SCHEDULE

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SCHEDULE
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Discussion Problems
Revisiting the road-side ditch question Water
flows faster in ditches than through the soil. If
you count the ditch segments that feed directly
into streams as part of the stream network, then
map the flow length to streams with and without
road ditches. By how much is the average
flowlength above a stream cell reduced by adding
the roads?
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Practice Problem Identify FlowDirection for each
cell (arrows are okay)
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Practice Problem Identify FlowAccumulation(nil)
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Practice Problem Identify streams as cells with
gt10 contributing cells
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Practice Problem identify flow distance to
streams
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OUTLINE

• EUCLIDEAN
• distance
• allocation
• direction
• COST
• distance
• allocation
• back-direction

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Euclidean Distance

• Shortest distance from the source cells to each
  cell in a grid

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Euclidean Distance

• Shortest distance from the source cells to each
  cell in a grid
• Example

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Euclidean Allocation

• Identified the nearest source cells for each
  cell in a grid

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Euclidean Direction

• Angle from each cell in a grid to the source
  cells
• There may be some use for this

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Coding Euclidean Distance

• aGrid.EucDistance (directionFN, allocationFN,
  maxDistance)
• aGrid.EucAllocation (distanceFN, directionFN,
  maxDistance)

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Cost Distance

• The cost from moving from one cell to a
  neighbor is provides the cumulative cost of
  getting from each cell to the source cell with
  the lowest travel cost to it.

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Cost Weighted Averaging

• The cost from moving from one cell to a
  neighbor is the average of the two values

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Cost Allocation

• The cost grid changes which source area is closest

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Back-link Direction

• The direction to the adjacent cell that leads
  back to the source grid
• Does this remind you of anything?

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Coding Cost Distance

• aGrid.CostDistance (costGrid, directionFN,
  allocationFN, maxDistance)
• We wont be getting into using files FN in
  Avenue
• We can instead use hydrologic functions to get
  direction and
• thus routing.

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Discussion Problems
We might use stream buffers to disperse sediment
and runoff before it reaches the stream. How much
larger will a 200 Euclidean distance stream
buffer be than a buffer that includes slopes that
have a 200 flowpath to the stream? How might we
use the zonalstats function to quantify the area
of each zone?