Reference Map
Erosion Map
The largest wildfire in the
Angeles National Forest, and 10th largest in California since 1933,
happened on August 26th, 2009. The wildfire occurred at the Los
Angeles River Ranger District/ Angeles National Forest and was later found to
be caused by arson. This arson contributed to severely burning more than
160,000 acres of forest and burned over 250 square miles of the San Gabriel
Mountains. Though many places/aspects can be affect by this large of a
wildfire, I was especially interested in the extent of erosion. ArcMap was
essential to be able to map which areas result in more erosion after a
wildfire, so that they can be controlled.
For this week’s lab, I wanted to
incorporate post-fire erosion around the Angeles National Forest area, where
there was a tremendous wildfire in 2009. My map shows the fire extent of the
2009 wildfire and the rankings of erosion according to the methods gathered
from CALFIRE. The color scheme on my map
shows tons/acres/year soil loss and ranks it that way from high to low. The
high values (in umber) show the highest levels of erosion which appear to be located
throughout most of the fire extent but mostly in the southwest region of the
extent boundary. I wanted to base my map on erosion because I think it is a
significant issue with hillside wildfires.
I chose this
data because it incorporated aspects of the area that I did not have to. Gathered
from the post-fire erosion methods pdf from CALFIRE, it incorporated levels of
vegetation and levels of fuel in an area, so places with low vegetation cover
and high fuel would be more prone to erosion. Therefore areas with high levels
of vegetation and low fuel, as shown in South LA County, will obviously have
lower erosion rates. I think it’s
important because wildfires burn vegetation and destroy the litter layer
(organic material) of the soil. Plant roots at this level are essential to
stabilize the soil in hillslope areas, such as the Angeles National Forest. It
also takes rainfall intensity into account, because as soil gets exposed to
rain, the silt ends up in streams and rivers, which can affect main ecosystems
and fish. What this map does not cover, however are other factors that affect
soil erosion such as percent cover, contributing area, slope, soil texture,
aspect, and precipitation that could be developed to predict sediment yields.
In my second map, I only showed the rivers of
LA County, not including the streams but all of these water sources can be
extremely affected by erosion, which can threaten ‘life, property and water
quality and water ecosystems.” The high runoff and erosion rates in headwater
areas deliver large amounts of sediment to downstream channels. I think it’s crucial
to map this because not only does erosion after fires cause many problems for
vegetation and soils in the areas but it can also affect diverse ecosystems
from small fish in estuaries to large animals that rely on them for drinking
water.
I think my few maps show where
more erosion control is needed in the future to protect against erosion from
wildfires causing silt deposits in the rivers that are located in high threat
locations. I think this information could be helpful for people in this field to prevent large devastation from erosion. Types of soil and
vegetation would be much more effective to use for this project, if it were
available for comparison before and after the 2009 wildfire.
Works
Cited
“All Station Fire Perimeters (as of September 2, 07:02) –
Complete set.”
http://egis3.lacounty.gov/eGIS/.
Mark Greninger, 2 Sep. 2009. Web. 28 Nov. 2012.
“LA County Boundary.” http://egis3.lacounty.gov/dataportal/2011/01/20/l-a-county-
b
oundary/drp_county_boundary/, 20 Jan 2011. Web. 29 Nov. 2012.
“Los Angeles County Highways.”
http://gis.ats.ucla.edu//Mapshare. ESRI, 1 April
2008. Web. 2 Dec. 2012.
“Los Angeles County Rivers.”
http://gis.ats.ucla.edu//Mapshare. ESRI, 1 April
2008. Web. 29 Nov. 2012.
MacDonald, Lee, and Peter R. RobiChaud. "Post-fire
Erosion and the Effectiveness
of Emergency Rehabilitation
Treatments over Time." Stream
Notes. 1-6.
Web. 13 Dec. 2012.
Moench, R, and J Fusaro. "Soil Erosion Control After
Wildfire." . Colorado State
University Extension, n.d. Web. 4 Dec 2012.
“Post-Fire Erosion.” http://frap.fire.ca.gov/assessment2010/data.html.
California
Department of Forestry and Fire Protection, 2010. Web. 29 Nov. 2012.
Pietraszek, Joseph H. Controls On Post-Fire Erosion at the Hillscope
Scale,
Colorado Front Range. Diss. Colorado
State University, 2005. Print.
"Station Fire." Inciweb.
Angeles National Forest, 10 2009. Web. 4 Dec 2012.







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