On the heels of the budget request testimony of the US Forest Service Chief Tom Tidwell to the Senate Committee on Energy and Natural Resources in April, fires in southern California started blazing in May.
The early arrival of fire season in the state-combined with the fact that state firefighters had responded to twice the average number of wildfires to that point-prompted Gov. Jerry Brown to caution that residents would have to get accustomed to more wildfires, warning that the changing climate and intense weather patterns jeopardize lives and property and can become a financial drain.
Tidwell’s testimony on the fiscal year 2014 budget request focused on three key areas, of which managing wild land fires is one (the other two being restoring ecosystems and strengthening communities).
In the president’s proposed overall budget for discretionary funding for the US Forest Service in fiscal year 2014, $62 million had been shifted from key programs to meet the requirement to fund the 10-year rolling average of fire suppression costs.
US Forest Service restoration efforts are partly in response to growing fire season severity. While the agency continues to suppress 98% of the fires on initial attack, the few that escape initial attack tend to get much larger much faster.
The spread of homes and communities into areas prone to wildfire is an increasing management challenge, the US Forest Service reports. From 2000 to 2030, the agency expects to see substantial increases in housing density on 44 million acres of private forestland nationwide.
The agency has a three-part fire strategy:
- Restoring fire-adapted ecosystems-More than 1,000 post-fire assessments reveal that fuels and forest health treatments are effective in reducing wildfire severity. The agency focuses treatments on high-priority areas in the wild land/urban interface, particularly near communities that are taking steps to become safer from wildfire, such as adopting the national Firewise program or developing community wildfire protection plans.
- Building fire-adapted human communities-With more than 70,000 communities at risk, the US Forest Service is working through cross-jurisdictional partnerships to help communities become safer from wildfires. Through the Firewise program, the number of designated Firewise communities-communities able to survive a wildfire without outside intervention-rose from 400 in 2008 to more than 700 in 2012.
- Responding appropriately to wildfire-Most of America’s landscapes are adapted to fire, and wild land fire plays a natural and beneficial role in many forest types. Where suppression is needed to protect homes and property, the focus of the Forest Service is to “deploy the right resources in the right place at the right time.” Using decision-support tools, fire managers make risk-based assessments to decide when and where to suppress a fire or use it to achieve management goals for long-term ecosystem health and resilience.
Although air tankers are a critical part of a wildfire response, the average age of the Forest Service’s fleet is greater than 50 years. The cost of maintaining the tankers is increasing, as are the risks associated with using them. The Forest Service is implementing a Large Air Tanker Modernization Strategy to replace its aging fleet with next-generation air tankers.
With respect to post-fire remediation, the agency is focusing on what works-and what does not.
Rod Clausnitzer is a forest botanist/plant ecologist for the Okanogan-Wenatchee National Forest in the state of Washington. In 2006, he was involved in efforts to mitigate the Tripod Complex fire, which burned more than 175,000 acres.
“It was one of the largest fires we’d seen in north central Washington,” says Clausnitzer. “It was pretty severe fire weather at the time, with a patchwork mosaic of conditions that created it.”
Rehabilitation work followed through into 2007.
“We initiated the assessment that would look at post-fire recovery and rehab efforts right away and determined that there were certainly risks to property, lives, and resources downstream of the fire,” Clausnitzer says, adding that those three criteria are always considered.
The response considers available resources. Response is based on a report that identifies areas of high-risk need in terms of the severity of the burn and soil conditions, such as areas that were highly erosive and areas with soil/water penetration issues.
After the Tripod Complex fire, the response entailed aerial and roadside mulching and seeding. Aerial mulching with Hamilton Manufacturing’s NaturesOwn mulch covered a 20,000- to 30,000-acre range with helicopters.
“We used wheat straw from the basin here and augmented it with rice straw from California,” Clausnitzer says, noting he was pleased with the end results.
“It was quite an operation,” he says. “It was done safely. It was very effective. That was a real accomplishment.”
Part of the confirmation of the success of the approach came as a result of the Forest Service using QuickBird imagery to detect cover and spread of post-fire straw mulch after the fire.
