U. S. Department of the Interior

Bureau of Land Management

Alaska State Offi ce

222 West 7th Avenue, #13

Anchorage, Alaska 99513

BLM-Alaska Open File Report 81

BLM/AK/ST-00/03-6710-040

September 2000

Aerial Photography Assessment of Riparian 

Areas in the Unalakleet Drainage, Alaska

Michael Scott
The BLM Mission

It is the mission of the Bureau of Land Management to sustain the health, diversity and productivity of 

the public lands for the use and enjoyment of present and future generations.

Cover Photos

Various views, Unalakleet drainage

Author

Michael Scott is employed by the Bureau of Land Management as an aquatic specialist at the Anchorage Field Offi ce.

Open File Reports

Open File Reports issued by the Bureau of Land Management-Alaska present the results of inventories 

or other investigations on a variety of scientifi c and technical subjects that are made available to the 

public outside the formal BLM-Alaska technical publication series. These reports can include preliminary 

or incomplete data and are not published and distributed in quantity.

The reports are available while supplies last from BLM External Affairs, 222 West 7th Avenue #13, Anchorage, Alaska 99513 and from the Juneau Minerals Information Center, 100 Savikko Road, Mayfl ower 

Island, Douglas, AK 99824, (907) 364-1553. Copies are also available for inspection at the Alaska 

Resource Library and Information Service (Anchorage), the USDI Resources Library in Washington, D. 

C., various libraries of the University of Alaska, the BLM National Business Center Library (Denver) and 

other selected locations.

A complete bibliography of all BLM-Alaska scientifi c reports can be found on the internet at: 

http://www.ak.blm.gov/affairs/sci_rpts.html. Related publications are also listed at http://juneau.ak.blm.

gov.
Aerial Photography Assessment 

of Riparian Areas 

in the Unalakleet Drainage, Alaska

Michael Scott

BLM-Alaska Open File Report 81

September 2000

U. S. Department of the Interior

Bureau of Land Management
4
5

Aerial Photography Assessment of Riparian Areas 

in the Unalakleet River Drainage

Introduction

The BLM Manual 1737 Riparian-Wetland Area 

Management (USDI, 1992), the BLM RiparianWetland Initiative for the 1990s (USDI, 1991), 

and 43 CFR 4, 1780, and 4100 provides policy, 

regulations and guidance for the identifi cation, 

protection, restoration and maintenance of 

riparian-wetland areas for BLM lands. While 

these documents emphasize grazing management, they include language that pertains to 

“other uses” which are pertinent to Alaska.

The 1990s initiative document suggested that 

Alaska concentrate on completing initial inventories and evaluations and maintaining these 

areas in their natural state. In 1990, Alaska 

estimated that 99 percent of their lotic riparian 

areas were functioning properly, but classifi ed 

90 percent as “unknown” since no inventories 

had been conducted. These fi gures were based 

on estimates by resource specialists familiar 

with these areas and submitted to the BLM 

Alaska State Offi ce (ASO). This information 

was incorporated into the Alaska Riparian Area 

Management Plan.

In the early 1990ʼs the Bureau of Land Management (BLM) provided a blueprint of 

management and restoration of riparian-wetland areas. The initiative recognized 

Alaska as a “special situation” in that only a small proportion has been disturbed. 

Most riparian documents about Alaska emphasize inventorying and maintaining 

these habitats. However, little emphasis has been given to inventorying Alaska 

riparian-wetland areas primarily due to the assumed condition of riparian habitat, 

limited funding, the remoteness of the water bodies, and the sheer magnitude of 

the number of miles of riverine habitat in the state. In 1998, BLMʼs Washington 

Offi ce directed BLM-Alaska to inventory 500 miles of riparian habitat. To meet this 

goal, BLM-Alaska fi rst assessed areas that were readily accessible but it became 

evident that to assess the large number of more remote areas in a cost effi cient and 

reasonable time frame would require a different approach. Advances in Geographic 

Information Systems (GIS) and techniques developed at BLMʼs National Applied 

Resource Sciences Center (employing small-scale aerial photography to assess 

Proper Functioning Condition) combined with a statistical procedure were applied 

to document the condition of vast amounts of remote and primarily pristine riverine 

riparian areas in Alaska. 

 

Fiscal Year 1999 Annual Work Plan directives 

emphasized the importance of implementing 

an inventory following the procedures outlined in technical reference TR 1737-9, Process 

for Assessing Proper Functioning Condition 

(Prichard et al., 1993), and technical reference 

TR 1737-15, A User Guide to Assessing Proper 

Functioning Condition and the Supporting Science for Lotic Areas (Prichard et al., 1998). The 

Alaska statewide assessment goal for FY99 

was more than 400 miles of which the Anchorage Field Offi ce (AFO) was to complete approximately 80 miles. To complete our assessment 

goal, Alaska requested proper functioning condition (PFC) training. This training was held 

in Fairbanks, Alaska, on May 4-6, 1999.

During the training, participants discussed differences between Alaska and contiguous states 

riparian-wetland situations. Most participants 

felt the contiguous states situation is complicated because many areas are classifi ed as nonfunctioning or functional at risk; Alaska has 

a larger proportion of riparian-wetland areas, 

but if inventoried, these would be classifi ed as 

functioning properly. 
6

Figure 1. 

