GIS Methodology for Establishing Greenway Corridors in a Fragmented Forest Landscape (presentation)


Baltimore County Dept. of Environmental Protection & Resource Management, 401 Bosley Avenue, Towson, MD 21204-4488. Phone: ?. Email: ?

The Baltimore County Department of Environmental Protection and Resource Management (DEPRM), in association with Biohabitats, Inc., has developed a rapid assessment methodology to address the problems of prioritizing forest patches and deforested tributaries for conservation and restoration in a highly fragmented forest landscape. The methodology utilizes digital data in a Geographic Information System (GIS) to produce a series of watershed maps of forest cover delineated into color-coded forest patch size classes with delineated interior and edge areas, and stream system resources. These maps serve not only as visual representations of forest patches and streams, but also as overlays for property maps.

Through the application of a series of ranking matrices of physical, ecological and cultural parameters, the office component of the methodology narrows the focus of the conservation targeting effort by comparing forest patches for ecological importance at the sub-watershed, forest patch, and land parcel spatial scales. The methodology also prioritizes low order stream reaches for riparian restoration. The benefit of this multi-tiered approach is that field investigations, indispensable for resource management decision-making, are reserved for only those areas that consistently show high resource protection value throughout the targeting process. On-site investigations are focused upon areas with the highest practical potential for conservation/restoration efforts.

The office component of the methodology can be summarized as follows:

  • The Level I ranking matrix is applied at the landscape spatial scale. This matrix compares sub-watersheds for percent forest cover and interior forest, sub-watershed drainage area and distribution of low order streams and other sensitive areas within the forest patches, extent of impervious surfaces in the sub-watershed, and pre-dominant zoning and land uses. Historical documentation of threatened or endangered species is also noted, although not ranked because many listed species are not forest-dependent.
  • The Level II ranking matrix compares forest patches in the highest scoring sub-watersheds using parameters for forest contiguity within and across sub-watershed boundaries, interior forest, interior forest gaps, edge gaps, and stream orders. This matrix selects forest patches for the Level III ranking matrix.
  • The Level III analysis consists of four matrices, one or more of which can be used depending upon the nature of the forest and stream resources, and the objective of the user. They include parameters for interior forest conservation, riparian corridor restoration, interior gap restoration, and exterior (edge) gap restoration.

Level IV constitutes the field component of the methodology. This analysis verifies the location and extent of forest and stream resources indicated by the GIS, and examines the forest patches for structural diversity, habitat heterogeneity, indigenous species richness and overall biological diversity of the vegetation, and disturbance parameters. Level IV also provides opportunities to assess open areas that are not critical habitat for non-forest T and E species for restoration.

This GIS-based methodology is applicable to any jurisdiction with highly fragmented forest resources. It uses readily available data, and ecological parameters that are supported by the scientific literature. A built-in flexibility allows users to add, remove or modify parameters in the ranking matrices, according to forest resource attributes and management goals.

Funding for this project was provided by the Maryland Department of Natural Resources, Chesapeake and Coastal Watershed Service, and the Greenways Commission.