Monitoring tree survival and performance in street-side stormwater management facilities
Street-side stormwater management facilities are increasingly common as cities try to find ways to increase local water recharge. These facilities are often planted with vegetation that includes ornamental trees. However, little is known about the survival, growth, and health of the trees. This is particularly true in northern California, where the success of ornamental trees planted in these small facilities has not been evaluated. Using sites throughout the San Francisco Bay Area, researchers evaluated tree survival, growth, and condition. The results were compared to the success of trees in Portland, Oregon, which has a longer history of monitoring trees in stormwater facilities. The study resulted in a standardized monitoring protocol for trees in stormwater management facilities that can be used by cities that are installing their own facilities.
Environmental Horticulture Advisor, Cooperative Extension San Mateo-San Francisco Counties
University of California, Division of Agriculture and Natural Resources
Street-side stormwater infiltration basins planted with vegetation that often includes ornamental trees are becoming increasingly common in cities. While their effectiveness in managing stormwater has been well documented, very little is known about the performance of trees – survival, growth, and health – planted therein.
This project evaluated tree survival, growth, and condition in stormwater management facilities over a period of two years with street trees of the same species and comparable age used as controls. We used the city of Portland, Oregon, which has more than 10 years of experience monitoring trees in stormwater facilities, as a long-term comparison for three cities in the San Francisco Bay Area (San Francisco, San Jose, and El Cerrito).
The study results were used to construct a standardized monitoring protocol for trees in stormwater facilities that can be used by cities that are installing their own management facilities. The protocol was informed by the study results as well as the suggestions from partner cities, and included instructions, data collection templates and calculation sheets, as well as a discussion of lessons learned in the study.
Trees planted in a street-side stormwater facilities. Intentionally located out of the central, deepest, part of the facilities, the trees are nevertheless potentially exposed to difficult soil conditions which may result in early their mortality, and thus diminish the overall performance of the facility. (all photos Igor Lacan)