Fire History – Techniques
CDF/FRAP and USDA Forest Service Region 5 Remote Sensing Lab are jointly developing a comprehensive fire perimeter GIS layer for public and private lands throughout the state. The data will cover the period 1950-1999 and include CDF fires 300 acres and greater in size and USFS fires 10 acres and greater. This project provides for annual updates. Whenever possible, CDF and USFS solicit additional fire perimeter data from other federal agencies (e.g., NPA, BLM, BIA, DOD) or local/county agencies for incorporation into the fire perimeter mapping project.
The project produces an annual statewide fire history GIS data layer through four steps:
- Standardize and combine existing digitized fire perimeters into a statewide GIS layer;
- Identify and remove duplicate fires;
- Fill in the gaps in data; and
- Perform annual updates of the GIS layer.
CDF ranger units fill in gaps in their fire perimeter data as part of the California Fire Plan . FRAP provides each ranger unit with a preliminary map of 1950-89 fire perimeters . Each ranger unit then generates a list of 300+ acre fires that started in the ranger unit since 1989 according to the CDF Emergency Activity Reporting System (EARS). The ranger unit uses this list to gather post-1989 perimeter maps for digitizing. Unit personnel also verify the pre-1989 perimeter maps to determine if any fires are missing or need to be re-mapped. Finally, vegetation management project maps are digitized, with a 50 acre minimum project size (individual burns within a project area may be smaller than 50 acres). The final product is a statewide GIS layer spanning the period 1950-1999. Annual updates will be made thereafter.
CDF includes selected fire history attributes in its fire history GIS layer. These attributes include the date the fire started, the name of the fire, the incident number (for linking to EARS), the cause of the fire, lead agency and the total size of the fire in acres. The combined CDF/USFS GIS layer will include an incident number for USFS fires that will allow for linking to data tables derived from the National Fire Management Integrated Database (NFMID).
The fire perimeter database developed by CDF and USFS is the most complete digital record of fire history in California. However it is still incomplete in many respects. Fires may be missing altogether or have missing or incorrect attribute data. Some fires may be missing because historical records were lost or damaged, were too small for the minimum cutoffs, had inadequate documentation or have not yet been incorporated into the database. Until the Fire Plan is fully implemented in all ranger units, some ranger units will only have data from 1950-1989. Furthermore, until the data capture process moves to the local level, the most recent fires will only be uploaded to the database at the end of every fire season.
Other errors with the fire perimeter database include duplicate fires and over-generalization. While the data capture process attempts to identify duplicate fires resulting from multiple data sources (i.e. the USFS and CDF both captured and submitted the fire perimeter), some duplicates may still exist. Additionally, over-generalization, particularly with large old fires may show unburned "islands" within the final perimeter as burned. Users of the fire perimeter database must exercise caution in application of the data. Careful use of the fire perimeter database will prevent users from drawing inaccurate or erroneous conclusions from the data.
 |
| In some cases, different agencies record
differing fire perimeters for the same fire. Above you can see two instances
of duplicates fires into different perimeters, the White Deer fire and the Pierce fire. In the Pierce fire
the most accurate fire perimeter is preserved along with the best metadata,
such as date, cause, etc. (see tables below). *Note: only
sampling of fires and not spatially accurate |
In the table below, the highlighted cells represent data which are
preserved as the primary record from different agencies historical records.
Combining these data eliminates duplication by selecting the most accurate and
complete record. In many cases only one agency recorded the fire perimeter,
its cause, and date; therefore only one record exists.
| Agency: |
CDF record |
Forest Service |
National Park (Sequoia-Kings) |
| Fire Name: |
Pierce |
Pierce |
Pierce |
| Number*: |
CA1987TUU00103300182 |
CA1987SQF00000000184 |
CA1987SNP1987085000 |
| Cause: |
Lightning |
Lightning |
Lightning |
| Date: |
19870829 (1987,
August 29) |
19870000 |
19870830 (1987,
August 30) |
| |
|
|
|
| Fire Name: |
White Deer |
White Deer |
(not on National Park lands) |
| Number*: |
CA1961SQF00000000195 |
CA1961FKU0000000089 |
|
| Cause: |
Human |
|
|
| Date: |
19610000 (no month/day) |
19610820 (1961,
August 20) |
|
*The INCIDENT_NUMBER is a unique identifier the combines state,
year, agency id, incident number, and fire number. For example CA1981MVU00112600461
is a fire perimeter with a year of 1981, from the MVU (San Diego) rangerunit,
incident number 1126, fire number 461. All missing or nonexistent data is "padded"
with zeros. For example:CA1981CNF00000000019 is a 1981 fire from Cleveland NF
with a USFS fire number 19.
Fire history data from the statewide database are constantly under development. The data are maintained as an
Arc/Info REGIONS coverage which provides effective tools for handling overlapping polygons (such as areas burned more than once). Data contained in this coverage come from many sources some more accurate or complete than others. The AGENCY field and the INCIDENT_NUMBER identify the data source. Not all sources report all information, so some records will have attributes with no values.
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