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Fire Management Tools
Burned Area Emergency Rehabilitation teams utilize GIS and remote sensing
By Mark W. Brennan and Paul E. Hardwick In recent years, there has been an influx of new technology for fire planning, suppression, and management efforts. One of the sources of the influx is geographic information systems (GIS) and remote sensing. GIS can put accurate information in the hands of those who need it, when and where they need it. Better and quicker information leads to better decision making, which in turn leads to fighting a fire more effectively, efficiently, and safely. GIS and remote sensing helps people visualize the situation and gives them a look at the big picture.
The USDA Forest Service Region 5 Burned Area Emergency Rehabilitation (BAER) program leader recognized that these technologies could combine to help BAER teams do their jobs more efficiently and accurately. Through a pilot project, it was determined that digital color infrared imagery of a burned area that was created and georeferenced would provide BAER teams with a tool that would greatly improve their burn intensity mapping efforts.
During October 1998, Pacific Meridian Resources, located in Emeryville, California, and TASC Emerge, located in Billerica, Massachusetts, teamed up to combine the GIS and remote sensing strengths of both companies to provide digital imagery to the regional BAER teams in California. Using new sensor technology, imagery was provided within 3-5 days of being called to a wild-land fire. What is Burned Area Emergency Rehabilitation
The BAER program is an emergency program that gathers information on fire-induced watershed conditions in the wake of large wildfires, and uses this information to determine if significant threats to life, property, or natural resources exist. If emergency conditions exist, immediate rehabilitation treatment measures are undertaken to reduce or eliminate these threats. The BAER inventory, analysis, and rehabilitation treatment prescriptions are completed within 3 days after the control of the fire, with actual rehabilitation initiated within a week of control of the fire.
Rehabilitation measures must be completed before the first damaging storms of the season. All potential treatment alternatives are subject to a least-cost-plus risk analysis to ensure that prescribed rehabilitation treatments are prudent and efficient. In a severe fire year, such as 1996, millions of dollars are spent on BAER treatments. US Department of Agriculture and US Department of Interior, as well as state and local agencies, have developed, or are developing programs tailored after the Forest Service BAER program for lands under their jurisdictions. This is a result of partnerships that emerged in the aftermath of fires in recent years.
To determine the flooding potential, and the specific flood source areas within the burned area, the BAER survey includes mapping burn intensity as a critical step. Burn intensity is the key measure of the severity of a fire's impact on an ecosystem. The term burn intensity refers to the fire effects on the watershed, not necessarily to the intensity of the fire as defined in flame height, canopy consumption, or rate of spread. Typically, burn intensity is mapped using a combination of intensive ground measurements (such as effective ground cover reduction, soil aggregate stability reduction, and hydrophobic soil development) based on a judgment sampling technique, followed by overlook point or aerial sketch mapping, and additional ground verification. These time-critical, rough sketch maps are used for area calculations, sediment yield calculations, and for locating treatment areas. Burn intensity maps may be further refined as more detailed information becomes available, but often the initial maps may be digitized and become part of the local GIS planning databases for use in subsequent long-term recovery planning and environmental analysis. BAER Requirements
The BAER program calls for a fast and cost effective way to map fire effects on a watershed. The rough sketch mapping techniques potentially result in over simplification and imprecise line placement and delineation of burn intensities. The burn intensity map needs to be accessible as a paper map and as a layer in a GIS for a variety of people involved in the assessment and subsequent rehabilitation program. The map needs to be available at varying scales for visual overlay and display with other resource information such as watershed boundaries, pre-fire vegetation, soils, and wildlife habitat.
The critical determination of whether a watershed emergency exists, and the magnitude and site specific location of potentially high cost rehabilitation measures are based in part on the burn intensity map. Therefore, it is essential that the burn intensity map be created with high accuracy and precision to maximize efficiency for this process. Imagery Collection Methods
Over the years, various attempts have been made at improving upon burn intensity mapping techniques. Technology including traditional film cameras, videography, and digital sensors have been used to acquire data to meet the current needs of the BAER effort.
Pacific Meridian Resources and TASC Emerge use a sensor system that includes a color infrared Kodak digital camera (DCS460CIR), inertial measurement unit (IMU), and GPS. The sensor system is mounted in a small airplane fuselage and is integrated with an on-board automated flight navigation system. The data captured by all three units (camera, IMU, and GPS) are stored on media that is removed after each flight mission and sent to a processing facility via overnight delivery.
Images are seamlessly processed to produce orthorectified geo-referenced images. This procedure uses only the data captured by the Emerge sensor without the need for ground control points or traditional stereo pair image collection. Therefore, using Emerge's patented imaging capability coupled with Pacific Meridian Resources' fire management knowledge allows for rapid response with highly accurate burned area mapping products at considerable cost savings.
