Tools for evaluating future impacts

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Single-objective tools



Caltrans Regional Advance Mitigation Planning (RAMP) Road impact footprint analysis:1 Thorne et al. (2009) applied appropriate buffer distances to spatial data on the location of funded road construction projects to identify the area impacted by each road project. Caltrans biologists defined these buffers to reflect the spatial extent of impact for each road classification so that, for example, road widening projects impacted a 30.5m buffer while passing lane projects impacted a 10m buffer. RAMP extended this "footprint" an additional 250m and overlaid the resulting area with habitat maps to calculate the proportion of each habitat type located in the general area of each project. For each project, RAMP then multiplied this proportion by the project's footprint area to estimate the total area of each habitat type impacted by each project and summed these totals across all projects in the study region. The total habitat area projected to be impacted throughout the region was then multiplied by anticipated mitigation ratios for each habitat type to identify Caltrans' mitigation needs.

Factor used in analysis

Data source

Location of funded road construction projects


Buffer area reflecting the impact area of each road classification

Caltrans biologists

Habitat maps


Mitigation ratios commonly applied for each habitat type

Caltrans biologists


Human Development Index (HDI):2,3 Kramer et al. (2012) quantified the presence of current and future threats within each HUC-12 by reclassifying eight datasets to a scale of one to nine and adding them to obtain a final HDI score. Examples of threats used in the model included stream fragmentation, percent impaired streams and rivers, and the change in wetland density between 1974 and 2008 (see below).

Factor used in analysis

Data source(s)

Stream fragmentation assessed using a fragmentation index (Merrill, 2001) to calculate the percent of stream miles that remained free-flowing in 2008 compared to 1974

1974 and 2008 NHD; USGS HUC-12 watersheds

Percent of impaired streams and rivers

GAEPD GIS dataset on 303(d) and 305(b) impaired streams and rivers; NRCS HUC-12 watersheds

Wetland Activity Index: the change in density of wetlands between 1974 and 2008

1974 and 2008 GLUT database; NRCS HUC-12 watersheds

Percent impervious surface

2008 NARSAL GISC database; NRCS HUC-12 watersheds

Projected future development in 2025 as measured by the difference in urban area per HUC-12 watershed between 2008 and 2025

SLUETH urban growth forecast model results for the state of Georgia for 2008 and 2025; NRCS HUC-12 watersheds

Change in average wetland continuity from 1974 and 2008 (measured using Fragstats)

2008 NARSAL land cover data; NRCS HUC-12 watersheds

Change in average wetland proximity from 1974 to 2008 (measured using Fragstats)

2008 NARSAL land cover data; NRCS HUC-12 watersheds

Riparian fragmentation measured as the change in mean length of riparian buffers using method of Kramer and Bumback (2005)54

Full buffered streams 120m; NRCS HUC-12 watersheds

Acronym definitions

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1Thorne JH, Huber PR, Girvetz EH, Quinn J, and McCoy MC. 2009. Integration of regional mitigation assessment and conservation planning. Ecology and Society 14(1): 47
2 Kramer E, Couch C. Carpendo S., Samples K., Reed, J. 2012. A statewide approach for identifying potential areas for wetland restoration and mitigation banking in Georgia: An ecosystem function approach.
3 Kramer, E., and B. Bumback. 2005. A Statewide Analysis of Riparian Vegetation Change, from 1974 to 1998 in K. J. Hatcher, editor. 2005 Georgia Water Resources Conference, held April 25 27, 2005 at the University of Georgia, The University of Georgia, Athens, Georgia.