Intersecting a flood raster with a population grid

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08-21-2018 10:50 AM
deleted-user-qIrrkfi_YpZh
New Contributor

I have two rasters: a flood inundation raster (depth grid) and a census grid. I would like to know how many people are affected at 0-1 feet, 1-3 feet, 3-6 feet, 6-9 feet, and more than 9 feet. I need to figure out how many are effected in each class (a count). What tool(s) do I need to use? Do I need to convert one (or both) rasters to a polygon? Thanks in advance!

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4 Replies
DanPatterson_Retired
MVP Esteemed Contributor

Combine—Help | ArcGIS Desktop 

will give you all the combinations.  You have integer rasters and they are classified..

If your population isn't in classes, then

Zonal Statistics as Table—Help | ArcGIS Desktop 

might do it 

You should do the conversion to raster explicitly because you will need to establish the cell size, processing extent and set your snap raster (to the existing raster extent)

XanderBakker
Esri Esteemed Contributor

In addition to what Dan mentions, if your population is expressed as density you will need to convert the density to number of people using the area of overlap. If they are absolute values, use the fraction of overlap to get the correct number of people.

deleted-user-qIrrkfi_YpZh
New Contributor

Wouldn't I need to convert my flood inundation raster to polygon so I had a "zone" to refer to?

My census grid is number of # people/cell

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DanPatterson_Retired
MVP Esteemed Contributor

zonal statistics as table will convert a polygon back to a raster in any event...  check the link I posted

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