SURFACE HYDROLOGY and HYDROLOGIC FUNCTIONS

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SURFACE HYDROLOGY and HYDROLOGIC FUNCTIONS

• FE423 - February 3, 2000

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OUTLINE

• Your labs
• Hydrologic processes
• Hydrology in GRID

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Labs

• filli con(dem gt i,dem,i)
• automate.aml vs. valley_fill.aml
• Discuss function and workings of macros
• Do and write your lab simultaneously

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Hydrology
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Hydrology

• water flows down hill
• (and payday is on Friday)
• many processes increase as Slope Area
• surface erosion
• stream power
• landsliding

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Doing Hydrology in GRID

• Flow Direction depends on local slope
• Flow is accumulated at each point
• along with everything it carries
• Streams require minimum flow
• The watershed is the cells upslope
• Stream Order is a measure of accumulation
• Delivery to streams decreases with distance
• We can convert stream cells into arcs

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Flow Direction (hint downhill)

• The steepest downhill gradient.

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Flow Accumulation
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Accumulating Stuff
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3
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Weight grid
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Streams

• Minimum Contributing Area
• stream con(flowaccumulation gt min_area)
• Minimum Stream Power
• stream con(fa slope(dem) gt min_sp)

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Sinks

• Sinks are commonly viewed as errors
• Sinks can be an artifact of the gridding process
• Sinks are filled with the FILL command

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Watershed (anti-accumulation)
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Stream Order

• An old version of Flow Accumulation
• Shreve counts headwaters
• Strahler counts in a log fashion.

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Flow Distance

• Filtering effects increase with distance

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Linearizing Stream Networks