Alternative scenarios depict the trade-offs among different planning decisions, but clearly communicating those tradeoffs to the community can be challenging. Scenario modeling tools can help citizens understand the outcomes and consequences of the strategies embodied in each scenario.
There are a variety of modeling tools that can be used when developing and evaluating alternate scenarios. Examples include: IMPACS, INDEX, CommunityViz, iPlaces, and ET+. To illustrate how land use modeling tools works, this section focuses on how ET+ can be used to create and measure impacts of alternate scenarios. Using ET+, alternative scenarios are developed, refined, and then compared and evaluated based on their indicator performances. Indicators enable Envision Tomorrow users to tie the scenario results to the community values and guiding principles.
Calibrate a range of building types (i.e. residential, mixed use, commercial) so they are financially feasible at the local level. The ET+ analysis process starts at the building level; therefore, anything that's known about a building can be tested in a scenario. In ET+, building-level data includes information on things like density, design, rents, sales prices, affordability, parking requirements, redevelopment opportunities, fiscal impacts, and energy and water use, so any of these measures can also be understood at a scenario level. The model enables planners to explore current or potential land-use regulations in relation to development feasibility and test the impact of various assumptions, ranging from parking standards, height requirements, construction costs, rents and subsidies to see what "pencils." The user can assess, for example, how preferred forms of development, such as mixed-use retail with housing above, might become more financially feasible.
Once a library of building types is calibrated, the building types can be plugged into the "scenario spreadsheet," where they can be combined to design different development types—combinations of buildings that work together to a create a place (i.e. a town center, main street, urban retail center, etc.).
The "scenario builder" adds scenario building functionality to ArcGIS. Once building types and development types are created, one can use the scenario builder to "paint the landscape" by allocating different building and development types areas across the study area to illustrate alternate scenarios. The tool allows real-time evaluation of each scenario's impacts on things like land-use-related issues.
ET+ provides a variety of indicators that can be used to evaluate scenarios to determine how they measure up to the community's values. Air quality, traffic congestion, housing mix, sensitive lands preservation, and access to recreation are all examples of indicators.
A Closer Look: Salt Lake City Depot District Scenario Evaluations
After developing alternate scenarios in the Depot District, ET+ was used to model the scenarios and evaluate the benefits and impacts of alternate scenario elements.
Scenario A: WORK/Live/Play
- Mid-rise office and R&D
- Service focus: restaurants, daycare, etc.
- Residential focused near Gateway
- Pocket parks
- Professional, working age
- Higher education
- 1500 Households
- 5400 Jobs
Scenario B: PLAY/Live/Play
- Fine-grained scale
- Arts and entertainment
- Plazas and public art
- Young adults
- 1600 Households
- 2600 Jobs
Scenario B: LIVE/Live/Play
- Residential throughout
- Neighborhood: housing, services, grocery, school
- Office/residential mix on major streets
- Playgrounds and playfields
- Family friendly in an urban way
- 2600 Households
- 2800 Jobs
National Spotlight: The Sustainable Places Project
The Sustainable Places Project is focused on the Austin-Round Rock-San Marcos five-county MSA, a region that, while experiencing ongoing economic success, must also face trends that could threaten this success as it becomes less attractive to employers interested in quality of place for their workforce. The region is adding over 60,000 new residents annually, housing affordability is decreasing, and traffic congestion is worsening. The city must change how this growth is planned for in order to beneficially impact these regional trends. Alternate scenarios were developed incorporating public input and helped demonstrate that sustainable activity center growth will benefit these communities and the entire region. Five cities were selected as "demonstration sites" and Envision Tomorrow+ (ET+) is being used to identify the long-term effects of the various scenarios on municipal budgets and the health of communities. This analysis to will also develop plans that align housing, jobs, and transportation options in a way that complements existing community values.