Joel Pederson, Joel Pederson,

Paul Petersen, Wally McFarlane Petersen, Wally McFarlane

and Scott Cragun and Scott Cragun

GULLY EROSION OF CULTUR

GULLY EROSION OF CULTUR
I. Erosion Control I. Erosion Control

II. Photogrammetry Photogrammetry

III. G

III. G

How do we 

How do we 

Why is it happening? Why is it happening?
Research Design

• 9 study sites, 22 gullies, 112 c• 4 photogrammetry study sites
Research Design

•comparison of data gathered before and after t

- success of checkdams - compare photogrammetry to ground su

•comparison of data gathered before and after t

- success of checkdams - compare photogrammetry to ground su
I. Erosion I. Erosion-Control Struc

Control Struc

Rock Linings Rock Linings Brush 

•Increase Increase roughness, slow flow ve

roughness, slow flow ve

•Trap sediment, reduce Trap sediment, reduce upchannel upchannel g

g

Are they effective? effective?
Results Results
Results Results

Box-and-Whisker Plot of Erosion/Deposition Associated with Intact an

intact damaged

Erosion (m)

-0.15-0.10-0.05

0.000.050.100.150.20

n=34 n=33

intact: 0.1

damaged damaged: 0

Mean Local Gradient Mean Local Gradient
February February

•may stay may stay intact better intact better

•retain sediment retain sediment

•encourage encourage less scour (permea

less scour (permea

brush checkdams checkdams superior to ro

superior to ro

dataset needs to be larg

dataset needs to be larg
Recommendations Recommendations

•Increase dataset Increase dataset

•Continue Continue using erosion using erosion treatments, especia

treatments, especi

•Maintain and repair structures to prevent er

Maintain and repair structures to prevent er

QUESTIONS? QUESTIONS?
II. Photogrammetric Photogrammetric Mon

Mon

produces topography produces topography from photo ste

photo ste

ours = highest resolution aerial photog

ours = highest resolution aerial photog
Point-to-point

Survey 

point Photogrammetry point - = Error

Methods Methods

Channels Channels

photogrammetry data photogrammetry data – survey data survey data 
Results Results—Photogrammetric Photogrammetric Vertic

Vertic

Interpolation Interpolation Interpolation Interpolation +

-+-

Site n mean stdev min (q0) q1 

Points 84 0.07 0.07 0.00 0.03 Profiles 983 0.06 0.06 0.00 0.02 Cross sections 207 0.09 0.09 0.00 0.04 Semi-auto TINs 4936 0.08 0.11 0.00 0.02 Manual TINs 5444 0.09 0.10 0.00 0.03 DEMs 20230 0.10 0.10 0.00 0.03 

Summary of February photogrammetry accuracy assessmen

Site n mean stdev min (q0) q1 

Points 77 0.08 0.08 0.00 0.02 Profiles 983 0.09 0.07 0.00 0.04 Cross sections 207 0.09 0.07 0.00 0.03 Semi-auto TINs 3636 0.10 0.10 0.00 0.03 Manual TINs 207 0.10 0.10 0.00 0.03 DEMs 19424 0.10 0.11 0.00 0.03 

Summary of October photogrammetry accuracy assessment 
Results Results—Photogrammetric Photogrammetric Vertic

Verti

Good

Bad

Ba
Log-bin Average Density/SDSE vs. Absolute Error for 

February Combined Sites

0.01

0.1

1

1 10 100 1000

Density/SDSE

Average Absolute Error (m)

Results Results—GIS Error Anal

GIS Error Anal

Log Bin Average of SDSE vs. Absolute Error for February 

Combined Sites

0.01

0.1

1

0.01 0.1 1

SDSE (m)

Average Absolute Error (m)

Log-bin Average P

Febru

0.01

0.1

1

0.1 

Average Absolute Error (m)

when densi

densi

average err

average err

Accuracy of Accuracy of pho

pho

1) Photogram

Photogram

2) Topograph

2) Topograph
Results Results—GIS Error Anal

GIS Error Anal

Density

Very useful for obtaining Very useful for obtaining 

accurracy, and eff

accurracy, and eff
Results Results—Change Detect

Change Detect

February February October OctoberFebruary February October October

10-20 cm of observed change during s

20 cm of observed change during s
Results Results—Change Detect

Change Detect

Photogrammetry Photogrammetry could not detect small could not detect small-scale 

scale 

Combined error between Feb and Oct 

Combined error between Feb and Oct 

problem is propagating erro

problem is propagating erro

Best likely at this photographic scale 

Best likely at this photographic scale 
Recommendations Recommendations

•Not yet useful yet useful for monitoring erosio

for monitoring erosio

•useful in larger gullies with larger eros

in larger gullies with larger eros

FIST data?

Cost?Impact?

this study
III. Geomorphology III. Geomorphology

Why is erosion happenin

Why is erosion happeni

How is erosion happeni

How is erosion happeni
τo = γDS

Pi – Ic = runoff

erosion = τo - τcr
Results Results

erosion and new erosion and new knickpoints knickpoints tend to correspon

tend to correspon

February

(before erosion)

October

(after erosion)

Erosion

Gradient-Area Index Slope-Area Index
Results Results—Slope-Area Erosion 

Area Erosion 

Area vs. Gradient at Gully Heads for all Grand Canyon 

0.001

0.01

0.1

1

0.001 0.01 0.1 

Area (ha)

Gradient (m/m)

No gullying

Gullying

Small, inactive

gully
Results Results—predictive mod

predictive mod

# Gullies Observed # G

68 

exa
baselevel baselevel hypothesis hypothesis

Initial work indicates a GIS Initial work indicates a GIS-based nume

based nume

could be constructed to predict er

could be constructed to predict er

Understanding erosion in this way will tell 

Understanding erosion in this way will tell 

Importance of each controlling factor, inclu

Importance of each controlling factor, inclu

AND 

be a powerful management to

be a powerful management to
Recommendations Recommendations

•increase and complete field and lab 

increase and complete field and lab 

including linking precipitation events to res

including linking precipitation events to res

•take the next take the next step in predictive mo

step in predictive mo

–vulnerable sites and precipitation vulnerable sites and precipitation

-eros

eros

•understand understand eolian system

•the baselevel baselevel hypothesis can be 

hypothesis can be 
Conclusions Conclusions

I. Initial data indicate erosion Initial data indicate erosion-control struc

control struc

brush checkdams checkdams, work if maintained , work if maintained

Other impacts of research: Other impacts of research: -topical contrib

topical contrib

-training of stud

training of stud

II. Repeat photogrammetry photogrammetry error is ~20 cm, error is ~20 cm, 

which is not good enough for monitoring 

which is not good enough for monitoring 

III. A GIS III. A GIS-based numerical model can likely p

based numerical model can likely 

erosion and the next step in research has 

erosion and the next step in research ha

for cultural resource management for cultural resource management