Analysis of Coastal Dune Vegetation Change: 2000 & 2003
• Coastal dune vegetation plays a vital role in maintaining shorelines.
• Tracking changes in vegetation allows for identification of problem areas more susceptible to washouts or breaches.
• This research project compared coastal vegetation dynamics along Kennedy Space Center (KSC) during the years 2000 and 2003.
Above: Satellite image of eastern Florida with the area of interest (AOI) highlighted in red.
Materials and Methods
• Hardware, software, and data were made available by the Earth Systems Modeling and Data Management Lab (ESMDM). Images acquired from color infrared (CIR) digital scanners and CIR aerial photography were used to measure vegetation along the dune line, using ERDAS Imagine’s Iterative Self-Organizing Data Analysis Technique (ISODATA).
• ISODATA classified every pixel into ten classes. Those
classes were reclassified into sand or vegetation by visual evaluation
performed concurrently with an accuracy assessment.
• The swath of shore was then divided into 5 m x 5 m plots. Each plot was assigned a numerical value equal to the proportion of vegetation present then converted to a single point.
• To track past and present changes of coastal vegetation, images for 2000 and 2003 were layered in a Geographic Information System GIS).
Results and Discussion
There were marked differences in image quality between the years 2000 and 2003. However, using ten classes from ISODATA, accurate analyses of the coastal dune vegetation were achieved. ISODATA correctly classified >90% of the pixels for 2000 and >95% for 2003. By dividing the swath into 5 m x 5 m plots, the perimeter-to-area ratio of the plot being compared was reduced and thus the effects of offset pixels within the GIS was diminished.
Above: ISODATA classification into two classes over the CIR image (left). ISODATA classification with 5 m x 5 m plots outlined (right).
Above: Proportion of vegetation present along the AOI for the year 2000 (left) and 2003 (right), displayed in points with each point representing a 5 m x 5 m plot.
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Left: Difference in proportion of vegetation present for 2000 and 2003. Green points represent an accretion in vegetation, red points - a recession, and yellow - no change.
There is evidence of more than 20 m of accretion at False Cape while there is recession in vegetation immediately north of False Cape and at three additional sites along the coast. This approach to data development was effective in identifying changes in coastal dune vegetation.
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Author: Erica Bowen, Ecology Emphasis Group, University of Alaska, Anchorage
Principal Investigator: Ron Schaub, Dynamac Corporation
Click here to download a printable Microsoft PowerPoint version of this research.
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