Date of this Version
Thesis (M.A.)--University of Nebraska—Lincoln, 1998. Department of Geography.
Many wetlands rely on rainfall and surface run-off as their primary source of water and consequently may fluctuate in size and occurrence both annually and seasonally depending on the climatological conditions of a given area. The most current inventories have delineated wetland boundaries using data from one point in time, not taking into account the spatial and temporal variability in wetland hydrology. The objectives of this research were (1) to develop a method to map spatial and temporal variations in wetlands, and (2) to determine the inter-annual and intra-annual variability in wetland occurrence and extent due to changes in hydrology.
Landsat Thematic Mapper (TM) imagery was chosen for the initial wetland classification. Ancillary data including digital soils data, the National Wetlands Inventory, and the McMurtrey historical wetland survey were incorporated into the analysis to improve the overall reliability of the classification. Three dates of TM imagery representing wet, dry, and normal years were selected to examine annual variability in wetlands. Three dates representing the late winter, spring, and summer of one year were used to examine seasonal variability of wetlands.
The results of the analysis showed the changes in the extent of wetlands in both the annual and seasonal dates of imagery based on the classification methods employed. The annual differences were found to be significant, while the seasonal differences were much more variable. It appeared that results of the classification of imagery from the wet year provided better results than the normal and dry dates, and the spring date of imagery provided the best results for classifying wetlands in a year with average rainfall, as compared to the late winter and summer imagery. The resulting maps representing seasonal and annual variability in wetlands were compared to the NWI to show areas that were classified as potential wetlands but were not delineated by the National Wetlands Inventory. They illustrate the importance of including temporal data in wetland mapping to take into account annual and seasonal variability in wetland occurrence and extent.
Advisor: James W. Merchant