Indicator
Percent of Land Coverage Within Land Capability Class 1a (allow up to 1% impervious coverage)
2019 Evaluation
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Lands classified as 1a are among the most sensitive in the Tahoe Region and can support the least amount of land disturbance. The percent of land coverage within land capability class 1a indicator measures the percent of land coverage on class 1a lands in the Tahoe Region. The indicator allows up to one percent impervious coverage within land capability class 1a.  Land capability class 1a generally includes natural areas, including steep mountainous terrain with shallow soils. These environmentally sensitive areas, with slopes exceeding 30 percent, are not generally suitable for intensive development, but class 1a areas support wildlife and dispersed recreation.  

Status
Percent cover in each Bailey land capability class relative to the allowable coverage in class.
2019 Evaluation
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Status
Considerably Better Than Target
Trend
Little or No Change
Confidence
Moderate
Applicable Standard
SC1: 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 1a - 1%.
Key Points
  • Impervious coverage within class 1a was estimated to be 211 acres, less than the threshold standard of 240 acres.
  • Projects to acquire and/or restore sensitive lands add to the natural function of the Region's ecosystem. The acquisition and restoration of sensitive lands protect watersheds by mitigating the effects of development, providing valuable habitat for special status species, and enhancing recreational opportunities in the Tahoe Region.
  • More than 215 acres of sensitive lands (land capability classes 1-3) were acquired between 2016 and 2019 by Environmental Improvement Program partners.
Evaluation Map
Description

Land capability Class 1a 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

EIP Indicators

  • Acres of Environmentally Sensitive Land Acquired

    Since 2007, EIP partners have aquired over 1,150 acres of environmentally sensitive land for protection or restoration.

  • Impervious Coverage Retired

    Between 2016 and 2019, EIP partners and private partners through projects retired (i.e., permanently remove from future use) 3,909 square feet (0.1 acres) of Class 1a coverage.

Example EIP Projects

Rationale Details
Impervious cover within each land capability class was determined by an analysis of LiDAR/multispectral data collected in 2019. Land capability Class 1a has fewer existing acres of impervious coverage than is allowed under Bailey, 211 acres of existing impervious surfaces with the threshold standard of 240 acres. This makes it "considerably better than target."
The trends for Impervious cover within each land capability class were determined to be "little or no change". TRPA Regional Plan policies limit new the amount of additional coverage that is allowed in sensitive land classes. And, the restoration, acquisition, and retirement of sensitive lands are priority actions for the Environmental Improvement Program projects.
Confidence Details
Moderate. TRPA has used the best available science and technology over time to assess the impervious cover threshold standard, different imagery datasets (4-band IKONOS collected in 2002, LiDAR and 8-band multispectral collected in 2010 and 2019). However, because of variation in the methods used to assess impervious surface features and estimate impervious cover, the comparison across evaluations is unsuitable.
Moderate. There is “moderate” confidence in the current estimates of impervious cover from the LiDAR data and the resulting impervious surface layer. There is "high" confidence in the reporting of added coverage from permitting activities and coverage removal results from Environmental Improvement Program reported in the EIP Project Tracker.
Moderate. There is “moderate” overall confidence base on the accuracy assessment of the impervious surface data and the land capability class results.
Additional Figures and Resources

No documents available.