Historical and Projected Coastal Louisiana Land Changes

Figure 15. 1990 to 2000 spatial trend data set in the vicinity of Calcasieu Lake in southwestern Louisiana.
Because of the scale of the available images, several years of shoreline erosion and internal
marsh degradation may occur before the loss is detectable by using Landsat TM based trend
analysis. However, visual examination of multiple dates of TM imagery using remote sensing
software clearly shows the slow degradation of wetlands. Small islands disappear and ponds
increase in size or coalesce to become larger ponds. Any such small gains experienced between
1990 and 2000 cannot be considered in this analysis but are unlikely to alter the trends and
patterns identified here.
Error Assessment
Classification Accuracy
Classification accuracy assessments were performed on the 1999 and 2002 Landsat TM imagery
to quantify the reliability of the data sets. The accuracy assessments were performed by an
experienced image interpreter who was not involved in the classification of the source TM
imagery. A stratified random sampling approach was used to create an equal number of
sampling points for the land and water classes merging each data set to provide overall accuracy.
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