A topical question.A few months ago after a period of heavy rain I had to recce a walk to see if it was too flooded as I had arranged to lead a group walk along the river. I found the flood line site which yields good data but not heights above sea level, but if I could calibrate the low points on paths and some roads the gauge levels from the other site it would be very precise way of seeing what is passable. Any ideas of how these way heights on ways could be put in and used in OSM for checking against this other data http://www.environment-agency.gov.uk/homeandleisure/floods/riverlevels/default.aspx
asked 27 Nov '12, 16:24
OSM is not really relevant for what you ask. Which part of the land can be flooded depends on water level and land elevation but also on flood flow. Any dyke or wall or drain can change the water flow. What is more appropriate is a high detailed DEM (Digital elevation model) eventually combined with the 2D OSM data saying which feature is where.
A possible workaround for some small and localized feature can be the use of the tag "ele". But be aware about the datum when you compare different data sources elevations ('ele' is normally expressed in the WGS84 datum).
answered 28 Nov '12, 14:06