Forest Stewardship Analysis Project - Pilot Overlay Study
Methodology for the State of Rhode Island
Outline
• Project Summary
• Factors of Influence and Data layer development
• The Overlay Model
Project Summary
The State of RI conducted a simple non-weighted additive model for 11 of the 12 layers
suggested as input for The Spatial Analysis Project (SAP). Because the model was
unweighted and because RI is such a small state, it was agreed that patch size was
unimportant. The RI Division of Forest Environment sees opportunity for Stewardship
on relatively small forest plots that might have been overlooked had we considered patch
size as an analysis factor. The SAP will prove useful not only to the State Foresty
Program, but also in ongoing work in land conservation and habitat protection via the
State Division of Fish & Wildlife.
Factors of Influence and Data layer development
Fire Protection Assessment: The only available fire assessment data came from the
NorthEast Compact Fire Assessment and was generously provided to us by the Maine
State Forestry Program. These data characterize risk based on both resource damage and
threat to life & property. Medium and high were combined to create the fire risk layer.
Risk of Insects/Pests: This layer shows areas of Rhode Island that have had measured
insect infestations within the last 5 years. Data provided by the USFS based on local
Aerial Detection Surveys.
Risk of Development (change in census block households): This layer shows areas of
Rhode Island were change in households per square mile between 1990 and 2000 where
the increase in the number of households has been 0 to 20. Change in this range is
considered high enough to highlight the need for Stewardship, yet low enough where
changes in attitude can still provide an alternative to urban sprawl. For Connecticut the
Census block group data was collected and combined by the USFS.
Private Forested Lands: These are forested lands not within the extent of the Analysis
Mask. The forested land coverage was derived from the Rhode Island Geographic
Information System (RIGIS) 1995 Anderson Level 3 Land-use/Land-cover dataset and
the RIGIS 1988 Wetlands data . These data have ½ acre resolution and were considered
superior to the MRLC National Land Cover Datalayer. The data are functionally
equivalent to the (NLCD) for forested uplands and woody wetlands. The table below
crosswalks the RIGIS data values with the MRLC/NLCD equivalents.
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Forested Land RIGIS/MRLC Crosswalk
RIGIS Dataset
Code
LU/LC 1995
310 Deciduous Forest > 80% Hardwood
LU/LC 1995
320 Evergreen Forest > 80% Hardwood
LU/LC 1995
330 MixedDeciduous Forest 50 to 80%
Hardwood
LU/LC 1995
340 Mixed Evergreen Forest 50 to 80%
Softwood
Wetland 1988
FOA Forested Wetland: Coniferous
Wetland 1988
FOB Forested Wetland: Deciduous
MRLC
41 Deciduous Forest
42 Evergreen Forest
43 Mixed Forest
43 Mixed Forest
91 Palustrine Forested
Wetland
91 Palustrine Forested
Wetland
Private Non-Forested Lands: Non-Forested undeveloped private lands, the counterpart to
the previous layer, were taken from following RIGIS LU/LC 1995 classes:
Non-Forested Land RIGIS LU/lc 1995/MRLC Crosswalk
RIGIS Class
MRLC/NLCD Class
210 Pasture
81 Pasture/Hay
220 Cropland
82 Cultivated Crops
230 Orchards, Groves & Nurseries
82 Cultivated Crops ?
250 Idle Agriculture
71 Grasslands/Herbaceous
400 Brushland
52 Shrub/Scrub
600 Wetland *
95 Emergent Herbaceous
96 Palustrine Emergent
750 Transitional Areas
21 Developed Open Space
760 Mixed Barren Areas
31 Barren Land
*Excluding Forested Wetlands that were included in the Forested Land Layer
Wetlands: 1988 ½ acre resolution statewide dataset based on Cowardin classification
scheme.
Forest Patches: RI did not consider forest patch size in it’s analysis because of the small
size of the state and the attendant belief that good stewardship can and is occuring on
small lot sizes.
Riparian Corridors: 300ft Riparian buffer based on 1:24,000 RIGIS Stream Centerline
and River Polygon data.
Natural Heritage Priority Habitats (Threatened and Endangered Species): Estimated
habitat and range of rare species and noteworthy natural communities.
Proximity to Publicly Protected Lands: All publicly protected permanent conservation
lands held by Federal, State or Local Government entities.
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Slopes: Slopes between 15% & 30% derived from a 1:5000 Digital Terrain Model
created in 1997 for a statewide orthophotography project
Public Water Supply Areas: This raster data layer is a composite derived from the
following 3 CT DEP vector data layers: Wellhead Protection Areas – Zone II, Wellhead
Protection Areas – Interim, and Surface Water Supply Protection Areas. The final grid is
a 1/0 layer that describes areas falling into the above categories.
Analysis Mask: The analysis mask represents all developed land use types including
commercial, industrial, residential, developed recreation, transportation, open water, and
protected public lands. Features in this layer are considered outside the areas where the
private stewardship will be applied; to be removed from the full analysis. As with
previous layers, the mask was based upon the RIGIS Landuse/Landcover 1995 layer.
Analysis Methodology
RI elected to use an unweighted analysis for this project. Previous efforts at developing
a weighting scheme for openspace and natural habitat protection could find little
agreement among participants on priortizing landscape characteristics. The RI Division
of Forestry staff agreed that they were not comfortable in applying weighting factors to
this analysis.
All of the model input layers previously described were converted to a grid format using
a 100-ft (10,000 ft^2) cell size. Each layer was coded as 0 or 1 indicating absence or
presence of the resource. For each analysis, layers were summed vertically to determine
how many co-ocurring resources were found for each 10,000 sq-ft cell. After summation
the data was classified using a natural breaks grouping and then reclassified as 1,2 or 3
representing a low, medium or high value for the cell. A mask was used to exclude lands
considered outside the stewardship program designation (developed land, open water,
public lands).
RI developed six maps according to the requirements outlined in the SAP documentation
provided us.
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