Cities with little vacant land and high growth rates draw their UGBs farther from the city limits, thus creating large areas of urbanizable land. Once the amount of land to be included in the UGB has been determined, the city and the adjoining county must decide which areas should be put inside the boundary. A UGB typically creates an urban growth area that encircles the city. But since much of that land may be annexed to the city someday, it is important for the city and county to work together in planning and zoning that area. Usually, the urban growth area is subject to the city's comprehensive plan, but the county controls zoning and land use permits there until the area is annexed or becomes developed to urban standards.
Interim controls are necessary to prevent haphazard, premature development.
Urban growth boundaries can be modified. The requirements from Goal 2 call for a review of alternatives. Oregon's 15 years of experience have shown urban growth boundaries to be highly effective. UGBs have helped to hold down the costs of public services and facilities. They have saved a great deal of farmland from urban sprawl.