Many communities are learning about the pitfalls of sprawl the hard way. First, they allow low-density development to replace surrounding farmland and natural areas that could have managed floodwater threats and separated people from wildfire and other hazards driven by climate change. Then, as roads, water mains, and sewer lines age, these communities realize that sprawl’s low assessed value per acre cannot pay for the increasingly expensive operation and maintenance of the extensive infrastructure networks needed to serve suburbia and exurbia. That forces them to choose between neglecting repairs, raising taxes, or both.
Boise, Idaho was headed toward this fate but began preserving its foothills decades ago. Then in 2026, this city of 236,000 people banned all further expansion of the city into its foothills and launched changes in its plans and regulations to minimize the potential impact of all development in those parts of the foothills that are already incorporated within the city.
Preservation
After World War Two, the rise in car ownership opened portions of the Boise foothills to residential development. The early indication that this might not be a good idea came in 1959. In July of that year, a wild fire left about 9,000 acres of the foothills vulnerable to erosion. A month later, rain storms generated mudflows that slithered into several Boise neighborhoods.
After this event, there were calls for greater protections but not full-scale preservation. However, a proposal to build hundreds of homes in Hulls Gulch spurred a movement that caught the attention of local leaders and US representatives. Eventually, advocates cobbled together enough money from donations, state sources, and federal grants to buy 289 acres from the developer in 1993 and give the land to the city.
At roughly the same time, local, state, and federal agencies agreed to coordinate planning for the entire foothill area. In 2001, Boise voters approved a ballot measure that dedicated $10 million of property tax revenue to buy hillside land. Within ten years, over 12,000 acres had been preserved at an estimated value of $35 million.
The success of that first ballot measure motivated the voters to approve a second $10 million levy in 2015 for the preservation of habitat and open space, the funding of water improvement projects in the Boise Foothills, along the Boise River, and open space sites throughout the city. A third levy worth $11 million was approved by over 80 percent of Boise voters in 2025 for ongoing preservation of habitat and open space as well as clean water projects and expansion of Boise’s already-outstanding park and pathway network.
Regulation
On January 27, 2026, the Boise City Council approved a resolution establishing a protection policy for the Boise foothills. It begins by recognizing the foothills as an important community resource for habitat, scenic value, and outdoor recreation. But it adds that the city has seen the impact of increased wildfires and that foothill development adds to fuel loads and complicates wildfire response and evacuation efforts. It declares that the car-dependent nature of foothill development exacerbates traffic congestion. The resolution also states that building and maintaining water and sewer facilities in this sloping terrain poses risks to water sources and hillside stability.
The Resolution limits new development in the foothills to land already incorporated into the city. It directs city planning staff to begin amending plans and codes to prohibit further expansion into the foothills and review the city’s current regulations pertaining to hillsides, stormwater drainage, and the wildland urban interface.
Beyond Boise
A growing number of communities are realizing how sprawl leaves cities holding the bag. Homes built at low densities may have higher value per home but the taxable value per acre is generally lower than infill development. The cities inherit the responsibility of operating and maintaining vast networks of roads, sewers, and water mains at costs that increase over time while also being held responsible for protecting poorly-located homes from floods and wildfires as well as having to facilitate reconstruction when disasters strike.
Ideally, more communities will follow Boise’s example and take a second look at the wisdom of continuing to be the victims of sprawl.
Notes
Boise. 2026. Boise Open Space Levy Property Purchases and Projects. Accessed at Boise Open Space Levy Property Purchases and Projects | City of Boise.
Hunt, Kymber. 2015. Development in Boise’s East Foothills and Castle Rock (1950 – 1975). Urban Environmental Boise – A Boise State Environmental Studies Project. Accessed at Development in Boise’s East Foothills and Castle Rock (1950-1975) | Urban Environmental Boise.
