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Using LiDAR-Derived DEMs to Predict Wet Soils

Using LiDAR-Derived DEMs to Predict Wet Soils. Gary Montgomery • GEOG596A Advisor: Patrick Drohan Funding partners:. Credits/Acknowledgement. Penn State University’s Soil Characterization Lab ( http://soilislife.psu.edu/ ) USDA-NRCS Pennsylvania Lycoming County Planning Department.

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Using LiDAR-Derived DEMs to Predict Wet Soils

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  1. Using LiDAR-Derived DEMs to Predict Wet Soils Gary Montgomery • GEOG596A Advisor: Patrick Drohan Funding partners:

  2. Credits/Acknowledgement • Penn State University’s Soil Characterization Lab (http://soilislife.psu.edu/) • USDA-NRCS Pennsylvania • Lycoming County Planning Department

  3. Study Goals • Identify potential wet soils (saturated above 50cm) • Identify potential hydric soils and unmapped wetlands. • Validate model for NCPA/Appalachian Plateau region • Demonstrate applicability with ground truthing • Determine correlation with other indices: SOM, depth

  4. Study Purpose/Application • Hydric soil identification • Wetland identification • Surface/stormwater runoff prediction • BMP implementation that enhances E&S plans • Landslide susceptibility • Road maintenance • Amphibian migratory pathways • Nutrient runoff potential in agricultural areas

  5. Methods • PAMAP 1m LiDAR Data • 42-tile study area • Mosaiced to new, export • With Whitebox GAT, run topographic wetness index analysis • Field verified by pit descriptions, well recording, soil moisture sensors, and “wet boot” monitoring.

  6. Topographic Wetness Index • Predictor of wetted areas based on grid analysis • Fill DEM (Planchon & Darboux algorithm) • Flow direction (D-inf) • Flow accumulation (D-inf) • Slope • Natural log(upslope catchment/tangent(slope))

  7. TWI vs other indices • Appropriate for rolling/hilly terrain • D-inf flow pointer and accumulation are multi-directional: high resolution DEM unsuited to single-direction flow algorithms

  8. Whitebox GAT UI (http://www.uoguelph.ca/~hydrogeo/Whitebox/index.html)

  9. Ground truthing • Cross-contour transects • GPS (Trimble GeoXT) • Soil profile every 30m • A and O horizon thickness • Depth to fragipan and/or Bt horizon (high clay) • Depth to redox

  10. Saturation expressed as visual depletions and concentrations of soil color. Redoximorphic features are used to identify soil drainage classes Drohan, 2011

  11. Drohan, 2011

  12. TWI > 7.89 Hydro C/D Hydro D NWI

  13. Preliminary Results Non-parametric, Mood median test: P = 0.09

  14. Preliminary Results

  15. Example Use: Gas Extraction • Infrastructure needs – access, clearing, roads, rights-of-way • Often in remote, rugged area • Soil effects from construction, support traffic • Soil moisture loss/compaction • Soil organic carbon loss • Change in surficial flow: “flashy”

  16. Drohan, 2011

  17. Gas Well Sites and Soil Drainage SwPD: Wet soil for significant periods; redox features in the upper 50 cm Drohan, 2011

  18. Drohan et al. (2011)

  19. Doherty et al. (2008)

  20. Project Timeline • Summer 2011 • Field forays wrap up • September – October 2011 • Paper revision/finalization • October – December 2011 • Conference presentation

  21. Future work • Other DEM sources • Comparison w/ 10 & 30m DEMs • Stats on C/D and D soil hydro group polygons

  22. References • McKergrow, L. A. et al. Modeling wetland extent using terrain indices, Lake Taupo, NZ. Proceedings of MODSIM 2007 International Congress on Modelling and Simulation. Modelling and Simulation Society of Australia and New Zealand, December 2007, 74–80. • Pei, Tao et al. Mapping soil organic matter using the topographic wetness index: A comparative study based on different flow-direction algorithms and kriging methods. 2010. Ecological Indicators 10, 610-619. • Schmidt, Frank et al. Comparison of DEM Data Capture and Topographic Wetness Indices. 2003. Precision Agriculture 4, 179-192. • Sorenson, R. et al. On the calculation of the topographic wetness index: evaluation of different methods based on field observations. 2006. Hydrology and Earth System Sciences 10, 101-112.

  23. Any questions?

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