Indicator
Percent of Land Coverage Within Land Capability Class 4 (allow up to 20% impervious coverage)
2023 Evaluation
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Lands classified as land capability class 4 are considered non-sensitive in the Tahoe Region and can support development. The percent of land coverage within land capability class 4 indicator measures the percent of land coverage on class 4 lands in the Tahoe Region. The indicator allows up to 20 percent impervious coverage within land capability class 4. This non-sensitive land capability class includes scattered areas with moderately steep slopes that have moderate erosion hazards.

Status
Percent cover in each Bailey land capability class relative to the allowable coverage in class.

Data was created by Tahoe Regional Planning Agency. Access detailed datasets on Tahoe Open Data, including, bailey land capability feature class, remotely sensed impervious coverage feature class, and the permitted coverage summary.

2023 Evaluation
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Status
Considerably Better Than Target
Trend
Little or No Change
Confidence
Moderate
Applicable Standard
SC6: Impervious cover shall comply with the "Land Capability Classification of the Lake Tahoe Basin, California-Nevada, A Guide for Planning", Bailey, 1974. Allowable percent of impervious cover in Land Capability subclass 4 - 20%.
Key Points
  • Impervious coverage within class 4 is estimated to be 1,323 acres, less than the threshold standard of 6,289 acres.
  • Approximately 16 percent of the land area in the Tahoe Region is class 4. 
  • Just over one acre of additional class 4 coverage was added between 2020 and 2023.
  • Only 21 percent of the regional allowable coverage in class 4 has been utilized. 
Evaluation Map
Description

Land capability Class 4 lands and impervious surfaces within the Tahoe Region

About the Threshold
This indicator measures the percent of land coverage on different land capability classes as described by Bailey (Bailey, 1974) and updated with the most recent soil survey by the Natural Resources Conservation Service (NRCS) in 2007 (Loftis, 2007; USDA-NRCS, 2007). Impervious cover is a primary indicator of land disturbance. Excessive impervious surface within a watershed contributes to sediment and nutrient inputs to Lake Tahoe and its tributaries impairing water quality, altering surface hydrology and groundwater recharge regimes. The results are often negative impacts on soil health, fisheries, wildlife habitat, and vegetation growth. Impervious surfaces include hard coverage such as roads, buildings, driveways, and parking lots, and soft coverage with soil compaction as a result of use, but where no structure is in place.
Impervious cover is created through use or development on natural lands. This could be for commercial, residential, recreational, and other activities, and encompasses the spectrum of human uses that involve physical modification of the environment. The economy plays a large role in the housing market and the business environment, which are both among the most important drivers of new land coverage in the basin.
Delivering and Measuring Success

No related projects or programs defined for this indicator.

Rationale Details
Considerably Better Than Target. Land capability Class 4 has 1,323 acres of existing acres of impervious coverage, 4,966 acres less than are allowed under the Bailey 4 threshold standard of 6,289 acres. This makes it "considerably better than target."

All permitted projects that add coverage pay a water quality mitigation fee. There were 720 projects that paid water quality mitigation fees between 2000 and 2023, with more than $2.37 million collected during the period for the creation of 1.275 million square feet of added coverage (29 acres) in all classes. During the period, more than 232,000 square feet of coverage (5.3 acres) was removed on 45 parcels as a requirement of permit conditions and from Environmental Improvement Program projects to remove and retire coverage.
Little or No Change. The trends for Impervious cover within class 4 was determined to be "little or no change". Between the 2019 Threshold Evaluation and the 2023 Threshold Evaluation, impervious coverage in class 4 increased by 1.2 acres, or 0.1 percent.
Confidence Details
Moderate. For the 2023 analysis, TRPA used the 2019 baseline and added or removed coverage based on the cumulative accounting of acres of cover added in each land capability class based on the rigorous tracking from TRPA permitting data and Environmental Improvement Program tracking. All permitted projects that add coverage pay a water quality mitigation fee; these fee collections were used to assess added coverage. Some inaccuracy is introduced due to unpermitted impervious cover that may have been added or created in the Region, for which no permit was acquired. This reduces the status confidence to moderate. The 2019 Threshold Evaluation for impervious coverage was based on an updated analysis of high-resolution aerial imagery and hand digitizing features from multispectral images collected in 2018 and 2019.
Moderate. Because of the change in source data to using permitting mitigation fees for the 2023 evaluation, comparison of the trend is rated as moderate confidence.
Moderate. There is “moderate” overall confidence based on the accuracy of the impervious surface data and the land capability class results.
Additional Figures and Resources

No photos available.

Coverage Changes 2020-2023
Uploaded On
10/18/2024
File Type
PDF
Description
This table provides the detailed accounting of coverage added by parcel between 2020-2023, based on TRPA permitting actions and the payment of water quality mitigation fees. The table also includes coverage removed and retired through permitting as well as coverage removed by Environmental Improvement Program projects. The coverage changes are reported by year and land capability class