SampLe Analysis Maps
The following four maps provide examples of
Streams that provide spawning or rearing habitat for
Figure 9
how resource managers can use a geographic
anadromous salmonid sh, as observed during
Road-stream crossings
information system to analyze data and show
Oregon Department of Fish and Wildlife surveys, are
links among different data sets.
also highlighted on the map. During the master
Subwatershed
'I
.
planning process for future urban areas, local and
Upper Clackamas River
8.9
regional planners can use maps like this to make
Hot Springs Fork Collawash River
Areas of PLanned Increase in
Land-Use Intensity
9 .4
decisions about the effects of urban expansion on
Collawash River
0
0
10.7
natural ecosystems.
Oak Grove Fork Clackamas River
8.9
This map is the result of comparing two maps shown
previously in the atlas: Existing Land Use and Future
Land-Use Plan. To create this map, we grouped all
possible and uses into five basic categories and
Fish Creek
Note: This mop shows on/y the actual areas where coho,
Roaring River
chinook and stee/head are known to be distributed.
11.2
Middle Clackamas River
or other fish.
3 - Single-Family Residential
By using GIS to compare or overlay the rankings in
the existing land-use data with the future land-use
data, we calculated a resulting number ranging from
+ I to +4. For example, a property that is currently
a farm (ranking
I ) and is slated for industrial zoning
in the future (ranking
5) received a +4. A ranking
of +3 could mean that a farm is slated to become
multi-family residential or that a rural residential area
is slated for commercial development. in the map
17.7
Deep Creek
Known Impediments to Fish
12.4
Richardson Creek
Passage
14.3
Clear Creek
adopted by the Metro Council and reserves designated by the city of Sandy. These areas may eventu-
ally be included inside the Metro or Sandy urban
growth boundaries and developed to accommodate
an increasing population. Once these areas are
developed, they would experience an increase in
16.4
This map shows both potential impediments to sh
24.9
Rock Creek
movement, known as road-stream crossings, and
0
0
Lower Ciackamas River
18.9
0
known impediments such as dams and waterlalls.
0.0
5.0
10.0
15.0
20.0
25.0
Crossings per square mile
S
S
S
because streams are often diverted into pipes, called
culverts,to pass under roads. Some culverts
S
a
Road-stream crossings are important to fish habitat
-
0
particularly small diameter pipes, culverts that are
alongside a road (within five feet) for some distance
Note: The most detailed stream data available were
( I 5.8 per square mile) than the rural residential
C
improperly installed, and culverts with a large drop
could show up as several road-stream crossings,
used to locate the crossings. Roads and streams are
subwatershed of Richardson Creek ( I 4.3
on the downstream side - can prevent fish from
even though the stream may not actually cross
mapped in greater detail on federal lands than on non-
per square mile), even though the Fish Creek
S
S
moving further upstream.
underthe road. In contrast, urban streams that have
1ederal lands; as a result, more road-stream crossings
subwatershed appears to have fewer road miles
S
long ago been routed underground are not mapped
appear on federal lands. Individual road-stream cross-
per square mile than the Richardson Creek
and thus would not show up as road-stream cross-
ings were not verified in the field. For more information
subwatershed (see Figure 3).
ings, even when streams are piped directly under-
about the base data displayed on this map, refer to the
It would be very time consuming for eld crews
to walk every road and stream to identify where
Also displayed on this map are urban reserves
14.0
Goose Creek
Road-Stream Crossings and
legend, the bright red color represents land that
could see the highest intensity ofchange (+4).
10.0
Eagle Creek
4 - Multi-Family Residential
5 - Commercial and Industrial
13.8
North Fork Clackamas River
lowest- to highest-intensity use.
2 - Rural Residential
1.5
South Fork Clackamas River
Nonhigh/ighted streams may or may not contain these
assigned each category a number ranking them from
- Farm, Forest and Open Space
0
0
0
0
0
0
0r
15.8
they meet, especially in a watershed as large as
neath roads.
base map description.
a GIS (geographic information system) to locate
Also shown on the map are known impediments
Figure 9 shows the number of road-stream crossings
road-stream crossings ( I .5 per square mile), likely
probable road-stream crossi ngs. These computer-
to fish passage, such as waterfalls, dams and large
per square mile for each subwatershed. A high
because of its low road density (0.7 road miles per
generated crossings, marked wherever a road and
culverts, as identified by the Oregon Department
number of crossings can be attributed to (a) more
square mile).
a stream come within five feet of each other are
of Fish and Wildlife and the U.S. Forest Service. The
actual roads (see Figure 3 for road density in each
shown on the map.
