The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development CE 394 K.2 By Dave Anderson

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Introduction and Background Development of the Two Elk Creek Watershed Using ArcView Determination of Annual Run-off Comparison of Results Conclusions

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development In 1985, Vail Associates, Inc. contacted the United States Department of Agriculture – Forest Service (Forest Service) and proposed to develop 4,100 acres of the Category III (CAT III) and Tea Cup Bowl areas on the White River National Forest –Four development scenarios developed –One out of four was “Proposed Alternative” –Proposed Alternative included: Construction of four ski lifts Ski Trails Ski/Roadway System Restaurant Two Warming Shelters and Food Service Facilities Ski Patrol Facilities Utilities Three small bridges spanning Two Elk Creek Background

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development The Forest Service accepted this Master Development Plan in a 1986 Decision Notice The DN withheld approval of the development of the CAT III area pending the completion of a site specific Environmental Impact Statement (EIS) The final EIS was completed in August It is possible that significant loss of vegetation in the CAT III area will occur if the EIS is approved This will affect the quantity and quality of surface (and ground) water in the immediate area

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Completed using: –Digital Elevation Models Downloaded from USGS Web Site –River Reach Data Downloaded from EPA Web Site –Hydrologic Unit Data Downloaded from EPA Web Site –CRWR Pre-Processing Tools Development of the Two Elk Creek Watershed Leadville-e DEM Leadville-w DEM Steps Included: –Import individual DEMs (3-arc second, 1:250,000 scale) into ArcView (Leadville, CO) –Combine 2 DEMs using Mosaic function of CRWR Raster –Project DEMs using ArcInfo DEMs originally in Geographic Coordinates Projected using Albers Equal-Area Method LeadAlb DEM

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Steps Included (cont.): –Identify appropriate Hydrologic Unit (HUC) using EPA Surf Your Watershed Web Site –Import shapefile for HUC (Eagle County, CO) into ArcView State of Colorado Upper Colorado River Basin Hydrologic Units HUC of Interest Steps Included (cont.): –Mask Grid for HUC shapefile onto projected DEM to obtain DEM for HUC –Import River Reach shapefile Into ArcView

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Steps Included (cont.): –Ran CRWR Preprocessor Tools to Delineate Watersheds in Order to locate Two Elk Creek Watershed Steps Included (cont.): –Vectorized Streams and Watersheds to Determine Extent of Two Elk Creek Watershed –Merged sub-watersheds within Two Elk Creek Watershed Two Elk Creek Watershed

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Completed using: –Historical Annual Precipitation Data Downloaded from Oregon State University Web Site Data from –State Soil Geographic (STATSGO) Data Downloaded from NRCS Web Site –Land Use/Land Cover Data Downloaded from USGS Web Site –Look-up tables and avenue scripts provided by Dr. Maidment and CRWR Determination of Annual Run-off Steps Included: –Import and project (Albers Equal-Area) annual precipitation data Data provided in contour format Converted to grid format using avenue script written by Andrew Romanek –Develop grid for Two Elk Creek watershed Masking precipitation grid with other grids previously developed

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Steps Included (cont..): –Import STATSGO soil data for coverage of entire State of Colorado Steps Included (cont..): –Import Land Use/Land Coverage data for coverage of two Leadville DEMs previously shown

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development These STATSGO tables were combined to generate a table that presents the percentages of each soil group in a particular Map Unit...

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Muidjoin.dbf was then combined with the look-up table (Rcn.txt) and the attributes of the land use table to generate a Curve Number grid...

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development With the Curve Number in each cell known, the annual runoff grid was calculated using the following equations: S = 1000/CN -10 (Storage in inches) (P-0.2S) 2 (Runoff in inches) P+0.8S Q = The total annual runoff for the Two Elk Creek Watershed was calculated by summing the annual runoff in each cell within the limits of the watershed to produce the runoff grid.

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development To determine the impact of development on the Two Elk Creek Watershed, the percentage of each hydrologic soil group (A, B, C, and D) in the study area was changed based on estimates of acreage disturbed during development for the Proposed Alternative (as listed in the EIS). The original values appear to the right; the new values appear below. The percentage of Group D soils was increased due to the existence of shallow soils underlain by a hard granite layer, and the construction of other impervious surfaces. The total annual runoff for the Two Elk Creek Watershed was then re-calculated using the same method described previously.

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development The results of the annual runoff calculation were compared to the values presented in the EIS for: –Existing Situation (no development of CAT III area) –Proposed Alternative (development of select areas of the Two Elk Creek Watershed Comparison of Results Large discrepancies can be seen in mean annual precipitation and existing annual runoff A comparison of the runoff grids is provided below

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development The effects of vegetation loss in comparison to the variability of annual runoff between the calculations in the EIS and those performed in ArcView is negligible. Two Elk Creek Watershed may be too small to effectively model with 3-arc second DEMs –Discrepancies in sub-watershed areas due to resolution –Soil data coverage too coarse to cover sub-basin changes in soil types –Land Use/Land Cover data more detailed than soil data Although there are significant errors when compared to the EIS text, the data needed to make a runoff analysis such as this is available now or in the near future Conclusions

The Effects of Vegetation Loss on the Two Elk Creek Watershed as a Result of the Proposed Vail Category III Ski Area Development Questions?