The characteristic length of the soil surface is the ratio of the surface area to the perimeter. For an infinite soil surface $L_{ch} = 0.5$.

Symbol
$L_{\mathrm{char}}$
Unit
-
Formulae
$0.5$infinite surface
$\frac{l w}{2 l + 2 w}$rectangular surface with length l and width w
Used in
$h_{\mathrm{tr}}$