10.4122/1.1000000270
Stothoff, Stuart
Stuart
Stothoff
sstothoff@swri.org
Stothoff, Stuart
Stuart
Stothoff
sstothoff@swri.org
Everglades landscape evolution: islands, ridges, and channels
XVI International Conference on Computational Methods in Water Resources
2006
2006
The Florida Everglades is a vast wetland mosaic of sloughs, ridges, and tree
islands, with extremely small hydraulic gradients and low relief. Elongated
ridges of peat separated by sloughs in the regional flow direction form a
strikingly rhythmic landscape pattern. Many parts of the Everglades have seen
extensive peat loss and ecological change due to drainage and other hydraulic
controls over the last century. A suite of numerical models has been developed
to examine interactions between surface-water and groundwater flow,
vegetation, peat dynamics, nutrient transport, and anthropogenic hydraulic
controls. These models are supported by a set of field experiments and
observations, and explanations for the landscape patterns have begun to arise
from this interaction. Organic peat soil oxidizes rapidly when dry, whereas peat
formation is a slow process controlled by water levels, vegetative turnover, and
possibly scour and organic soil transport. Formation and maintenance of raised peat
levels in the face of oxidation, separated by lower sloughs, is partially explained
by net phosphorus transfer from slough to ridge during dry-season
evapotranspiration-driven subsurface lateral flow, which helps concentrate the
limiting nutrient (phosphorus) in higher ground, thus enhancing plant growth and
fueling more evapotranspiration. Plume-like tree islands on and downstream of local
bedrock rises may have phosphorus export due to phosphorus mining and selective
deposition of guano in addition to experiencing the evapotranspiration-driven
phosphorus enrichment process. Although historic records are scanty, there is
anecdotal evidence of sharp transitions between peat ridges and exposed limestone
channel bottoms. Exposed-bedrock channels between peat beds may be the result of
water levels gradually rising as peat forms, leaving sufficient water depth in
low-lying areas to scour clean the deeper channels without affecting the shallower
peat. Numerical simulations demonstrate the plausibility of the postulated ridge and
channel formation processes.