watervulnerability

Ouachita National Forest Watershed Vulnerability Assessment, Southern Region (R8)
activities, such as past and current land use and roads and trails, are factors directly affecting hydrologic
change within a watershed.
Buffers that modify the anticipated hydrologic changes
Land use and changes in land use is a useful tool to anticipate changes in sediment. This is the primary
vehicle used in the ACE model to address cumulative effects. For the purposes of this exercise, the
current land use condition was frozen for both scenarios and time frames. In addition, forest management
was not addressed. No forest management activities (e.g. clearcuts or thinnings) were modeled.
Roads and trails (including their current condition and level of use) is the other useful stressor to address
changes in sediment yield. Currently, many forest roads on the Ouachita National Forest are seeing
increased off highway vehicle (OHV) use and substantial reductions in maintenance. Bringing these forest
roads/trails up to an acceptable level of construction standard and providing maintenance is the easiest
way to buffer sediment losses. Reducing user created trails is another method to buffer sediment losses.
For this exercise, the current road and trail condition and potential current condition (assuming roads and
trails built to standard and maintained) were used in the climate change predictions.
Other methods not addressed could include
reducing road and trail miles (obliteration
or maintenance level 1) or reducing the
numbers of OHV users. County road
maintenance and design could also be
addressed and improved.
Method used to characterize watershed
risk
Increases in sediment can directly affect
stream habitats by reducing available
substrate, and reducing pool volumes and
pool depths. Indirectly changes
in habitat can affect fish
communities. The sensitivity of
these changes was established by
taking known fish population
samples and determining the
annual sediment contribution
from the watershed above the
sample location. Percent
sediment increase (over a
baseline condition) was
compared to the relative
abundance of various fish guilds.
Ecoregions and slope (how steep
the watershed is) were used to
generate broad categories. When
a wedge pattern was found,
sensitivity thresholds were
231 Assessing the Vulnerability of Watersheds to Climate Change