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Specifying vegetation properties (update)

Arnold van Rooijen, modified 3 Years ago.

Specifying vegetation properties (update)

Swell Posts: 239 Join Date: 11/7/11 Recent Posts
Hi all,

In case you are using the vegetation module of XBeach, you may have noticed that in the Kingsday Release version, vegetation is specified per vertical section, where the number of sections is given by nsec. In case of vertically non-uniform vegetation, e.g. mangroves, you would then specify the characteristics for each section, see also the manual.

In the current trunk version of XBeach we are slightly changing this, thereby making it more consistent with other models (e.g. Delft3D), where we specify vegetation characteristics per vertical point / coordinate rather than section. XBeach will then interpolate the drag effect in between these points. This new method also gives some opportunity for a more realistic specification of the vegetation (you can actually describe a plant shape, rather than a number of blocks piled on each other), and is also implemented with the idea that it would be more intuitive once we will incorporate vegetation effects on morphodynamics.

These changes will be part of the next official release version, and will be described in the (new version of the) manual then. However, in case you are using the trunk version of XBeach now, you can from now on specify vegetation as follows in the veggiefile:

Example 1: vertically uniform vegetation (e.g. seagrass):

npts = 2 (if not specified, default is 2)
zv = 0 0.2 (bottom and top of vegetation)
bv = 0.01 0.01 (characteristics for each coordinate zv)
N = 1000 1000
Cd = 0.2 0.2

Example 2: vertically non-uniform vegetation (e.g. mangroves):

npts = 5
zv = 0 0.2 0.5 0.6 1
bv = 0.05 0.1 0.1 0.02 0.02
N = 1000 50 50 1000 1000
Cd = 1 1 1 1.5 1.5

Note that the former way to describe vegetation (using nsec and ah, see also current manual) should still work, however, may be more inaccurate in case of vertically non-uniform vegetation.

Let me know if you have any questions.

Cheers,
Arnold