Name: Plantable Areas in Privately Owned Parcels and ROWs
Display Field: LandCategory
Type: Feature Layer
Geometry Type: esriGeometryPolygon
Description: To gain a more accurate idea of where infill tree planting was possible, Facet utilized the City’s existing tree canopy20, unsuitable soil21, unsuitable vegetation22, surface water23, and impervious surface24 layers. Using these layers, Facet applied the following assumptions to estimate a more accurate plantable area and potential tree count: -Minimum of 16 square feet of unpaved area per tree, -Minimum planting area width of 4 feet, -At least 8 feet from major impervious structures such as buildings, bridge overpasses, and driveways, -At least 2 feet from minor impervious features, such as roadways, sidewalks, parking lots, patios, decks, concrete pads, storage, railroad yards, and other impervious surfaces. Dimensional requirements (minimum area and width) were applied first, followed by buffer distances from impervious surfaces in an attempt to prevent buffering requirements from encumbering plantable area dimensions. Therefore, the resulting refined plantable areas may contain some polygons that appear smaller than 16 square feet or more narrow than 4 ft.The planting areas were then overlayed with various spatial metrics to gain a planting prioritization layer. See accompanying report for further details. This geospatial analysis is intended for use at the neighborhood level and for planning purposes only. The refined plantable area analysis, plantable tree calculations, and maximum additional potential tree canopy analysis were performed in aggregate and do not look at any individual site for practicality. Any further breakdown of planting locations would require additional information, up to or including ground-truthing, site observation, and survey. As in all geospatial analyses, data sources play a role in study limitations. The initial tree canopy layer and subsequent calculations depend on the accuracy and resolution of PlanIt Geo’s tree canopy layer. Features, such as but not limited to watercourses and surface water areas, may not represent present on the ground conditions. No attempt to verify or correct PlanIt Geo’s data was included with this study. The refined plantable area analysis also uses PlanIt Geo’s tree canopy and landcover datasets and additionally incorporates the City of Kenmore’s impervious surface layer. The maximum additional potential tree canopy analysis builds on the refined plantable area layer and assumes total canopy infill within planted areas and an 8-ft canopy overhang extending beyond planted area boundaries. For the purposes of this analysis, the 8 ft canopy overhang was conservatively reduced from 11.7 ft which assumes a 15’ tree canopy radii, although street tree canopy sizes vary in the field. The refined plantable area analysis, the subsequent maximum potential canopy analyses, and the planting prioritization analyses do not take into account a variety of requirements when determining urban tree planting locations. These include, but are not limited to: -Aboveground and belowground utilities. The presence of utilities restricts areas where trees can be planted, or in the case of overhead power lines, what size tree can be planted to avoid conflicts. Utility data was unavailable for this study. If available, buffering the utility GIS data can refine and remove areas from both the potential plantable area and maximum potential canopy analyses. -Road intersection requirements. Often, jurisdictions have limitations on tree planting around intersections to maintain lines of sight for vehicle and pedestrian safety. Creating an intersection geospatial layer can also refine and reduce the amount of area available for tree planting. -Stormwater and drainage facilities. Stormwater design standards prescribe specific requirements for planting within stormwater and drainage facilities, including prohibiting tree planting in some cases. Stormwater facilities and design standards were not considered in the initial study data; therefore, the results of the analysis may overestimate the potential for planting with regard to these facilities. Modifying the root data to remove stormwater and drainage facilities where tree planting is prohibited, prior to running subsequent analytic steps, could improve the accuracy of the findings. -Preserved open space. Many cities have open lands that are intended to be preserved for open space. This analysis does not attempt to exclude areas that are intended to be kept as open space, such as through maintenance and/or operational decision making on the part of a landowner or land manager. Identifying and excluding areas of preserved open space could further enhance the accuracy of the findings. -Impervious surfaces conversion. Locations where trees can be planted in existing paved areas (such as parking lots, road medians, and asphalt blacktop) are not included in the plantable area analysis. Identifying locations for impervious surface conversion would increase Kenmore’s potential plantable area, and subsequently, Kenmore’s potential canopy. This study is also limited temporally. Input data ranges from 2021 to 2024. Change in city conditions and data availability and accuracy will impact findings, such as: -Growth of existing canopy -New tree plantings. It takes a few years for new trees plantings’ contribution to tree canopy to register in remote sensing processes -Updated impervious surface dataset. Expansion of Kenmore’s impervious surface dataset will further reduce and refine the available area for tree planting. The City has done some refinement on the impervious spatial data but it was not provided in time for this analysis Finally, the study does not account for private landowners’ willingness or unwillingness to plant trees. Plantable areas are treated the same regardless of whether they occur on public or private land. Realistically, it will not be possible to persuade every landowner to plant the required trees to achieve the city’s maximum potential canopy.