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AlASKA RESOURIT:S ll'SR:\RY
u.s.Department of the Interior
REPORT
ON
EROSION OF WILDFIRE AREAS IN ALASKA
Narrative Report - - - - -Pages 1-15
Photos - - ---Attachment 11
Soil Characteristics Attachment 12
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Submitted by:
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S 1 Scientist
~~A:sLV~~t:!!~
PSC Soil and Wa ~rshed Staff
Date ~/...('&~j;
Property of EI.M
AK.RESOU[\C~S Ub";',,Y
-.."
REPORT
C:~
EROSION OF WILDFIRE AREAS IN ALASKA
Summary
On-the-ground inspections were made of three Alaska (Fairbanks District)
wildfire burns by Alaska State Office,Fairbanks District,and Portland
Service Center personnel during the week of June 3-7,1968.These burns
were inspected to determine (1)possible changes in future fire line
construction methods to minimize resulting erosion,(2)rehabilitation
measures which might be used to stabilize dozer-constructed fire lines
following mop up of future fire,and (3)stabilization measures to curb
accelerated erosion which has developed on 1966 C.Y.burns.
Briefly,the recommendations are as follows:(1)restrict to a minimum
c=J the use of crawler tractor dozer-constructed fire lines on north slopes
and in drainage bottoms (areas where permafrost is near the ground sur-
face);(2)where dozer-constructed fire lines are absolutely required
on critical areas (north slopes,drainage bottoms,etc.),use follow up
treatment to prevent water from concentrating in fire lines by blocking
the lines at intervals with fire line debris;(3)to facilitate re-
establishment of vegetative cover,seed all dozer-constructed fire lines
on critical areas with adaptable grasses after the fire;(4)initiate
a minimum level field trial for rehabilitation of existing fire line
erosion using practices such as gully plugs (fire line debris,thawed
soil,etc.),grass seeding,and tree seeding and/or planting;and (5)
undertake (2)and (3)above through use of 1520,Fire Rehabilitation,
funds (see l63l.l2I4).
~..."-_i
Purpose
During the past year Alaska personnel observed that severe erosion had
resulted on some of the 1966 C.Y.wildfire burns where heavy equipment
was used in controlling the fire.Damage was evident on dozer-constructed
fire lines,particularly on north slopes and in drainage bottoms where
permafrost is normally near the ground surface.
With the prospect of expanding the use of heavy equipment on wildfire
control in the future,the Alaska State Office and the Fairbanks Dis-
trict Office were particularly concerned as to the magnitude of the
accelerated erosion.For this reason a field evaluation to be made
jointly by State Office,District Office,and Portland Service Center
personnel was proposed.Such an evaluation was arranged and scheduled
C;for the week of June 3-7,1968.The evaluation was set up to include
a field inspection of burned areas followed by a report on recommendations
by the PSC participants.
Objectives
The objectives of the field inspections were established as (1)an
observation of several burned areas to determine the extent and magni-
tude of current erosion,(2)a determination of the cause (or causes)
of the accelerated erosion,(3)a recommended change in construction
methods and location of dozer-constructed fire lines to minimize erosion,
(4)recommended rehabilitation practices which might be employed during
and immediately following fire control work to reduce erosion potential,
2
c;
and (5)recommended rehabilitation measures which might be used to con-
trol existing erosion if such is necessary.To meet these objectives,
field observations were scheduled for both 1966 burns and aged burns
(1958)where heavy equipment was used to construct lines.
Observations
Field inspections were made of three fires,Goldstream (1966),Y-34
(Chicken,1966),and Murphy Dome (1958),where tractors were used to
construct fire lines.Other fires were observed from the air but no
ground observations were made.
Personnel making the helicopter field inspections were Jerry Wickstrom,
Fairbanks District,Curt McVee and Sal DeLeonardis of the Alaska State
Office,and Jim Hagihara and Glenn Lipscomb of the Portland Service
r"'.
"-.j Center.Wandell Elliot,Delta Resource Area Manager,met with the
group during the Y-34 inspection.
Goldstream and Murphy Dome were inspected on June 4,while Y-34 was
flown on June 5 and 6.Ground observations were made on each fire in
areas where erosion appeared to be severe.
After viewing some of the eroded fire lines on the Goldstream and Y-34
burns,it is quite clear that some areas in Alaska belong in the fragile
or "frail"category.Removal of the vegetation and organic accumulation
in areas underlain with shallow permafrost and with deep loess soils
can result in severe soil erosion.(See Photo No.1)Melt from perma-
frost and thick ice lenses together with runoff from rainfall provide
3
the eroding forces.(See Photos No.2 and 3).Such areas are generally
located on north slopes and in drainage bottoms and are characterized
by spare stands of stunted black spruce.On the other hand,well
drained soils generally found on south slopes,along ridge tops and on
points do not appear to be a problem.Field investigation revealed
very little erosion where fire lines were constructed on these areas.
