Wetlandscape Fractal Topography

• Published in: Geophysical research letters 2018-07, Vol.45 (14), p.6983-6991
• Main Authors: Bertassello, Leonardo E., Rao, P. Suresh C., Jawitz, James W., Botter, Gianluca, Le, Phong V. V., Kumar, Praveen, Aubeneau, Antoine F.
• Format: Article
• Language: English
• Subjects: Biogeochemistry; Coastal zone management; Data; DEM analysis; Distribution; Elevation; fractal dimension; Fractals; Geologic depressions; Harbors; Hydrology; Identification; Landscape; Moisture content; Nature conservation; Properties; Scaling; Shape; Shorelines; size distribution; Slope; Statistical methods; Statistics; Surveying; Surveys; Topography; Topography (geology); Water content; Wetlands; wetlandscape
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2018GL079094

Natural wetlands are ecological, biogeochemical, and hydrological hot spots yet continue to disappear under human pressure. Their shapes and sizes control their hydroecological functions. We propose that elevation data can be used to delineate potential wetlands and that the (statistical) distributions of potential wetlands should be identical to the distributions of actual wetlands. We compare the shape and size distributions of wetlands reported in the National Wetland Inventory with those of potential wetlands identified using a topographic depression identification model. We estimated area and perimeter distributions as well as shoreline fractal dimension in six contrasting locations in the United States. Pareto distributions described the tails of these distributions, with similar slopes for both model and data. The shape of shorelines was also similar, and their fractal dimension clustered around D = 4/3, a pervasive value in nature. We also analyzed the entire wetland inventory data set for the conterminous United States (~20 million wetlands) for reference and found the statistics to be invariant across scales. Our results demonstrate that a simple topographic model can identify most reported wetlands as well as potential wetlands missing from the inventory. These findings could inform strategic surveys and the conservation of wetlandscapes. Plain Language Summary Wetlands provide important hydrological and ecological services. Their diverse sizes and shapes control the amount of water they can hold and the species they can harbor. Because water accumulates at low elevation, we proposed that topography alone can reveal the location of wetlands. We also hypothesized that the (statistical) distribution of the (potential) wetlands identified from elevation data would be identical to the distribution of actual wetlands. We used a topographic depression identification model to delineate potential wetlands in six 10 × 10 km landscapes across the United States and compared the modeled wetlands to real wetlands cataloged in the National Wetland Inventory. The distribution of shapes and sizes were similar for both potential and real wetlands, indicating that topography data alone can be used to identify wetlands' properties. Widely available elevation data may thus be used to guide surveying and management when inventories are scarce. The scaling of area and perimeter distributions was similar across the six contrasting locations we analyzed and across scal