Location of Unalakleet drainage area, Alaska.
7

The discussion then addressed ways Alaska 

could assess the vast amounts of riparian-wetland areas in the state. The approaches ranged 

from (1) assessing only those areas known to 

be impacted by various activities, assuming 

that non-impacted areas are properly functioning to (2) assessing all areas on a basin-wide 

basis, a monumental task because of the number of miles of lotic riparian habitat.

Because of the magnitude and remoteness 

of riverine riparian areas managed by the 

Anchorage Field Offi ce, a landscape-scale 

approach using aerial photography was considered the most viable option to evaluate Proper 

Functioning Condition (PFC). 

Description of the Study Area

The Unalakleet River drainage is located in 

the northwestern part of Alaska on the Seward 

Peninsula (Figure 1). The drainage encompasses about 2,082 square miles and has 3,246 

miles of streams as depicted on 1:63,360 USGS 

quadrangle maps. The mountains rise from 

sea level to elevations up to 2,000 feet. The 

headwaters of the main stem originate in a 

section of the Nulato Hills called the Kaltag 

Mountains. Approximately 81 miles of the 

Unalakleet River, from its headwaters to the 

confl uence with the Chiroskey River, is designated as part of the National Wild and Scenic 

River System. (Photo 1) 

Winter temperatures average -5°F to -12°F. 

Average summer temperatures range from 

42°F to 61°F. Prevailing winds are generally 

easterly (Unalakleet means “place where the 

east wind blows”) and average 10 mph. During 

fall storms, wind speeds can exceed 50 mph. 

Average annual precipitation is 14.2 inches, 

including 37 inches of snowfall. 

Plant species common to riverine riparian areas in the drainage are listed in Table 1 (Reed, 

1988).

Photo 1. 

An overview of the Unalakleet River valley. 

Note the diverse age classes and vigor of the 

willow. The younger-age classes of willow on 

the point bars are revegetating.
8

Table 1.

Common plant species that occur in Alaska wetlands.

Riparian-Wetland Vegetation Region A Indicator Habitat

1. Salix subsp. (willow) FACU to OBL Native shrub

 31 species

2. Alnus subsp (alder) FAC Native shrub

 6 species

3. Calamagrostis canadensis FAC Perennial native grass

 (bluejoint)

4. Potentilla palustris OBL Perennial native forb

 (marsh fi ve fi nger) emergent grasslike

5 Carex aquatilis OBL Perennial native

 (water sedge) emergent grasslike

6. Picea glauca (white spruce) FACU Native tree

7. Picea mariana (black spruce) FACW Native tree

8. Populus balsamifera FACW Native tree

9. Populus tremuloides FAC Native tree

 (quaking aspen) 
9

Study Design

Objectives for this assessment included:

1. developing cost and time effi cient procedures to assess riparian habitat in Alaska.

2. estimating the number of reaches that are 

in Proper Functioning Condition within the 

drainage such that the estimated river miles 

are within 5 percent of the true proportions 

95 percent of the time.

3. estimating the proportion of riverine 

habitat that is PFC such that the proportion 

is within 5 percent of the true proportion 95 

percent of the time.

 4. determining if these procedures are applicable to assess PFC in other major basins 

administered by the BLM Alaska.

The Unalakleet River riparian area assessment involved the following tasks:

• using a Geographic Information System 

(GIS) to analyze and document results of this 

assessment.

• identifying riparian areas/reaches within 

the Unalakleet River drainage using GIS.

• developing a photo index for the Unalakleet River drainage.

• applying a statistical procedure to determine the number of aerial photos that 

needed to be assessed to provide a 95 percent 

accuracy for the entire drainage.

• using photo interpretation procedures outlined in Prichard et al., 1999 to assess PFC.

 • visiting fi eld sites in the Unalakleet River 

drainage to validate photo interpretations.

• determining reportable units using land 

status and the routed Digital Line Graph 

(DLG) coverage in GIS.

This assessment incorporated GIS to help 

analyze and document the results. Four base 

layers were used in the assessment including 

two U.S. Geological Survey (USGS) digital 

elevation models (DEM) which were hillshaded 

and a DLG hydrography dataset which was 

routed by BLM Alaska State Offi ce personnel. The two other layers (a Unalakleet River 

drainage boundary and a point coverage of 

the centroid of the aerial photography) were 

produced at the BLM Anchorage Field Offi ce. 

Many of the themes and coverages used in this 

project are shown in Figure 2.

The coverage of the centroid of the small scale 

aerial photographs was generated from an ascii 

text fi le containing the latitudes and longitudes 

downloaded from BLM’s Alaska State Offi ce 

Alaska Lands Information System web site. 

The coverage was overlaid on the drainage 

boundary to determine the extent and distribution of areal coverage in the drainage.

Statistical Sampling

A single-stage cluster sampling technique was 

employed for this analysis (Cochran, 1980). 

The primary sampling unit (psu) was the effective area of the individual aerial photographs. 

Stream reaches were the elementary units 

whose characteristics were assessed. In singlestage sampling all streams in the psu were 

sampled. 

