Quantification of ephemeral gully erosion with close-range

digital photogrammetry

K.R. Gesch, R.R. Wells, H.G. Momm, S.M. Dabney, R.M. Cruse

July 28, 2014

Research team

1

Robert Wells Henrique Momm

Rick CruseSeth Dabney

Key ideas1. Close-range digital photogrammetry

(CRDP) can be used to reconstruct ephemeral gully morphology.

2. CRDP generates time-sequenced physical data of channels that can improve soil erosion models.

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Soil erosion

Data: Montgomery, 2007 3

0.01

0.1

1

10

100

Soil production Geological Nativevegetation

Conventionalagriculture

Conservationagriculture

Med

ian

rate

(Mg

ha-1

y-1 )

Erosion scenario

Soil erosion models• Conservation planning• Field-scale models

» RUSLE: Revised Universal Soil Loss Equation 2

» WEPP: Water Erosion Prediction Project hillslope model

Estimate only sheet & rill erosion

Flanagan et al., 1995; USDA-ARS, 2013 4

Ephemeral gully erosion• Small channel (≤ 50 cm deep)• Re-form in similar location

SSSA, 2008; Momm et al., 2012 5S. Rasmussen

Ephemeral gully erosion• Removes topsoil & nutrients and

decreases yields• Interferes with farm operations• Connects landscape drainage

network

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Status• Ephemeral gully erosion poses on-

farm and off-site problems• Soil conservation works• Conservation planning tools "ignore"

ephemeral gully erosion

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Needs• Field-scale soil erosion models that

accurately predict channel erosion• Data to validate models• Technique to supply data

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Research goals1. Establish method to produce data.

Close-range digitalphotogrammetry

2. Apply CRDP to generate data for validation of predictive models.

Digital elevation modelsCross-sections

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Photogrammetry

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CRDP: A hybrid technique1. In-field measurement

» High detail2. Remote sensing

» Non-contact» Digital data

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Research siteNeal Smith National Wildlife Refuge• Experimental

watersheds» Area: 0.5 to 3.2 ha» Slope: 6.1 to 10%

Helmers et al., 2012 13

Field setup

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R. Cruse

Field setup

15

H. Li

Field setup

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H. Li

Photography

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Wirelessrouter Camera

Referencemarkers

Photography

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H. Li

S. Lee

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Upstream Downstream

3D model

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Geo-referencing

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Coordinate 1 X,Y,Z

Coordinate 2 X,Y,Z

Coordinate 3 X,Y,Z

Coordinate 4 X,Y,Z

3D model…

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…dense surface model

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265.43 m

264.80

Point cloud

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265.43 m

264.80

Time-sequence analysis

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T0 T1268.02

267.47

267.89

267.43

Time-sequence analysis

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T0 T1

Cross-section

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Elevation change

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OutputIntermediate data Final products1. GPS coordinates 1. Cross sections2. Photographs Graphical3. Point clouds Tabular

2. Volume changeErosion

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Field-scale erosion• Morphometric channel evolution• Estimate erosion to verify CRDP data

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Field-scale erosion

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Field-scale erosion• Channel volume = 6.39 (± 0.20) m3

• Bulk density = 1.24 Mg m-3

• Field area = 0.73 ha• Erosion = 10.87 (± 0.34) Mg ha-1

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Quality: LiDAR

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LiDAR CRDP

Quality: LiDAR

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LiDAR CRDP

Quality: Uncertainty

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A B

Quality: Uncertainty

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Quality: Uncertainty

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• 72 replications• ∆volume precision = 0.0014 m3

• Area = 2.11 m2

• Average vertical precision = 0.65 mm• Vertical change uncertainty = 1.3 mm

Benefits of CRDP• Post-initialization, this technique

requires only 1 researcher• Speed

» Data collection (photography)» Data processing

• High data accuracy

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Future research• Tabular cross-section data

» Time-sequenced & geo-referenced• Soil properties• Topographic characteristics• Rainfall & runoff measurements

Improve field-scale soil conservation planning tools

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Key ideas1. Close-range digital photogrammetry

(CRDP) can be used to reconstruct ephemeral gully morphology.