Researchers from the Rocky Mountain Research Station noted that agricultural straw mulch is a commonly applied treatment for protecting resources at risk from runoff and erosion events after wildfires. High-resolution QuickBird satellite imagery was acquired after straw mulch was applied. The imagery was tested to see if it was suitable for remotely assessing the aerial coverage of the straw mulch treatment. Straw mulch was easily identified in the imagery because of the distinct spectral signature of the mulch against the burned background. Results encourage further exploration of the use of high-resolution imagery for research applications and post-fire management, the researchers say.
Assessing the Situation on the Ground and From the Air
Michael Harding, a senior consultant with Geosyntec Consultants’ San Diego Old Town office, who has worked on 45 fires in his career, points out that each one is different.
In doing a post-fire damage assessment, the first factor that should be considered is whether there are any associated impacts.
“The fire in itself is a hazard,” Harding says. “From our standpoint, it really is a combination of erosion and sediment control and dust control.”
Hazards can entail everything from landslides to mud flows to fugitive dust.
“There are always hazards after a fire, but the question is, are there any impacts?” Harding points out. “You may think you need to get out there and do something, but not necessarily. A lot of that stuff is in areas where there may be a hazard from a mud flow or from a landslide, but there is no impact to human health and safety.”
Geosyntec Consultants typically treats 1 to 2% of the burn area, usually at the urban interface and particularly where a fire burns in to the edge of a city, Harding notes. For example, after a 2003 California fire, fewer than 2,000 acres were treated out of half-million burned acres.
“The only exception to that is occasionally you’ll get a fire like Oakland in 1991; that was an urban fire that burned from the middle of the town out, so that was all urban area,” he says. “That was about 1,500 acres. We treated that entire watershed, because it was all within the city. Most of the time, you just treat the fringes.”
To assess the downstream impact of a fire, Geosyntec Consultants uses satellite photos and topography maps.
“I usually run a helicopter and fly the areas to assess where there may be some downstream impacts associated with the fire,” says Harding. “Sometimes they’re large watersheds. There may be houses sitting on a hillside and the water’s got to go around them. Sometimes we have people sitting down below in what I call a “˜bowling alley,’ and they didn’t even realize the whole slope behind them was a bunch of boulders. Now all of the vegetation is gone and the boulders are going to come down on them when they get slides after a rainfall.”
Sometimes crews on the ground help with the watershed impact analysis.
“Then you’ve got to convince the sponsor-in most cases, it’s the city, a county, or a state-that they need to do something. That’s the hardest thing to do,” says Harding. “A lot of work hasn’t been done in the last six years on fires because nobody has any money.”
Usually, the sponsor makes an initial financial outlay that is reimbursed by the Federal Emergency Management Agency (FEMA).
“They may not get reimbursed for a long time, so they have to have the wherewithal to say they’re going to dedicate themselves to protect the citizenry; sometimes they do and sometimes they don’t,” says Harding.
He recently met with the assistant director of a state environmental agency regarding a large fire “and they told me they only have so much money and really couldn’t do anything about it. I told them they owe the public because they are public servants, and that if they don’t have money to do the remediation work, at least do an assessment to warn people to get out of Dodge when there’s a threshold amount of rain. It does take some convincing in some cases to say to public leaders that they need to take action.”
Harding points out that when the public works director of Laguna Beach, CA, was faced with post-fire remediation in 1993, he made the decision to proceed and “worry about the money later.” As a result, Laguna Beach subsequently did not have a lot of problems, he adds.
“Other towns waffled on it, and then they suffered,” Harding points out. “You’ve got to have the buy-in from the local sponsor to determine whether they’re going to have an all-out effort.”
Government entities sometimes don’t have the staff or monetary resources to handle post-fire remediation. “Being on the consultant end of it, we’re usually the ones that get the call to come in and augment their staff and get it organized. We generally work hand in hand with the sponsor, giving them an appraisal of the situation. You’ve got to say there are hazards out there that we need to remediate-or maybe there aren’t,” Harding says.
After doing a damage assessment and then ensuring that initial actions will be reimbursed, the third step is to determine the response.
“Nowadays, we don’t add any seed to the mix,” Harding says. “That’s almost a political consideration. It’s gotten to a point where in California, they think we’re out here hydroseeding, when in fact we’re not. We’ve learned over time if we use nice mulch with a tackifier-and we’ve tested a lot of this at San Diego State College before the 2003 fires-we can hold the ground, and Mother Nature will come back faster than we can augment it.”
