Terrain & Relative Elevation Assessment (Screening)

Objective

Determine whether the subject parcel in Sterling, CO occupies a relative topographic low or exhibits terrain characteristics that could influence perceived flood or drainage risk.

• Compare parcel elevation to surrounding 300-ft buffer
• Quantify terrain variability using zonal statistics
• Support floodplain interpretation with terrain context

Data used

• USGS 3DEP DEM (30-m) - terrain surface for statistical analysis
• Parcel boundary geometry - subject analysis zone
• Derived 300-ft buffer polygon - surrounding terrain comparison
• FEMA Flood Insurance Rate Map (FIRM) data regulatory floodplain context (Zone AE & floodway proximity)

All datasets were projected into a common coordinate system and clipped to the study extent prior to analysis.

Approach

• DEM Preparation
  ArcGIS Pro Solar Radiation tool used to model relative insolation across rooftop surfaces.
• Zonal Statistics – Parcel
  Roof planes evaluated for pitch and orientation to identify favorable installation angles.
• Zonal Statistics – 300-ft Buffer
  Land cover and structural limitations screened to exclude unsuitable areas.
• Comparative Interpretation
  Evaluated mean elevation differences and variability to determine whether the parcel occupies a relative low point.

Key outputs

• Parcel mean elevation: ~1198.16 m
• Parcel elevation range: ~0.08 m
• Buffer elevation range: ~0.80 m
• Comparative statistics table (parcel vs. buffer)
• Floodplain context mapping (Zone AE and regulatory floodway proximity)

Summary of findings

• Parcel elevation variability is minimal.
• Surrounding terrain shows greater elevation range.
• Mean parcel elevation aligns with nearby terrain.
• Topography alone does not indicate elevated flood risk.

Limitations

• 30-m DEM resolution limits fine-scale detail.
• Small parcel size reduces statistical sensitivity.
• Elevation-only analysis excludes drainage infrastructure.
• Screening-level assessment, not an engineered study.