The Emerge sensor system has a spectral response similar to color infrared film SO134, or 9443 with significantly higher dynamic range (12 bits per band versus film 6-7 bits per band digitized). Each image consists of a 3072x2048 array of picture elements (pixels) and are captured approximately once every 8 seconds with ground sampling distances in the range of 2 feet to 6 feet. One advantage of this system is that it allows for better highlight detail delineation in low-response areas such as burns, shadows, and wetlands. In addition to dynamic range, the digital sensor is capable of acquiring natural color images if the target delineation is better suited to RGB. Slow air-speed, variable altitude, and short exposure provide improved resolution and sharpness. At lower altitudes, collections can be optimized by flying under cloud coverage; at 3,500 feet, the sensor system can image below clouds and derive no shadow data sets under overcast conditions, where film cannot operate.
As the imagery is digitally acquired, all data sets may be printed on hard copy at the user's specified photo scale. Digital capture and distribution also increase product access. This is a critical aspect in responding to BAER requirements for quick (3-5 day) responses. Data sets are available in ESRI compliant format on CD-ROM or via the Internet. Burn Intensity Mapping
While the image acquisition process is underway, the BAER team, who normally would have spent much time sketch-mapping the area from a helicopter, is instead able to increase the number of ground observations compared to the previous methodology. BAER GPS data collectors are loaded with a data dictionary to help in recording important burn intensity parameters. All ground observation points are logged in the portable GPS unit for electronic overlay later with the digital image of the burned area.
Additional information or base layers such as pre-fire vegetation, streams, soils, and topography is needed to properly map the different burn intensities. This information is found in a clearinghouse for geospatial data, also known as a GIS database. Each national forest, regional office, or other land management unit collects and maintains geospatial data for the land under its jurisdiction.
By integrating ground and aerial observations, digital imagery, and GIS layers, the BAER team is able to make better decisions on how to delineate burn intensities. The delineation of the burn intensity polygons takes place right on the computer screen. The pre-fire vegetation, topographic information, and GPS data can help the cartographers interpret the information they are seeing on the screen. The result is a more accurate burn intensity map that allows BAER teams to pin-point their rehabilitation efforts.
Once the burned area derivative layers exist within a GIS, they can be used by other resource professionals to make land management decisions. The wildlife biologist, for example, could immediately identify how much critical habitat areas burned at high intensity by combining the information with a habitat layer. The hydrologist could quickly calculate percent of watershed in high burn intensity condition, as well as identify where in the watershed those conditions occur and what soil types they occurred on. The archaeologist could overlay burn intensity with heritage resources.
The burn intensity map serves as a proxy for cover and runoff factors used in erosion and runoff models. The burn intensity map, soils layer, and slope groupings from digital elevation models (DEMs) are used in the Universal Soil Loss Equation. The soil scientist could overlay the burn intensity map with the GIS data layers of soil erosion groups and slope groups and quickly derive the areas of various burn intensity soil-slope combination figures needed for calculating predicted soil loss, which is part of the BAER program's cost-benefit analysis requirement.
The imagery and resulting burn intensity map can also serve as an excellent public relations tool. By creating 3D (perspective) views using the imagery and burn intensity layers, land managers can demonstrate to the public how burn intensity, slope, and location combine to create hazardous areas. They can be used to show the public where those areas are and what rehabilitation measures are being used to prevent further damage to property and natural resources. Additionally, perspective views serve as an aid in the mapping process by allowing the cartographer to 'see' potential effects, possibly due to runoff, that may otherwise be missed. Conclusion
The combinations of new technologies (GIS, remote sensing, and GPS) have provided BAER teams with a better, more efficient way to create burn intensity layers and maps. The technology has given BAER teams more time to collect ground data and the ability to concentrate their efforts on rehabilitation. In order to implement this new technology across the region, training has begun. Last spring, BAER team members and GIS specialists were brought together from several national forests within the region. The course participants learned how to use the GPS units to collect data, to interpret the color infrared imagery, where to find the geospatial data necessary, and obtained hands on experience creating burn intensity maps. The most important aspect of this course, which was developed by the USDA Forest Service and Pacific Meridian Resources, was that it brought together BAER and GIS personnel and allowed them to understand each other's needs and expectations.
For the 1998 BAER program activity, Pacific Meridian Resources and Emerge teamed up to respond to BAER requests in California. This arrangement was very powerful because it combined the talents of forestry and information technology professionals from two separate companies into one focused entity. Together, both companies are working toward an end goal of providing information that can be used by multiple resource managers to lessen the impacts of wild-land fires. About the Author:
Mark Brennan is a project manager at Emerge, a part of Litton/TASC. He coordinated the Emerge efforts for the Los Padres National Forest fire collection in October 1998. He can be reached at 978-262-0672 or [email protected] Paul Hardwick is the Rocky Mountain operations manager for Pacific Meridian Resources. He developed the methodologies for the BAER imaging process in collaboration with the USDA Forest Service Remote Sensing Applications Center. He can be reached at 801-325-1006 or [email protected]
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