The unplanned addition of a large number of high-rise buildings in a relatively small area, leading to problems with traffic, parking, and infrastructure.
Using an aerial image of the so-called “vertical sprawl,” high-rise contemporary apartments of Shanghai as an example, Dittmar explored the negative trend of standardizing and effectively de-humanizing urban dwellings — lessening culture and quality of life.
—Caitlin Schudalla, “Conference at OU examines national living solutions,” The Norman Transcript, April 4, 2013
The proposed complex would bolster the entertainment district’s cultural landscape, he said, but it also opens the door to a planning dispute on the proposed 80-storey height of the condo towers.
This phrase is based on its horizontal cousin, urban sprawl, which the OED defines, tidily, as "the uncontrolled expansion of an urban area into the surrounding countryside," and traces back to 1934. Variations on the theme are suburban sprawl (1938) and, simply, sprawl (1955).