[talk-ph] mangroves, tidal lands

maning sambale emmanuel.sambale at gmail.com
Fri Jul 9 08:39:39 BST 2010


On Fri, Jul 9, 2010 at 11:15 AM, Ed Garcia <eppgarcia at gmail.com> wrote:
> Can I have your opinion on this, guys?  it is about coastal mangrove areas.
> It is suggested, and I agree, to map mangrove areas as inland (inside the
> coastline).  But I encountered the mangrove areas at Alburquerque, Bohol and
> the mangroves (seen on wms Lansat) are currently lying on the ocean side.
> The current coastline is along the actual edge of what is definitely the
> actual land.  I have personally seen the coast myself when I was in the
> Albuquerque area.
>
> http://www.openstreetmap.org/?lat=9.6127&lon=123.954&zoom=14&layers=B000FTF
>
> Question:  Shall I move the coastline seaward so that the mangroves would
> apear inland?

IMO, no.  Some mangroves in Lian, Batangas are more on the sea side.
Hence, I didn't move the the coastline.

http://osm.org/go/4yfxfytF5-

I've walked around these mangroves stands for two full days.

> This would in a way state that mangroves (or tidelands) are
> land and thereby also state that coastlines for tidal lands and flats are to
> be drawn using the exposed areas during the lowest low tide (not just the
> mean tide as this will "cut" some mangrove areas in half).  Classic case for
> tidal flats are in Calatagan, where the low tide exposes an additional 150+m
> of "land".

I have this similar case in Talim Bay (Lian, Batangas).  During low
tides, the inter-tidal flats (locally known as tangkulan) are in
hundreds of meters from the mean coast.

http://farm2.static.flickr.com/1440/541589816_bf5bf812a2_b.jpg

> Also, the above considers that some islands become "land" only on low tides.
The "if in doubt, map as land" mantra applies only if you're
unfamiliar with the area.  For everything else, it's your call
provided you have verified on the ground.

I think we should map inter-tidal zones as lines (this needs to be defined more)



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-- 
cheers,
maning
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