Floods in Big Sur
The Big Sur River reached flood stage after more than 5 inches of rain fell last weekend. Highway 1 was blocked Monday by a mudslide/debris flow near the Pfeiffer Big Sur State Park entrance.
Some excellent photos of the flooding are [here].
The photos were posted by Big Sur Kate [here], who blogged about the Basin Fire up close and personal. Some blogs rise above the mundane. Big Sur Kate’s is one of those — it is not only a triumph of art, her blog provides an invaluable public service by promoting public health and safety and a deep understanding about living on this Earth.
The Big Sur River watershed and a few other watersheds on the Los Padres National Forest were burned by the Basin [here], Indians [here], and Chalk [here] Fires.
The Basin/Indians Fire (they merged) cost over $120 million while burning 244,000 acres. It was the third largest fire and the most expensive fire in California history, and the second most expensive in U.S. history (the Biscuit Fire in Oregon in 2002 had $150 million in suppression expenses). The Chalk Fire added 16,269 acres and $24 million to those totals.
Most of the dollars and acres burned up were due to backfires set by firefighters. Fire managers announced at the onset that they were applying the “accountable cost management strategy” and then they proceeded to break the bank. When the Basin Fire reached homes dozens of miles from the ignition point, the firefighters fled and homeowners fought the fire themselves. At no time during the last 30 years did the USFS initiate any fuels management or fire road construction in the area, because Congress designated the area a wilderness, even though human beings have been living there for 10,000+ years.
The Monterey Herald reported a flash-flood warning [here]:
By Daniel Lopez, 03/03/2009
Another inch of rain is expected today and Wednesday in the urban areas of Monterey County, the National Weather Service said.
Beginning Friday though, the storm clouds are expected to clear, leading into what should be a dry weekend.
Early Monday, heavy rain prompted the weather service to issue a flash-flood warning for small streams and rivers in the Big Sur area.
The National Weather Service issues such warnings when there is a rapid rise in stream levels, said forecaster Steve Anderson.
The Big Sur area was scarred by wildland fires last summer and officials fear the damaged land may be more prone to landslides, flooding and debris flows in the surrounding creeks and streams.
“Once the mud and debris starts coming downhill, there’s nothing to stop it,” Anderson said.
The Big Sur River did peak at about 7½ feet Monday but there were no reports of damage or significant problems. …
Scientists who studied the burned area said there is a risk for flooding and landslides for about five years.
We have essayed about post-fire watershed destruction in more than a few posts, most recently in Floods Follow Fires [here]:
Catastrophic forest fires impact more than the vegetation. Fires destroy habitat, pollute streams, foul the air, and inflict public health and safety problems. Sometimes, as was the case in the Biscuit Fire (2002), forest fires burn so intensely that the soil is stripped away [here].
After intense fires the soils, baked and/or blown away, cannot absorb water as they did previously. Rain does does not infiltrate the damaged soils due to collapse of soil structure, increased bulk density, removal of organic matter, reduction in soil porosity, clogged soil pores, and increased reaction to rainfall droplet kinetics. Soils can become “waterproof” through decreased soil wettability (hydrophobia), concretion, and increased water repellence. That can lead to increases in surface flow, increased soil particle transport, rilling, gullying, and increased erosion.
And floods. Fire-damaged soils across a watershed can cause increases in discharge rates, seasonal streamflows, and especially peak flows, including flash flooding.
Before the fire the soil acts like a giant sponge; after the fire the soil becomes water repellent. As a result, floods happen more frequently.
The Salmon River watershed in central Idaho was subjected to an 800,000 acre burn in 2007. Mudslides tore out roads and filled streams the following winter [here]. This winter more of the same is expected.
Flash floods followed the Zaca Fire (2007) [here], which burned 240,000 acres over a two month period, cost more than $120 million in direct fire suppression expenses, and was (at the time) the most expensive fire in California history.
That is, until one year later when the Indians/Basin Complex Fires burned 244,000 acres and cost $124 million.
The effects of catastrophic fire on forests and watersheds are both immediate and long lasting. The final cost-plus-loss totals for the Basin Fire are not yet tallied, and will not be for years to come.
Oh, and thank you so much for your nice comments about my blog!!
Actually, the Basin Complex Fire and the Indian Fire were never “merged” officially or unofficially. The reason they never “merged” officially was because their origins were by different means. The origin of the Basin Complex fires was lightning strikes. The origin of the Indians Fire was man-caused, by a campfire which escaped. Unofficially, while the two fires burned right up to each other, they did not actually overlap.