The Oceano Dunes are a very special place along the famed California coastline. Driving on the beach in California is a rare and coveted opportunity. Southern California has no legal beach driving access. Central California’s only option is here at Oceano Dunes/Pismo Beach, and the wild expanse of Northern California holds the few other places that beach driving is allowed.
This earthcache will highlight the current dune restoration effort underway. Sand dunes are a very important part of a land’s geology and hydrology, and they offer some ecosystem services that cannot be replicated. Dunes provide great protection against storms and ocean sea level surges. Sand dunes are a coastline’s first level of defense against natural disasters and sea level rise. Sand dunes are classified into one of five types: crescentic, linear, star, dome, and parabolic. The most common sand dune type on Earth (and Mars!) is crescentic. “Crescent-shaped mounds generally are wider than long… Straight or slightly sinuous sand ridges typically much longer than they are wide are known as linear dunes… Radially symmetrical, star dunes are pyramidal sand mounds with slipfaces on three or more arms that radiate from the high center of the mound… Oval or circular mounds that generally lack a slipface, dome dunes are rare and occur at the far upwind margins of sand seas… U-shaped mounds of sand with convex noses trailed by elongated arms are parabolic dunes” (USGS, 1997).
The shapes of dunes are always being altered by the wind. This natural force constantly blows sand down to the beach, or up to an obstacle like a plant. The movement of sand is a natural process, and actually acts as an effective barrier against coastline erosion. Erosion can take place during storms or gradual sea level rise, and poses a threat to habitat, different species, and man-made developments on the coast.
The Oceano Dunes have been threatened over the years by the constant degradation from off-road vehicles. Naturally, plants like grasses help keep the dunes stabilized, and create a barrier for how far the wind can push sand inland. ATV’s, motorcycles, and dune buggies have contributed to significant native plant loss, and thus made the dunes highly susceptible to wind erosion. In fact, so much sand was beginning to blow into nearby communities like Pismo Beach, residents became concerned about air quality. Since the recreational vehicle use has destroyed such large parts of the dunescape, specific restoration strategies have been implemented to reverse the effects of the dune buggies. The main strategy seen here may look odd to the viewer, but it consists of planting native seedlings and spreading straw over them to hold the sand in place. The seedlings themselves would not be strong enough to root themselves, so the straw provides some stability while they take time to get settled. Additionally, the straw is just loose and will eventually blow away, but by that time the seedlings will have taken hold. The end-goal is a restored dune with the original variety of native plants that provide stability and erosion control to the dunes. The seedlings used here at the dunes are grown right here in Oceano Dunes SVRA’s greenhouses on Cabrillo Highway (Hwy 1).
To log this Earthcache please send a message with the following:
- Name of cache and number of people in your group.
- What type of the 5 types of dunes do you see while cruising through Oceano Dunes?
- Based on what you observe, do you think the erosion control/restoration efforts are working?
- Why do you think the effects of motor vehicles are so much different than other strong forces, like rough waters or high wind events?
Sources:
https://ohv.parks.ca.gov/?page_id=25712
https://giving.calpoly.edu/news/learn-doing-takes-root-oceano-dunes
https://www.surfertoday.com/environment/the-importance-of-sand-dunes-to-the-coastline
https://pubs.usgs.gov/gip/deserts/dunes/
Work experience on this specific restoration project, 2020