land-use intensity. Howeve because local comprehensive plans have not been updated since reserves
Not all ofthe road-stream crossings shown consist
were adopted, the map does not show specific areas
of culverts. Some road-stream crossings may have
within the urban reserves where growth will occur
bridges, while very small or intermittent streams may
flow across a road. Also, areas where a stream runs
number of known fish impediments is small com-
subwatershed); (b) more detailed road data, such
pared to the number of potential barriers indicated
as the gravel road data kept by the USFS; (c) more
by the road-stream crossings. (Whether an impedi-
streams; or (d) streams that run close to roads. For
ment actually blocks fish passage depends on the size
example, Fish Creek subwatershed in the Mt. Hood
ofthe waterlall, whether the dam has a fish ladder
National Forest shows more road-stream crossings
and the fish species trying to pass.)
0;
0
The Roaring River subwatershed, also in the Mt.
Hood National Forest, has the lowest number of
the Clackamas. Instead, resource managers can use
0
Note: The road density data were produced in I 988-
0
0
S
S
S
C
C
C
I 996 and may not reflect current conditions. For
example, because USFS road data were produced in
I 994, they do not include logging roads abandoned
or removed since then. New roads built since I 996 in
urban areas are also not included.
S
S
S
S
Relative Susceptibility to
To create this map, we combined the inherent
Figure 10
Mass Wasting
stability of each geology unit with slope categories,
High susceptibility to mass wasting
This map shows the relative susceptibility of different
areas in the watershed to mass wasting, the large
movements of soil that occur as landslides and debris
forming a geology-slope matrix with rankings for
each combination (Booth; King County). For ex-
S U bwatershed
ample, an area with unstable, old landslide deposits
Upper Clackamas River
13%
(QIs) and steep slopes would show up as high
flows.
Hot Springs Fork Collawash River
64%
susceptibility." An area with moderately stable
Coltawash River
Mass wasting can transport vast amounts of soil, and
49%
sedimentary rocks (Qts) could show up as either
Oak Grove Fork Clackamas River
often trees and rocks, from hillsides to nearby
medium susceptibility" orlow susceptibility" deFish Creek
streams, This process can affect fish habitat by
41%
pending on slope. In the Lower Clackamas area, the
Roaring River
clogging streams with sediment, washing out habitat
pools and woody debris, and scouring riparian areas.
abundance of gentle slopes means that the entire
South Fork Clackamas River
area is considered to have low susceptibility" to
found there are only moderately stable.
other than geology and slope. Heavy rainfall, rain-on-
geology and slope.
snow events, and certain soil types, textures and
19%
Eagle Creek
in all watersheds, including undisturbed, forested
frequency and severity of natural mass wasting are
31%
North Fork Clackamas River
Mass wasti ng happens naturally, although infrequently,
Mass wasting events are also influenced by factors
25%
Middle Clackamas River
mass wasting, even though some geologic materials
watersheds. The two major factors that affect the
22%
17%
Goose Creek
0%
Deep Creek
0%
Richardson Creek
0%
Clear Creek
thickness can make an area more susceptible to mass
Geology is important because some types of geo-
8%
Rock Creek
0%
wasting. Mass wasting can also be aggravated by
logic materials, particularly certain rock types, are
Lower Clackamas River
7%
human activities such as land clearing, road building
very strong and stable and thus resistant to sliding.
0%
and some timber harvesting practices. These factors
10%
20%
30%
40%
50%
60%
70%
Other types of geologic materials are mechanically
were not included in the analysis because current
Percent with high susceptibility
rather weak or unstable, and thus susceptible to
data is not available forthe entire watershed.
landslides.
The map also shows ancient landslide deposits,
The geologic units in the Clackamas watershed can
including debris flows, rock falls, earth flows and
As shown in Figure I 0, the subwatersheds in the
active slumps. Because soil in these areas has already
upper Clackamas (top ofgraph) generally show a
Generalized Stream Gradient
landslides, which can deliver the disturbed soil to
be classified by their stability:
nearby streams. Stream channels with fast moving
This map provides another example of how a GIS
greater percentage of areas with high susceptibility to
Unstable: Qls,Tfc,Tu,Tus
been disturbed, they are susceptible to further sliding.
Moderate: Qts, Qs
This landslide data was provided by the U.S. Forest
Stable: All other geologic units shown on the
Service and covers only sites located on federal
Fork ofthe Clackamas River and the Upper
forest lands.
