[Talk-ca] Canvec 10 and landcover issues

[Pierre Béland]

Harald,

I am not an expert either and it would be interesting to have the opinion of an expert. But I can say that a wetland is an area were the groundwater is at the surface of the soil. It can be grass or covered by forest.  For years you see no problems and pretend the situation do not exist.

The government of Québec is producing very detailed maps of risk zones. It would be interesting to see. But it is not free.

There are different types of wetland. The tag natural=wetland is combined with wetland=type for more precision.
wiki http://wiki.openstreetmap.org/wiki/Tag:natural%3Dwetland


 
Pierre 



>________________________________
> De : Harald Kliems <kliems at gmail.com>
>À : Pierre Béland <infosbelas-gps at yahoo.fr> 
>Cc : Talk-CA OpenStreetMap <Talk-ca at openstreetmap.org> 
>Envoyé le : Vendredi 19 octobre 2012 15h46
>Objet : Re: [Talk-ca] Canvec 10 and landcover issues
> 
>Hi Pierre,
>thanks for the response.
>
>On Fri, Oct 19, 2012 at 3:25 PM, Pierre Béland <infosbelas-gps at yahoo.fr> wrote:
>> I dont know how you conclude that there is no wetlands around this area in
>> Laval.  It is not sufficient to see houses around to conclude that there is
>> no wetland. These are often wooded areas with water all over.  Google
>> physical also shows a stream starting from this area.
>>
>> The link below shows a comparison of this area with Google imagery.  Are you
>> sure that there is no wetland in this area.
>> http://tools.geofabrik.de/mc/?mt0=mapnik&mt1=googlehybrid&lon=-73.91012&lat=45.69989&zoom=17
>This is a misunderstanding. I did not mean that there is _no_ wetland
>in the area. But I'm pretty certain that the boundaries of the wetland
>are wrong:
>
>http://tools.geofabrik.de/mc/?mt0=mapnik&mt1=googlehybrid&lon=-73.90457&lat=45.69533&zoom=17
>
>Aside from the wetland issue (see below), we can probably agree that
>the area is not natural = wood, even if some people might have planted
>trees in their yards.
>
>> The link below shows an aera in Saint-Jean-sur-Richelieu were houses have
>> been built for over 30 years. Look how many houses were flooded last year.
>> Zoom in to see areas that were flooded.
>> http://pierzen.dev.openstreetmap.org/hot/openlayers/inondation-richelieu-2011.htm?zoom=16&lat=45.28568&lon=-73.24907&layers=B000TFFFF
>>
>> My experience, as a volunteer for SOS-Richelieu, last year, showed me how
>> that too often the municipalities have accepted that contractors build
>> houses over wetlands. And this was often the case with Laval.
>Okay, this is a different issue, coming down to the definition of what
>"wetland" is. I'm by no means an expert, but in my understanding you
>can't have a residential area in wetlands. In order to build houses
>you must first use drainage channels etc. to turn wetland into
>developed land. The fact that there can be flooding in a given area
>doesn't make it into wetland to me. The wiki isn't very explicit about
>this (http://wiki.openstreetmap.org/wiki/Tag:natural%3Dwetland) but
>the specific subtypes seem to hint at a definition stricter than
>yours. Maybe someone can tell us what definition is used for Canvec.
>
>Cheers,
>Harald.
>
>
>
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