SOUTH LAKE TAHOE, Calif. — The Caldor Fire burned hottest in decimated communities and the landscape has dramatically changed on the main highway leading to South Lake Tahoe.

Blackened earth, scorched trees and burned homes are prominent alongside U.S. Highway 50 from Echo Summit to Kyburz.

The USDA Forest Service Burned Area Emergency Response Team recently completed data gathering and analysis of the Caldor burned area to produce a soil burn severity map of the 219,578-acre, 76% contained blaze.

---

---

The map and data display soil burn severity categories that include Unburned/Very Low, Low, Moderate, and High. Approximately half of the acreage of the fire (47%) are either unburned/very low or low SBS, while 40% sustained a moderate SBS and about 13% high SBS.

While the fire didn’t burn the hottest on Echo Summit according to the map, many of the cabins overlooking the basin are no longer there with the fire reducing them to rubble.

---

---

Many work crews had chainsaws fired up in the forest right beside US 50 and in the Echo Summit area falling burned trees on Tuesday. The highway was fully reopened at 8 a.m. for the first time since Aug. 20 and vehicles shortly after started streaming into the basin.

The SBS map shows the fire burning hottest in the decimated Grizzly Flats community where hundreds of homes were lost and along US 50 where houses were destroyed on both sides of the highway in Phillips near Sierra-at-Tahoe.

BAER teams are multi-disciplinary teams sent to federal lands following significant wildfires to characterize the fire effects to watersheds, identify imminent post-fire threats to human life and safety, property, infrastructure, and critical natural and cultural resources. The team assesses the effects to soils, not vegetation. Soil burn severity characterizes the effects at the soil surface and below-ground whereas vegetation effects are determined based on mortality and vegetation canopy changes.

Once the assessment is done, the team develops emergency treatment recommendations to mitigate identified risks. BAER teams then implement its recommended treatments and action stabilization measures. These teams begin their assessment immediately after the fire threat passes. The team focuses on the direct damage caused by the fire, rather than from fire suppression activities. Post-fire conditions such as loss of vegetation and the changes in the soils will increase the likelihood of floods and may cause potential debris and sediment flow impacts.

For complex fires such as the Caldor, assessments are done as an interagency effort which includes a California State Watershed Emergency Response Team. The Cal Fire WERT team is evaluating burned private and state lands from the fire. Both teams share information as they complete their evaluations, analysis and subsequent reports.

Changes in soil cover, water repellency, and soil physical/biological changes determine the severity level of soil burn severity. Changes in water repellency is a much-discussed fire effect. Fire can increase the severity and the thickness of the water repellent soil which has significant effects on post-fire water runoff.

Low SBS indicates there was only partial consumption of fine fuels while litter coverage remains relatively intact on the soil surface. Burning time at the soil surface was short, leaving root systems and root structure undamaged. Vegetative recovery time in the low category will vary based on ecological community but is expected to recover in the short-term.

Moderate SBS indicates nearly all soil cover of vegetative litter and fine fuels was consumed or converted to ash. Because soil cover is significantly reduced, accelerated water runoff is expected. Charring of the mineral soil occurs in Moderate SBS as well as shallow root burning. The extent of the burning of the leaves and needles on the trees (aka tree canopy) can be unpredictable and can range from high to relatively low mortality.

High SBS is the result of higher intensity fire behavior or longer burning time at the soil surface. As a result of the high heat, nearly all the soil cover of vegetative litter and fuels has been consumed leaving bare soil prone to the impacts of precipitation and resulting water runoff. The surface mineral soil has been reduced to powder (single grain) and often several inches thick. This single grain soil is very easily transported or moved during rain events resulting in excessive soil erosion and sediment loading in rivers, streams, and creeks. The roots in the High SBS areas tend to be completely consumed by the resulting heat of the fire above the soil surface. Water repellency does not exist at the surface because water repellent compounds have been vaporized and tends to be found below the powdered soil surface, but the repellency thickness and more severe burning tend to be much greater than a Moderate SBS soil. Generally, there is 100% tree mortality in High SBS soils.

The map can be viewed here.

“Everyone near and downstream from the burned areas should remain alert and stay updated on weather conditions that may result in heavy rains over the burn scars,” said a press release. “Flash flooding may occur quickly during heavy rain events, be prepared to take action.”

For weather and emergency notifications visit the National Weather Service website at http://www.weather.gov/sto/.

Bill Rozak is the editor of the Tahoe Daily Tribune, a sister publication to the Sierra Sun. He can be reached at brozak@tahoedailytribune.com