Percent of Land Coverage Within Land Capability Class 1a (allow up to 1% impervious coverage)
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
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.
Evaluation Map
Land capability Class 1a lands and impervious surfaces within the Tahoe Region.
2023 Evaluation
- Status
- At or Somewhat 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.
- Less than 0.1 acre of impervious coverage was removed from class 1a from 2020 to 2023 through mitigation requirements from permitting. No additional coverage was added to class 1a during this period.
- 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 613 acres of sensitive lands (land capability classes 1-3) were acquired between 2020 and 2023 by Environmental Improvement Program partners.
- The TRPA Code of Ordinances restricts new land coverage or permanent disturbances in sensitive areas, specifically in classes 1a, 1b, 1c, 2, and 3, with only a few exceptions allowed.
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
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Acres of Environmentally Sensitive Land Acquired
Since 2007, EIP partners have acquired over 1,642 acres of environmentally sensitive land for protection or restoration.
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Impervious Coverage Retired
Between 2020 and 2023, EIP partners and private partners through projects retired (i.e., permanently remove from future use) 2,744 square feet (0.1 acres) of class 1a coverage.
Example EIP Projects
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Clancy-Pohl Sensitive Land Acquisition
Nevada Division of State Lands used excess coverage mitigation funds to purchase this parcel and retire the coverage, including class 1a coverage.
Rationale Details
- At or Somewhat Better Than Target. Land capability class 1a has 211 acres of existing acres of impervious coverage, 29 acres or 12 percent less than allowed under the Bailey 1a threshold standard of 240 acres. This makes it "At or Somewhat 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 (see attached table in the Additional Figures and Resources section below). - Little or No Change. The trends for Impervious cover within class 1a was determined to be "little or no change." Between the 2019 Threshold Evaluation and the 2023 Threshold Evaluation, impervious coverage in class 1a changed by less than 0.1 acre, or -0.03 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.
- Uploaded On
- 10/18/2024
- File Type
- 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.