Identifing flood area from measurements data

[gisCoder]

Hi everyone,

I have a mass point feature class which has x y and z value, where z is topology height value.

And I have another mass point feature class which has x y and z value, where z is water level when study area is flooded (under z value, the position at x, y value is under water level (flooded), above z value, the position at x, y value is above water level (not flooded).

Both of 2 feature class is on the same study area.

Now, my problem is how to extract flooded area to polygon?

Please help me!

[CarrieDavis]

Hi,

Sounds like what you want to do is interpolate each of these mass point feature classes into a raster surface using the Interpolation tools available in the 3D Analyst or Spatial Analyst extensions. You would have one surface that is the digital surface model and one that is the surface area that is the hypothetical flooded/not flooded surface.

An overview of the Raster Interpolation toolset
http://resources.arcgis.com/en/help/main/10.1/index.html#//00q900000034000000

I would suggest to define an extent for the output rasters as your polygon study area using the environment settings in the interpolation tool you select.  The IDW technique is good to use with dense datasets.

After creating the interpolated raster surfaces you may use many other Spatial Analyst or 3D Analyst tools to extract the values above or below a particular z value or do other types of analysis on surface volume or difference.  You could also compare the two surfaces using Cut/Fill tool or visualize them in ArcScene or ArcGlobe.

The Reclassify, Extraction tools or Raster Calculator will allow you to select and group particular values from the surface flood zone raster to determine flood areas.  The output raster then could be converted to polygon using the Raster to Polygon Conversion tool.

Reclassify (Available in 3D and Spatial Analyst extensions)
http://resources.arcgis.com/en/help/main/10.1/index.html#/Reclassify/00q90000007n000000/

Extract by Attributes (Spatial Analyst)
http://resources.arcgis.com/en/help/main/10.1/index.html#/Extract_by_Attributes/009z00000029000000/

Raster to Polygon (Conversion tools)
http://resources.arcgis.com/en/help/main/10.1/index.html#//001200000008000000

Not sure what your experience is working with rasters. With the information that you have provided, this is the procedure I would use to extract a flood area from mass points.

Best wishes,

Carrie D.
Esri Support - Raster