Clackamas Rivec These two subwatersheds include
Geology Map
can combine data from several sources to help
mass wasting. Two exceptions are the Oak Grove
downstream (Montgomery and Buffington).
resource managers analyze a particular issue. In this
case, the stream gradients can be used to analyze
Generally, sediment carried by the water will be
possible relationships between sediment production
deposited in stream reaches where the flow slows
in one part ofthe watershed and fish habitat down-
down. These reaches, which often contain pools, are
high plateaus, which provide gentle slopes compa-
Slope is also a facto because rock and soil of any
Note: Because moss wasting depends on so many
type on steep slopes are more susceptible to mass
f-actors, this map can be used to indicate general areas
wasting than rock and soil on gentle slopes. The
susceptible to landslides, but not to predict sites where
slope categories used forthis map were:
slides will occur In addition, because this map was
derived from the geology data, it is subject to the
Gentle slope: 0-24 percent
Moderate slope: 25-49 percent
Steep slope: 50-69 percent
Very steep slope: 70 percent or greater
water then act as conduits to carry the sediment
limitations ofa coarse scale (1:500,000). The USFS has
more refined geology information for federal forest lands,
information that is more appropriate for site-specific
analyses.
rable to those found in the lower watershed. Such
stream.
gentle slopes minimize the susceptibility to masswasting, even in areas with unstable geologic materials.
In contrast, the two subwatersheds with the
Because ofthe coarse scale ofthe digital elevation
also used by anadromous salmonids for spawning
and rearing. Sediment deposits can affect fish habitat
by burying spawning beds and degrading water
and slope data, this map can be used only to illustrate
quality.
largest percentages shown - the Hot Springs Fork of
large-scale, watershed-wide patterns of sediment
the Collawash River (64 percent high susceptibility)
transport, but not to identify specific locations where
and the Collawash River (49 percent high susceptibil-
sediment is being produced or carried downstream.
The Generalized Stream Gradient map shows five
types of areas:
ity) - both have steep slopes, as indicated on the
Slope map.
Sediment can enter waterways through surlace
Areas with high mass wasting susceptibility: poten-
erosion orthrough large mass wasting events such as
tial sources of sediment from landslides and other
mass wasting events (see the Relative Susceptibility
Figure 11 (see text on page 39)
to MassWasting map for more information).
Stream eLevation profiles for Clackamas tributaries
Stream gradient of I I -20 percent (transport
Note: Stream elevations /n feet are shown on the left side ofeach graph. River miles (in these graphs, measured from the
reaches): these stream reaches with steep gradients
source ofeach tributary) are shown along the bottom ofeach graph.
6000
North Fork CLackamas River
4000
2000
0
are likely to have fast-flowing water rapids, or cas-
5
10
15
20
25
cades that can quickly transport sediment delivered
6000
6000
from upstream.
Hot Springs Fork ColLawash River
EagLe Creek
4000
4000
2000
2000
.
Stream gradient of 5- I 0 percent (secondary response reaches): Depending on the topography and
sediment loads, these these stream reaches may
0
5
10
15
20
0
25
5
10
15
20
either transport sediment or allow sediment to
settle.
6000
C
C
6000
ColLawash River
Stream gradient of 0-4 percent (primary response
25
Goose Creek
4000
4000
2000
2000
reaches): in these areas with gentle stream gradients,
the stream often widens and slows down, allowing
0
sediment to settle. These low-gradient reaches also
5
10
15
20
0
25
5
10
15
20
25
provide an ideal habitat for salmonid spawning and
6000
rearing.
6000
Oak Grove Fork CLackamas River
Known salmonid habitat: observed areas of spawning and rearing habitat for coho, chinook or steelhead
4000
Deep Creek
4000
2000
.S
S
2000
4000
4000
S
S
S
S
S
S
S
S
2000
2000
S
(see the Salmonid Fish Distribution map for more
0
5
detailed information).
The transition zone between a transport reach and a
response reach is particularly important because a
10
15
20
25
6000
0
5
10
15
20
25
6000
Fish Creek
Richardson Creek
transport reach usually deposits sediment into the
first downstream reach that can no longer carry the
sediment load. In primary response reaches, sedi-
0
S
5
10
15
20
25
0
5
10
15
mentation can have prolonged impacts, changing the
shape ofthe stream channel and bottom as well as
6000
20
25
6000
Roaring River
affecting habitat for fish and other aquatic animals.
Clear Creek
4000
4000
2000
2000
S
S
S
S
When evaluating possible impacts from sedimenta-
tion, it is important to considerthe physical link
0
between sediment sources and response reaches.
5
10
15
20
25
0
(
5
10
15
20
25
(
For example, some subwatersheds are landslide-
prone, but the map may show that sediment-produc-
S
6000
6000
South Fork Clackamas River
continued on page 39
Rock Creek
4000
4000
2000
2000
0
5
10
15
20
25
0
5
10
15
20
25
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