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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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Presentation Transcript
methods data
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
create dem of lake bottom
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.

lake bottom dem cont d
Lake Bottom DEM Cont’d
  • Points file  mass points for terrain creation
  • Interpolate terrain to raster DEM with cell size 6.35m*
establish shoreline
Establish shoreline
  • Kml shoreline doesn’t make ‘elevational’ sense...
  • Modified using aerial imagery, DEM
  • Flood level established from photos taken in Summer 2011...
create dem of lake surface
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
depth raster
Depth Raster
  • Raster subtraction using Lake bottom DEM and Lake surface DEMs

Normal Height

Flood Height

analysis volume
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)

discussion
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