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Last updated: October 11, 2002
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Part 3: Vegetation Classification and Resistance
Vegetation Classification
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Ground truthing.
(Click on photo for full-sized version.)
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This vegetation-classification map (below) was developed specifically to serve as
the basis for quantifying evapotranspiration, frictional-resistance, and wind-forcing
processes in the SICS model. Twenty land-cover classes, derived from Landsat
Thematic Mapper imagery, were combined into seven vegetation classes and one
water class using field information on vegetative composition and structure as well
as extensive ground-truth observations. The classes are generalized to match the
model scale, with each representing a broader variety of vegetation than the class
name implies. The mangrove/buttonwood class, for instance, also represents other
dense trees and shrubs. These vegetation classes are being further refined using
more recent Landsat imagery and ground-truth data.
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Vegetation classification map.
(Click on map for full-sized version.)
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Vegetation Resistance
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Velocity measurement.
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Resistance coefficient related to depth and (depth x velocity).
(Click on graph for full-sized version.)
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Resistance to water flow caused by plants and periphyton is expressed in the
model by a mathematical expression involving an empirical coefficient.
Water-surface slope, flow, velocity, flow depth, and detailed vegetation- description
data, as seen below, are being collected to quantify the coefficient and determine
its relation to vegetation type and density. In the illustration to the right, the
coefficient Manning's n is plotted against the product of flow velocity and depth at
two sites in Shark River Slough that have vegetation characteristics similar to
Taylor Slough. These results demonstrate that the coefficient needs to be adjusted
with changes in flow depth for model simulation.
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Sample plot.
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Sample vegetation-description plot.
(Click on graph for full-sized version.)
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Next: Wind effects, Boundary and Internal Flows,
and Topography and Bathymetry
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