A 60 percent buffer theme was created around 

the centroid of 91 aerial photos. The buffer had 

an area that approximated the stereo coverage 

of the aerial photos and was used to estimate 

the number of reaches in the effective area of 

the aerial photographs. The statistical simulation was based on pilot data consisting of the 

number of reaches within the 91 buffered plots.

For each combination of sample size and assumed PFC, 10,000 percentages were run to 

determine the chances of a sample percentage 

being different from the assumed PFC. This 

test only determined if a given reach was or 

was not PFC. The statistical design did not 

consider whether a reach was Functional-At 

Risk. 
10

Figure 2.

Unalakleet drainage, subdrainages and photo points.
11

The simulation used realistic parameters and 

data ranges to determine the approximate 

sample size that would result in a sample 

that would be above a specifi c PFC level x, y 

percent of the time if the true percentage is z. 

The PFC level x was determined by setting y at 

90 or 95 percent and the assumed true percentage z took on the values of 95, 97 and 99 

percent. The estimate of the PFC reaches was 

calculated as:

where: I = 1 if the reach is PFC and 

0 if not PFC, and

r = the number of reaches in photo plot p

Appendix A contains the SAS code used in the 

simulation. 

Based on the summary of the statistical simulation, 10 photos were randomly selected by 

their frame number using a spreadsheet. The 

photo frame numbers were exported from the 

attribute table of the centroid theme of the 

aerial photo distribution. Using ArcView’s 

query capabilities, the centroids of the selected 

photos were identifi ed and highlighted. 

PFC Assessment

Available photography was used in this assessment to avoid the increased cost of obtaining 

current photography. The most current color 

infrared (CIR) photography available was 

fl own in the 1980s at 1:60,000 and 1:40,000 

scale. Transparencies of the 10 randomly-selected photo pairs (for stereo coverage) were 

requested through the BLM Alaska State 

Offi ce Branch of Mapping Sciences. Five of the 

transparencies had to be ordered and did not 

Figure 3.

Identifi caton 

of reaches.
12

arrive in time to be included in the assessment. 

All photographs were taken during July except 

those for photo plot 4960 which were taken in 

August.

A 6x6-square-mile theme representing the 

effective area of each of the randomly-selected 

photos was created in ArcView. Reaches were 

then defi ned within the effective area of the 

photographs (Figure 3). The theme was centered on the centroid of the respective photo. 

All streams within the effective area were 

stratifi ed into reaches. Reaches were delineated primarily on gradient but confi nement 

and sinuosity were also used as criteria in the 

process. Data layers used to defi ne the reaches 

included hillshaded relief of the DEM and the 

routed DLG data. An ArcView Avenue script 

utilized the event tables up and down indices 

in the Aquatic Resource Information Management System (ARIMS) database to defi ne 

reaches on the routed DLG coverage. 

After the reaches were defi ned, they were 

numbered consecutively. The number consisted 

of a numeric code which was formatted as the 

frame number of the selected photo followed 

by an alpha code (R) to indicate that the reach 

was a lotic water body, followed by a numerical 

identifi er for each reach in the effective area of 

the photo. If two or more reaches were identifi ed on the same stream, the unique number 

used to identify the reach was followed by an 

alpha character to distinguish them. 

A map of each photo plot with the hillshaded 

relief of DEM and DLG coverages was created 

using ArcView layout. The stream reaches 

were labeled with their respective reach 

numbers on each of the maps. The maps were 

provided to all interpreters involved with the 

project to help them identify reaches on the 

aerial photographs. (Photo 2.) 

Attributes and process identifi ed in TR1737-9 

(Prichard, 1993) and the photo interpretation 

key in TR 1737-12, Using Aerial Photographs 

to Assess Proper Functioning Condition of 

Riparian-Wetland Areas (Prichard et al., 1999) 

were used as guidelines for this assessment. 

The photo interpretation key (based on hydrology, vegetation, and erosion/deposition charPhoto 2 

Light table, aerial photos and printout of the 

effective area of the aerial photo (far right). 

The print out with reaches and reach numbers 

created in ArcView layouts was useful in identifying reaches on the aerial photo.
13

acteristics) was modifi ed to meet conditions 

common to Alaska (Appendix B). Stream fl ow 

characteristics, developed from a regional model for an instream fl ow study on the Unalakleet 

River, were used to evaluate the questions 

related to hydrology on the checklist (Klein et 

al., 2000). Interpretations were recorded on a 

hard copy of the PFC checklist to be entered 

into the PFC module of the ARIMS database 

upon completion of fi eld verifi cation. 

Results of the photo interpretation were verifi ed during a three-day fi eld survey of selected 

reaches. Some reaches were randomly selected 

while others were identifi ed during the photo 

interpretation process as sites that needed to 

be visited. The random selection of reaches 

to be included in the fi eld verifi cation phase 

was based on the proportion of the number 

of reaches in each of the fi ve plots. Twenty 

randomly-selected reaches and 18 questioned 

reaches from the photo interpretation effort 

were visited on site.

