I think you’ll have a hard time with getting acceptance of the bridge=boardwalk tag. It’s been used to describe a certain type a bridge, a walkway made of wooden boards or planks, for a long time and is a common structure in the U.S. Also, the walkways along khlongs are not actual bridges nor are they on layer=1 like most other bridges. There is a conversation going on right now in the tagging forum about the differences between footway and path here: http://gis.19327.n5.nabble.com/highway-footway-Advanced-definition-Distinction-footway-vs-path-td5851506.html
Based on that thread I think highway=footway (a path is not as well defined as a footway) and surface=concrete is the way to go. Optionally, you can add other attributes as well: width=?, wheelchair=, bicycle=, access=*. Also, in the above photo you could tag the fence with barrier=fence if you want to tag everything comprehensively.
I think with the variety of khlong-side walkways it wouldn’t be right to describe a single tagging scheme to cover all of them. I tend to agree with Dave in that bridge=boardwalk doesn’t seem to lend itself well to describing walkways such as the ones in Mishari’s example. Also, in many areas they run on top of the embankment rather than jutting over the water, so tagging those with bridge=* wouldn’t be appropriate. However, there are others like this one which are obviously bridges, and might be described as boardwalks, depending on whom you ask. So I’d say it depends.
As for the path vs footway issue, I can’t seem to form a consistent opinion in support of either.
And Paul, you’re not alone concerning the path vs. footway issue. The thread I referred to above (ongoing) is trying to add clarity to the distinction but isn’t making much progress. It may eventually share the same fate as so many other tagging questions, which is to say, get bogged down and never resolved. To my mind, a path is a narrow and sometimes obscure way going through rough country. Other people see it differently. In my mapping I have used footway to mean something like a sidewalk, a way used primarily by pedestrians but where bicycles could also pass.
@Paul I’m describing specifically the part that goes over water. If not boardwalk then what shall we use? bridge? It’s not exactly a bridge either, nor a pier, nor an embankment.
One example I found was in Japan https://www.openstreetmap.org/way/271778208 which is tagged merely as highway=footway but it doesn’t look like there was much thought put into it but I suppose highway=footway along with bicycle=yes is kinda ok, but how to describe that it’s raised over the water?
This OSM rule is a little strange from my point of view but all ground level features are “above the water” yet still appear on the same layer, that is, layer=0. If the way crosses a water body by going over it, then it needs a layer=1 tag and some sort of bridge tag. Many mappers in this situation would prefer using a layer=-1 tag for the canal to make things seem nearer to the actual situation. The walkway is indeed above the water. But that doesn’t matter. Both the canal and ways are on layer=0.
For walkways such as the pictured example I don’t really think showing the overlap with the water surface matters that much. However, the same question could apply to stilted buildings, etc. that commonly extend out over the banks of canals and rivers. What would be the proper way to map them, if we wanted to be perfectly accurate?