At San Diego State's soil erosion lab, the rain is feigned, but the results are real

Despite that demand, there's only a handful of comparable facilities in the United States. That means SDSU's lab, paid for by Caltrans as part of a $3.2 million study in the late 1990s, already has projects scheduled into 2009.

Though erosion is a natural phenomenon – think of the Grand Canyon – it has been dramatically increased in some places by humans.

One reason is that large paved surfaces collect water and send it rushing downhill, gathering sediment and scouring bare lands below. Another is that exposed topsoil at the countless construction sites around Southern California can easily be washed or blown away if nothing is holding it down.

SDSU's erosion control facility is credited with updating the best management practices for state highway construction projects and helping control erosion after the massive 2003 fires in San Diego County.

“The thing about San Diego State's lab is that it's practical research. What we learn today, you apply tomorrow,” said Mike Harding, a storm-water erosion consultant in San Diego who has helped design, build and operate the lab.

One recent day, Beighley's students set the rainmaker to test soils that the U.S. Environmental Protection Agency had imported from Phoenix and Las Vegas. In the corner was a large pile of typical Southern California dirt that will be used for other experiments.

“To have (a rain lab) on the West Coast I think is really important because our rain here in Southern California is different from even in Northern California,” said Helene Bell, erosion control specialist with Caltrans in San Diego. “We have to take those things into consideration when we are developing our ... methodologies.”