Run Buildable Area Analysis

This page walks through the steps to run the Buildable Area Analysis on all parcels on a project.

The Buildable Area Analysis can only be run on parcels/site boundaries that have been saved to a project. Don't have parcels saved to the project yet? Add them via one of these methods first.

Open the Buildable Area Analysis Task

  • From a project, go to the Parcels tab

  • Click the 'See Actions' button

  • Click 'Project Tasks'

  • Select 'Project Buildable Area Analysis'

This will bring up the Buildable Area Analysis form.

Fill in Buildable Area Analysis form

In the Buildable Area Analysis form, turn on the desired layers for analysis, input hazard parameters (e.g. max slope %), and customize setbacks.

No layers are required so skip any that don't apply to the site.

Setback

The first field in the form applies a general setback around the internal property boundary and around any identified hazards.

  • Input a general property boundary and hazard setback (ft.)

    • While the general setback can vary by municipality and project type, it's pretty common to apply a setback of about 25-50 ft.

If this setback value doesn't apply for all hazards, you can override the setback in any of the layer specific settings as shown below.

Slope

Analyze slope on a parcel and mark areas with high slope as hazards/not buildable.

  • Toggle on Slope setting

  • Input a max slope %. Anything above that slope % will be marked as not being buildable.

    • 10% is a fairly common cutoff point (check with your engineering team if unsure).

  • Input a slope setback (ft.) (if nothing input, it will defer to the general setback at the top of the form).

    • Add a 0 ft. setback if no setback desired around high slope areas.

Flood

This setting will analyze any known 100-year and 500-year flood zones on the property.

  • Toggle on Flood setting

  • Input desired setback (ft.) for each flood zone.

    • ~50 ft. is fairly common for both but check with permitting/engineering team if unsure.

Sometimes the 500-year flood zone is still buildable; if that is the case, uncheck the checkbox on the right-side of the form. This will display the 500-year flood zone on the constraint map but will still keep it marked as buildable.

Wetlands

This will analyze any NWI wetlands on the property and mark them as wetlands hazards.

  • Toggle on Wetlands setting

  • Input desired setback (ft.) around wetlands

Trees

If the project is in an area where land with heavy tree cover is still usable, then leave this setting OFF. If the project is in an area where land with heavy tree cover is not usable for siting, then turn this setting ON.

Land with significant tree cover will be marked as not buildable due to tree hazards. This step analyzes 30mx30m tiles for tree cover density of each tile. Only tiles within a parcel that exceed the tree density % (as set below) will be marked as not buildable due to tree cover.

  • Toggle on Trees setting

  • Adjust tree density threshold, if desired

  • Input desired setback (ft.) around trees

Soil Bedrock

Skip this setting if bedrock depth is not a concern for the area. The bedrock layer used for this analysis has limited coverage in some parts of the U.S. (turn on the bedrock layer in the Layers Menu to see layer coverage).

Land with shallow bedrock will be marked as not buildable due to bedrock hazards.

  • Toggle on Bedrock setting

  • Input minimum bedrock depth (ft.)

  • Input desired setback (ft.) around bedrock

Infrastructure

Mark buildings, public roads, railways, and airport runways as hazards and apply custom setbacks around each category.

  • Toggle on Infrastructure setting

  • Input desired setbacks (ft.) around each infrastructure type

(Optional) Buildable area settings

Scroll up to the top of the form to access the 2nd tab and customize the buildable area requirements.

Use these settings to help get a more realistic final calculated buildable acreage / constraint map by filtering out sections of a parcel marked as 'buildable' that are too small (acreage-wise) to be practical for siting.

Ex.: If a 1 acre section of a parcel was not in a hazard or a setback, then it would technically be marked as being 'buildable', but in practice, if that buildable area is not connected to a larger buildable section, it shouldn't count towards the total buildable acreage.

Min Size Buildable Area

  • Input minimum buildable acreage size (acres)

    • Depending on the size of the parcels on the project, it's best to set this much LOWER than the total desired acreage. Goal is to remove no-brainer sections that are too small -- not over-automate out sections that would still be usable.

    • Start with 2-3 acres for projects with smaller parcels; for projects with larger parcels, try starting with 5-10 acres.

Sliver Removal

Long skinny sections of buildable area (slivers) are often not a good fit for siting projects. Remove these 'slivers' of buildable area to get a more accurate final buildable acreage calculation.

  • Choose sliver removal setting level:

    • Regular - uses 40 m. in diameter circle to check for sliver width; anywhere that the circle doesn't fit will be marked as too small to be buildable)

    • Aggressive - uses 40 m. in diameter circle to check for sliver width; anywhere that the circle doesn't fit will be marked as too small to be buildable)

Run the task

Once desired inputs and settings have been configured, hit 'Run' at the bottom of the Buildable Area Analysis form to start running the analysis.

In the background, each of the layers will be reviewed, hazards analyzed, setbacks added and buildable area calculations run.

Track the progress of the buildable area analysis in the notifications on the project window:

No need to keep the project up while you're waiting for the analysis to finish processing! This task runs in the background even if you close the project window. Turn on the constraint maps when you reload the project: Map toolbar > Drawings > Load all drawings.

On the project map, the parcel constraint maps will load in as they complete.