Coordinates were derived from the GIS to 

facilitate locating the reaches in the fi eld. A 

lat/long converter in ArcView determined 

geographic coordinates of those reaches to be 

evaluated. The coordinates were entered into 

the helicopter GPS and used by the pilot as 

waypoints to effi ciently locate the reaches. 

Interpreters used a portable light table and 

a stereoscope in the fi eld to help them review 

reaches before and after fi eld verifi cation. By 

using these tools in the fi eld, the team members could match their fi eld observations to the 

photos more precisely.

Results

The statistical simulation used to determine 

the number of photo plots indicated that very 

few photos were required to assess PFC for this 

drainage. Results ranged from 91.35 percent 

compliant with an assumed PFC of 95 percent 

using fi ve sample plots at a 5 percent quantile 

to 98.09 percent compliant with an assumed 

PFC of 99 percent using 10 sample plots at a 

10 percent quantile (Table 2). 

Two hundred and sixty-one reaches were 

delineated within the effective area of the fi ve 

photographs. Photo plots 4960, 75, 79, 247, 

and 104 had 47, 96, 45, 36, and 37 reaches 

respectively.

The initial attempt by the members of the team 

from Alaska to assess PFC from the photos was 

not encouraging. Less than 10 percent of the 

total number of reaches were interpreted, all of 

which were PFC. The results of these interpretations along with the aerial photos were sent 

to BLM’s National Applied Resource Sciences 

Center (NARSC) for review and further evaluation. (Photo 3.)

Photo interpretation by the NARSC Team 

proved much better. This team was able to assess all reaches on photo plots 79 and 104, 

Table 2. 

Summary of simulations for 5- and 10-plot samples.

5-Plot Sample 10-Plot Sample

 Assumed PFC 5% 10% 5% 10%

Quantile Quantile Quantile Quantile

 95 91.35 92.23 92.42 93.07

 97 94.08 94.89 94.97 95.47

 99 97.22 97.69 97.79 98.09

Assumed PFC 5% 10% 5% 10%

Quantile Quantile Quantile Quantile

91.35 92.23 92.42 93.07

94.08 94.89 94.97 95.47

97.22 97.69 97.79 98.09

Assumed PFC 5% 10% 5% 10%

Quantile Quantile Quantile Quantile

91.35 92.23 92.42 93.07

94.08 94.89 94.97 95.47

97.22 97.69 97.79 98.09
14

all but two reaches on photo plot 247, all but 

three reaches on photo plot 4906, and all but 

11 reaches on photo plot 75. The NARSC Team 

found all remotely assessed non-questioned 

reaches were PFC. NARSC could not assess 18 

reaches on the edge of the photography because 

these reaches were outside the stereo coverage.

These reaches could have been interpreted if 

the proper adjacent photography was available. 

Other reasons reaches were not interpreted 

included time of photography and darkness at 

the edge of some photos.

Members of the Alaska team, personnel from 

NARSC and the National Riparian Service 

Team conducted fi eld validations in June. 

Geographic coordinates derived from GIS 

proved to be very accurate in locating the 

reaches selected for fi eld verifi cation. All but 

four coordinates were within a few hundred 

feet of the selected reach. Three of those four 

were about 11 nautical miles off, probably due 

to transcription error.

With few exceptions, all the reaches proved to 

be lotic habitats and PFC. Exceptions included 

reach number 75 R16 (interpreted from aerial 

photography as a riparian area). In all probability was not be treated as a riparian area. 

Reach 79R12 turned out to be lentic, not lotic. 

Reaches 79R34, 35 and 36 were part of a large 

lentic wetland and would not be assessed as 

individual lotic systems. Although these sites 

eventually drained into the Unalakleet River, 

they should have been assessed as a lentic 

unit. (Photo 4.)

Other reaches questioned from the original 

interpretations 247R12 and 14, and 4960R25, 

Photo 3. 

A typical small drainage that presented problems to the members of the team from Alaska. 

Open water and the channel were not readily 

visible from the small scale aerial photos. 

Meander patterns and spectral response 

were important attributes in assessing these 

streams.
15

26 and 27. Photo interpretations for 247R12 

and 14 indicated drier sites. These sites were 

probably ephemeral and would not be considered riparian areas. Concerns for 4960R25, 

26 and 27 related to date of the photography 

(August). Results from fi eld investigations 

indicated that there were lotic riparian areas 

that should have been assessed because they 

had a riparian-wetland community. The early 

fall (August) photography revealed the spectral 

response of the understory vegetation instead 

of alders and willows. Local fi eld knowledge 

about these sites would have reminded the interpreters to adjust the interpretation key and 

identify them as riparian areas rated as PFC. 

(Photo 5.)

The team observed other reaches in the drainage on a random fl y-through on the last day. 

This fl y-through validated that the randomlyselected photo plots and their reaches provided 

reliable information related to PFC for the 

entire watershed.

For the most part, reaches defi ned using 

hillshaded relief of DEM were found to be 

adequate. Reaches, such as short fi rst order 

streams that have no side drainages, probably 

should not have been included in this assessment. Reach breaks on some Rosgen’s C type 

streams evaluated were not correct and required some adjustments.

