Need to calculate several polygon`s average slope

[FrikanErwee]

Hi All
I need to calculate several land parcels average slope and insert it into the attributes table. As a side note I need to do the same for several short line features known as storm water routes?

I have constructed a TIN and created a DEM with the elevations but this is where my knowledge left me and now I am stuck.

Can anyone maybe point me in the right direction? Busy calculating this by hand and it takes ages.

[PrasantaBhattarai]

Hi,
First create a slope raster from your DEM using Slope (Spatial Analyst) tool. Once you have the slope raster, you can use Zonal Statistics as Table (Spatial Analyst) tool to calculate MEAN values of slope for each Zone (parcels or storm water route).

[ChrisSnyder]

Ocasionally you might encounder a feature that is too small to be included in the ZonalStatistics layer - for example, a parcel that is smaller than a pixel or perhaps just happends to not in the center of the pixel. In that case, you can convert these features that "didn't make it" to points (use the FeatureToPoint tool), and then get the coresponding Slope value using the Sample tool in Spatial Analyst.

[FrikanErwee]

Thanks I have finished the slope field. Is there a way to calculate the length between corners, that is the longest apart, of the parcel?