Trees and Hydrology in Urban Landscapes

Effective implementation of urban greening strategies is needed to address legacies of landscape change and environmental degradation, ongoing development pressures, and the urgency of the climate crisis. With limited space and resources, these challenges will not be met through single-issue or individual-sector management and planning. Increasingly, local governments, regulatory agencies, and other urban planning organizations in the San Francisco Bay Area are expanding upon the holistic, portfolio-based, and multi-benefit approaches.

This effort, presented in the Trees and Hydrology in Urban Landscapes report, seeks to build links between stormwater management and urban ecological improvements by evaluating how complementary urban greening activities, including green stormwater infrastructure (GSI) and urban tree canopy, can be integrated and improved to reduce runoff and contaminant loads in stormwater systems. This work expands the capacity for evaluating engineered GSI and non-engineered urban greening within a modeling and analysis framework, with a primary focus on evaluating the hydrologic benefit of urban trees. Insights can inform stormwater management policy and planning. 

A central component of this effort was advancing the GreenPlan-IT toolkit, a modeling and optimization framework for analysis of GSI, such that it could represent hydrologic processes within the tree canopy. To explore the role of trees in stormwater runoff, several test case sensitivity analyses were conducted. A demonstration analysis was performed for the City of Sunnyvale to assess the degree to which trees at the landscape scale affect city-wide runoff. Lastly, the report outlines a potential technical approach for expanded integrated multi-benefit assessment of urban greening.

View and download the report