Nonetheless, there are areas that do need seed, Harding points out. A black ash indicates a relatively cool burn, and root and seed survive, he says.
“But if you have white ash, it was really hot,” he adds. “It means the ground is sterile and there is nothing there that is going to grow. It’s probably hydrophobic, which means it’s going to repel water, and it’s really going to move on you. In those areas, you probably put some seed.
“Unfortunately, it seems in most cases, it’s an either/or. You’re either going to seed or you’re not going to seed, and if you seed, you’re going to catch a lot of hell for it, so we tend to go without seed and as a result, we get a lot of weed invasion.”
While Harding’s crews may add some seed in white-ash areas, most of the time they will hydromulch.
“People don’t really think about it, but one of the chief attributes of hydromulch is dust control,” Harding says. “We’re doing this where there might be some sort of impact from a water-based erosion issue. It also calms the dust quite a bit for a long period of time around these homes we’re protecting.”
One only needs to stand out in a Santa Ana wind after a burn in ash that is 4 to 6 inches deep to appreciate that, Harding says.
“I’ve gotten sties in both of my eyes from dust from the post-fire work I’ve done,” he says.
The decision on what approach to take after a fire is largely up to the Geosyntec team, but it must be approved, Harding says. Usually, that’s done by the Natural Resources Conservation Service (NRCS), which has an Emergency Watershed Protection (EWP) program.
“We usually go out two or three times to a site,” says Harding. He looks at it from his helicopter in the air while others on the technical team do ground observations. A Geosyntec geologist or engineer will go out with the county’s equivalent. They report back, and Harding will go back out with them, along with a representative from the NRCS EWP program.
An example of how decisions to treat are made: “We’ll all decide jointly that particular area doesn’t get any treatment because there are no resources down below to protect,” Harding says. “Then we’ll go to another area and decide that we’re going to put some wattles behind that house. We’re going to spray that with a hydraulic matrix and we’re going to put some K-rails right around the back of the house to divert the mud if it does get loose, and everybody will agree on that.”
The team creates a damage assessment report that is sent to Washington DC for funding.
“A lot of people think I make those decisions or a Geosyntec person makes those decisions; the fact is, it’s a joint decision,” Harding says. “We aren’t the ones who select the materials. The county or city will buy any materials they want. We’re the ones who receive them and make sure the actual work is done. The county or the city will hire the contractors to come out and do the work.”
A local hydroseeding contractor usually performs the hydraulic work, while the work with sandbags, K-rails, and other types of sediment control is generally conducted by the California Conservation Corps. Geosyntec oversees the entire project.
“It’s the opposite way of how I like to do things,” notes Harding. “I like to start at the top of the hill and work my way down when it comes to erosion and sediment control, but after fires, it takes a long time to mobilize hydraulic equipment to get the mulch on the slopes. So we generally start at the bottom of the slope and go up.”
The first task is to protect people’s homes by placing sediment diversion or sediment containment devices down as “land dividers.” These can include K-rails or sandbags.
“Generally in California, fires occur in October and the rains follow shortly thereafter, so we know that the ash and sediment is going to get mobilized long before we get everything treated,” Harding points out. “We’ll do the sediment control first, and then we’ll put the wattles out on the slopes long before we put the hydraulic mulch out there.”
Harding says that these days, he is more of a minimalist.
“I try to disturb as little as possible,” he says. “We try to put in as few check structures as possible too, because there’s not money to go back and maintain them. We try to go as high as we possibly can with hydraulic actions, and we’re pretty successful with that.”
Drawing on Experience
Because of the vast amount of land the Forest Service manages, its experience provides a blueprint for anyone having to address sediment control measures in post-fire mitigation. Early this year, the Forest Service released a final draft of a science synthesis on post-wildfire management, making the point that wildfires, especially uncharacteristically severe ones, exert major influences on socio-ecological systems and can result in undesirable outcomes.
The draft is part of an effort to help guide land management of the nation’s forests. It is the culmination of an effort of more than a dozen scientists from the Forest Service’s Pacific Southwest and Pacific Northwest research stations, universities, and the Region 5 Ecology Program that helps inform forest managers as they revise plans for the national forests in the Sierra Nevada and southern Cascades of California.
