Because of a lack of consistent information across the three forests regarding watershed conditions, the following procedure was developed. This procedure loosely follows the procedures in Determining the Risk of Cumulative Watershed Effects Resulting from Multiple Activities, USDA Forest Service, February 1993. The format and procedure also loosely follows that developed in Region 3 of the Forest Service and discussed in their "Hydrology Notes," February 17, 1981, titled: A System for Focusing the Watershed Management Program in the Southwestern Region for the 1980's, by Doug Shaw, Rhey Solomon, Jim Maxwell, and Larry Schmidt (both documents available in planning file).

Introduction

The following process integrates two levels of analysis. The first rates the sensitivity of the watersheds by their naturally occurring attributes, while the second rates the existing condition of the watersheds by examining past land use impacts. The two ratings are integrated into a single rating of low, moderate, high, or very high risk of cumulative effects.

The information was originally to be used to input limits into an "optimization model" integrating forest, fire, watershed, wildlife, and people into landscapes and polygons that maximize some variables and minimize others. This model was not run, but the information developed was useful and helped develop the alternatives. Much of this information is presented here.

Other uses of this analysis will include recommendations for future Watershed Analyses (also referred to as Landscape Analyses) and a ranking of watersheds for restoration analyses and "riparian restoration projects," as called for in the Herger-Feinstein Quincy Library Group Act.

Analysis Process

Criteria were developed that describe the sensitivity of watersheds to disturbances, both human-caused and natural, as well as existing conditions. Existing watershed condition criteria are evaluated both using known data and using subjective evaluations by experienced earth scientists familiar with portions of the Pilot Project area. Generally, no weighting is applied to any criteria, therefore all criteria are evaluated equally, as prescribed in the Forest Service Handbook (FSH 2209.22, Chapter 20). Each criteria is rated as 1, 2, or 3, based on its applicability as defined. The total score under each rating is the sum of the individual criteria scores. The final rating multiplies the results of the two individual scores into a single score and a descriptor or risk is assigned.

Watershed Sensitivity Criteria

· Erosion Potential. The percent of the watershed with high to very high Erosion Hazard Rating (EHR).

· Part of Watershed with Slopes Greater Than 60 percent. A primary indicator of potential instability.

· Percent Alluvial Stream Channels. Sensitive, depositional landforms and the channels draining through them usually occur where stream channel gradients are less than 2 percent. This criterion compares the channel miles with less than 2 percent gradient with the total miles of channels within the watershed.

· Rain-on-snow and/or Thunderstorm Potential. Based on the climatic regime of the watershed, this criterion evaluates the primary mechanism(s) involved with erosion and movement of material to channels. The primary erosional mechanism can be either rain-on-snow runoff events or thunder-storm runoff events, or both. In the following table, elevation and average annual precipitation are considered the primary delineators for the two mechanisms.

· Vegetation Recovery Potential. The potential of an average area in the watershed to revegetate after becoming bare. This criteria is based mostly on climate, using the following table as a guide, but should also take into account general soil moisture conditions.

Watershed Condition Criteria

· Road Density (miles per square mile). A measure of the potential impacts caused by roads, it is calculated as miles of roads per square mile of watershed area. This is a two-fold analysis. First, because roads within Riparian Habitat Conservation Areas (RHCA's) and Streamside Management Zones (SMZ's) have a very high potential for causing impacts to the aquatic/riparian system, the road density within the protection zones is weighted by a factor of 10. Second, the riparian road density (times 10) is added to the road density in the remainder of the watershed to give a final density. This final value is used to decide the factor rating.

The factor rating for this element is added to the factor rating for Road-Stream Crossing Density below to derive a final rating.

· Road-Stream Crossing Density (number per square mile). Wherever a road crosses a stream there is almost always a direct connection between the road and the stream that affects runoff and sediment discharge. Crossing density is calculated as the number of crossings per square mile of watershed area.

The final score to be used in evaluating the impacts of roads on watersheds is the sum of the two factor ratings (Road Density + Road-Stream Crossing Density) divided by two.

· Condition of Alluvial Channels. Using A User Guide to Assessing Proper Functioning Condition and the Supporting Science for Lotic Areas, TR 1737-15 1998, published by the USDI and USDA, as a guide, the following definitions can be used.

· Land Use Disturbance. A subjective rating of the percent of the watershed impacted by land use disturbances, other than roads, that have occurred in the past 30 years, using SRS data (Stand Record Cards) and visual estimates. The percentage is adjusted by an average recovery factor of 70 percent (equivalent to 7-10 years of recovery). This means that 30 percent of the land use disturbance area is still recovering.

· Tolerable ERA 1 Increase. Figure 6. "Risk of Cumulative Effects," page 15 of the Determining the Risk of Cumulative Watershed Effects resulting from Multiple Activities document, listed above, will be changed to a table of "Tolerable ERA Increase" for each watershed sensitivity/condition score. The objective is to not exceed the moderate risk of cumulative effects. The values on the abscissa of the graph in Figure 6 will be changed to reflect the ERA increase that a watershed can sustain before reaching a high risk of cumulative watershed effects.

1. An average score of fair, or moderate, implies that the condition actually ranges from good to poor, or high to low. Watershed size will influence the ability of the scores to display actual conditions.

2. The range of values developed for the Watershed Sensitivity analysis represent actual values for the entire Pilot Project area, not just a portion of it.

3. All criteria ratings are equal and weighting is not necessary.

4. Vegetation recovery does not equate to restored soil conditions. It is used to indicate reductions in erosion and sedimentation.

5. As much as possible, private lands are included along with Federal lands to determine each factor rating.

6. Where a watershed contains a lot of variation, the average score is skewed towards the high side.

7. This exercise provides documentation of watershed sensitivities and conditions. The final output will be given a reality check by specialists familiar with the watersheds and the final risk ratings adjusted accordingly.

8. All watersheds that contain less than 25% federal lands were eliminated from this analysis because of lack of information. If projects are developed for these areas, impacts will be evaluated in project-level watershed analyses.

Watershed Identification__________________________ Date_____________________________

Final Score and Risk of Cumulative Effects. Multiply the two scores derived above:________________

(< 39 = Low) (39 - 72 = Moderate) (73 - 85 = High) (> 85 = Very High)*

*Based on sorting and grouping the scores of 348 watersheds averaging almost 10,000 acres in size and contained within the HFQLG Act Pilot Project area.

2Condition Rating. Based on the road density inside and outside the near stream area, the number of road/stream crossings, the condition of the alluvial channels, and the amount of area disturbed by land uses, minus a recovery factor.
A rating of 1 is low/good, 2 is moderate/fair, and 3 is high/poor.

3Sensitivity/Condition Score. This is simply the Sensitivity score multiplied by the Condition Score. The numbers were sorted as shown in Table N-9.

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