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Assessment of Flow Paths in Upland Areas and Vegetated Buffers

Assessment of Flow Paths in Upland Areas and Vegetated Buffers

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Assessment of Flow Paths in Upland Areas and Vegetated Buffers

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  1. Assessment of Flow Paths in Upland Areas and Vegetated Buffers ASAE Annual Meeting 2004 August 2, 2004 I.J. Kim, S.L. Hutchinson, and J.M.S. Hutchinson* The department of Biological and Agricultural Engineering *The department of Geography Kansas State University, Manhattan, KS

  2. Research Background (1) • Model assumption: • Uniform overland flow • Ex) WEPP, REMM, VFSMOD • Reality: • Concentrated surface runoff in fields • Dillaha, 1986 / Fabis et al, 1993 / Dosskey, 2002

  3. Research Background (2) • Digital elevation model (DEM) • Calculation of hydrological attributes • Slope, contour line, hill shade, aspect, etc • Flow path and length • LS factor • Delineating contributing area (e.g. watershed) • Risk assessment for landscape susceptibility • 30 m DEM widely used for GIS-Hydrologic model • Accessible data source (i.e., USGS 30m DEM) • Less costly

  4. Typical grid resolution in DEM High Cost and data storage

  5. Purposes of Study • Delineating flow path networks and drainage boundaries for hillside areas and vegetated buffers • Determining a suitable grid size for parameterizing model inputs at field scale site

  6. The study area: Fort Riley NE NIR Image Kansas River

  7. Buffer: brushes / trees Study Site Hillside: grass

  8. GPS Receiver Settings • Date: March 24th, 25th and April 14th 2004 • Base station for DC: Range Control Office Station, Ft. Riley • PDOP*: position dilution of precision • Accuracy: ± 50 cm • Vertical accuracy error • a vertical control point (KF0640) • root mean square error (RMSE)

  9. Elevation Data Collection

  10. Method for Creating DEM • TOPOGRID is essentially based on a discretised thin plate spline technique and an iterative finite difference interpolation.

  11. Limitations and Assumption • Accuracy of grid DEM is dependent on GPS accuracy • Becoming overland flow to channel flow is dependent on the contributing area (the number of cells)

  12. Drainage network delineation:Eight direction (D8) model N, 26 E, 20 W, 24 S, 22 • FILL / FLOWDIRECTION / FLOWACCUMULATION • Define flow paths from the specific accumulation area (# cell) • BASIN / FLOWLENGTH

  13. Hillside and Buffer Zone Data Points # of points: 2998 AVG PDOP: 2.68 Highest: 399.0 m Lowest: 382.5 m RMSE - 0.307 (XRS) - 0.526 (XR)

  14. Surface Elevation Variability 30m DEM USGS 30m DEM 10m DEM 3 m DEM

  15. Highest and Lowest Elevationat the Entire Areas and within the Buffers

  16. Flow Path and Catchment Area Boundary (CAB) 30m DEM USGS 30m DEM 10m DEM 3 m DEM

  17. Longest Flow Length & CAB *Flow length is the longest in the catchment boundary

  18. Flow Path and CAB (3 m DEM) TH:90m2 TH:9m2 TH:450m2 TH:900m2

  19. Conclusions • 30m resolution should be avoided for determining flow paths, especially in the buffer areas • Grid size significantly influences flow direction, catchment area shape, and surface terrain complexity on the hillside and buffer areas. • 3m DEM provides the most detailed flow paths and catchment area boundaries • 90m2 (10 cells) in 3m DEM required for flow path delineation with in the buffer

  20. Future Studies,,, • Applying larger resolution (e.g. 1m DEM) to the area and/or Ft. Riley • Applying advanced method to the flow direction • Evaluating effects of the flow length to hydrologic responses in a model

  21. Acknowledgements • The Strategic Environmental Research Development Program (SERDP) • Kansas State University Agricultural Experiment Station

  22. Questions and Comments?

  23. Buffer: brushes / trees Study Site Hillside: grass