WMS Investigation: Travel Time Variability with Method, Area, and Slope

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WMS Investigation Travel Time Variability with
Method, Area, and Slope

• Ryan Murdock
• May 1, 2001

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Data Collection

• USGS DEMs
• 30m resolution
• UTM projection
• 3 locations
• Cuyahoga River Cleveland, Ohio
• Provo River Provo, Utah
• Town Creek Johnson City, Texas
• DRG background maps

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Watershed Delineation

• Smooth DEM
• Flow directions flow accumulations
• Convert raster streams to feature arcs
• Choose outlet
• Set accumulation threshold
• Delineate basin boundaries
• Convert basin to polygon
• Compute basin data

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Choosing Accumulation Threshold
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Cleveland, Ohio
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Johnson City, Texas
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South Fork of Provo River, Utah
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Land Use/Land Cover Soils Data

• BASINS Coverages
• Geographic Coordinates

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Projecting and Clipping

• ArcView
• Project land use and soils data to UTM Zone 12
  using the Projector Utility
• Export basin boundary from WMS
• Clip themes using Spatial Analyst Geoprocessing
  Wizard

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Coverages in WMS

• Import shapefiles into WMS
• Assign land use and soil type coverages

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Automated CN Calculation

• Import CN table
• Composite CN0.5?
• Estimated CN75

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Flow Data

• USGS gaging station at watershed outlet
• Use 1963 peak flow of 500cfs

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HEC-1

• Calibrate to measured
  peak flow by changing
  precipitation
• Basin average precipitation,
  type II-24 hr series
• SCS curve number method
• SCS unit hydrograph

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Hydrographs!

• P1.22 in, CN65

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Travel Time Calculator
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Assumptions/Simplifications

• Each basin
• Same impervious
• Same CN
• Same roughness
• Changed slopes in calculator, not re-delineated

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Analysis

• More dispersion of results in larger basins
• Increasing slope causes the standard deviations
  to decrease
• No strong trends with slope in the coefficient of
  variation
• Different sized basins with the same slope have
  similar coefficients of variation

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Equation Evaluation

• Pretty Robust
• Putnam, Kerby, Denver
• Touchy
• Fort Bend County
• Taylor
• SCS method predicts longer travel time
• Remember the conditions under which the equations
  were developed

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Time is Running Out

• Revisit the composite CN process
• Confidence in HEC-1 calibration
• Include Cuyahoga River travel time results
• Look at the equivalent velocities represented by
  each equation/method

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That's the end of todays modeling adventures,
kids.