Coastal saline vegetation

posted 29 Mar 2012, 16:08 by David Pairman   [ updated 1 Jul 2012, 21:29 ]
Currently 'mangrove' and 'herbaceous saline vegetation' polygons are mapped but these generally fall outside any coastline definition e.g. Topo50 defined as mean high water spring. If we clipped to a coastline then valuable information on coastal saline vegetation would be lost. How do we solve this situation in an elegant way? See also the separate Topo50 coastline issue. Would a "land/sea" attribute be sufficient to tag polygons beyond the whichever coastline is used?

Parengarenga Harbour. Click on image to expand.


At the April 2012 Technical Advisory Group meeting it was resolved to allow three classes; "Estuarine Open Water", "Herbaceous Saline Vegetation", and "Mangrove" to exist outside of the Topo50 coastline. An "onshore" attribute is used to indicate when a polygon is inside or outside the Topo50 coastal boundary. As part of the process of burning in the Topo50 coastline, slivers of other classes that may have been previously mapped outside the coastline were merged with one of the above classes provided the sliver was completely trapped (surrounded) by these classes (otherwise it was removed altogether to become part of the world polygon). Slivers were merged with the offshore-class that had the longest common boundary where there was a choice. Note, the process was recursive so that all "onshore-only" classes were removed or relabeled when not onshore, even if they didn't initially have a boundary with one of the three classes named above. See also the Topo50 coastline issue.