Winter 1991

CWE Assessment for Ski Area Development

Andrea Holland
USFS, Lake Tahoe Basin Management Unit

There is a new species of CWE in the makings at the Lake Tahoe Basin Management Unit. A spinoff of Region 5's CWE analysis process for timbered watersheds, we're currently calling this animal "Ski Area Cumulative Watershed Effects Analysis" (SACWEA). Warm and fuzzy it's not, but it is a baby.

Conceived as a decision making model, the LTBMU anticipates applying it in the evaluation of future development plans in the Heavenly Valley Ski Area. SACWEA's purposes are to:

Account for the current resource condition of a ski area and track any resource protection improvements there.

Identify and set priorities for areas in need of erosion control work.

Provide a management tool to assess alternatives to techniques for ski area development and rehabilitation, and guide the forest manager to areas needing more detailed analyses.

Assist the Forest Supervisor in the decision making process concerning a ski area's proposed development.

In late September the first SACWEA development meeting was held in Tahoe. The core group (some of them CWE gurus) included Don Haskins, Geologist from the Shasta-Trinity, Ken Roby, Ken Cawley and Doris Grinn, Hydrologists from the Plumas, Roger Poff, Soil Scientist from the Tahoe, Chuck Mitchell and Joan Carlson, Soil Scientist and Hydrologist respectively, from the El Dorado NF, and myself.

Other participants to the September meeting included Al Todd, Watershed Staff Officer for the Lake Tahoe Basin Management Unit and Andrew Strain and Dan Greenley of the Tahoe Regional Planning Agency (TRPA). These folks have a keen interest in the output of the SACWEA Team and provided useful input to help guide us into producing a practical tool for management of a ski area.

The main effort of Team SACWEA is to develop a cumulative effects model for Heavenly Valley Creek, which drains most of Heavenly Valley Ski Area on the California side. In addition, the TRPA and several other National Forests hope to take the process we develop with SACWEA and apply it to other ski areas. The TRPA is especially interested in the SACWEA outcome, hinging their Basin-wide Ski Area Development Guidelines on it.

While consistent with R-5's CWE procedures (outlined in the Soil and Water Conservation Handbook, FSH 2509.22), the SACWEA differs somewhat from the CWEs most land managers are currently familiar with. This is due to the inherent differences between a logging activity (for which the initial CWE was developed) and ski area development. For instance, soils at many ski areas have been drastically altered with extensive excavation and blasting throughout the developed portion. Thus modified, they may handle water runoff and infiltration differently than naturally formed soils.

As a result of altering the landscapes, drastic changes in drainage patterns have developed. Ephemeral drainages have been buried in some cases, and in others even perennial creeks have been rerouted. Thus, the assumptions made for timber-oriented CWEs are not necessarily appropriate for ski area development.

One major difference between SACWEA and typically applied CWE analysis is that the latter usually looks at off-site and on-site disturbances for a particular land management activity (usually timber oriented). The theory behind this approach is to determine if off-site effects can be mitigated by treating on-site disturbances for a given watershed without compromising the integrity of its drainage.

However, Heavenly Valley Creek has already sustained serious peak flow damages stemming from ski area developments resulting in channel cutting, bank failures and significant sedimentation downstream. Our objective now is to prevent any further ski area erosion from adversely affecting water quality. While peak flow is an important constituent of the watershed's processes, the emphasis of SACWEA is cumulative sediment delivery to the channel. The SACWEA process, therefore, evaluates only on-site disturbances, drawing the boundary of the watershed upslope from the point where the drainage leaves the ski area.

Acreages of disturbance will still be evaluated as part of SACWEA but with additional attention paid towards implementation and effectiveness of Best Management Practices (BMPs). Roads, ski runs, ski area facilities and drainage crossings will be evaluated individually and factors inherent in their development rated according to their erosional effects and sedimentation within the stream channel. The key element in this analysis is a delivery coefficient assigned to each development factor. Deciding the values of delivery coefficients is the goal of a future Team SACWEA meetings, as is defining the threshold of concern for the Heavenly Valley watershed.

Because of the political interest in SACWEA, our goal is that the model be defined by April, 1991, with the understanding that field testing be performed when possible to confirm the critical assumptions of the model. We who are developing SACWEA welcome all constructive comments and suggestions that may help us in this complex task.

Andrea may be reached at (916) 573-2600