COS 226-2 - Anticipating the impacts of urban infill shadows on existing flora using modeling and snapshot site visits

Wednesday, August 9, 2023

3:45 PM – 4:00 PM PDT

Location: E146

Presenting Author(s)

KF

Kelly Farrell

Landscape Designer/Ecologist
Sasaki
Burlington, Vermont, United States

Coauthor(s)

MM

Meredith McCarthy

Architect
Sasaki
Boston, Massachusetts, United States
SP

Scott Penman

Design Technologist
Sasaki
Boston, Massachusetts, United States
HW

Helen Wu

Architectural Designer
Sasaki
Boston, Massachusetts, United States
XG

Xinduo Guo

Interior Designer
Sasaki
Boston, Massachusetts, United States
AS

Andrew Sell

Landscape Architect/Ecologist
Sasaki
Boston, Massachusetts, United States

Abstract: Infilling and densifying urban cores is often suggested as a means towards combating sprawl, concentrating amenity needs, and promoting public transit and other measures that are essential for preserving open space and mitigating climate change. Yet there are few studies that directly address the potential impacts of infilling and new building development on the health of plants and the urban tree canopy. When tasked with studying the shadow impacts of a new urban development on a beloved historic park in Boston, Sasaki needed to understand not only where new buildings would extend shadows, but for how long, during what times of year, and what the potential impacts on the existing landscape might be, with the goal of positioning and massing the buildings in a way that minimized new shadow impacts. Because development decisions typically occur over a shorter timescale than a traditional ecological study would require, we needed to creatively pair detailed digital modeling of new shadows with site visits to determine whether there would be negative impacts to the existing flora.

After iteratively adjusting building massing and position, the majority of new shadow cast on existing greenspace will last for under 90 minutes on the vernal equinox, with several small areas receiving up to 120 minutes of new shadow. As the season progresses, new shadows decrease in both extent and duration. Initial shadow modeling of the proposed buildings and surrounding urban fabric identified several nearby areas of the park that already receive the amount of shadow that the new buildings are projected to cast. This is allowing us an opportunity to compare flora, phenology, and walking path conditions between areas that currently receive a baseline amount of shadow to an area that receives the projected amount of shadow. Initial site visits do not reveal substantial differences in flora composition or health. Ongoing observations will reveal whether the areas’ mature trees and existing understory display different phenology. Based on observed species composition and the timing of the shadows, the design team does not anticipate substantial negative impacts to existing flora. While this is only a snapshot of shadow impacts on an urban greenspace, it reflects the abbreviated data-gathering needs, and value of extensive digital modeling, that is required to anticipate impacts in a fast-paced industry.