WMS Investigation: Travel Time Variability with Method, Area, and Slope Ryan Murdock May 1, 2001

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

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

Choosing Accumulation Threshold

Cleveland, Ohio

Johnson City, Texas

South Fork of Provo River, Utah

Land Use/Land Cover & Soils Data BASINS Coverages Geographic Coordinates

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

Coverages in WMS Import shapefiles into WMS Assign land use and soil type coverages

Automated CN Calculation Import CN table Composite CN=0.5? Estimated CN=75

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

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

Hydrographs! P=1.22 in, CN=65

Travel Time Calculator

Assumptions/Simplifications Each basin –Same % impervious –Same CN –Same roughness –Changed slopes in calculator, not re-delineated

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

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

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

That's the end of today’s modeling adventures, kids.