All lotic reaches verifi ed in the fi eld were found 

in PFC. The use of small-scale aerial photography and GIS allowed us to effi ciently assess 

2,964 miles of riverine riparian on BLM land in 

the drainage. The results suggest more than 97 

percent of the reaches were compliant, using 

an assumed PFC of 99 percent with fi ve sample 

plots at a .05 level of signifi cance. 

 

Discussion

While it is generally accepted that the most 

current photos will yield the most accurate results, much of the high altitude photo base for 

Alaska is old. However, fi eld verifi cation of a 

remote riparian assessment in the eastern part 

of the Crow Indian Reservation using 16 to 17-

year-old photographs was found to be 95 percent accurate by the Natural Resource Conservation Service (USDI, 1999). Despite the age 

of the Unalakleet photography, characteristics 

between reaches interpreted from the photographs were very similar to those observed 

on the ground. Field validation indicated the 

remote assessment to be very accurate. 

 

The use of statistical evaluation to determine a 

sample size resulted in an assessment that was 

not only repeatable, but it also permitted us to 

place a high degree of confi dence in the assessPhoto 4.

Reach 79 R34, one 

of the 18 questioned 

reaches that drained an 

area of low relief and 

was depicted on the 

DLG as terminating on 

the tundra.
16

ment. The advantage of estimating the number 

of reaches for the statistical simulation was 

not having to defi ne them in all of the photos 

(using the “up and down” indices in ARIMS). It 

is estimated that there would have been more 

than 5,000 reaches to delineate in the drainage.

The buffers and criteria used to estimate the 

number of reaches for the statistical simulation 

resulted in an underestimate of the number of 

reaches that were identifi ed later to interpret 

the photos. It is unlikely that the underestimate affected the results of the assessment 

because the chance of a sample percentage 

being much different from the assumed PFC is 

directly related to the total number of reaches 

in the sample. Because the number of reaches 

in the assessments increased as a result of 

using the effective area of the photo rather 

than the buffer, the likelihood that the sample 

percentage was closer to the assumed PFC 

also increased. Consideration should be given 

to more accurately estimating the number of 

reaches in the simulation.

Primary consideration was given to the breaks 

in the hill-shaded relief coverage to defi ne 

reaches. The use of this data proved adequate 

particularly on the medium-to-large drainages 

within the photo plots. Several adjustments 

should be made in the way reaches are defi ned 

on the sample plots. Accretion of fl ow should 

be one of the criteria used to defi ne reaches. 

However, the upper reaches of many small, 

moderate-to-steep gradient, notable fi rst-order 

systems with no side drainages should have 

been truncated approximately midway up the 

drainages because it was determined that these 

reaches were not riparian areas. (Photo 6.) 

 

More accurate reach defi nitions could have been 

made on moderate-to-steep gradient streams 

by using the aerial photography in conjunction with GIS to determine whether small side 

drainages would contribute enough fl ow to 

Photo 5.

A Rosgen E type channel about one foot wide 

and 1.5- to 2 feet deep that is preamial. Dense 

willow and alder makes seeing open channels 

on small-scale photos diffi cult.
17

create riparian habitat. A logical break should 

have been made on several of the reaches due 

to their size. On the larger drainages, more 

consideration should have been given to using 

sinuosity and confi nement to defi ne reaches. A 

tool available through ArcView that generates 

contour intervals from DEM data was not used 

and could have helped defi ne the reaches.

The Alaska team was not comfortable interpreting the aerial photos. The team attempted 

to strongly adhere to some of the guidelines 

used to assess riparian areas. Specifi cally, 

if they could not see the channel, they felt 

they could not assess the stream reach. This 

presented a problem with small drainages, 

particularly fi rst and second order streams. 

Their results, when compared to those made by 

NARSC, clearly showed that experience is an 

important aspect in assessing riparian areas. 

In addition to reviewing our interpretation, 

NARSC also provided suggestions and adjustments to the interpretation key before and 

after the assessments were verifi ed in the fi eld. 

NARSC efforts will be of assistance in future 

efforts. The adjusted interpretation key can be 

found in Appendix B .

GIS greatly reduced the time required to create 

and analyze all related aspects of this project. 

Much more time would have been required to 

manually create and track the many overlays 

that this effort demanded, including the aerial 

photo distribution coverage, photo index and 

reach indices. Some query capabilities of GIS 

used to great advantage included determining 

the number and lengths of reaches and extracting geographic coordinates that were used to 

locate selected reaches in the fi eld.

Several attempts were made to obtain reportable units based on land status. ArcView 

clipped the stream coverage to BLM, state and 

native-selected lands. It was soon apparent 

that ArcView’s subroutine would not work with 

the events tables in the routed hydrography 

coverage. The length header was in the table 

of the clipped coverage, but records did not 

contain the information necessary to obtain the 

total miles in the clipped coverage. However, 

the table of an un-routed DLG contained the 

necessary information. 

Photo 6.

An example of a fi rst-order stream in the 

basin that is represented on the digital line 

graph. Typically, the upper portions (above 

treeline) of these systems have few, if any, 

side drainages and should not have been included in the assessment. The lower portion 

(having channel or vegetaion 

attributes characteristic of lotic systems) 

should be assessed.
18

BLM’s ESRI support person in NARSC, Mike 

Badar, suggested using an ArcView script 

named calcapl.ave on the clipped version of the 

routed DLG coverage. This script calculates 

area and for polygon themes and length for line 

themes However, there was a two percent difference in the number of stream miles when we 

compared the results of a clipped coverage of 

unrouted data to the routed coverage on which 

the script was used. 