The three most southern national forests in the Sierra Nevada-Inyo, Sequoia, and Sierra-will be among the first of the 155 national forests to update their management plans in concert with the new planning rule that requires the forests to consider the best available science and encourages a more active role for research in plan development. The full report is available at http://goo.gl/Jun1Y.
One of the areas addressed by the science synthesis is that of post-wildfire management, in a section authored by Jonathan Long and Lenya Quinn-Davidson with contributions from Carl Skinner, Susan Charnley, Ken Hubbert, and Marc Meyer.
The Forest Service indicates further research is needed to understand effects of wildfires, and high-severity patches in particular, over long periods-and after multiple fires-including effects on fuel beds, ecological trajectories, wildlife species associated with post-fire conditions and old forests, streams, watersheds, economic values, and social well being.
Re-burns, such as the Chips Fire of 2012, may occur and present valuable opportunities to better understand long-term changes in ecological conditions and how to promote socio-ecological resilience through interventions before and after re-burn events.
The Forest Service in California recently developed a post-fire restoration strategy template to help guide national forests in planning for restoration and long-term management of burned landscapes.
The Forest Service suggests targeting post-fire treatments to particular contexts where the expected benefits exceed the costs of interventions; this may help to avoid cost-ineffective practices and unintended negative effects. Such conditions are more likely to occur in high-severity patches that are larger than the range of expected variation.
In the 1970s, federal agencies adopted Burned Area Emergency Response (BAER) programs as a coordinated approach to address short-term threats to life, property, and natural and cultural resources.
BAER involves teams whose members represent multiple resource concerns and disciplines; they collaborate to inventory damage, assess future impacts, identify values at risk from potential flood events and accelerated erosion, and recommend cost-effective mitigation treatments.
These responses are commonly limited to the first three years after a fire, which aligns with the period during which flood and erosion risks may be particularly elevated. Short-term post-fire response varies depending on the values at risk, fire severity, topography, and other context-specific factors.
The Forest Service notes that a trend in scientific publications has been to regard post-fire tree mortality and erosion as important disturbance mechanisms for rejuvenating habitats and promoting resilience to changing climates.
Recent reviews have found that many widely used techniques to mitigate erosion and other post-fire damage have demonstrated relatively low effectiveness at reducing erosion and sedimentation, or can have unintended ecological consequences such as the introduction of non-native species or genotypes, increased homogenization, and inhibition of natural succession processes.
Significant areas of short-term post-fire concern include post-wildfire flooding, erosion, and sedimentation. These are interconnected in complex ways, because water and sediment can be routed and stored in different places at different times.
Post-fire flooding is a function of excess overland flow from hill slopes, although conditions of downstream channel networks can exacerbate flood hazards through potential failures of debris jams, culverts, and dams.
The report points out that hill slope erosion can be a significant problem, although it may be greatly exceeded by erosion from channels. Rehabilitation strategies often target hill slopes in part because of a general principle of treating the problems as close to the source as possible and because hill slope treatments appear generally more successful than in-channel treatments.
Few post-fire in-stream treatments have been widely recommended, because they are considered costly to engineer and susceptible to failure. Although straw bales and log check dams are the two most common techniques, their effects are relatively short-term and failure rates are high, the report states.
Straw mulch has been demonstrated as a highly effective-and cost-effective-means of providing ground cover on hill slopes burned at high severity and has consistently been shown to reduce post-fire erosion by 50 to 94%. In addition to providing ground cover, it protects the topsoil against rain splash to slow surface flows and helps control hydrophobic soil conditions. While it is one of the most widely employed post-fire erosion control techniques, it may be problematic to apply in windy conditions.
Hydromulch-a mix of bonded-fiber matrix combined with a non-water-soluble tackifier-allows the aerially applied mulch to penetrate into and bond with the soil substrate. Although considered highly effective, it is usually several times more expensive than straw mulch, with its effectiveness decreasing after the first year as the product breaks down.
Contour-felled log erosion barriers (LEBs) and fiber rolls are used to improve infiltration, to slow overland flow velocity by breaking up the slope length, and to a lesser degree to capture and keep sediment on the slopes. Reviews show that effective use of these treatments requires a skilled work force for proper placement. Poor installation and foot traffic during installation can be a source of hill slope disturbance and rilling if water flows are concentrated.
