Tujunga Canyon:  Within Angeles National Forest, Arundo initially propagated downstream from the Stonyvale settlement of vacation cabins.  Higher in the watershed, Arundo was later introduced near 4000 ft. elevation at a mine on Iron Mountain, from which Arundo spread downstream about one mile along Monte Cristo Creek and Mill Creek.

6.6  Big Tujunga Wash:  Outside Angeles National Forest, below the canyon mouth near Sunland, the Los Angeles Co. Dept. of Public Works implemented the Big Tujunga Wash mitigation bank in late 2000 to offset county-wide flood control impacts, employing Chambers Group and Natures Image (Orange County) to clear 30 acres of Arundo below Interstate 210 using a hammer-flail mower and chainsaw crews.  Also, in 2001 the California Environmental Project secured grant funding to start removal work between the Forest Service boundary and Oro Vista Ave.

6.7  Arroyo Seco:  Arundo is limited to several clumps, starting at a City of Pasadena water diversion facility a quarter-mile upstream from the canyon mouth.

6.8  Glendale Narrows:  On a soft-bottom, non-concrete-lined portion of the Los Angeles River, North East Trees manually cleared Arundo from a half-mile length of the channel in 1998, downstream from Los Feliz Blvd.

6.9  Eaton Canyon:  After introduction at the Forest Service's Henninger Flat station, Arundo spread somehow along the Mt. Wilson Toll Road and down Eaton Canyon.  A one-mile reach of abundant Arundo stands below the toll road crossing was cleared mainly by excavation of continuous stands and cut & spray of more isolated clumps, in 1996 as off-site mitigation for housing construction.

6.10  Rio Hondo:  In the Whittier Narrows Flood Control Basin, the Mountains Recreation & Conservation Authority sponsored excavation of a 250-ft-long Arundo stand in 1997 at the Bosque del Rio Hondo park; and in 2000 the San Gabriel Mountains Regional Conservancy initiated work north of the Pomona Freeway, employing the L.A. Conservation Corps for chainsaw removal and Agri Chemical & Supply for foliar spraying.

7.  San Gabriel River and tributaries:

7.1  San Gabriel River:  Within Angeles National Forest, Arundo occupies several isolated upland locations but has not become established along the upper tributaries.

Along the 3-mile length of San Gabriel Canyon between Morris Dam and Roberts Creek, scattered Arundo clumps were partly removed during 1999-2000 by Forest Service and CA Environmental Project (CEP) chainsaw crews, funded by Los Angeles Co. Dept. of Public Works (DPW).

Along the one-mile channel length between Roberts Creek and the Azusa Rock/Vulcan Materials conveyor belt crossing, scattered Arundo clumps were mostly removed during 2000-2001 by a CEP crew and Riparian Repairs, funded by a grant from the Center for Natural Lands Management to the San Gabriel Mountains Regional Conservancy.

Along the nearly 2-mile channel length from a conveyor belt crossing to Foothill Blvd., abundant to semi-continuous Arundo stands were cleared during 2000 by chainsaw crews from Fairfield Landscaping Service (Pasadena), funded by Azusa Rock/Vulcan Materials to mitigate construction of the conveyor belt crossing.

Along the half-mile channel length from Foothill Blvd. to Interstate 210, Arundo was removed during 1999-2000 by Los Angeles County, with work performed by the Dept. of Forestry and funded by DPW.

Above the Whittier Narrows flood control basin, about 22 acres of dense Arundo was removed from a 2-mile reach between Walnut Creek and San Jose Creek in 1997-98 by Los Angeles Co. DPW for the purpose of flood channel maintenance.

During Fall 2001, Army Corps of Engineers contractor Reyes & Sons used bulldozers to cleared about 30-40 acres of Arundo from 1.2 miles of the San Gabriel River channel below San Jose Creek, with debris trucked to landfills.  Another mile of dense Arundo remains in the channel upstream of Whittier Narrows Dam.

7.2  Eastern tributaries of San Gabriel River:  In Big Dalton, Little Dalton and San Dimas Canyons, Arundo became established in the vicinity of water retention and debris basins near the canyon outlets, and has been removed by a cooperative program managed by Angeles National Forest and funded by Los Angeles Co. Dept. of Public Works.  Starting in 1997 above the debris basin dams, Forest Service crews and the CA Environmental Project cleared one mile of scattered clumps in Big Dalton Canyon and half-mile of large stands in Little Dalton Canyon.  Above San Dimas Canyon Reservoir, in 1998 Forest Service crews cleared scattered Arundo from half-mile sections in two canyons; and in 2000 Forest Service and CEP crews started work below the reservoir on continuous Arundo stands between the dam and golf course.  Below these canyon areas the stream courses are channelized.

