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How to identify downhill cells for a dispersing frog?

Question asked by Herpnerd on Feb 16, 2015
Latest reply on Feb 16, 2015 by xander_bakker

Hello! I'm hoping that someone on here can help me out with a task. First, let me set the scene.


1.) I'm working on a movement/cost analysis for frogs dispersing from 135 wetlands located in Maine's mountains..

2.) I have a lot of wetlands, so I'd like to automate this task in Model Builder using an iterator.

3.) The cell values (i.e., cost values) of my cost surface are based on the terrain ruggedness index (TRI); cells that correspond with rugged areas (e.g., mountainside) have greater cell values than cells that correspond with flat areas (e.g., plateau).

4.) Using the Cost Distance tool, I will delineate an "area of influence" around each wetland; this will be based on the cost surface and species-specific dispersal distances.

5.) Finally, I will estimate covariate values (e.g., cumulative stream length [NHD] and wetland area [NWI]) within the "area of influence" around each wetland.


My question is this: what is the best way to identify those cells that correspond with downhill movements for frogs? Imagine that a frog leaves a wetland; it will encounter "ups" and "downs" as it disperses. Cells corresponding with "ups" (i.e., elevation gains) should retain their respective TRI value, while cells corresponding with "downs" (i.e., elevation losses) should be reclassified as a 1 (i.e., low cost) because frogs likely have little trouble moving downhill. It seems to me that this analysis should somehow consider the location of each wetland and the direction of the frog's movement because an elevation gain from one direction may be an elevation loss from another direction.


I'd really appreciate some insight and any suggestions on how I should go about this task. I tried to keep this post brief, so please ask for clarification if needed. Thanks so much!