watervulnerability

Grand Mesa, Uncompahgre and Gunnison National Forest Watershed Vulnerability Assessment, Rocky
Mountain Region (R2)
rankings based on the different types of sensitivities were each related to the three aquatic resource
values. The process used to compare the Resource Values Rankings to the Sensitivities x Stressors Risk
Rankings is displayed in the following matrix.
Values × Sensitivity Stressors
Risk Ranking Matrix
Values
Sensitivity × Stressors
Low High
Low Low Low
Moderate Low High
High Low High
Subwatersheds with a High Sensitivity × Stressor Risk Ranking and a High or Moderate Values ranking
were rated as High. Subwatersheds with a High Sensitivity × Stressor Risk Ranking but a Low Values
ranking were rated Low because of the reduced level of concern for the values. All Subwatersheds with a
Low Sensitivity × Stressor Ranking were rated as Low when compared to Values because there is lower
risk from the existing conditions within these subwatersheds. The results of the values related risk
rankings are discussed below.
Infrastructure Values Vulnerability
Infrastructure in and near streams and rivers are vulnerable to flooding and/or sediment and debris flows
that may result from climate change-related disturbances. These effects are most likely to occur in
subwatersheds that have the highest risk due to inherent sensitivities for erosion or runoff response and a
concentration of past management activities.
Infrastructure values were related to Erosion Sensitivity × Activity Stressors with results displayed in
Figure 26. Subwatersheds where infrastructure values are at the highest risk from erosion or sediment
production are in the Upper Taylor, San Juans, and West Elk geographic areas. Infrastructure values were
related to Runoff Response Sensitivity × Activity Stressors with results displayed in Figure 27.
Subwatersheds with the highest risk from rapid runoff response are mostly in the San Juans, with some
localized areas in the Grand Mesa, Upper Taylor, and Cochetopa geographic areas.
Increased runoff could erode sections of roads and trails, and could wash out crossings and structures.
High densities of roads and trails can collect overland flow and divert it into stream networks, adding to
high flow conditions. Road networks with undersized pipes to accommodate existing flows will become
more vulnerable. Increased sediment or debris loads could also plug culverts at crossings or bury sections
of roads or structures. All results could threaten public safety and greatly increase maintenance costs.
100 Assessing the Vulnerability of Watersheds to Climate Change