DC Estimated Tree Root Zone (Structural)

The dataset is the estimate of a tree’s structural root zone, which must not be impacted during construction. Buffer distances are calculated for trees on all land types in the District that will be used for tree preservation planning purposes.

DC 2022 LiDAR was used and processed using the “Extract Trees using Cluster Analysis” script which is included as part of Esri’s 3D Basemap solution. 

The
extracted tree data set was merged with the UFA tree inventory data, with
preference given to the UFA tree inventory data. All LiDAR-derived trees within
2 meters of a UFA tree were removed as being duplicates. 

Tree diameter (DBH, in inches) was estimated for the LiDAR-derived trees from calculated tree height (in feet) based on the equation: DBH = 0.4003*height - 1.9557. This equation was derived from a statistical analysis of a detailed park inventory tree data set and has an R^2 = 0.7418.

Extreme outliers were also modified, with any DBH larger than 80 inches being converted to a DBH of 80 inches.

Critical Root Zone (CRZ) was calculated as a buffer of 1.5 feet for every inch of DBH, whereas Structural Root Zone (SRZ) was calculated as a buffer of 0.5 feet for every inch of DBH.