Two phasing approaches are used in combination with urban containment boundaries: intermediate growth boundaries (See, IGBs.) and urban development reserves. Metropolitan Dade County (FL) has a long-term urban growth boundary (UGB) that is designed to meet development needs to about the year 2010. The long term development plans anticipate the need to expand the supply of buildable land into particular areas located within an urban development reserve. This area has sufficient land to accommodate five to ten years’ development when the UGB is filled in. The urban reserves will be managed as to prevent low-density development that could preempt efficient UGB expansion. Case/Example: Metropolitan Dade County (FL) and Metropolitan Portland (OR). Source/Reference: Nelson and Duncan, 1995, pp. 81.