8.  Santa Ana River watershed:

Upper tributaries are being cleared of Arundo by the Santa Ana Watershed Association (SAWA) of Resource Conservation Districts, funded by the SAWA mitigation trust fund.  Similarly, with separate mitigation banks, the Riverside County Regional Parks and Open Space District is responsible for the river's main channel from Riverside to Norco, and the Orange County Public Facilities and Resources Dept. (PFRD) is responsible for restoration of Santa Ana Canyon below Prado Dam.  Future state bond funding to these organizations will be administered by the Santa Ana Watershed Project Authority (SAWPA).   

8.1  Cajon Wash:  Starting below Highway 38, abundant Arundo clumps grading downstream to mostly scattered densities were cut and treated during 1999-2000 by crews from Washburn Grove Mgmt. (Hemet) contracted by the Inland Empire West RCD.  Also a large Arundo stand at Lost Lake was removed.

8.2  San Bernardino area:  The Arrowhead Springs resort was the introduction site for continuous stands of Arundo in the lower parts of Waterman Canyon, Hot Springs Creek and East Twin Creek.  Along City Creek, Arundo is absent in the National Forest down to Highland Blvd., below which scattered clumps are present.

8.3  San Timoteo Canyon:  Starting near Highway 60 below Beaumont, contractors (Washburn Grove Mgmt., Pestmaster Services) employed by the East Valley RCD cleared about 6 miles of riparian corridor during 1996-99 and another 5 miles during 2000 to the natural channel's terminus below Allesandro Road, as well as most of Live Oak Canyon through Yucaipa.

8.4  Riverside area:  Starting in 1993, Riverside Co. Parks staff cleared Arundo along a one-mile length of the Santa Ana River near the Van Buren bridge, funded mainly by a mitigation bank.  Using a variety of methods, contractors employed by the Riverside-Corona RCD cleared Sycamore Canyon during 1997-98, Fairmont Park during 1998-99, Alessandro Arroyo during 1999-2000, the Castle View drainage during 2000-01 (Agri Chemical & Supply, Pestmaster Services, Washburn Grove Mgmt., Natures Image).

8.5  San Jacinto River:  Arundo appears to be absent from the Idyllwild community and National Forest land, and the highest mapped location is a private inholding 3 miles upstream from the Forest Service's Cranston Station.  In the San Jacinto Valley below the Saboba Reservation, San Jacinto Basin RCD staff cleared scattered amounts of Arundo east of Highway 79 during 1998-99, and Washburn Grove Mgmt. crews cleared tamarisk and isolated Arundo clumps from Bridge St. to Davis St. during 1999 and between Sanderson Ave. and Bridge Street during 2001.

Below Canyon Lake, Arundo is absent from Railroad Canyon above Interstate 15 and present downstream from the freeway.

8.6  Temescal Canyon:  Downstream from Lake Elsinore, Walker Canyon adjacent to Interstate 15 is Arundo-free, and although Arundo is planted near Lake Street, it has not yet invaded the stream channel.  Downstream, Arundo becomes established below Lake Corona and semi-continuous near El Cerrito.  Starting in 1997-98, a quarter-mile reach of dense Arundo near El Cerrito has been cleared and revegetated by Glenn Lukos Associates and Canyon Landscaping as mitigation for 3M Co. quarry operations; initial clearance by Estill's Windbreak Trimming Inc. (Ojai) employed a hammer-flail mower.   

8.7  Prado Basin:  Along the Santa Ana River northwest of Corona, the Riverside-Corona RCD employed Pestmaster Services and Washburn Grove Mgmt. (?) to remove 30 acres of Arundo during 1997-98 to reduce flood hazard above the River Road bridge.

8.8  Santa Ana Canyon:  On the south side of Featherly Regional Park, between the Santa Ana River and Riverside Freeway, county staff treated Arundo resprouts with herbicide during 1989 following an accidental brush fire east of Gypsum Canyon.  On the north side, chainsaw clearance of a 2-mile strip totaling 60 acres downstream from the Gypsum Canyon bridge was started in 1992 but conducted mainly during 1994-98, by county staff and the Orange Co. Conservation Corps, mainly for off-site mitigation of county flood control projects.  In 2000 mechanical excavation of stalks and roots using a front-loader tractor was initiated on the north side east of Gypsum Canyon.  Continuous stands of Arundo remain in the central part of the flood channel.

