Monthly Archives: January 2018

News

NEW STUDY: Design Strategies for Maximizing Stormwater Capacity of Urban Tree Pits

January 25, 2018

Sustainable Healthy City researchers Patricia Culligan and Robert Elliott of Columbia University have co-authored a new study  looking at design and management strategies to maximize the stormwater management capacity of tree pits. See coverage of the study as published by Columbia News below. Read the full  study in the journal Ecological Engineering.

Credit: GraphicStock 

So Much Depends on a Tree Guard

January 23, 2018
In a big city, trees, like people, like their space. In a new study, researchers at Columbia University found that street trees protected by guards that stopped passersby from trampling the surrounding soil absorbed runoff water more quickly than trees in unprotected pits. The results are published online in the journal Ecological Engineering.
Comparing the infiltration rate of street trees with and without guards in Manhattan’s Morningside Heights neighborhood, the researchers found that trees in protected pits absorbed water six times faster on average than tree pits without guards —3 millimeters versus .5 millimeters per minute. The researchers hypothesize that the guards improve infiltration by limiting soil compaction in tree pits.

“Placing guards around tree pits allows urban trees to absorb more storm water runoff, taking pressure off the city sewer system,” said the study’s senior author, Patricia Culligan, a professor at Columbia Engineering and a member of Columbia’s Earth Institute and Data Science Institute.

The researchers were surprised at what a difference the guards made, and how little mulch or additional vegetation improved results. City-recommended tree guards cost about $1,000, depending on their style and size of the tree pit, but an improvised $20 fence can work just as well, said the study’s lead author Robert Elliott, a recent graduate of Columbia Engineering and cofounder of Urban Leaf, a New York City startup helping city dwellers grow food at home.

“Only 14 percent of New York City trees have protective guards,” he said. “Our results suggest street trees could manage six times as much storm water if every tree pit were enclosed,” he said.

New York’s 660,000 trees cover about 6 percent of the city. Besides cleaning and cooling the air, trees benefit the city by soaking up rainwater that runs off its impervious roads and buildings. During heavy storms, the aging network of sewers is unable to keep up with the combined flow of wastewater from streets and homes. As a result, heavy flows are often released directly into nearby rivers, raw sewage and all. To reduce these combined sewer overflows the city has turned to ‘green infrastructure,’ or engineering solutions that harness trees and other vegetation to drain the built landscape.

The push has spurred a related effort to measure the cost-effectiveness of each solution. In a related unpublished study, Elliott and his colleagues compared the relative costs and benefits of guarded tree pits to bioswales, which are pits dug into city sidewalks and planted with shrubs to serve as catch basins. They found that bioswales substantially outperformed guarded tree-pits when factoring in their initial cost plus maintenance over 10 years; Bioswales captured 141,886 gallons of water per year, at 20 cents per gallon, compared to a guarded tree pit’s extra 1,132 gallons per year, at 49 cents per gallon.

But trees become more competitive, says Elliott, if the cost of guards is reduced or water flows are increased by digging out the tree pit’s curb so water from the street can flow in (much like a bioswale. Trees also tend to attract less controversy, he points out. Residents have complained that some of the 3,000 bioswales New York City has installed in the last five years in Brooklyn, Queens and the Bronx are ugly.

The study’s other authors are Elizabeth Adkins, a graduate of Columbia Engineering, and Matthew Palmer, a professor in Columbia’s Department of Ecology, Evolution, and Environmental Biology.

Study: Stormwater infiltration capacity of street tree pits: Quantifying the influence of different design and management strategies in New York City

—Kim Martineau


News

COMMENTARY: Six Principles for Energy Innovation

January 25, 2018

Sustainable Healthy Cities researcher Gabe Chan has co-authored a commentary piece about key principles of energy innovation in the journal Nature. An excerpt of the commentary as published by the Humphrey School of Public Affairs is below. Read the full commentary from Nature.

Renewable energy infrastructure, unidentified location. Credit: Kenueone

December 6, 2017—

Last month, the European Union marked the tenth year of its Strategic Energy Technology Plan. It is one of many policy initiatives worldwide to accelerate innovation in energy technologies to reduce greenhouse gas emissions. As the window of opportunity to avert dangerous climate change closes, we urgently need to take stock of these initiatives—what works and why?

Public investments in energy research, development, and demonstration (RD&D) have risen since the low levels of the mid-1990s and early 2000s. In 2016, member countries of the Organisation for Economic Co-operation and Development spent US$16.6 billion on energy RD&D, compared with $10 billion in 2000 (adjusted for purchasing power parity). In October, the United Kingdom set out its Clean Growth Strategy to invest more than £2.5 billion ($3.3 billion) in low-carbon innovation between 2015 and 2021. In 2015, the EU and 22 nations pledged to double their investment in energy RD&D under the Mission Innovation adjunct to the Paris climate agreement. However, the overall goal might be out of reach given the proposed 35% cut in President Donald Trump’s 2018 budget for energy RD&D.

Different nations are pursuing various strategies and creating new types of institution. For example, the Advanced Research Projects Agency-Energy (ARPA-E) run by the US Department of Energy (DOE) targets grants at key technologies such as affordable energy storage. The DOE Energy Innovation Hubs form research teams to work on technologies such as nuclear reactor modelling.

The United Kingdom has set up the Energy Technologies Institute (ETI), a public–private partnership to accelerate the development of low-carbon technologies. It also launched the Catapult programme, which aims to build bridges between universities and industry, and sustainability advisory services that are run by bodies such as the Carbon Trust. And China is reforming the Chinese Academy of Sciences and its national labs, as well as creating larger lab facilities.

At the international level, the United Nations Framework Convention on Climate Change (UNFCCC) Technology Mechanism enables technology development and transfer in developing countries to support the Paris agreement. Since 2013, the World Bank Group has opened seven climate-innovation centres in developing countries such as Kenya. The centres provide seed financing, policy guidance, networking and technical training. The Nairobi centre, for example, advises startups such as Futurepump, which is developing solar-powered water pumps.

Most of these bodies can claim successes. But a comprehensive global assessment of energy innovation programs is needed to learn from collective experience and to establish best practices. As a starting point, we recommend six principles to guide public initiatives for energy innovation.

Gabe Chan is an assistant professor at the University of Minnesota’s Humphrey School of Public Affairs. He is an affiliated faculty researcher with the Sustainable Healthy Cities Network.