2. CRDP generates time-sequenced physical data of channels that can improve soil erosion models.

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ReferencesFlanagan, D.C., J.C. Ascough II, A.D. Nicks, M.A. Nearing, J.M. Laflen. 1995. Chapter 1: Overview of the

WEPP erosion prediction model. In USDA-Water Erosion Prediction Project Hillslope Profile and Watershed Model Documentation, NSERL Report #10.

Helmers, M.J., X. Zhou, H. Asbjornsen, R. Kolka, M.D. Tomer, R.M. Cruse. 2012. Sediment removal by prairie filter strips in row-cropped ephemeral watersheds. Journal of Environmental Quality, 41(5):1531-1539.

Momm, H.G., R.L. Bingner, R.R. Wells, D. Wilcox. 2012. AGNPS GIS-based tool for watershed-scale identification and mapping of cropland potential ephemeral gullies. Applied Engineering in Agriculture. 28(1):17-29.

Montgomery, D.R. 2007. Soil erosion and agricultural sustainability. Proceedings of the National Academy of Sciences, 104(33):13268-13272.

Soil Science Society of America (SSSA). 2008. Glossary of soil science terms. Soil Science Society of America. Madison, WI.

USDA-Agricultural Research Service (ARS). 2013. Science documentation: Revised universal soil loss equation version 2 (RUSLE2). Washington, D.C.

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AcknowledgementsRobert Wells

Henrique MommSeth DabneyRick Cruse

Kevin ColeChris Witte, Matt Helmers, STRIPS

Pauline Drobney, Neal Smith NWR, USFWSGary Van Ryswyk

Hao LiScott Lee

Victoria ScottSarah AndersonAnthony Miller

Iowa State University Department of Agronomy

USDA National Institute of Food and AgricultureGrant number 2012-03654

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Thank you.Research teamKarl Gesch – kgesch@iastate.eduRobert Wells – robert.wells@ars.usda.govHenrique Momm – henrique.momm@mtsu.eduSeth Dabney – seth.dabney@ars.usda.govRick Cruse – rmc@iastate.edu

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Calculations

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Uncertainty Erosion

Quantification of ephemeral gully erosion with close-range digital photogrammetryK.R. Gesch1, R.R. Wells2, H.G. Momm3, S.M. Dabney2, R.M. Cruse1

1Iowa State University, 2USDA-ARS, 3Middle Tennessee State University

AbstractSoil erosion in agricultural landscapes poses a substantial challenge to conservationists. Soil erosion estimation models are useful tools for conservation planning; however, commonly used models such as the Revised Universal Soil Loss Equation 2 (RUSLE2) or the Water Erosion Prediction Project (WEPP) Hillslope Model cannot predict soil erosion due to topographically concentrated runoff –ephemeral gully (EG) erosion. While the physical processes of concentrated flow erosion that occur in EG channels are similar to those of rill erosion, EG erosion differs because EG channels are larger and locations are non-random. There is a critical need to improve the capability of models by incorporating EG erosion. High-precision data of physical EG development is necessary in order to calibrate new or improved models. This research seeks to augment current scientific knowledge of EG erosion processes through the generation of time-sequenced high-precision digital elevation models (DEMs) of EGs using a novel systematic and practical methodology based on geo-referenced close-range digital photogrammetry (CRDP) technology. Photograph pairs collected throughout the year are used to generate detailed sequences of channel DEMs at 5 mm resolution and cross-sections of EGs. DEM post-processing determines volume difference between two time steps and EG cross-section profiles. Measured changes in surface topography will be analyzed with reference to observed rainfall and runoff. Preliminary results indicate that CRDP is an effective method for estimating EG morphology and changes in EG volume over time. Coupling CRDP and DEM analyses with observed rainfall data provides precise three-dimensional data of the time-evolution of EGs. This type of data will be highly beneficial to existing erosion models such as RUSLE2 or WEPP or for the development of new models that explicitly account for EG erosion. Improved data will enhance models and allow for more effective conservation planning.

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