Quantification of ephemeral gully erosion
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The document discusses the use of close-range digital photogrammetry (CRDP) to quantify ephemeral gully erosion, highlighting its potential to enhance soil erosion models by providing detailed, time-sequenced data. It identifies significant gaps in current erosion prediction models, specifically their inability to address ephemeral gully erosion, and outlines research goals aimed at improving data collection and analysis methods. Preliminary findings indicate that CRDP can effectively capture changes in gully morphology, offering valuable information for soil conservation planning.
Quantification of ephemeral gully erosion
- 1. 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
- 2. Research team 1 Robert Wells Henrique Momm Rick CruseSeth Dabney
- 3. Key ideas 1. 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. 2
- 4. Soil erosion Data: Montgomery, 2007 3 0.01 0.1 1 10 100 Soil production Geological Native vegetation Conventional agriculture Conservation agriculture Medianrate(Mgha-1y-1) Erosion scenario
- 5. 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
- 6. Ephemeral gully erosion • Small channel (≤ 50 cm deep) • Re-form in similar location SSSA, 2008; Momm et al., 2012 5 S. Rasmussen
- 7. Ephemeral gully erosion • Removes topsoil & nutrients and decreases yields • Interferes with farm operations • Connects landscape drainage network 6
- 8. Status • Ephemeral gully erosion poses on- farm and off-site problems • Soil conservation works • Conservation planning tools "ignore" ephemeral gully erosion 7
- 9. Needs • Field-scale soil erosion models that accurately predict channel erosion • Data to validate models • Technique to supply data 8
- 10. Research goals 1. Establish method to produce data. Close-range digital photogrammetry 2. Apply CRDP to generate data for validation of predictive models. Digital elevation models Cross-sections 9
- 12. CRDP: A hybrid technique 1. In-field measurement »High detail 2. Remote sensing »Non-contact »Digital data 11
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- 14. Research site Neal Smith National Wildlife Refuge • Experimental watersheds »Area: 0.5 to 3.2 ha »Slope: 6.1 to 10% Helmers et al., 2012 13
- 21. 3D model 20
- 22. Geo-referencing 21 Coordinate 1 X,Y,Z Coordinate 2 X,Y,Z Coordinate 3 X,Y,Z Coordinate 4 X,Y,Z
- 23. 3D model… 22
- 24. …dense surface model 23 265.43 m 264.80
- 28. Cross-section 27
- 30. Output Intermediate data Final products 1. GPS coordinates 1. Cross sections 2. Photographs Graphical 3. Point clouds Tabular 2. Volume change Erosion 29
- 31. Field-scale erosion • Morphometric channel evolution • Estimate erosion to verify CRDP data 30
- 33. 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 32
- 38. Quality: Uncertainty 37 • 72 replications • ∆volume precision = 0.0014 m3 • Area = 2.11 m2 • Average vertical precision = 0.65 mm • Vertical change uncertainty = 1.3 mm
- 39. Benefits of CRDP • Post-initialization, this technique requires only 1 researcher • Speed »Data collection (photography) »Data processing • High data accuracy 38
- 40. Future research • Tabular cross-section data »Time-sequenced & geo-referenced • Soil properties • Topographic characteristics • Rainfall & runoff measurements Improve field-scale soil conservation planning tools 39
- 41. Key ideas 1. 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. 40
- 42. References Flanagan, 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. 41
- 43. Acknowledgements Robert Wells Henrique Momm Seth Dabney Rick Cruse Kevin Cole Chris Witte, Matt Helmers, STRIPS Pauline Drobney, Neal Smith NWR, USFWS Gary Van Ryswyk Hao Li Scott Lee Victoria Scott Sarah Anderson Anthony Miller Iowa State University Department of Agronomy USDA National Institute of Food and Agriculture Grant number 2012-03654 42
- 44. Thank you. Research team Karl Gesch – kgesch@iastate.edu Robert Wells – robert.wells@ars.usda.gov Henrique Momm – henrique.momm@mtsu.edu Seth Dabney – seth.dabney@ars.usda.gov Rick Cruse – rmc@iastate.edu 43
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- 47. Quantification of ephemeral gully erosion with close-range digital photogrammetry K.R. Gesch1, R.R. Wells2, H.G. Momm3, S.M. Dabney2, R.M. Cruse1 1Iowa State University, 2USDA-ARS, 3Middle Tennessee State University Abstract Soil 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. 46