Buffers (150 ft. and 300 ft.) around 2nd order and higher stream reaches,
as extracted from the NH National Hydrography Dataset.  Buffers were generated
around each individual reach and overlain on the 1998 land use data set, and the
land use within each buffer was tabulated.  The buffers were then
categorized based on the degree to which each buffer was impacted by human
activity.

AltCategory (or "altered category"), is populated with the
following values:

I 	Intact			< 10% impacted (developed or ag land)
M	Mostly intact		10-25% impacted
SM	Somewhat Modified	25-50% impacted
A	Altered			>50% impacted

Note that for areas with overlapping buffers, the most impacted buffer category
prevailed in the final coding.