8.9  Carbon Canyon:  Arundo forms continuous stands along Carbon Creek below the settlements of Olinda Village and Sleepy Hollow, yet in Chino Hills State Park undeveloped Telegraph Canyon is Arundo-free.  This is one of few examples in southern California where converging tributaries exhibit maximal differences in Arundo density.  During 2000 Chino Hills State Park staff and CDF fire crews initiated Arundo removal on about 2 acres along Carbon Creek.

8.10  Santiago Creek:  In response to forecasts of El Nino flooding in early 1998, during 1997 residents of Silverado Canyon cleared Arundo from 2 miles of private property along Silvarado Creek, with herbicide applications conducted by county staff.  In Modjeska Canyon Arundo is established in the rural developed area below the Cleveland National Forest boundary.

9.  Southern Orange County:
9.1  Aliso Creek:  In the late 1990's two sections of Aliso Creek were cleared of Arundo by Orange Co. employees for off-site mitigation:  Whiting Ranch Park near the top of the drainage, and between Trabuco Road and Jeronimo Road.

9.2  Arroyo Trabuco:  The highest occurrence of Arundo is near cabins in Holy Jim Canyon, about 2 miles upstream from the Cleveland National Forest boundary.  During the winter of 2000-01, the upper 2 miles in O'Neill Regional Park was cleared by county staff and prison crews.(?)  

9.3  San Juan Creek:  Arundo spread downstream from early plantings at San Juan Hot Springs and nearby cabins outside the Cleveland National Forest boundary.  The hot springs area in Caspers Regional Park was cleared of Arundo during 1997-98 by county staff and prison crews as mitigation for downstream bridge construction.  In San Juan Capistrano, Arundo clearance during 1995 between La Novia Ave. and Interstate 5 was not maintained so Arundo reinvaded.  

10.  Orange/San Diego County Line:
10.1 San Mateo Creek: Scattered to abundant Arundo was present on the lower portion of San Mateo Creek within Marine Corps Base Camp Pendleton. The Base and the Navy funded treatment by foliar spraying from the Base entrance gate to Interstate 5 in 1998, and upstream of this area in fall 2001.  West of I-5 in San Onofre State Beach, starting in January 2001 California State Parks contracted Innovative Inclosures (Fallbrook) to excavate 1.5 acres of Arundo from the beach near the creek outlet.

10.2 San Onofre Creek:  Previously Arundo was present in scattered and abundant densities along the lower 5 miles of river length.  Marine Corps Base Camp Pendleton treated these areas in 1996.

11.  Santa Margarita River watershed:

Primary upstream introduction sites were the towns of Temecula and Rainbow.  Arundo did not become established along the primary tributaries in Riverside County -- Murrieta Creek upstream of Temecula, and Temecula Creek draining the north side of Palomar Mountain

On Tucalota Creek above Lake Skinner, at least 3 Arundo clumps are established in the channel in the community of Sage, but have not yet spread downstream.

In 1995 the Mission Resource Conservation District in Fallbrook initiated clearance work in Santa Margarita Canyon between Rainbow Creek and Sandia Creek, with mitigation funding from Camp Pendleton.  Treatments of the lower portions of the river were initiated in 1997 by Camp Pendleton.  Approximately 12 of the 18 river miles have been treated (350 of 500 acres of Arundo).  Arundo stands on the Base are dense and mature, forming monotypic stands over 200 meters wide and up to 1000 meters long.  The Arundo removal work has been a mixture of foliar application of herbicide (AgriChemical & Supply, Oceanside) and mechanical extraction (Innovative Inclosures, Fallbrook

With the formation of the Santa Margarita and San Luis Rey Watersheds Weed Management Area (SMSLRWMA) in 2000, control work has expanded to include the entire main channel downstream from Interstate 15, tributaries in Fallbrook and Sandia Creek.  This work has been funded by a grant from the National Fish and Wildlife Foundation and an Army Corps of Engineers In-Lieu-Fee Mitigation Bank set up for the watershed.  All applications are foliar herbicide application with limited biomass removal at some locations after the Arundo has died.  Work has been performed by a variety of contractors (AgriChemical & Supply, Kelly & Associates, Pestmaster Services).