Overall, this approach appears to be an effi cient and cost-effective means to document 

PFC in remote areas landscape basis where 

most streams are expected to be properly 

functioning. An estimated 65 staff days were 

required to complete the assessment, including 

travel time. Helicopter costs for three days to 

validate the photo interpretation cost approximately $10,500. There was an average of 50 

reaches per photo.

One hundred and four photos were used to 

cover the drainage with some overlap. Assuming an assessment could be accomplished 

with 75 photos that averaged 50 reaches per 

photo, assessing the entire drainage using 

either aerial photography and fi eld validation 

or site-based assessment would have required 

signifi cantly more time and money.

Acknowledgements

This project was the result of efforts of many 

people. Tim King, presently the only GIS support staff at the BLM Anchorage Field Offi ce, 

provided invaluable GIS support and encouragement. Andy Hall and Paul Bartschi from 

the BLM Alaska State Offi ce provided timely 

fi xes to the ARIMS data base and ArcView 

interface which facilitated the uses of GIS for 

this effort. Jim Alegria from the BLM Oregon/

Washington State Offi ce and probably the only 

biometrician with the BLM graciously donated 

his valuable time to provide statistical input 

and the programming code used for the statistical analysis. Scott Guyer, the BLM Alaska 

State Offi ce vegetation expert who along with 

myself learned much about the assessment 

process, was of great assistance in our initial 

attempt to interpret photography; his expertise 

with vegetation proved invaluable during the 

fi eld evaluation. Janis Staats, a US Forest 

Service hydrologist on the National Riparian 

Service Team, was an excellent note taker. 

Her knowledge of geomorphology and stream 

systems during the fi eld evaluation provided 

consistency in evaluating the hydrography 

questions in the key. Finally, the assistance 

of Pam Clemmer and Don Prichard from the 

BLM Center National Applied Resource Sciences Center was of great benefi t; their intimate knowledge and experience with the PFC 

assessment processes and interpretation of 

aerial photography were much needed during 

the initial phases of the project. They were 

able to make timely adjustments to the key 

which will assist us in the future. During the 

fi eld evaluation, they were able to demonstrate 

key features on the ground and relate them to 

the aerial photography which will be of benefi t 

with future efforts. 

References

Cochran, W.G. 1980. Sampling techniques. 

Third edition. John Wiley & Sons. New York.

 

Klein, J., M. Scott, and B. G. Sterin. 2000. 

Unalakleet National Wild River, Alaska: resource values and instream fl ow assessment. 

BLM Alaska State Offi ce, Anchorage, Alaska, 

56 pp.

Prichard, D., H. Barrett, J. Cagney, R. Clark, 

J. Fogg, K. Gebhardt, P. Hansen, B Mitchell, D 

Tippy. 1993. Riparian area management: process for assessing proper functioning condition. 

TR1737-9. Bureau of Land Management, 

National Applied Resource Sciences Center, 

Denver, Colorado. 60 pp.

Prichard, D., J. Anderson, C. Correll, J. Fogg, 

K. Gebhardt, R. Krapf, S. Leonard, B. Mitchell, 

J. Staats. 1998. Riparian area management: 

a user guide to assessing proper functioning 

condition and the supporting science for lotic 

areas. TR-1737-15. Bureau of Land Management, National Applied Resource Sciences 

Center, Denver, CO. 126 pp.

Prichard, D., P. Clemmer, M. Gorges, G. 

Meyer, K. Shumac, S. Wyman, and M. Miller. 
19

1999. Riparian area management: using aerial 

photographs to assess proper functioning condition of riparian-wetland areas. TR1737-12. 

Bureau of land Management, National Applied 

Resource Sciences Center, Denver, Colorado. 

64 pp.

U.S. Department of Agriculture. 1999 (draft). 

Assessing conditions of riparian-wetland corridors at the area wide level, using properly 

functioning condition (PFC) methodology—an 

interdisciplinary assessment tool. Watershed 

Science Institute Technical Report. Seattle, 

Washington. 16 pp.

U.S. Department of the Interior. 1991. Riparian-wetland initiative for the 1990s. Bureau of 

Land Management, Washington, DC. 50 pp.

____________. 1992. 1737 - Riparian-Wetland 

Area Management. Bureau of Land Management, Washington, DC. 38 pp.

Richmond, S.B. 1964. Statistical Analysis, 

second edition. The Ronald Press Company, 

New York.

Reed, P.B. Jr. 1988. National list of plant species that occur in wetlands: Alaska (Region A). 

USDI Fish & Wildlife Service, National Wetlands Inventory.
20

Appendix A

SAS Code

/* This is a simulation for unequal cluster sizes 

for proportion with the number of subunits 

within each PSU following a lognormal distribution.

