Developing GIS indicators and metrics

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Developing GIS indicators and metrics

• David Theobald
• Natural Resource Ecology Lab
• Colorado State University

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Goals of indicator development

• Develop and evaluate landscape-level indicators
  suitable for spatial and temporal analyses of
  EMAP data
• Investigate limitations of currently-available
  data and offer new, robust methodologies

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Current effort

• Linkage between watershed and hydrologic networks
• Refine surrogates with direct measures of area
  and discharge
• GIS-based tools
• RWTools for ArcView
• Catchment delineation discharge in ArcGIS

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1. Watershedhydrological network linkage

• in every respect, the valley rules the stream.
  Hynes 1975
• Indirect measures based on hydrological
  properties (e.g., Strahler order, drainage
  density, etc.)

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Distance

• As the crow flies (Euclidean)

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Distance

• As the crow flies
• As the seed floats (downstream)

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Distance

• As the crow flies
• As the seed floats
• As the fish swims (down up stream)

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Distance

• As the crow flies
• As the seed floats
• As the fish swims (down up stream)

• Upstream length
• mainstem (2)
• arbolate (1234)

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Distance

• As the crow flies
• As the seed floats
• As the fish swims
• Upstream length
• Network (dams, fragmentation)

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What indicators measure watershed-stream linkage?

• Length of stream line
• Dam alteration of flow at a downstream gauge?
• RWTools extension (ArcView v3.2)

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Upstream 66 km
Mainstem Upstream 37 km
Network 16 km (down) 6 km (up)
Downstream 298 km
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2. Direct measures of discharge

• Surrogates developed, e.g. Strahler order
• The usefulness of stream order assumes, with a
  sufficiently large sample, that order is
  proportional to stream discharge
• Strahler 1957
• Alternatives
• basin area
• discharge

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Delineate reach catchments

• Robust method (no pre-processing)
• 1 to 1 relationship NHD reach and catchment
• Grow watershed from reach line based on flow
  direction iteratively

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Stream discharge

• Precipitation
• D C P

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R20.7282 P-value3.407e-006
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Stream discharge

• Encouraging preliminary results
• Additional factors (Infiltration, E.T.)
• Geology
• Land cover
• Exposure
• D f(C, G, L, E)

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3. GIS-based tools

• Interactive query and analysis of watersheds
  (RWTools) (ArcView v3.2)
• ArcGIS Geometric network

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Plans for next year

• Initial release of GIS tools
• RWTools for ArcGIS
• Functional-based spatial weights

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Spatial weights
W
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1
0 1 0 0 0 1 0
1 0
1
1
2
3
5
4
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Functional weighting
W
0 0 0 0 0 0 0 0.7 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0
0 0 0 0 0.7 0 0 0 0.2
0.8 0 0.2 0.8 0 0 0.1 0.2 1.0 0.1
0.2 1.0 0
1
1
3
2
4
5
7
6
E.g., downstream hydrology
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Functional weighting
W
0 1 0 0 0 0 0 1 0 0
0 1 1 0 0 0 0 0 0
0 0 0 0 0 0 1 0 0 0
1 0 1 0 1 0 0 1 0
0 1 0 1 0 0 0 0 0
1 0
1
1
3
2
4
5
7
6
E.g., macroinvertebrates
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Plans for next year

• Initial release of GIS tools
• Perennial/intermittent frame problem in western
  US
• Development of network fragmentation indices