RESTORATION / WINTER 2023

OVLC has worked for over a decade to remove invasive giant reed (Arundo donax) from the Ventura River and San Antonio Creek. Giant reed consumes massive amounts of water, presents a serious fire hazard, alters hydrology, and as we saw in these recent storms, can dislodge, clogging infrastructure and causing flooding downstream. To date, OVLC and Ventura County Watershed Protection District have removed more than 250 acres of giant reed from the Ventura River Watershed. 

Since giant reed is so prolific in the Ventura River Watershed, and giant reed upstream can dislodge and start new strands downstream, over the past two years, OVLC has taken a watershed-wide view to completely eradicate this aggressive invasive species. We received funding from the Wildlife Conservation Board to survey 36 miles of rivers and streams north of Foster Park in the upper portion of the Ventura River Watershed to identify remaining giant reed populations. With this mapping of about 70 acres, we developed a plan to eradicate these discrete stands and secured funding from Cal Fire for watershed-wide permits. In the final months of 2022, OVLC worked with Ventura County Fire Department to remove 20 acres of dense, matted stands from three sites across the watershed. Removing these strands likely prevented downstream flooding in the January 9-10 storms. 

But the recent storm that brought record rainfall and widespread damage drastically changed the nature of our watershed, especially riparian zones. High flows led to severe flooding— boulders rolled like dice, mature trees were ripped up from their roots and swept downstream, and entire embankments were scoured away. The dense riparian canopy we remember in the Ventura River is gone, but this is also what it has evolved to do. Major disturbance also brings new life. 

While we are still assessing these changes, we know that we have a lot of work ahead of us; although the path looks a bit different. While nature ripped out much of the remaining acreage of giant reed for us, we now need to focus our efforts on cleaning up the debris before bits of root are able to re-establish downstream. Giant reed is a bit of a zombie plant; even a small section of root can resprout and start a new infestation! This dramatic change has created an opportunity for us to eradicate this invasive species, but we need to be prepared (and permitted) to move quickly to target resprouts immediately. In the invasive plant world this is referred to as “Early Detection & Rapid Response.” 

As the water recedes, we will see our riparian areas start to revegetate—but invasive species will continue to compete with our native riparian species like willows and sycamores if we don’t give them some help. If we can pair a watershed-wide Early Detection & Rapid Response program for giant reed with restoration plantings, we can give native riparian habitats a jump start for recovery, but we need to work fast before these invasive species take root again. 

The Ojai Valley Land Conservancy website offers a summary of scientifically proven best practices: ovlc.org/arundo-removal If you have giant reed on your land, contact us and we can help: restoration.programs@ovlc.org / (805) 649-6852 

Vivon Crawford
Restoration Program Director