Flood Havoc May Outstrip Fire Damage, Officials Say

Recent wildfires that charred 300,000 acres of brush and timber in California have caused “tremendous environmental damage” and are likely to cause disastrous floods and mud slides when the rains start this fall, according to scientists and U.S. Forest Service officials.

In the Ojai Valley alone--where the watersheds were completely denuded by the gigantic Wheeler fire--the flooding could affect hundreds of homes and businesses.

“The situation there is set up for a much bigger disaster than the fire,” said Dave Haney, the district ranger who supervises the Los Padres National Forest watershed above Ojai. “When the rains come some of those watersheds will blow out, like freight trains.”

Problems Nearly Inevitable

Even if the burned-over areas are quickly reseeded, as planned, and the winter is mild, the 27,000 people living in and around Ojai probably will not escape the environmental aftermath of the big fire, according to research scientists, who say the size and intensity of such wildfires create unusual conditions that almost guarantee disaster.

The situation is similar in many, if not most, of those 30 areas in the state that have been hit by major wildfires this summer in what experts say is already one of the worst fire seasons ever.

The primary problem caused by a big fire is its searing impact on the soil’s ability to absorb rainwater, said Richard Minnich, a wildfire research scientist at the University of California, Riverside. “The sediment comes off no matter what. . . . The rains are no longer absorbed by the soil.”

Phillip Riggan, a research scientist at the U. S. Forest Service’s Forest Fire Laboratory in Riverside, said the heat from the fires liquefies hydrocarbons in the soil, producing a varnish-type substance that, when it cools, forms a layer close to the surface that is almost impervious to water.

Even in the gentlest storms this layer prevents the rains from penetrating into the soil, Riggan explained. Instead, the water runs off in torrents, creating flash floods, erosion and mud slides that rush down the canyons and all too frequently slam into populated areas.

Various Effects on Environment

While this “hydrophobic layering” causes the most immediate concern in places like Ojai, it is not the only environmental consequence of wildfires.

Experts say big fires:

- Initially destroy wildlife and radically alter the existing balance of an ecosystem. Soil structures are baked by intense heat, changing their composition. Almost as soon as the fire cools, however, nature begins the struggle to heal the denuded landscape that is so vulnerable to erosion. The increased availability of sunlight and moisture allows new kinds of plants to thrive, and animals and insects are attracted to this new food source.

- Are self-perpetuating because in their wake, large, uniformly aged areas of chaparral will grow back over several decades, slowly recreating the same highly combustible fuel conditions that flared in the first place.

- Pollute water with sediments and destroy watersheds, causing reservoirs to fill with silt.

- Recycle decades of air pollution, sending tons of debris, carbon dioxide, nitrates and sulfates into the air. Some of the nitrates--which settle out of the air onto plants and are washed by rain into the soil, where they are absorbed by the plant roots--stimulate plant growth, which adds more fuel to the next fire. Some oxides of sulfur and nitrogen contribute to acid rain, while others caught up in the smog-fire cycle wash into the soil and pollute ground water.

This year, scientists studying the interrelated effects of fire and air pollution have begun to link the nitrogen released by a big fire to the almost unprecedented dying out of certain kinds of brush now being seen throughout the Southern California mountains.

One theory being studied by fire laboratory scientists holds that the fertilizing effect of the smog-fire cycle has greatly overstimulated brush growth in recent wet years. Then, in this unusually dry year, lack of moisture is killing the brush, creating an even greater hazard.

Fire is an “integral part” of all forest and brush ecosystems, according to fire laboratory scientist Robert Lockwood. Only during the last century have wildfires been suppressed. Before man intervened, these fires seldom flared up into major conflagrations, researchers now know.

Lower Temperatures

Smaller fires burn at cooler temperatures, and the rains that follow are readily absorbed into the soil, Lockwood said. “The next spring you see the wild flowers and grasses. Seeds that were dormant in the soil for 50 or 60 years germinate, brush begins to sprout . . . and wildlife habitat is greatly improved.”

Natural wildfire acts as both a stimulant within the ecosystem and a guardian that works to keep an optimum balance in the complex relationships among plants, insects and other animals. In the natural scheme, it takes a fire to set off the biological time clock that allows seeds to germinate and sprout. Fire removes older competing plants and opens the soil to sunlight.

“When a fire like the one near Ojai goes over 100,000 acres, you know something has gone wrong in the ecosystem,” said wildfire expert Minnich, who has been comparing major Southern California wildfires to those of northern Baja California, where fires are almost never suppressed. As a result, the fires in Mexico are more frequent, much smaller and less destructive to the environment.

Ojai Fire Predictable

“The big Ojai fire was predictable,” Minnich said, because the whole 100-square-mile area of the Los Padres National Forest had not burned since the 1930s and, as a result, had become a tinderbox fueled by the most extensive growth of old, highly flammable brush in Southern California.

The ecosystem had become unbalanced because for the last century firefighters have been suppressing fires. In doing so, they have interrupted the natural sequence of smaller and cooler fires that prevented the massive accumulation of chaparral.

As the ashes of the 116,000-acre Wheeler fire cool on denuded mountains and slopes of deep canyons, county and federal engineers are assessing the damage to the watersheds that supply domestic water to large parts of Ventura County. Flash flooding and heavy erosion are anticipated with the first rain.

“We’ll reseed the watersheds, of course, but that only mitigates the impact a little. Once an area gets burned with the intensity of this fire there isn’t much you can do,” Haney said.

Plans are now being drafted to clear water channels so they can carry maximum flows this fall and winter.