2.1. Study Area 
  
  
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CERVANTES / 
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Figure 1: Cervantes to Coolimba coastal wetlands. 
Cervantes and Coolimba in Western Australia. Wetlands 
included in the study area are shown in Figure 1. The study area 
covers wetlands within approximately 12 km of the coast 
between 
2.2. Wetland Boundaries 
The hydroperiod analysis was restricted to areas within mapped 
wetland boundaries. Boundaries were manually digitized from 
aerial photography. Areas of water accumulation (derived from 
a 10 m Digital Elevation Model), soil maps and four winter 
Landsat images were used as reference data sets. À total of 263 
individual wetlands were mapped. The accuracy of the wetland 
boundaries was then checked in the field and is the subject of an 
ongoing study. 
2.3. Landsat imagery 
Calibrated and co-registered Landsat imagery captured in 
summer and supplied by the Land Monitor Project (Furby, 
2010) were used in the analysis. The study area was covered by 
the Landsat path/row, 113/81. Image dates used in the analysis 
were 11/2/88, 13/1/90, 22/2/92, 26/1/94, 1/2/96, 26/3/98, 
19/1/00, 9/2/02, 17/1/03, 23/2/04, 9/2/05, 27/1/06, 14/1/07, 
2/2/08, 18/12/08, 22/1/10, 10/2/11. 
2.4. Threshold development 
A single Band 5 threshold value to separate inundated from not 
inundated needed to be defined. Field work to determine this 
threshold was carried out between 15 and 19 August 2011. 
Comparing field results from the summer Land Monitor 
imagery was not possible as conditions had changed 
considerably since the date of image capture. For this reason a 
Landsat image captured 5/8/11 was used to compare field 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012 
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia 
measurements to index values. The scene was downloaded from 
the United States Geological Survey (USGS) and calibrated to 
Land Monitor values. 
A total of 16, 90 m by 90 m plots which covered relatively 
homogenous index values were chosen as validation points. 
Plots were chosen in easily accessible locations running 
perpendicular to estimated water body boundaries. Across each 
site the average water depth, percent vegetation cover and 
percent inundation were estimated. Vegetation cover was 
estimated by visual interpretation with the assistance of a 
template (Hnatiuk et al., 2009). The depth to which a secchi 
disk was visible and salinity were recorded at 3 points across 
the site and averaged. These field measures were then compared 
to index values. 
2.5. Hydroperiod classification 
Perennial vegetation maps produced by the Land Monitor 
Project for each year were used to remove perennial vegetation 
within wetland boundaries from the analysis. The inundation 
threshold was applied to the Land Monitor sequence to create an 
inundation map for each year. These raster datasets were then 
converted to polygons. The area of each of the 263 wetland 
polygons inundated in each year was then calculated. When 
wetlands had greater than 10% coverage of surface water in a 
given year they were considered inundated. Wetlands which 
were inundated 12 or more times were classified as 
“permanently inundated”. Those inundated less than 12 times 
were classified as “seasonally inundated” (Jones, 2008). The 
total area inundated each year was also calculated. 
3. RESULTS 
3.1. Threshold development 
To determine an appropriate Band 5 threshold for separating 
inundated from not inundated areas Band 5 values were 
regressed against field measures of percentage surface water 
coverage. In general Band 5 values decrease with increasing 
surface water coverage, however 2 outliers appear in the 
regression (points 1 and 2 in Figure 2). These sites recorded 
high vegetation cover along with high percentage surface water 
coverage. 
  
  
  
  
  
  
  
  
200 
160 
t: 120 
"0 
$ 80 1 25 
e O C 
Ó O 
40 Ó 
0 20 40 60 80 100 
surface water cover 96 
  
  
  
Figure 2: Regression of Band 5 values and percent surface water 
cover. 
Figure 3 is a photo taken at a site which corresponds to point 2 
in Figure 2. While 100 percent of the site was covered with 
    
  
  
   
     
    
      
  
    
   
     
    
   
    
      
  
    
  
  
     
   
    
   
   
   
    
   
     
   
    
     
  
    
     
      
   
    
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