The soil characteristics found on the wildfire areas are as follows:
1.The geology of the uplands is primarily composed of schists,
a Precambrian formation made up of folded and strongly jointed quartz-
mica and quartzite schist.Out croppings of granite,quartz diorite,
and basalt occur along the ridge tops.Gold can be found in the quartz
veins within the schist.
All of the sites investigated in the uplands were found to be covered
by a mantle of micaceous loess that was blown in from the adjoining
flood plains.This loess layer ranges from about one foot thick on the
high ridges to about 200 feet thick on the lower hills.Colluvial silt
that has moved from the hillsides and accumulated on the lower slopes
and in the narrow upland valleys is more than 300 feet thick in places.
Permafrost underlies the alluvial fans,bottom of drainageways in the
uplands and the north-facing slopes.It is absent on the moderately
(12-20%)to steeply (20-30%)sloping swth-facing slopes.Large ice
masses are commonly found within the colluvial silt deposits.
4
Properfy of BUW
AK.RESOURCES L1BRARl
.,,----'.
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2.The following six majar soils were examined during the investi-
gatian of erosion problems.All of these soils had one common significant
factor,they were susceptibTe to severe water erosion and gullying upon
removal of the organic mat.This susceptibility to erosion by water is
due to the poor mechanical and engineering properties of the soils that
do not have the ability to resist detachment.Some of the major soil
characteristics are shown on attachment #2.
a.The Fairbanks Soil is found on the gently sloping (7-12%)
to steep (20-30%)uplands with southerly exposures.It occupies low
scattered hills and long,smooth slopes.These soils are found in
association with the Minto soils on the low hills and foots lopes and
with the Gilmore soils at the higher elevations.The dominant natural
C vegetation consists of white spruce and paper birch,but quaking aspen
is dominant on the burned or cleared areas.Annual precipitation is
about 13 inches and the frost free season averages 108 days.Elevations
range from 800 to 1500 feet.
These soils are deep well drained silt loam soils underlying a mat of
roots and partially decomposed forest litter.The loess mantle ranges
from 30 inches to many feet in thickness over bedrock.The texture
is dominantly silt loam.Runoff and susceptibility to erosion is
severe upon removal of the organic layer.
5
b.The Minto Soil is found upon all exposures at the base of
upland slopes and footslopes of ridges and hills.The lower boundaries
are found in association with the Goldstream soils.On south-facing
slopes they are associated with the Fairbanks soils along the upper
boundary.These soils support stands of white spruce,paper birch,
quaking aspen and also stands of black spruce.The annual precipitation
is 13 inches with an average frost free season of 108 days.Elevations
range from 700 to 1200 feet.
The Minto soils are deep poorly drained soils that are commonly under-
lain by large masses of ice at depths of six feet or more.Perennial
permafrost is common on the north slopes and discontinuous on the south
slopes.The depth to bedrock is normally more than six feet.
Upon removal of the organic layer and vegetation,this soil is suscept-
ible to uneven settling,pitting and piping as a result of the melting
of subsurface ice masses.The susceptibility to erosion is also
severe upon removal of the organic layer.
These soils were found with the subsurface ice masses and permafrost
in the severely gullied fire lines on the Goldstream and Y-34 Wildfire
areas.Although,this soil was observed on the fire line constructed
on the lower slope in the Murphy Dome area,the severe gullying had not
occurred.
6
c;
c.The Goldstream Soil is found on the bottoms of upland
valleys,low terraces and alluvial fans.The vegetation consists of
black spruce,low shrubs,mosses,and sedge tussocks that are about 12
to 18 inches high and about 12 inches in diameter.(Photo #4 depicts
these tussocks).Elevations range from 600 to 1200 feet and the
average frost free season is 108 days.
The Goldstream soils are poorly drained with perennially frozen sub-
strata underlying a thick mat of moss,roots and partially decomposed
organic matter.The depth to perennially frozen material ranges from
10 to 24 inches and contains lenses of clear ice.Under natural con-
ditions the soil above the permafrost table is always wet.Upon removal
of the organic mat,these soils thaw to greater depths increasing the
C=)susceptibility to water erosion.
These soils were observed along the severely gullied fire lines on
the Y-34 fire.
d.The Saul1ch Soil occupies the lower parts of long north-
facing slopes andts perennially frozen at depths of 10-20 inches.
They are found at the base and footslopes of north-facing hills and
ridges.The dominant vegetation is black spruce and scattered clumps
of alder and willow.Annual precipitation is 13 inches and the average
frost-free season is 108 days.The elevation ranges from 900 to 1800
feet.
