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Lake Volumetrics

Lake Volumetrics. Introduction. Methods: Data. DEM from USGS Digitized version of 1:24,000 topo quadrangle Vertical accuracy 5m, 30m resolution KML files, digitized from Google Earth Lake perimeter Drain line for dam Drain depth estimations in 400ft increments BING aerial imagery.

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Lake Volumetrics

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  1. Lake Volumetrics

  2. Introduction

  3. Methods: Data • DEM from USGS • Digitized version of 1:24,000 topo quadrangle • Vertical accuracy 5m, 30m resolution • KML files, digitized from Google Earth • Lake perimeter • Drain line for dam • Drain depth estimations in 400ft increments • BING aerial imagery

  4. Lake perimeter and drain line depths (m)

  5. Methods Overview

  6. Create DEM of Lake Bottom • Convert 30m raster DEM to center points • Edit points within the lake perimeter to reflect drain depth estimations Center-point values edited to reflect the lake bottom. Values are based on drain line depth estimations.

  7. Lake Bottom DEM Cont’d • Points file  mass points for terrain creation • Interpolate terrain to raster DEM with cell size 6.35m*

  8. Establish shoreline • Kml shoreline doesn’t make ‘elevational’ sense... • Modified using aerial imagery, DEM • Flood level established from photos taken in Summer 2011...

  9. Create DEM of Lake Surface • Select all points within lake perimeter at each height • Assign new value to selected points • Create terrain from points and interpolate to raster

  10. Depth Raster • Raster subtraction using Lake bottom DEM and Lake surface DEMs Normal Height Flood Height

  11. Analysis: Volume • Performed in Excel • Normal and flood depth rasters converted to ascii and imported to Excel • Volume: Cell Length x Width x Height (depth) • 6.35m x 6.35m x (depth) • Sum all volume calculations Normal Water Level: 85,569.16 m3 (112,095.6 yd3) Flood Water Level: 190,154.91 m3 (249,102.93 yd3)

  12. Discussion • Data: • 30m DEM from topo contour digitization/ interpolation poor quality for scale of analysis • Lake depths estimations from lake users • Terrain to Raster • Raster grid size (6.35m): questionable • Should match input size (30m), but too coarse for lake perimeter—excludes large amounts of lake area • ESRI default: based on the overall dimensions of the minimum bounding rectangle and the number of input elevation points

  13. Questions?

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