Modeling Urban Growth in the Treasure Valley, Idaho

The future of farmland, forests and wetlands in the Treasure Valley depend directly on how much population grows, as well as the decisions made about housing density. We projected urban growth from 2011 to 2100 based on nine different scenarios of population growth and population density.

Most residents of the Treasure Valley in Southwestern Idaho, home of the state capital of Boise, will not be surprised to learn that urban development is rapidly encroaching on agricultural land, wetlands and forested areas.

The Treasure Valley has undergone episodic periods of rapid population growth since the late 19th century.

What we have not understood very well is the rate at which these changes have been happening, and the rate at which they might continue to happen into the future. To explore the possible impacts from urban expansion, we developed a model to predict the extent of urban expansion in the Treasure Valley based on different scenarios of population growth and population density. The scenarios aim to capture and graphically represent the range of possibilities decision makers may face. 

Our projections demonstrate that both the rate of population growth, and the population density has important implications for the future of agricultural land. For example, our “Business as Usual” scenario assumes a population of 1.5 million in 2100, and assumes that population density remains the same as it was in 2011. In this scenario, urban land will increase by 220,000 acres by 2100, including a 190,000 acre loss of agricultural lands. By comparison, if population density increases over time, for example by smart growth strategies, urban land would grow by only 140,000 acres, including a loss of 110,000 acres of agricultural land. In our population growth scenarios, we found that if population grows to 1.75 million instead of 1.5 million at the current (2011) population density, urban land will increase by 280,000 acres, including 240,000 acres of agricultural land. 

Our maps show land use in 2100 based on different scenarios of population growth and population density. 

The local landscape in the Treasure Valley will be greatly influenced by how much population grows, as well as the decisions made about housing density. This envisioning exercise gives important insights about potential future development patterns and should be considered when planning for the future.

Please click here to find the White Paper which explains our results in more detail.

Please click here to find the Story Map about future urban growth in the Treasure Valley.

Please click here to go to where the full dataset of urban growth projections can be downloaded.

HES Researchers

Other Research Collaborators

Christian Sprague, Boise State University
Ana Costa, Boise State University

Products

McSherry, L., Narducci, J., Sprague, C., Costa, A., Brandt, J., Fragkias, M., Schneider, J., Benner, S. 2017. Urban Growth in Treasure Valley Idaho. Retrieved from http://arcg.is/1DC08f

Sprague, Christian; Fragkias, Michail; Narducci, Jenna; Brandt, Jodi; Schneider, Jen; Moroney, Jillian; and Benner, Shawn G.. (2017). Raster Data, Figures and White Paper for Projecting Urban Expansion in the Treasure Valley (Idaho) to Year 2100 Under Different Scenarios of Population Growth and Housing Density [Data set]. Retrieved from https://doi.org/10.18122/B20693

Narducci, J., Sprague, C., Brandt, J., Schneider, J., Moroney, J., Fragkias, M., & Benner, S. (2017). Projecting Urban Expansion in the Treasure Valley to 2100. Boise, ID: Boise State University.

Funding Sources