Step 1:  Defining/Refining a landscape scale for the study area

This section guides the user through the considerations used in the selection of a landscape level study area that is scaled appropriately to the particular project. The project may range from a new roadway alignment with multiple alternatives, to a capacity and safety improvement at an existing interchange, to a simple rehabilitation or preservation project along an existing roadway. When setting the landscape scale for any project size, the following items should be considered:

  • Define the landscape scale as broadly as possible:

    Prior to attending a Scoping Meeting with agency partners, the initial landscape scale should be set to encompass a landscape area that encompasses all potential areas that could be affected by the project. For larger projects, the extent of the study area should include project limits as defined in the Project Need statement or Statewide Transportation Improvement Plan (STIP). Wildlife movements extend beyond typical transportation project study areas. In its broadest sense, the landscape scale study area should reasonably include the project limits where the roadway design will result in traffic volume increases extending out to encompass habitats that could be affected (fragmented) by the construction of the alternative(s). A project study area encompassing all reasonable alternatives should be considered.
  • Utilize available Geographic Information Systems (GIS) database information and aerials:

    The use of GIS is integral with the mapping and spatial analysis associated with habitat fragmentation assessments. Typically, states and most federal agencies have GIS database sources that are publicly available and are potentially useful to provide base map information. An example of an on-line source includes the USGS Landcover Database for all of North America, and the University of Oregon’s Library system which maintains links to a national clearinghouse  for state and federal  GIS data. Data sources that are useful in assessing the study area landscape include:
    • Digital Aerial photographs
    • Wetland and Land Use Cover mapping
    • Topography and soils
    • Watershed or Hydrologic Unit Code (HUC) boundaries
    • Natural Lands, Parks, Wilderness Areas, Wildlife Refuges, National Forests, Forest Reserves, Recreational Areas, and other managed or protected natural areas.
    • Land ownership, land use zoning and urban growth zones
  • Review pertinent information sources:

    Most federal and state agencies have a variety of natural resource databases, inventories and other information sources that can be used to initially identify regionally significant ecosystems, wildlife species of concern, critical habitats and habitat corridors. This information is useful in defining potential target species, species at risk, and key landscape features and objectives for maintaining or improving habitat connectivity. Examples of information to review include:
    • Watershed Management Plans
    • State Wildlife Action Plans (http://www.wildlifeactionplans.org)
    • Natural Resource Management Plans
    • State Natural Heritage Database
    • State or Federal Resource Agency Data
    • County or local community tax maps/property ownership data
    • NatureServe

In addition to these information sources, locations of known concentrations of wildlife-vehicle collisions, or hotspots, should be incorporated into the baseline information. Hotspot data may not be readily available but methods to collect and analyze the data are available and are discussed in Bissonette and Cramer (2008).

  • Determine the Watershed Boundaries: 

    Aquatic resource networks are defined in part by watershed boundaries and resources within individual networks should be tracked based on the watershed level. Using watersheds as a landscape unit is also recommended for consistency with other regulatory programs, including the US Army Corps of Engineers (USACE) and US Environmental Protection Agency (USEPA) use of a watershed approach in reviewing Clean Water Act related impacts and compensatory mitigation. Most aquatic resource impacts would also be regulated under this program. Hydrologic Unit Codes (HUC) at the 11-digit to 14-digit level is typically used by USACE. When defining the watershed limits for the study area, the boundaries should encompass the outermost project traffic nodes and all of the adjacent HUCs.  If HUC data at the 11-digit or 14-digit level is not available, then watershed limits can be developed using a Digital Elevation Model (DEM) and the Strahler stream order hierarchy (Strahler, 1957), or GIS based tools.

Resources that can be consulted for more information concerning this step include:

Once the initial landscape level study area map is prepared, the terrestrial and aquatic habitat networks should be prepared prior to the project Scoping Meeting.

go to Step 2: Define Terrestrial and Aquatic Habitat Networks