Land-use analysis quantifies striking differences in two states’ approach to growth
Portland, Oregon – If Portland’s Metro region had grown like Clark County in the 1990s, development would have overtaken an additional 14 square miles of farmland and open space. That’s one finding of an analysis released today by Seattle-based research center Sightline Institute (formerly Northwest Environment Watch) . Titled “Sprawl and Smart Growth in Metropolitan Portland,” it finds that while greater Portland’s three Oregon counties “grew smarter,” encouraging compact, efficient communities, neighboring Clark County sprawled—and lost more rural land and open space per new resident, as a result.
“Few areas in North America provide such a stark illustration of different approaches to planning,” says Sightline research director Clark Williams-Derry, who will be presenting the research to Portland’s Metro Council today. “And with a measure on Oregon’s May 21 primary ballot designed to weaken Portland’s growth management—making it more like Clark County’s—the comparison is especially interesting.”
The study used satellite imagery of open space, farmland, and pavement, plus digital mapping of US Census data to track growth during the 1990s, in Multnomah, Washington, and Clackamas Counties, Oregon, and in Clark County, Washington. (See maps at www.sightline.org/press/portland_sprawl.html.) Findings include:
- In the 1990s, greater Portland’s total population grew at a faster pace than many developing-world megacities, such as Cairo, Egypt, and Jakarta, Indonesia.
- In the Oregon counties, total population increased by 270,000, and the number of people living in compact, transit-oriented neighborhoods (defined as 12 or more people per acre) increased by 141,000. By 2000, 28 percent of residents in the three-county region lived in compact neighborhoods.
- In contrast, Clark County sprawled, Seattle-style. The population grew by 106,000, and the number of residents of low-density, car-dependent areas (defined as less than 12 people per acre) increased by 78,000. By 2000, only 13 percent of Clark County’s residents lived in compact communities.
- Per capita, Clark County converted about 40 percent more land from rural to suburban population densities than did the Oregon counties. If the Oregon counties had grown in a pattern similar to that of Clark County, suburban development would have overtaken an extra 14 square miles of farmland and open space.
- Person for person, Clark County’s sprawling residential development fully or partially covers 23 percent more land with pavement, rooftops, and other human-made “impervious” surfaces—which are harmful to streams and salmon—than Oregon’s more compact residential neighborhoods.
Sightline’s analysis also looked at the relationship between traffic congestion and density, and found that although population growth increases traffic congestion, neighborhood density has less effect than total metropolitan population. “In fact,” says Williams-Derry, “compact urban designs may slightly decrease the number of hours we lose to traffic jams.”
Clark Williams-Derry and Sightline executive director Alan Durning will present “Sprawl and Smart Growth in Metropolitan Portland” to Portland’s Metro Council on Thursday, May 9, at 2 pm. Sightline Institute (formerly Northwest Environment Watch) is a Seattle-based nonprofit research and communication center. A full copy of the report and maps is available at www.sightline.org.