[OSM-newbies] Canal Wharf?

[Dave F.]

Hi

A canal is mapped with a single line but there are numerous wharfs where 
the width is increased significantly. I've mapped it as an area but 
can't find an appropriate tag.

What would be really useful to map wide waterways is a polyline with a 
width attribute to map it correctly. I don't suppose there is such a 
thing & I've just missed it?

Also, a general question, - are all the keys/tags available in both JOSM 
& potlatch?

Thanks
Dave F.