7
-
~./
C)
The Saulich soils are moderately deep poorly drained soils underlain by
bedrock at 30 inches plus.The organic mat ranges in thickness from
10-14 inches.
These soils are susceptible to severe water erosion upon removal of the
organic mat.Although gullies were not observed in this soil during our
investigation,they become quite susceptible to water erosion if dis-
turbed.
E.The Gilmore Soil is found on moderately sloping (12-20%)
to steep (20-30%+)uplands on south-facing slopes.They generally
occupy the steeper slopes near the tops of high hills and ridges.The
dominant vegetation is paper birch,white spruce,and quaking aspen.
Annual precipitation is 13 inches and the average frost-free season is
100 days.The elevation ranges from 800 to 2000 feet.
The Gilmore soils are shallow,excessively drained and underlain by
partially shattered schist bedrock at 10 to 20 inches.The organic
layer is thin,ranging in thickness from 0 to 3 inches.Surface
runoff is medium and the toiater erosion hazard is severe if the vege-
tation and organic mat are removed.Although,the erosion hazard is
severe,deep gullies will not develop because of the shallow depth to
bedrock.
The fire lines constructed on the Gilmore soils in the wildfire areas
did not indicate serious deep gullying.However,the artificial
establishment of vegetation on these fire lines will be difficult.
8
c
f.The Ester Soil is found on long steep slopes near the tops
of high hills and ridges on north-facing slopes that receive little
direct sunlight.They support stands of stunted black spruce,scattered
alder and willows,and a thick ground cover of mosses J lichens and low
shrubs.The elevation ranges from about 1000 to 1900 feet.Annual
precipitation is 13 inches with a frost-free season of 90 to 100 days.
The Ester soils are shallow,poorly drained with perennially frozen
subsoils at a depth of 3 to 10 inches below a thick organic mat.
Shattered rock or schist bedrock is encountered at a depth of 12 to
20 inches.Most of the plant roots are found in the organic mat with
a few penetrating several inches into the frozen silt loam mantle.
The water erosion hazard or susceptibility is very severe upon removal
of the natural vegetation and organic layer.Although,the erosion is
very severe,these soils will not develop the deep gullies found upon
the fire lines along the drainageways and valley bottoms.Revegetation
by artificial means may be difficult,but it was observed that natural
slides have healed themselves over a period of years.
9
Several specific observations were made during the field inspection and
these are as follows:
1.Areas with deep loess soils and containing shallow permafrost
(plus ice lenses)have high erosion potential when the ground cover
(vegetation plus organic accumulation)is removed.
2.Dozer constructed fire lines over permafrost areas (drainage
bottoms,north slopes,etc.)appear to thaw rapidly after removal of
the insulating ground cover,and new drainages or channels are created
as the melt water from frost and ice lenses erode away the noncohesive
loess.(Photos No.5 and 6 show similar adjacent areas --No.5 contains
no fire Une while No.6 contains a gullied fire line).In some areas
fire line debris acted as a training dike confining water flow to the
cleared line resulting in additional erosion.(Note left center of
Photo No.1).
3.Fire lines constructed by dozers on south slopes,ridges,points,
and other well drained,warmer sites have very little erosion even on
steep slopes.(PhomNo.7 shows a well drained soil on south slope -
however,cleared line in drainage bottom has eroded to bedrock).
4.A few slumps and slides were observed particularly on Y-34.
However,these slope failures were not all associated with fire lines.
Some were observed in areas undisturbed by fire line construction while
others were observed in unburned areas.
10
5.MOst of the 1966 burns (excluding dozer fire lines)are well
covered by grasses (calamagrostis).(See Photo No.5).
6.The Murphy Dome (1958)fire lines appear to be well stabilized.
No serious erosion was observed even along drainage bottoms and on
north slopes (permafrost remains in adjacent unburned areas but has
withdrawn to a greater depth on the fire lines).Good reproduction of
spruce as well as all deciduous species has occurred on the fire lines.
Mosses and lichens are also becoming established.
7.Debris from the eroded lines and newly formed gullies is being
carried downstream and poses a damage threat.For example,on Y-34
sediment deltas were observed at the confluence of eroding drainages
and lower drainages,while on Goldstream sediment appeared to be plugging
railroad drainage structures as well as filling a small lake downstream.
Large amounts of sediment have probably already entered downstream
rivers.
8.Erosion damage on wildfire areas not disturbed by tractor
clearing appeared to be minimal.Sufficient organic duff remains follow-
ing the fire to provide adequate ground cover within the observed burn
areas.
11
C-\Conclusions
The absence of serious gully erosion on the Murphy Dome burn (1958)
indicated the possibility that the heavy rains of 1967 may have
accelerated erosion on the 1966 burns.~lliile neither the Goldstream
nor the Y-34 burns appear to have received the heavy rainfall Which
produced the Fairbanks flood,it is possible that some runoff-pro-
ducing rainfall was received.
