Calculating distance between two point layers through a polygon layer

[TJLawson]

Hi

I have two point layers, one representing river mouths and the other representing beach sites. I also have a water polygon layer. I am trying to calculate the shortest distance from my beach site layer to the nearest river mouth but it has to be through the water layer. The proximity tools wont work as they calculate the shortest distance but in areas where there i have a beach site on one side of a headland and a river mouth on the other it will take the path across land but i need it to go through the water. I also can't use the outline of the coast as a network along which to travel as in areas like the Gulf, the shortest distance will be straight across not via the coastline. Any suggestions?

Thanks

[XanderBakker]

Hi

I have two point layers, one representing river mouths and the other representing beach sites. I also have a water polygon layer. I am trying to calculate the shortest distance from my beach site layer to the nearest river mouth but it has to be through the water layer. The proximity tools wont work as they calculate the shortest distance but in areas where there i have a beach site on one side of a headland and a river mouth on the other it will take the path across land but i need it to go through the water. I also can't use the outline of the coast as a network along which to travel as in areas like the Gulf, the shortest distance will be straight across not via the coastline. Any suggestions?

Thanks

Hi TJ,

I guess you can do this analysis in raster by using Cost Distance (Spatial Analyst):
http://resources.arcgis.com/en/help/main/10.2/index.html#//009z00000018000000
... and you'll find more info here on how it works:
http://resources.arcgis.com/en/help/main/10.2/index.html#//009z000000z5000000

In the description it states:
If areas with a value of zero represent areas that should be excluded from the  analysis, these values should be turned to NoData before running Cost Distance, by first running the Set  Null tool.

By using a cost raster you can define those "dry" areas as Null (NoData). The Cost Analysis will interpret this as areas that cannot be crossed. Specify your river areas as 1 in the same raster and the result of the cost distance will be a raster defining the distance from your sources.

Kind regards,

Xander