Calculating nearest distance to landscape element taking direction into account (i.e. slope, prevailing winds) using ArcGIS Spatial Analyst?

Question

I am trying to build a layer of distance to relevant landscape elements in a watershed. To be relevant, a landscape element must be downstream with respect to the runoff direction. 

Clearly, I want to assign to each point belonging to a regularly spaced points layer, the distance to the nearest landscape element, which is in the direction of the slope.

To do so, I have :

• A polygon shapefile of « LANDSCAPE ELEMENTS » which are polygons of hedgerows, and forests (that are not distinguished).
• A Digital Elevation Model
• A shapefile of a regular point grid (50 m x 50 m, a total of 500 000 points )

Note : I'm using ArcGIS 10.1 with Spatial Analyst

Answer 1

Take a look at the Near tool, or the equivalent Generate Near Table tool, which determine the distance from each feature in the input features to the nearest feature in the near features.

Optionally, you can specifies whether the near angle values in decimal degrees will be calculated and written to a new field, NEAR_ANGLE. A near angle measures from the x-axis (horizontal axis) to the direction of the line connecting an input feature to its nearest feature at their closest locations, and it is within the range of 0 to 180 or 0 to -180 decimal degrees - 0 to the east, 90 to the north, 180 (-180°) to the west, and -90 to the south.

I think one of the two will suit your needs.