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I'm working on a project where I need to show which direction the water would flow from a water pipe in case there is a pipe burst. I also need to show catchment polygons(area affected). This was previously done by someone else and I'm doing it from a fresh start. I've attached a screenshot showing a sampling of the previous work. The blue/grey line is the water pipe, the red outline shows the polygons/area affected and the blue arrows show the flow direction.

I'm using ArcGIS Desktop 10.2 and Spatial Analyst. I have access to contour line data as well as the water pipe data. I've done a little bit of googling and have seen a lot of information on watersheds, however, I think this project is the opposite of watershed analysis where instead of showing drainage towards a water channel/pipe, I need to show drainage away from a water channel/pipe. I'm quite familiar with ArcGIS Desktop but pretty green to Spatial Analyst. I can perform watershed analysis using various tutorials online but as I said, I think my analysis requires showing the opposite of watershed analysis, I think. I need some help being pointed in the right direction as far as steps/tools to use.

Previous Work

Sample data I'm working with

Corrected DEM

Results

  • Where do those arrows come from? They don't appear to be D8 flow pointers. They almost appear to be flow pointers from a model, like a ground water model or something. Any idea? – traggatmot Dec 8 '14 at 0:58
  • The arrows come from a point feature class. The arrow rotation is based on the "grid_code" field. – Steve Dec 8 '14 at 17:44
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You need to create a hydrologically corrected (depressionless) DEM from your contours through interpolation to a raster DEM. Then you need to perform a flow accumulation operation, such that the pipes serve as the seed points and the downslope flowpaths issuing from these locations are traced. Many GIS have specific tools to perform this type of flowpath tracing operation but in ArcGIS, your best bet is to use the Flow Accumulation tool and to specify your pipes network as the weight raster. Before you can do this however you'll need to rasterize your pipes vector layer to a grid of the same dimensions as your DEM/flow pointer raster. The result will be be a Boolean raster where cells containing a pipe will have a value of 1 and all non-pipe cells will have a zero value. If you use this for your weight raster, the output of the flow accumulation tool should be the downstream flowpaths issuing from each pipe grid cell, and therefore the dispersal areas for your pipe network.

  • Thanks for the response. These are the steps I've done so far. – Steve Dec 5 '14 at 21:13
  • Thanks for the response. These are the steps I've done so far. 1. Convert contour lines to raster(DEM) using “Topo to Raster” tool. 2. Hydrologically correct the DEM using “Fill” tool. 3. Use “Polyline to Raster” tool on the water pipes. 4. Use “Flow Accumulation” tool. I'm not getting the desired results. When rasterizing the water pipes, it requires a "value". I'm not sure what I should be using here and perhaps thats causing the problem. – Steve Dec 5 '14 at 21:22
  • @steve you should edit your question (link at the lower left of it) to provide additional information. And rather than linking to offsite images, embed them in the post - see meta.stackexchange.com/questions/75491/… – Chris W Dec 5 '14 at 21:27
  • Edited question with additional screenshots corresponding to my comments here. – Steve Dec 5 '14 at 21:32
  • @Steve I'd just create a new field in your pipe's attribute table and fill it with 1's. Then use this new field as your value in the rasterization process. Either that, or you could also use the FID and then simply reclass the resulting raster pipes grid to be a Boolean. – WhiteboxDev Dec 5 '14 at 21:57

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