Cottonwood Canyon Preserve in Pasadena is a gateway for wildlife traveling between the San Rafael Hills and the Arroyo Seco. It features a remarkable resource: a rare perennial spring. At Cottonwood, a bear traveling through the corridor finds a watering hole and refuge from hot summer days under the thick canopy of native trees.
But like the Arroyo Seco, the course of Cottonwood’s stream has been subverted by human intervention. We are partway through a long-term project to bring more of the stream to the surface from an underground culvert.
The culvert is buried, carrying spring water down the slope to the Arroyo bottom. Our multi-step plan for the Preserve envisions a free and naturalized waterway.
PHASE ONE
We removed invasives from the creek bed west of Linda Vista: eupatory that gulped up water, and Mexican fan palms and ash trees that competed with native trees. Now the native blackberry is thriving and the California maples, coast live oaks, and sycamores have more water and room to spread out.
Volunteers helping remove invasive palms from Cottonwood, October 2025
PHASE TWO
We’re designing a restoration project for the soft bottom of the Arroyo from Devil’s Gate Dam to lower Cottonwood Canyon. Once past Devil’s Gate Dam, wildlife make their way down the Arroyo a short distance to Cottonwood. We’ll remove non-natives that dominate the area and reintroduce the once prevalent cottonwood trees to make this corridor healthier with native habitat.
PHASE THREE
We will abandon much of a century-old culvert that redirects Yokum Creek underground. Daylighting the stream will increase the amount of surface water in the Preserve. The spring-fed stream that once flowed freely in the lower part of the Preserve will be brought back to support native plants and wildlife, like the bobcats that frequent the Preserve and the diverse bird species that find shelter in the canyon’s canopy.
DAYLIGHTING
Uncovering and restoring waterways that have been buried or contained, bringing them back to the surface and integrating them with the surrounding habitat.
Visionary projects like this take time and resources, but we know our efforts will be worth the wait.
Please make a donation today to support this work. Your gift helps us care for the lands we’ve already protected, and makes it possible to conserve more in years ahead.