Other conclusions are:
1.Frail lands exist in Alaska where deep loess underlain with
permafrost on moderate gradients is located.Such soils are extremely
erosive when the ground cover is removed through disturbance such as
fire line construction.
2.Fire lines constructed on frail areas produce high erosion
hazards,and such lines should be kept to a minimum.
3.Fire lines constructed on gradient and continuing out over
streambanks produce a hazard from headcut erosion back upslope.
4.Rehabilitation measures may be necessary to stabilize fire
lines constructed on gradients in frail areas.
5.Treatment practices required to stabilize existing gully
erosion are at present not fully known.Trials should be conducted
to identify successful practices.
12
6.Revegetation trials should be undertaken to identify seeding
and/or planting practices (and species)which would accelerate estab-
lishment of ground cover on fire lines constructed in frail areas.
7.Wildfire burn areas not disturbed by dozer-constructed fire
lines require no artificial rehabilitation.
Reconnnendations
To insure that total resource loss is maintained at a minimum from
both (1)wildfires,and (2)fire line erosion,the following recommen-
dations are offered:
1.Continue use of dozer-constructed fire lines on fires where
areas are accessible to heavy equipment.
2.Restrict to a minimum the construction of dozer fire lines in
frail areas such as north slopes,drainage bottoms,stream banks,
permafrost areas,etc.
a.Achieve through education of fire control personnel
(overhead)on erosion hazards on frail areas.
b.Require fire control overhead to locate all fire lines
andaccempany tractor operators during construction of fire lines in
frail areas.
c.Consider sacrificing additional area within constructed
fire line where threat of life and/or property is not involved rather
than locating fire lines in close proximity to fire and on frail areas.
13
(~)
3.Initiate fire rehabilitation on dozer fire lines constructed
in frail areas (to be done ilIDllediately following the fire or during
mop up).
a.Install rehabilitation practices while heavy equipment is
still in fire area.
b.Implement rehabilitation through use of 1520,Fire
Rehabilitation,funds (1631.12I4)•Timing will be sensitive and
critical so suggest that a request for special approval procedures be
made to WO (RPM).
c.Use such practices as (1)checks or water bars on fire
lines at frequent intervals using the organic debris removed from the
C=)line,(2)seeding with grasses and other plant materials adaptable and
available,and (3)planting with such fast growing species as willow,
aspen and alder where adaptable.
4.Maintain observations of gully erosion conditions annually at
Goldstream and Y-34 (photo repeats,range lines,etc.)for a minimum
of three years (1968,1969 and 1970).
5.Consider a trial treatment of existing gullied area (1966 fire)
for rehabilitation purposes.
a.Select area where treatment would be most economically
feasible.(Goldstream would be preferable if cooperation and easement
could be arranged with Alaska Division of Lands since State lands are
r involved -Otherwise,select an area in Y-34).
14
('
c
b.Use such practices as gully plugs (thawed soil,fire line
debris)at frequent intervals,grass seeding of all disturbed area
including gully plugs,and tree seeding or planting using adaptable
species.
c.Use 1260 funds for financing the rehabilitation through
submission of a tfpackage.n
6.Defer rehabilitation of existi~g gully erosion areas until
results of (4)and (5)above are evaluated.
15
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Attachment 111
Page 1 of 4
PHOTOS
OF
EROSION OF WILDFIRE AREAS IN ALASKA
Photo No.1 -Dozer-constructed fire line on Goldstream
Fire showing debris berm in left center,gully in
center,and unvegetated cleared line to right.
\
Photo No.2 -Deep gully (approx.10')on Goldstream
Fire showing melting ice lenses and permafrost.
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Attachment #1
Page 2 of 4
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Photo No.3 -Active gully on Y-34 Fire area showing
melting ice lenses and sediment laden water.Note
that water is emerging from a tunnel formed in
melting ice lenses.
Photo No.4 -Sedge tussock commonly found on the
Goldstream soils --Y-34 Fire area.
•
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Attachment #1
Page 3 of 4
Photo No.5 -Looking upstream at a small drainage in
Y-34 Fire area.Note the reproduction of grasses
and sedges.Photo taken at junction with drainage
shown in Photo No.6.
)
Photo No.6 -Looking upstream at small drainage in l·~~
Fire area where fire line was constructed.Photo No.5
was taken from same point but to the left up adjacent
drainage.
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Attachment ttl
Page 4 of 4
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Photo No.7 -Shows a well
slope --Y-34 Fire area.
drainage bottom adjacent
bedrock.
drained soil on south
Fire line constructed in
to slope has eroded down to
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