California turns from fighting fires to preventing mudslides
Firefighters in California have brought the last of the major wildfires under control. But authorities are now faced with the challenge of breaking the familiar Western cycle -- fires followed by mudslides. State agencies are about to drop tons of grass seed on burned hillsides, which, without firm roots to anchor the soil, may slide away with the first strong rain.Skip to next paragraph
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While the intense burst of fires across the West will soon fade from the headlines, government scientists are studying the subject year round.
Fire's effects reach far beyond the visible charred hillsides. Mudslides that run off denuded hills damage homes and clog waterways and reservoirs.
As with any environmental phenomenon, man's tinkering can affect the natural balance, explains Enoch Bell, assistant director of the Pacific Southwest Forest and Range Experimental Station (a part of the United States Forest Service).
For example, the seeding of denuded hillsides with rye grass -- an inexpensive, fast-growing, and firmly rooting grass -- may save homes from floods this winter but rye grass is highly flammable when dry and may add to the fire danger next summer. There is also debate over introducing a nonnative plant that might overwhelm wild grasses in the area.
``Fire is a normal occurrence in the wilderness,'' says Mr. Bell.
Some plants such as southern California's chaparral actually need fire, depending on the intense heat to spread its seeds. He notes that fires are more likely to occur in the forest because man is there, but that fires are also more likely to be suppressed because of man's presence.
So the bulk of research being done by government scientists is aimed at understanding how fires act so that they can be controlled better and so that their effects on areas of ``public value'' can be protected.
For example, explains Bell, the ``main impetus to get involved in fire research in 1934 was strictly because of the effects of fire on watersheds. In southern California fire was destroying watersheds and they wanted to get more water out of the watershed.''
A whole series of federal fire labs grew out of that need to protect a natural resource for an urban area, he explains.
Similarly, the current effort in California to reseed hillsides focuses mainly on areas of ``public value,'' explains Dale Weirman, a California Department of Forestry vegetation management forester.
Mr. Weirman explains that soil eroded from mountains flows into streams and moves toward lakes or the ocean.
``If streams flow directly into the ocean, and Highway 1 is not in danger, there's no justification'' to tamper with postfire landscape in these areas, he says. But he notes that following a 1961 fire near Los Gatos the silt flowing off unprotected hillsides reduced one small reservoir's storage capacity by 50 percent.
Fire research being done in the federal Fire Effects Project under Bell's department is focusing on the variables that determine the effects of fire.
One current study aims to determine the amount of precipitation runoff associated with different levels of burning -- for example, would fewer mudslides and less erosion occur if vegetation were burned off periodically? Or would there be less erosion over time if brush were just allowed to grow naturally? This, experts say, is a key question in budgeting for the cost of catch basins for debris in residential areas.
Another study involves creating a ``mosaic'' of old and new vegetation across large areas of land as a natural fire break -- the age of some growth determines its flammability, and a mixture of old and young in an area may make it less vulnerable to fire. This would be preferable to the bulldozed firebreaks that mar many hillsides in southern California.
Meteorology, too, is being studied by fire experts because highly refined prediction methods are needed to determine how the wind will blow in a particular canyon that might be on fire.
Physicists are studying fire behavior to try to understand the relation between intensity of heat and the rate of speed of fires -- in hopes of providing on-scene guidance to those fighting erratic wildfires.