Please have a look at these links and PDF attachments.

http://link.springer.com/article/10.1007/s13157-015-0626-6#page-1

https://www.researchgate.net/post/Time-series_of_wetland_surface_water_depth

https://pubs.er.usgs.gov/publication/70161998

Please have a look at these links and PDF attachments.

http://link.springer.com/article/10.1007/s13157-015-0626-6#page-1

https://www.researchgate.net/post/Time-series_of_wetland_surface_water_depth

https://pubs.er.usgs.gov/publication/70161998

The water depth varies in wetlands.  If you use the Corps of Engineers 1987 Wetland Delineation Manual, many hydric soils have brief periods of flooding or standing water, but maintain a high water table for hydrophytic plants and hydrologic indicators.  We often use infrared photos to estimate vegetation change in riparian areas.   Many early wetland remote maps used the Cowardin et al approach to mapping relative persistence of surface waters in wetlands that may be of some use. 

Some new technologies using radar, LIDAR, green LIDAR, high resolution aerial photos and ground  truth of fine color changes with water depth may be useful.  Our abilities continue to expand with technology, but since some wetland would require mapping of shallow groundwater depths, I don't know if we can do that beyond using vegetation and perhaps detailed topographic indicators.

It is possible in LIDAR data 

• I have no answer to this question.
• ram