We demonstrate that algal accumulation is dependent
of a stimulatory effect of roughness, which is constrained
by flow conditions. When drag force is sufficiently strong
to dislodge algae, the roughness variation will be important
for algae development on flowing habitats. We finally
suggest that the physical properties of texture can provide
heterogeneous hydraulic microhabitats, which may lead to
different colonization dynamics and constraint the roughness
stimulatory mechanisms.