Assessment of Flow Paths in Upland Areas and Vegetated Buffers

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
(No Transcript)
4
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

5
Typical grid resolution in DEM
High Cost and data storage
6
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

7
The study area Fort Riley NE
NIR Image
Kansas River
8
Buffer brushes / trees
Study Site
Hillside grass
9
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)

10
Elevation Data Collection
11
Method for Creating DEM

• TOPOGRID is essentially based on a discretised
  thin plate spline technique and an iterative
  finite difference interpolation.

12
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)

13
Drainage network delineationEight 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

14
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)
15
Surface Elevation Variability
30m DEM
USGS 30m DEM
10m DEM
3 m DEM
16
Highest and Lowest Elevationat the Entire Areas
and within the Buffers
17
Flow Path and Catchment Area Boundary (CAB)
30m DEM
USGS 30m DEM
10m DEM
3 m DEM
18
Longest Flow Length CAB
Flow length is the longest in the catchment
boundary
19
Flow Path and CAB (3 m DEM)
TH90m2
TH9m2
TH450m2
TH900m2
20
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

21
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

22
Acknowledgements

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

23
Questions and Comments?
24
Buffer brushes / trees
Study Site
Hillside grass