Scenario Building

3-4 weeks

Visualise and project how the situation of the municipality may change in the future under certain scenarios.

  • Definition of the baseline, optimal and strategic scenarios

  • Projection of variables describing the city according to the identified scenarios, including population, urban expansion, equipment and required public space


This activity contains qualitative and quantitative tools that allow the description and calculation of future scenario (that might include desirable and undesirable situations) analyse their impacts on the territory and thus clarify and anticipate possible futures. Scenarios should be defined on the basis of a time horizon. They can also be calculated on the basis of short-, medium - and long - term projections. 

Scenarios can include the baseline or "as usual", the optimal, and the strategic. The first assumes that existing trajectories will not change in the future and conditions will be extrapolated from what is currently and has been happening in the past. It is important that this scenario is considered because it allows to visualise and identify what would happen if no action is taken in the urban development of the city, map any undesirable conditions, and plan to avoid them. The optimal scenario is the one where all strategic variables are considered to reach the best possible status, but which will not necessarily be feasible or achievable. The strategic scenario is the desirable scenario and considers what is realistic under current conditions. This scenario should be aligned with the vision and objectives that will be set out in the next activity. 

To build the scenarios, some assumptions need to be first established, defining what are the minimum conditions needed for each "as usual", optimal and strategic scenario to develop. To do this, review the narratives of each of the scenarios developed previously (T25 Scenario Building Narratives). Then, there needs to be a selection of variables that will be studied under each scenario. These can vary and depend on the scope of the planning process but need to be linked to sustainable development, such as population growth, urban expansion projections, requirements for public space and urban services, etc. After the variables are selected, they need to be calculated for each of the scenarios.

To calculate population growth and urban footprint, the team can use T19 Urban Expansion Projection. This uses population census data to first estimate projections in a defined timeframe. Then, the required urban land area to fit that population growth is calculated, according to different density scenarios that correspond to the scale and current development of the city. Density averages by type of single-family or multi-family housing should be considered, as well as ensuring that the growth rate of the urban footprint (area that the city expands) is aligned to the projected population growth.

Additionally, the T43 Facilities and Public Space Projections can be used to estimate the deficit and current coverage of each type of facility (healthcare, education, commercial, sports, cultural, etc.), as well as to determine the number of units of each type needed to cover, as the case may be, the current unmet demand and the future demand based on projections. The analysis should be carried out with special attention to the demand for facilities according to the scale of the city and its population. The tool also allows to calculate and compare the necessary public space surface and the current and future coverage, according to national ratios and international recommendations. It is important to clarify that this calculation is done on an aggregated basis for the whole city, and it is necessary to analyse the distribution of existing and future public facilities and spaces. In order to do so, the scenario building can be complemented with spatial analysis to evaluate which areas of the city lack accesibility to these facilities, defining buffers that correspond to walking distances (e.g. accessibility in 5, 10, 15 minutes), according to the scale of the city and the capacity of facilities. These analysis could be taken from Block D Analysis and Diagnosis.

Finally, it is recommended to estimate the provision of public services such as water demand, electricity consumption, sanitation services, solid waste management, road network infrastructure, etc. in order to know the demand for each type of service, and to establish a basis for the strategies to propose the amount of primary infrastructure or public investments required.


1. Define the timeframe for the scenarios.

2. Identify the assumptions for each of the scenarios: baseline / "as usual", optimistic, strategic. This can be done by reviewing the different narratives and then identifying key assumptions (T25 Scenario Building Narratives).

3. Define the variables that need to be considered and calculated for each of the scenarios.

4. Calculate the population and urban expansion projections (T19 Urban Expansion Projections).

5. Calculate the rest of the variables, including the requirement for urban facilities and public spaces (T43 Facilities and Public Space Projections) as well as accessibility and provision of public services.