In the Northern Appalachians, intact riparian corridors and floodplains are linear features, averaging about 200 acres in area (Map 1 above), with size varying with subregion (Figure 1). About 22, 000 intact, or semi-intact, examples occur in the ecoregion, accounting for 3% (2.7 million acres) of the ecoregion. Most are found at low to mid elevations on sedimentary till, coarse sands or fine silt deposits.
Critical floodplain and riparian occurrences identified by TNC Ecoregional Planning amount to 3% by count and 18% by acreage of all the floodplain features in the ecoregion. These total roughly one half percent of the entire region by acreage. Riparian ecosystems are truly among the least protected systems in the ecoregion: currently 27,000 acres are on lands protected for biodiversity, leaving 776,951 acres remaining for active protection efforts.
Please see NAP Ecoregional Plan 2005, Floodplain and Riparian Ecosystems (Anderson, 2005) for more information.
1: Gridded size 2,3,4 rivers (including miscoded lakeshore arcs) on sizeclass to 90m cells (with Grid "linegrid" command, using a weight table to resolve conflicts in cell value assignments in favor of the larger river arc size classes).
2. Made a 90m grid of lake/pond/reservoir cells for the US portion of NAP, registered to river arc grid of previous step -- original source is National Hydrography Dataset (NHD), and value assigned was 42. Expanded by one cell, and burned onto the gridded size 2-4 rivers (using Grid "merge").
3. Removed all value = 42 cells from this last grid: this leaves only cells representing size 2-4 rivers.