High-resolution Tracking of Marsh Inundation Patterns from Tidal Creek Flooding Revealed by Balloon-based Low-altitude Aerial Photography
Elizabeth Madsen and Scott White
University of South Carolina, Department of Earth and Ocean Science
The inundation pattern of the marsh surface influences the sediment dynamics and erosion processes controlling the headward expansion of salt marsh creeks, and has implications for the threat of sea level rise, biological zonation, and marsh ecosystem services. Tidal flooding, hydroperiod, defined as the frequency, duration, depth and flux of water across the marsh surface, is a key factor in salt marsh ecology, but remains poorly understood due to lack of data at relevant spatial scales. The hydroperiod in the headwaters of a salt marsh is observed through low-altitude aerial photography, (75-100 meters altitude), from a Helikite. High-resolution aerial photographs provide the level of detail necessary to resolve the waterline and delineate the hydroperiod during half tidal cycles. Time series maps of the hydroperiod are created by capturing snapshots of the waterline as water progressively floods the surface.
Headward expansion is also a result of crab burrowing. Individual crab burrows in the headwaters are detected by automated image classification. The number of crab burrows and their spatial density is tracked from January-August. Crab burrows are associated with the unvegetated region at the creek head, and we relate their change over time to the propagation of the creek into the tidal basin.
Plant zonation is influenced by the hydroperiod among other factors including salinity, water table depth, soil water content species competition, adaptability, and groundwater flow. Inundation frequency shows the most pronounced relationship to zonation. Vegetation patterns are delineated by image classification from helikite aerial photographs and GPS survey.
AAPG Search and Discovery Article #90182©2013 AAPG/SEG Student Expo, Houston, Texas, September 16-17, 2013