Rainwater Harvesting for Drylands and Beyond by Brad Lancaster

Tucson, Arizona, Green Streets Policy

The Tucson Green Streets Policy requires new and reconstructed roadways be designed to harvest the first 1/2 inch (13 mm) of rainfall in order to grow streetside and median vegetation. The policy is technically the Tucson Department of Transportation’s “Active Practice Guidelines.”

This is a dramatic 180º shift in how our streets and adjoining rights-of-ways are designed and built. In the past, lifeless grey infrastructure of asphalt and concrete drained nearly 100% of the rainfall, while generating higher summer temperatures due to the heat-island effect from all the exposed hardscape. Now living green infrastructure is being built and planted along and within the streets to harvest and reinvest nearly all the rainfall and street runoff from a typical storm to generate and grow living air conditioners and water/air/soil filters of beautiful, shading vegetation. Note: The next time this policy is reviewed, I’d like to see if it would be possible to revise the Performance Goal (under section D) which states that “Green Infrastructure basins are designed to accept a maximum final pooling depth of 8 inches,” to allow for deeper, higher-capacity pooling depths to increase capacity.

A related policy is an ordinance requiring commercial landscapes to provide at least 50% of their landscape irrigation needs with rainwater harvested on site.

For a Tucson, AZ, study looking at the cost-to-benefit ratio of retrofitting existing infrastructure with green infrastructure, see Solving Flooding Challenges with Green Stormwater Infrastructure in the Airport Wash Area. This study utilizes a Holistic Cost Benefit analysis to assess a full range of benefits that would be achieved with a Green Stormwater Infrastructure (GSI) retrofit of residential properties, rights-of-way (ROW), and streets, as well as commercial properties, schools, churches, other community nodes, and their associated parking lots within three built-out watersheds in the south of Tucson. Results from modeling show GSI can have a significant impact on both large and small storm events. GSI resulted in reducing the 100-year 3-hour event peaks in the three watersheds by 24%, 19% and 10%. GSI implemented throughout these watersheds in the 25-year scenario of the study would result in over $2.5 million dollars of annual community benefits as a result of flood reductions, water conservation, property value increases, reduced urban heat island impacts, improved stormwater quality, reduced heating and cooling needs, air quality improvements, and the energy associated with pumping CAP water and groundwater in Tucson. Residential rain gardens, curb-cut rain gardens, and Green Street features have benefit/cost ratios greater than 1 showing that benefits outweigh the costs by 4.4, 2.7, and 2.1 for those features respectively.

Drops in a Bucket Blog

 »Read all blog posts...

Sign up for the Newsletter

Upcoming Events

  1. 2021 Rocky Mountain Natural Building Conference

    October 14 - October 16
  2. Water Harvesting Design Certification: Fall 2021

    November 8 - November 20
  3. Water Harvesting Design Certification: Spring 2020

    February 28, 2022 - March 12, 2022

Umbrella Newsletter

The Umbrella: Summer 2020

THE UMBRELLA: A catch-all of resources, events, media, and more from Brad Lancaster In this time of Covid-19 and spending more time at home to be safe, I’ve been grateful for the solace, inspiration, and bountiful sustenance my water-harvesting gardens, landscape, and neighborhood forest has provided me, my family, friends, and neighbors. Record summer heat […]

 »Read all newsletters...

Like what this website offers?

Donations are greatly appreciated as they enable us to continuously update this expansive resource and generate new content. Thanks!