Section 2 - Inventory and Analysis
Section 2 - Inventory and Analysis
Section 2 tests how you gather, verify, and interpret site data into a defensible analysis - physical, biological, cultural, and regulatory - that drives design decisions.
Sources and what they can support
- USGS topographic quadrangle: contour interval, datum, scale, and photo date. It is a screening tool, not a survey.
- NRCS Web Soil Survey: map units, hydric soils, depth to seasonal high water table, permeability, plasticity index, and bearing capacity. It never substitutes for borings or infiltration testing.
- FEMA FIRM: distinguish the floodway (no-rise, severely limited development) from the 1% annual-chance floodplain and base flood elevation.
- Regulatory overlays: zoning setbacks, lot coverage, FAR, easements, deed restrictions, USACE jurisdiction under Section 404, state wetland rules, and Section 106 cultural review.
Analysis techniques
- Overlay mapping and GIS suitability models weight each resource layer and expose conflicts.
- Slope analysis bins terrain by percent slope (rise ÷ run × 100); aspect and sun/shade mapping drive planting and comfort decisions.
- Viewshed, noise, wind, and circulation diagrams convert raw inventory into opportunities and constraints.
Worked example
Two 2-ft contours measure 25 ft apart on the map. Slope = 2 ft ÷ 25 ft × 100 = 8%. The run is horizontal map distance, so elevation change is never added to it. An 8% band is walkable but marginal for active lawn; it favors terraced seating or stormwater benches. Confirm with a field check before committing the program to that band.
Traps
- Confusing floodway with floodplain.
- Treating a county soil survey as site-specific geotechnical data.
- Counting easement area as buildable.
- Ignoring off-site drainage and upstream contributors.