Mapping wetland change of prairie pothole region in bigstone county from 1938 year to 2011 year

Combining historical white and black aerial photo with more recent LiDAR and high resolution imagery, this research mapped wetland with high accuracy from 1930s to 2010s in object-based image analysis approach (OBIA). This research shows good potential in combining grey level information with OBIA method to map accurate historical wetland. We found that there were more small wetlands in 1938, but more large wetlands in 1978. In 2011, there were similar amount of small wetlands with 1938. Though 2011 had fewer large wetlands than 1978, 2011 year´s individual large wetland had much larger area than those in 1978 and thus contributed to much larger total wetland area in 2011 than in 1978. We found significantly increasing precipitation and decreasing temperature over the time series, also drought in 1938, and this may explain wetland change well.