See additional satellite image processing articles at www.PANCROMA.com menu selection 'White Papers'

Proof Sheet Old Crow Yukon Territory Flood Maps

A client was conducting a flood analysis for the small village of Old Crow in northern Canada. Old Crow is built on an alluvial fan close by the banks of the Porcupine River and is vulnerable to flooding. These images combine available CDED DEM data with overlay images prepared from bands 1, 2 and 3 from free GeoBase SPOT data. The images were processed with PANCROMA™ to produce pseudo true color images and then pan sharpened. These is the final set of proof images that were used to develop the final study. Note the flooding animation at the bottom of the page. Contact me for similar studies of your area of interest.

Reference map.

River level 251m. With airstrip and town location and annotations. (1/2 full scale)

Contour shading set to show river bed elevations. Note the scour to the east and the alluvial fan debris on which the town is built that extends into the river. The alluvia have apparently been graded to form the airstrip since this DEM was recorded. (1/2 scale).

Base map. (1/2 full scale)

River level 251m. (Probably close to normal stage.) (1/2 full scale)

River level 251.5m. (1/2 full scale)

River level 252m. (1/2 full scale)

River level 252.5m. (1/2 full scale)

River level 253m. Moderate/severe flood stage. (1/2 full scale)

Grayscale DEM. River level 251m. With annotations (1/2 full scale)

The reason for the waterline "jumping" as it rises is an artifact of the DEM. CDED DEMs were prepared by the Canadian government from contour line data, which they interpolated to fill in the DEM values between the contour lines. A common problem when performing such an interpolation is a terracing effect. The interpolation has produced terraces with smoothed edges. As the water line reaches a flat section of the DEM surface, it advances rapidly in a horizontal direction, like a wave rushing up a flat beach. This study has pushed the limits of the available free DEM data. A higher resolution DEM is really needed.