Last Updated on Tuesday, 03 July 2012 06:33
Monday, 02 July 2012 00:00
2011 Status of Tahoe Soil Conservation Effort
“The land coverage category that needs accelerated improvement is our sensitive wetland category,” says Marchetta. She goes on to say, “These sensitive wetlands continue to be over-covered from legacy development. That’s why we are not making the progress that we need to make.”
photo: Tahoe East Shore by Michelle Sweeney
July 2, 2012
By Michelle Sweeney
Soil serves many important functions, including sustaining forest vegetation, storing water and moving water toward streams, rivers and lakes. If soil is unprotected and mobilized it is a significant threat to water quality. The mass of phosphorus and nitrogen that mobilize in the watershed affect the clarity of Lake Tahoe. Soil contains phosphorus and nitrogen. Soil itself is a cause of lake clarity decline. Very fine particles of soil (those smaller than the diameter of a human hair/<16 microns) are a major cause of lake clarity decline. Fine sediment particles remain suspended in the water column in Lake Tahoe—absorbing the light—and contributing to factors that support algae growth. For all of these reasons it is critical to the environment that soil integrity be maintained.
The majority of fine sediment particles are generated in urban areas where most soil disturbance occurs. The Lake Tahoe TMDL project found that 72% of fine sediment particles reaching Lake Tahoe first mobilize in the urban areas around the lake. Commercial, residential and roadway areas all contribute fine particles to the lake. In order to conserve soil and keep it immobile in the watershed, the Tahoe Regional Planning Agency (TRPA) regulates land coverage. “You can think of soil conservation as our land use controls,” says Joanne Marchetta, Executive Director of the Tahoe Regional Planning Agency.
Soil conservation is the subject of Chapter 5 of the TRPA Threshold Evaluation Report which describes soil conservation as “a set of management strategies” for preventing soil erosion or chemical alteration—“alteration by overuse, acidification, salinization, or other chemical contamination”. Limiting land coverage (aka development) and preventing erosion and runoff are the general soil conservation strategies.
“The good news is that our policies have been very effective in stopping development in sensitive lands,” says Marchetta. “In fact that rate has gone to zero,” she says. Stream restoration projects being implemented by California and Nevada agencies partnering with TRPA are “achieving wetland restoration goals”, adds Marchetta.
“The land coverage category that needs accelerated improvement is our sensitive wetland category,” says Marchetta. She goes on to say, “These sensitive wetlands continue to be over-covered from legacy development. That’s why we are not making the progress that we need to make.” For this reason the draft Regional Plan Update document targets the removal of harmful legacy development—development that causes soil erosion and which is on sensitive land that connects the mobilized soil directly to streams and Lake Tahoe. “We are also targeting environmental redevelopment that is going to reduce existing coverage on sensitive lands [in order to] accelerate progress toward attainment of the soil conservation threshold standard,” says Marchetta.
Tahoe Regional Planning Agency Regional Plan | Draft 2011 Threshold Evaluation Report