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
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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
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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 – [email protected] Wells – [email protected] Momm – [email protected] Dabney – [email protected] Cruse – [email protected]
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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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