Gravel Extraction in Alluvial Rivers

1
Gravel Extraction in Alluvial Rivers

• Gravel Extraction as a Historical Economic
  Industry and its Morphological Effects on the
  West Branch of the Little River, Stowe, Vermont
• Erin Turner
• Geography 246
• November 18, 2004

2
Objective

• Link changes in channel morphology of the west
  branch of the Little River to gravel extraction
  by
• Observing two time periods (1962 and 2000).
• Determining profile, sinuosity, area, and width
  of the channel for each time period.
• Determining presence and area of gravel bars for
  each time period.
• Obtaining historical information about gravel
  extraction amounts.

3
Methods

• Digital orthophotos (2000) and aerial photos
  (1962) - georeferenced.
• Digitized the stream channels for both
  years-calculated areas.

• Digitized gravel bars-calculated areas.
• Digitized and calculated stream lengths, measured
  valley length - sinuosity.
• Digitized data collection points (10) - measured
  stream width for both years, measured how far
  each bank had migrated over time.
• Looked at historical records of gravel extraction
  (1980-1986).

4
Results

• Digitized stream channels for 1962 and 2000

5
Results

• Digitized gravel bars 1962 and 2000

6
Results

• Digitized lengths, calculated areas of river and
  gravel bars, and calculated sinuosity

• 1962 larger area, shorter length, moderate
  meanders, less gravel bars, smaller area of
  gravel bars.

7
Results

• Digitized data points

8
Results

• Measured widths and shift of the channels at the
  data point locations

9
Conclusions

• There was obvious channel change between 1962 and
  2000.
• Can not attribute change to gravel extraction
  alone because..
• Vertical channel change was not measured.
• Role of other contributing factors including
  deforestation, development, or other stream
  alterations not considered.
• Limited time period analyzed.

10
Coming Soon

• Gravel extraction amounts 1980-1986.
• What does it all mean?
• A paper synthesizing all of my findings and
  discussing results.
• Continued research into next semester