*/

options ls=80;

%global loop size;

%let pfc=99;

%LET LL=5;

%let mean=3.; /* the mean of the lognormal 

distribution. This is approximately the mode 

of the pilot data. */

%let sigma=.5; /* the standard deviation of the 

lognormal distribution. This was estimated 

using SAS Insight and the pilot data and later 

verifi ed within the Excel spreadsheet. */

%let range=.55;

/* This macro has two primary functions 1) 

reduces a lognormal variate with mean and 

sigma defi ned that represents the number of 

reaches within a photo. 2) Repeats #1 ‘size’ 

times which represents the number of photos 

drawn from the population. 3) Repeats #2 ‘loop’ 

times which represents the number of samples.

*/

%macro psu(loop,size);

Data fi le1;

seed=7519;

do k=1 to &&loop;

bi=0;

do i=1 to &&size;

LL=5;

call ranuni(seed,x); /* draws a uniform random 

variate */

rnum=log(&range*x*100+&LL+.5); /* takes the 

natural log of the uniform random variate */

miln=rannor(seed)*&sigma+&mean; /* 

creates a lognormal random variate with 

mean=&mean and sigma=&sigma */

mi=round(exp(miln)); /* rounds to the nearest 

whole number. This represent the number of 

Appendices

reaches per photo */

bi=

o j=1 to mi; /* The probability that a reach 

fails to be PFC is simply the probability that a 

uniform random variate exceeds the targeted 

PFC */

call ranuni(seed,x1);

intx3=x1*100;

if intx3 ge &pfc then bi=bi+1; /* accumulates 

the number of reaches that fail to be PFC */

end;

output fi le1;

 end;

end;

%mend psu;

%MACRO ALL(LOOP, SIZE); /* A convenient 

loop that processes the macro PSU, summarizes the data by sample, calculates the estimated 

PFC or the non-PFC percentages and creates a 

historgram of the frequency of PFC or non-PFC 

compliant samples. */

%PSU(&LOOP, &SIZE);

proc summary data=fi le1 (where=(mi ge 6));

by k;

var bi mi;

output out=fi le2 sum(bi mi)=;

ata fi le3;

set fi le2;

pi=(1-bi/mi)*100;

fake=1;

run;

title1 “The distribution of &&loop samples, 

each drawing 

proc gchart data=fi le3;

vbar pi;

run;

quit;

%MEND ALL;

%ALL(10000,5); /* the fi rst argument is the 

number of samples and the second is the number of ‘photos’ to randomly draw within each 

sample. */
21

Appendix B

Alaska Interpretation Key

CIR

Aerial photos are an excellent tool for defi ning 

reaches because they provide a view of a large 

area that defi nes changes in landforms and 

other variables. However, pay close attention to headwater streams (stream order 1/no 

tributaries), moderate-to-steep gradients, and 

less than mile long as these may not be riparian areas.

Before assessing a particular reach look at the 

entire photo for similarities and differences. 

Try to note size differences, landform (confi ned/

unconfi ned), and vegetation types (herbaceous, 

shrubs, or trees) for areas being assessed. 

Note the time of year of the photos relative to 

the growing season; this is important for determining spectral responses. Look for introduced 

elements (roads, power lines, gas lines, etc.) so 

you have an idea of what disturbances might 

look like. Overall try to set in your mind what 

might be natural and what might be altered. 

Key in on areas that you have knowledge about 

to help defi ne what you are seeing elsewhere.

Hydrology

1. Is the fl oodplain above bankfull inundated 

in “relatively frequent” events?

Look for bright red spectral response of 

vegetation

Look for dark spectral response of water

Look for changes of elevation (out of the 

norm) with landform remaining constant.

2. Where beaver dams are present, are they 

active and stable?

Look for ponding or enlargement of a 

stream as indicated by dark spectral 

response of water. Then look for a dam, 

usually indicated by a pattern (lines/

grid) that contains a white/gray spectral 

response.

Look for bright red spectral response of 

vegetation on a dam to indicate stability. If you see no indication of vegetation 

capturing the dam then look for erosion 

(white/gray spectral response) around the 

dam or below the dam that might indicate instability.

3. Are sinuosity, width/depth ratio, and gradient in balance with the landscape setting (i.e., 

landform, geology, and bioclimatic region)?

First defi ne the surrounding landform. 

Should the riparian-wetland area be narrow, straight, and steep or should it be 

wide, sinuous, and fl at?

Next, review the entire reach for any indication of a meander pattern. For large 

systems this is usually easy to see as the 

spectral response of water is dark.

Where open water is not visible, look for 

vegetation patterns. Assess the type of 

vegetation and look for any red spectral 

response indicating it is riparian-wetland 

vegetation.

When there is no indication of a meander 

pattern (channel or vegetation) and there 

is a red spectral response indication 

riparian-wetland vegetation, think about 

the area being lentic instead of lotic.

4. Is riparian-wetland area widening or has it 

achieved potential extent?

Again defi ne the surrounding landform. 

Should you have a broad riparian-wetland area or a narrow riparian-wetland 

area? Assume a reach has achieved 

potential extent.

Look for factors that tell you it has not. 

These factors usually have a white/gray 

spectral response indicating areas with 

little or no vegetation.

