Compact development cuts water runoff
Compact development is the best for protecting watersheds because it reduces per capita runoff, according to this graph from the Crabtree Group. Most stormwater narratives state that density is bad because the increased runoff is only considered on a per-acre basis instead of both per-acre and per-capita, notes civil engineer Paul Crabtree. Often this results in regulations at odds with best management practice (BMP). Density itself is an important consideration in stormwater BMP, he says.
An article by Laurence Aurbach on Pedshed explain this more fully: "Well-intentioned stormwater standards and regulations can put compact urban development at a disadvantage. They may have the unintended consequence of promoting sprawl, which hurts watersheds more than compact development."
The graph is based on a 2006 EPA report, Protecting Water Resources with Higher Density Development, written by then-EPA staffer and current CNU president and CEO Lynn Richards, and research by John Jacob of the Texas Sea Grant program.