Dolores River: Pre- to Post-Flood Elevation Change, April 2023 to February 2024

Change in surface elevation between a pre-flood and a post-flood drone survey (February 2024 DSM minus April 2023 DSM), shown over the February 2024 drone imagery and terrain.

Map: Stephen Conklin
Drone DSMs used in the analysis were collected for the DRAMS project by Jonathan Harvey, Ph.D., Fort Lewis College.

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Basemap
Elevation Change, Post-Flood (Feb 2024) − Pre-Flood (Apr 2023) DSM
≤ −1.5 m±0.2 m not shown≥ +1.5 m
◀ Lowering (erosion)Raising (deposition) ▶
Drone Imagery Mosaic, Feb 2024 (post-flood)
Terrain: Feb 2024 DSM
About this map

Surveys:

  • April 2023, pre-flood: right before a large flood was released out of McPhee Dam due to high snow levels the winter before.
  • February 2024, post-flood survey.

Elevation change:

  • Post-flood February 2024 DSM minus pre-flood April 2023 DSM (a DEM of Difference).
  • Stretched diverging colour ramp centred on zero: warm colours for lowering (erosion), cool for raising (deposition).
  • Default stretch ±1.5 m: about 90% of the change shown falls within it, while ±2 m would leave most erosion (median 0.37 m) in pale colours. Change between 1.5 and 2 m (about 10% of shown pixels, almost all raising) takes the end colours. Colours and stretch can be changed in the panel.

Values not shown:

  • Changes smaller than ±20 cm are not shown because they fall within the uncertainty of the measurements (the minimum level of detection). This threshold can be changed in the panel.
  • Changes greater than ±2 m are also excluded because they are likely due to survey artifacts rather than actual surface change.

Data details:

  • Feb 2024 DSM: cell size 1.82 cm
  • Apr 2023 DSM: cell size 1.53 cm
  • Difference analysis: cell size 1.82 cm
  • Map projection: NAD83(2011) / UTM zone 12N (EPSG:6341); displayed in Web Mercator (EPSG:3857).
  • The web tiles display the 1.82 cm analysis raster averaged to about 6 cm.

Imagery and terrain: February 2024 drone orthomosaic and DSM. Outside the survey area, terrain comes from AWS Terrain Tiles.

Scale bar: measured at the centre of the view; in tilted 3D views the scale varies across the map, so use "Zoom to site" (overhead view) for measurements.

Basemaps: Esri World Imagery, OpenFreeMap.