12.  San Luis Rey River watershed:
12.1  East of Interstate 15:  Along the river's main stem, Arundo was introduced on private land upstream of Wilderness Gardens County Park east of Pala.  Higher segments of the river appear to be Arundo-free, including the heavily wooded portion from Lake Henshaw down to the Escondido Canal intake, and the dry, sparsely vegetated channel through Rincon Springs and Pauma, despite the presence of Arundo clumps planted at upland sites in Rincon Springs.

When mapped in 1999, Arundo densities decreased from "abundant" at Wilderness Gardens to "scattered" near Pala to "isolated" above the Couser Creek confluence.  During 2000-01 the SMSLRWMA program cleared Arundo from 5 miles of riparian corridor from Wilderness Gardens to Pala Reservation (Agri Chemical & Supply).  Two small tributaries between Pala and I-15, Rice Canyon and Double Canyon, remain to be treated.

12.2  Keys Creek:  North of Valley Center, Keys Creek is Arundo-free at Cole Grade Road, but two miles west, above Lilac Road, Arundo continuously fills the understory space beneath a tall canopy of native trees.  The introduction site is on inaccessible private property about midway between the two county roads.  About 40 acres of Arundo are present from the introduction site to a treated half-mile length of lower Keys Creek near the confluence with the San Luis Rey River Interstate 15. Arundo in this area was mechanically removed in 1996 using a slope mower (Fire Prevention Services, Alpine CA) followed by herbicide treatments (San Diego Co. Dept. of Agriculture staff) as mitigation for bridge repairs.

12.3  West of Interstate 15:  Within two miles below the Keys Creek confluence, Arundo densities in the San Luis Rey floodplain decrease sharply to levels mapped as "scattered".  Some of these areas have been treated by CalTrans.  Continuing downstream, at the confluence of Live Oak Creek, Arundo densities return to levels mapped as "abundant", presumably owing to propagules from the two heavily infested tributaries of Live Oak Creek (24 acres of Arundo) and Ostrich Creek (25 acres of Arundo).  The remaining 14 miles of the San Luis Rey River from Ostrich Creek to the ocean is mapped as "abundant" or "dominant", with 340 acres of Arundo, often forming dense 200-meter-wide monotypic stands.

13.  Escondido Creek:  In San Elijo Canyon below Escondido, Arundo dominates the understory beneath eucalyptus.  In the late 1990's a quarter-mile length in the Elfin Reserve was cleared of both non-native species by the Olivenhain Water District, with physical work performed by the CA Conservation Corps, as mitigation for construction of a water storage reservoir.  Along the lower part of Escondido Creek near Olivenhain, Arundo is present as isolated clumps although other invasive exotics are plentiful.   

14.  San Dieguito River/Santa Ysabel Creek:  Arundo is not evident near Santa Ysabel Mission, nor below the Lake Sutherland Dam to Pamo Valley, nor between the confluences of Boden and Clevenger Canyons.  The highest occurrence is about 1/2 mile downstream from Clevenger Canyon, where the proximity of State Highway 78 is the only unusual feature compared to upstream areas.  Control work in the watershed has been limited to CNPS volunteer projects around Lake Hodges.

15.  San Diego River:  
15.1  Above San Vicente Reservoir:  Along the West Fork of San Vicente Creek, Arundo starts abruptly in the community of Fernwood and extends downstream 2 miles to the reservoir.  Along San Vicente Creek, Arundo is present as isolated, dispersed clumps of uncertain derivation in rural San Vicente Valley; further downstream, the remote portion between Klondike Creek and the reservoir was not surveyed.  Along Barona Creek, Arundo is absent on the Barona Indian Reservation.     

15.2  Above El Capitan Reservoir:  Arundo is not observed at tributary crossings and in ranchette yards along the Boulder Creek Road between Descanso and Julian.  Arundo clumps reported along the reservoir shore may have originated from the community of Alpine at the reservoir's south end.

15.3  Lakeside area:  Below El Capitan Dam, the San Diego River channel has riparian foliage for approximately one mile, then is abnormally dry with abundant tamarisk but no Arundo nor native trees (except in adjacent yards) for a distance of 6 miles to the San Vicente Creek confluence.  Below San Vicente Dam, the channel of San Vicente Creek supports both abundant Arundo and tamarisk and is the apparent source of Arundo in the San Diego River channel below Lakeside.

15.4  San Diego area:  As reported by Mike Kelly in the Spring 2000 CalEPPC News, during the 1990's Arundo was removed from 3 miles of riparian corridor in Mission Trails Regional Park and 2.5 miles from the lower river between Highway 163 and Interstate 5  (AgriChemical & Supply, Kelly & Associates).

