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Image analysis of aerial photography to quantify changes in channel morphology and instream habitat following placer mining in interior Alaska
- GILVEAR, DAVID J., WATERS, TERTIA M., MILNER, ALEXANDER M.
- Freshwater biology 1995 v.34 no.2 pp. 389-398
- aerial photography, alluvium, biocenosis, gold, habitats, image analysis, mining, reflectance, rivers, spectral analysis, stream channels, surface water level, Alaska
- 1. ‘Placer' mining for alluvial deposits of gold in a number of stream systems in interior Alaska represents a major disturbance to the stream bed and affects habitat for biotic communities. 2. The potential of analysing aerial photographs to map changes in channel habitat and morphology within gravel-bed rivers is outlined with reference to the impact and recovery of Faith Creek, a second-order stream with a history of placer mining. 3. A strong correlation between the reflectance of the channel bed and water depth is necessary to use the technique succesfully, together with a knowledge of the effects of ‘broken'water on the spectral characteristics of rivers. 4. Image analysis demonstrated that a wide range of water depths and instream mesoscale habitats existed prior to mining. During mining, the stream was confined to a channellized reach with negligible deep water or habitat diversity. 5. Since mining ceased the stream has abandoned its channellized course and formed a new channel with few deep pools. It is suggested that geomorphological recovery and associated habitat recovery takes a number of large flood events and is likely to require more than 10 years.