Fiber rolls may be easier to place and entail less ground disturbance than the placement of LEBs. These treatments are used primarily for protection of high-value areas because they are considered both expensive and labor intensive.
Both treatments lose effectiveness as the barriers fill with sediment, so they require maintenance. Use of LEBs has decreased in recent years because other treatments are considered more effective, according to the report.
The percentage of burned areas treated with grass seeding for post-fire hill slope stabilization has decreased since the 1970s, although more has been spent on reseeding as the use of native species for seeding has increased.
The report points out that treatment may be unnecessary when natural revegetation is sufficient or when erosive precipitation events do not occur; treatment also may fail when erosive precipitation events wash out the seeds.
There is a relatively narrow window of conditions when seeds would successfully germinate and prevent erosion. Some research shows seeding is minimally effective for reducing erosion and that there can be unintended detrimental impacts on native plants and annual fire-followers.
Use of mulch with seeding increases the establishment of seeded grasses, but the combination generally does not provide greater cover than mulch by itself, according to the report. The Forest Service indicates that more research is needed regarding the effectiveness of seeding for reducing non-native invasive plants after fire, as current research is mixed.
With climate change expected to increase the incidences of severe wildfire, high-intensity storms, and rain-on-snow events, the threat of post-wildfire debris flows is expected to increase and become more widespread. Some researchers suggest there is a lack of good options to prevent post-fire debris flows.
Debris flows are a critical concern in BAER assessments because of the threat they pose to life, property, and ecological values for a few years after wildfire. Post-fire erosion associated with debris flows can negatively affect downstream public water supplies. Although the effects of severe wildfires in channels can rejuvenate aquatic habitats, they can also kill aquatic life and result in destruction of vulnerable aquatic species unable to recolonize the affected streams. If post-fire landforms persist beyond the wildfire recurrence interval, successive wildfires are believed to have an important cumulative impact on watershed morphology.
One post-fire study reports that a combination of well-designed, well-implemented, and well-maintained hill slope treatments-straw mulch, seeding, LEBs, and channel treatments such as check dams and debris racks-can reduce debris-flow volumes. The forest service indicates further research is needed to evaluate where and when such interventions are likely to be an efficient response. Roads are a focus of post-fire treatments because they can concentrate runoff, obstruct stream flow, and alter other hydrologic processes. Research from western Oregon indicates roads and debris flows can interact to facilitate spread of invasive plants, a post-fire concern.
Erosion hotspots can be identified using landscape analysis tools. Rising treatment costs highlight a need to prioritize areas threatened by undesirable levels of erosion, debris flows, invasion of non-native species, and other hazards. The concept of designing forest treatments according to topography has parallels in design of post-fire treatments from a water resources perspective.
The spatial distribution of post-fire effects can be mapped in relation to landscape features using remote sensing and geographic information system tools. In addition to topography, strategic design of mitigation treatments has to include a range of factors, such as vegetation, precipitation, soil types, post-fire cover, and burn severity.
Research suggests that particular landscape areas, such as convergent swales, have greater potential for post-fire erosion. Post-fire monitoring of burned watersheds can enhance understanding of post-fire erosional processes, help to develop models to inform and improve treatment strategies, and inform forest treatment planning by identifying areas that appear particularly vulnerable to post-fire erosion. Tools to predict post-fire debris flows in southern California and the Intermountain Region could be tested and refined to be used for BAER and longer term planning in the synthesis area.
The report states that a key challenge is to develop sufficient capacity for post-fire restoration plans to be quickly implemented before various thresholds such as soil erosion, vegetation development, or use of harvested materials have already passed.
Increased collaboration and integration of post-fire considerations into management plans in anticipation of potential fires may facilitate implementation of post-fire restoration. One study suggests there could be substantial economic benefits from advance planning by reducing the potential for delayed salvage.
Monitoring post-fire landscapes can assist managers in determining the likely trajectory of ecosystem recovery in the post-fire environment, prioritize areas for treatment, and evaluate when important thresholds might be crossed. Some fires may warrant investments in more rigorous study designs to answer key research questions, such as impacts to priority species.