16.  Sweetwater River:

Arundo was not observed in Cuyamaca Rancho State Park, nor in the vicinity of Descanso, nor at the Interstate 8 crossing, nor above or below Palo Verde Lake southeast of Alpine.  Above Loveland Reservoir, small abundant clumps of unknown derivation extend less than 1 mile upstream of Japatul Road.  Around the Loveland Reservoir shore and below the dam are larger clumps that probably were introduced earlier than those below Palo Verde Lake

The community of Harrison Canyon on a small tributary (Harrison Creek) harbors the densest and presumably oldest Arundo infestation in the upper Sweetwater River watershed.  Below the junction of Harrison Creek and the Sweetwater River, Arundo is present mostly in scattered densities where the river channel has not been converted to golf courses.

Continuing downstream on the Sweetwater River, since the early 1990’s staff of the Sweetwater Authority have partly cleared Arundo and tamarisk at the upper end of Sweetwater Reservoir. Sizeable patches of both Arundo and tamarisk intermixed with native riparian habitat still remain on the reservoir property and upstream areas of the National Wildlife Refuge. Below the dam in Sweetwater Regional Park, volunteers and County Agricultural Commissioner staff removed 3 to 5 acres of Arundo along the river near Chula Vista from 1996 to 1998 (Mike Kelly 1999).

17.  Otay River:  As reported above, on Dulzura Creek Arundo starts in the community of Dulzura and clumps diminish in size and abundance downstream.  The riparian corridor is abnormally watered by water captured at Barrett Lake.  On drier Jamul Creek, a 1-acre stand was cleared by Kelly & Associates for a Wildlands Inc. commercial mitigation bank.  Below Lower Otay Lake, the Otay River channel is dry and nearly barren below the dam, then supports abundant tamarisk and Arundo which outnumber native trees approaching I-805.

18.  Cottonwood Creek:  Arundo is absent along tributaries above Barrett Lake and Lake Morena, although one clump was observed in Morena Village.  Water from the upper watershed would naturally drain to the Rio Tijuana, but is diverted at the Barrett Lake dam by pipeline to the top of Dulzura Creek which flows to Lower Otay Lake.  On the relatively dry part of Cottonwood Creek below the dam, Arundo starts at a trailer park one mile upstream of Barrett Junction.  On Potrero Creek, Arundo is absent in the community of Potrero but starts at an isolated private residence below the turnoff to Tecate.  Downstream of Barrett Junction, the density of Arundo Appears to diminish toward the Mexican border.

19. Tijuana River:  Arundo is thought to be present in light to heavy densities on the Mexican side of the boarder and is present on the U.S. side of the border when the river crosses back into the U.S.  Two miles of river ending at the ocean have been treated on Imperial Beach Naval Air Station and Imperial Slough National Wildlife Refuge.

ACKNOWLEDGEMENTS
Contributors of information about Arundo distributions and removal project histories include, in north to south order: Larry Fausett, Santa Barbara Co. Flood Control & Water Consv. District; David Chang, Santa Barbara Co. Agricultural Commissioner's Office; Dennis Kanthack, Ventura Co. Flood Control District; Paul Nicholson, Hill Canyon Conservancy; Shawna Bautista & Nancy Mahaffie & Karen Fortus, Angeles National Forest; Jeff Van Diepen & Bob Carney, Pestmaster Services; Mark Subbotin, Newhall Ranch Co.; Jo Kitz, Mountains Restoration Trust; Patricia Wood & Jason Pereira, Los Angeles Co. Dept. Public Works; John Caruana, Natures Image; Chuck Arnold, North East Trees; Mickey Long, Eaton Canyon Nature Center; Paul Edelman, Mtns. Recreation & Consv. Authority; Jennifer Ares, East Valley Resource Conservation District; Kerwin Russell, Riverside-Corona RCD; Jim Gilmore, San Jacinto Basin RCD; David Washburn, Washburn Grove Mgmt.; Greg Everett, Glenn Lukos Associates; Dave Matias, Canyon Landscaping; Paul Frandsen, Riverside Co. Park & Open Space District; Bill Tidwell & Chris Kubasek, Orange Co. Public Facilities & Resources Dept; Tom Hummel & David Pryor, California State Parks; Adrian Wolf, Harmsworth Associates; Rick Fox, City of San Diego Water Dept.; Kirsten Winter, Cleveland National Forest; Mike Kelly, California Exotic Pest Plant Council; Pete Famolaro, Sweetwater Authority.

Partial financial support from the Santa Ana River Watershed Conservation Trust Fund

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