Inventory and Analysis
Domain 2 - Inventory and Analysis. This section tests whether you can collect the right site data, read it correctly, and convert it into constraints that drive design - rather than dumping data onto an analysis sheet.
Inventory layers
- Topography: contour interval and horizontal distance give slope as rise ÷ run × 100. Hachured contours mark depressions.
- Soils: NRCS/SSURGO mapping gives permeability, depth to seasonal high water, shrink-swell potential, and bearing capacity; it is a screening tool, not a substitute for borings.
- Hydrology: watershed boundaries, FEMA flood zones (A = approximate, AE = base flood elevation published, X = minimal hazard), and wetland limits with their regulatory buffers.
- Climate and microclimate: sun angles, prevailing winter and summer winds, frost depth, and heat-island exposure.
- Cultural resources: historic districts and Section 106 review when a federal agency funds, permits, or licenses the project.
Regulatory constraints
- Zoning sets setbacks, lot coverage, height, floor-area ratio, parking minimums or maximums, and buffers.
- Clean Water Act §404 permits govern dredge or fill in waters of the United States, which can include wetlands.
- Endangered species consultation, state tree ordinances, and local stream buffers often control more area than the zoning code.
Analysis technique
Overlay suitability mapping: rate each resource, then stack the layers. The output is a constraint map - buildable, restricted, and conserved zones - not a design. Design begins after that composite exists.
Worked example
Two contours with a 2-ft interval sit 0.75 in apart on a drawing at 1 in = 20 ft. Run = 0.75 × 20 = 15 ft. Slope = 2 ÷ 15 = 0.133, or 13.3%. That exceeds the 5% maximum running slope for an accessible route and the practical limit for most turf, so the path must switchback, cut, or be built as a boardwalk or ramp.
Traps
- Reading contour labels downhill instead of uphill, or missing depression hachures.
- Treating a wetland boundary as a design line rather than a regulated line with a buffer.
- Using county soil mapping as if it were site-specific geotechnical data.
- Forgetting that a view is an inventory item the design itself can destroy.