Arundo mapping

Arundo Donax in Matilija Canyon

One of Matilija Dam’s many environmental impacts is the infestation of Arundo donax, a non-native giant reed, in the Matilija Reservoir above the dam.The gentle-sloping, soft-soiled delta created by fifty years of heavy sedimentation provides the ideal environment for Arundo to thrive.

During the summer of 2001, interns from Great Pacific Ironworks in Ventura and Matilija Coalition staff mapped Arundo in the upper Matilija Canyon as an initial study into the extent of infestation. The mapping crew found isolated "clumps" many miles upstream from the reservoir, likely caused by human transport. Arundo concentration increased while moving downstream to nearly 100% within the delta area of the reservoir.

Our mapping has been integrated into a GIS map that is available on-line courtesy of , at Matilija Coalition/GPIW Arundo Survey Map

Matilija Coalition/GPIW Arundo Survey Final Report

Mapping Field Guide


Eye On the Environment” Arundo article, Ventura County Star, 12/23/01

Invasive arundo donax clogs county's waterways

By Eric R. Reed, Guest writer

pictureTwo hundred years ago California met an enemy for the first time. Originating from the Indian subcontinent, it first invaded Europe before coming ashore in California with Spanish settlers. This enemy was arundo donax, the tenacious giant reed now infesting California and many other regions of the United States.

If you live near a river or barranca, you know arundo. Often mistaken for bamboo, it grows rapidly in water-rich environments to heights over 30 feet. Transported downstream during flooding, thickets of dead arundo arrive on our beaches after major storms. Uprooted plants left upstream settle on stream banks and sandbars, where small amounts of arundo root, or rhizome, can sprout easily and become large patches in a few months and colonies in a few years. To observe the pervasive infestation of arundo in our waterways, simply look to your right or left when crossing the Santa Clara and Ventura freeway bridges. The shimmering green forests of this giant reed clog these rivers from the mountains to the sea.

Like yellow star thistle in the Imperial Valley and kudzu in the Southeastern United States, arundo donax does not belong in Ventura County's waterways for several reasons. It promotes excessive algae growth and raises water temperature by eliminating streamside shade and raising the water temperature. The plant grows densely and diverts natural stream flow, accelerating erosion that causes property damage and necessitates expensive repairs. Arundo also wastes water in Ventura County's drought-prone climate by using five times more water as native plants. Although commonly stocked at nurseries and historically useful for fencing, roofing and fiber production, the benefits of arundo clearly do not outweigh the damage it causes to a watershed.

The locally led Ventura County Arundo Task Force has set its sights on eventual total eradication of arundo from Ventura County. Eradication of arundo will be difficult if not impossible. Simply reducing its presence in the floodplains of our watersheds will require the cooperation of landowners, as diligent eradication efforts on one's property are futile if clumps are left untouched on adjacent properties. However, the prevention of new arundo infestation is a simple and attainable goal.

First, do not contribute to proliferation by purchasing this plant at your local nursery. Second, if you live near a stream or river, monitor your property for even the smallest clumps at risk of washing away during high flows. And if you do not live near a water source but do have arundo infestations, ensure that any clippings or waste are responsibly removed to a location where it cannot access water and spread.

The Ventura County Arundo Task Force has members with broad expertise who are anxious to work with landowners to address the streamside invader problem. Participation in the task force is open to all comers. For more information on the task force or a copy of "Arundo: A Landowners Handbook," contact task force coordinator Peggy Rose at 386-4685.

For additional information, visit Team Arundo del Norte, a multi-stakeholder partnership dedicated to the control arundo, at To learn more about broader watershed issues on the Ventura River, visit or e-mail

-- Eric Reed is assistant program coordinator for the Matilija Coalition, a conservation program of the Surfrider Foundation, Ventura County Chapter.

Ventura County Star, December 23, 2001