watervulnerability

Grand Mesa, Uncompahgre and Gunnison National Forest Watershed Vulnerability Assessment, Rocky
Mountain Region (R2)
Infrastructure Values
Infrastructure includes roads, trails, culverts, bridges, recreation developments, and other structures that
have been constructed for some purpose. Infrastructure associated with stream channels, floodplains, and
riparian areas was believed to be most vulnerable to changes in timing or magnitude of stream flow. The
NHD flowline data were used to identify stream courses. Floodplains and riparian areas were identified
using the Forest riparian habitat layer (created from aerial photo interpretation to identify wetlands, fens,
waterbodies, and 100-foot buffer of perennial streams).
The infrastructure values evaluated in this WVA are listed below, along with the metric used to rank these
values by watershed. Note: Data for riparian areas, roads and trails, recreation developments, and
recreation residences were limited to National Forest System lands and what is available in USFS
databases. Stream network information extended off-Forest. The discrepancies in data extent means the
confidence in results varies for subwatersheds that are completely or mostly within the GMUG as
compared to those subwatersheds that extend beyond the GMUG boundary or that have developments on
private inholdings.
Road and Trail Stream Crossings - number of open road and trail crossings per miles of perennial and
intermittent streams within a given subwatershed. Stream crossings were determined by intersecting
perennial and intermittent streams with existing and open roads and trails. Figure 5 shows where these
stream crossings occur. The crossing count for a given subwatershed was then divided by the miles of
perennial and intermittent streams for that same subwatershed, to get a count of crossings per mile of
perennial and intermittent streams within a given subwatershed. Counts of crossings per mile of perennial
and intermittent streams by subwatershed ranged from 0 to 1.2.
Note: The NHD Flowline and the roads and trails layers are approximations and the resulting intersection
point layer is not necessarily an accurate representation of all actual crossings. This information also does
not identify if the crossing is a culvert, a bridge, or a ford. Existing culvert and bridge inventories are not
complete. These are data gaps that need to be addressed in the future.
70 Assessing the Vulnerability of Watersheds to Climate Change