5. Is upland watershed contributing to riparian-wetland degradation?
22

Start by looking for any mass wasting 

within the watershed of a particular 

reach. This is usually indicated by a 

white/gray spectral response. If you notice any, then look to see if it has entered 

the riparian-wetland area and resulted 

in degradation.

Look for introduced elements such as 

roads and pipelines that might result in 

degradation of a riparian-wetland area. 

These would include features such as 

mid-channel bars and recent alluvial 

fans.

Vegetation

If CIR photography is done at the right time of 

year, it allows for an easier separation of riparian-wetland vegetation from upland vegetation. If you do not have this clarity, then you 

need to separate the different colors of red. 

Select a known area and review what that vegetation looks like. Then apply this knowledge 

to the reaches you are assessing and apply that 

color difference to each question (6-11).

Be aware that at times some vegetation that is 

normal for specifi c streambanks will not give 

off a clear red refl ectance (such as evergreens). 

Also, be aware that if the photography is late 

in the year and vegetation has started to turn, 

your spectral response might vary from the 

understory vegetation.

6. Is there diverse age-class distribution of 

riparian-wetland vegetation (recruitment for 

maintenance/recovery)?

For shrubs and trees look for height differences which indicate young, middle, 

and old age. Also analyze the red spectral responses, 

For herbaceous species, look for a dense 

matting which indicates age-class.

7. Is there diverse composition of riparian-wetland vegetation (for maintenance/recovery)?

Differences in red spectral response 

indicates different species. Also analyze 

textural patterns.

8. Do the species present indicate maintenance of riparian-wetland soil moisture characteristics?

Use red spectral responses to determine 

this.

9. Streambank vegetation is comprised of 

those plants or plant communities that have 

root masses capable of withstanding high 

streamfl ow events.

Again, use red spectral response to fi nd 

whether the right plants are in place. 

Also analyze textural patterns.

10. Do the riparian-wetland plants exhibit 

high vigor?

A deep red spectral response for any vegetation is saying that plant exhibits high 

vigor. If you start to see a more yellow 

signature, assume you are dealing with 

stressed and/or unhealthy plants.

11. Is adequate riparian-wetland vegetative 

cover present to protect banks and dissipate 

energy during high fl ows?

Look for a continuous band of red spectral response.

When you observe a lot of white/gray 

spectral responses, it usually is indicative of little or no vegetation. However, 

be aware that it could also be a rock 

outcrop or in the case of large systems a 

normal nonvegetated point bar.

12. Are plant communities an adequate 

source of coarse and/or large woody material 

(for maintenance/recovery)?

For the Unalakleet watershed we felt 

this process was an N/A. Yes, there is 

wood in places but we felt that it was not 

mandatory for large wood to be in place 

to help dissipate energy.
23

Erosion/Deposition

13. Are fl oodplain and channel characteristics 

(i.e., rocks, overfl ow channels, coarse and/or 

large woody material) adequate to dissipate 

energy?

Review the existing landform to give you 

an idea of the channel characteristics 

that should be in place. For example, 

do not expect oxbows to be in a small 

headwater stream that is in a confi ned 

landform. Then look for these features.

For items such as rocks you will see a 

white/gray spectral response. For oxbows and overfl ow channels you should 

see a dark spectral response if water is 

present. You should also see the vegetation that characteristically lines these 

channels exhibit a red spectral response. 

For areas where water is not visible, 

there still should be the vegetation response.

14. Are point bars revegetating with riparianwetland vegetation?

Determine if the system you are looking 

at should have point bars. For example, 

this item would be N/A for most systems 

that are confi ned by landform (steep and 

straight).

If it is a system that has point bars, look 

for red spectral responses that indicate 

riparian-wetland vegetation is present 

on the point bars. Look for variation 

in heights as you move away from the 

water’s edge. A variation in heights indicates that the point bar is revegetating 

over time. Be sure to separate what is a 

normally-scoured point bar from where 

vegetation should start on the larger 

river systems.

15. Lateral stream movement is associated 

with natural sinuosity.

Be sure to defi ne if you are looking at 

a single channel system or a multiple 

channel system. For any single channel 

system you should see a well-defi ned line 

of open water (dark spectral response) 

and/or vegetation (red spectral response) 

that would indicate its lateral movement 

is natural. If there are problems and 

lateral movement is not natural it will 

trend toward being multiple channels 

and have a strong white/gray spectral 

response in the channel.

If you are looking at a multiple channel 

system you must determine if you are 

dealing with a vegetated system or a 

braided system as the spectral response 

will be different. A healthy vegetated 

system will have black spectral responses for water and red spectral responses 

for vegetation on islands and streambanks. A braided system will have a lot 

of white/gray spectral responses along 

with some black and red spectral responses.

16. Is the system vertically stable?

Look for a negative change in extent 

of riparian-wetland area within same 

landform. Most of the time this will be 

refl ected in a change of spectral response 

due to loss of vegetation or change in 

composition.

17. Is the stream in balance with the water 

and sediment being supplied by the watershed 

(i.e., no excessive erosion or deposition)?

Where open water is visible, look for 

black spectral response as this indicates 

there is little sediment. For any single 

channel system the evidence of any 

mid-channel bars (white/gray spectral response) is a strong indication of a system 

being out of balance.