I had posted the beginnings of this question on the Network Analysis forum but now that I have a better idea about what I need to do, I thought I would reach out to the Hydro community for help. I am using state level NHDS data and my own event points, facilities and testing sites.
My goal is to create a data table with each of my facilities (currently located in a shape file), the closest downstream testing site (sites located in a separate shape file), and the distance between them. Yes, I could manually trace each one using the Utility Network Analyst, but I have over a hundred facilities and over a thousand testing sites.
Therefore, I would like to be able to use the Network Analyst => Analysis => Make Closest Facility Layer and treat my rivers/streams like roads, the flow direction like one way streets, my facilities like accidents, and my testing sites like the nearest hospitals. Understand?
The problem is that the NHDS network is not a Network Dataset that can be used with Network Analyst but a Geometric Network. Does anyone have any idea how I can build a Network Dataset from the Geometric Network?
A quick response or ANY clues would be really helpful. Don't be afraid to post.
You can generate a network dataset from the geometric network shapefile in ArcCatalog. Right-click your shapefile, choose 'new network dataset' and follow through new network dataset wizard. Give it a name and accept defaults, and when you get to the window for adding attributes for the network dataset, choose 'add', give your attribute a name like length, usage type of cost, and choose the distance unit you want to use. Once you've added your distance attribute, click the 'evaluators' button and right click the type column to set to field, then right click the value column and you can choose either shape or a distance field in your shapefilie. Once you've built your network dataset this way, should be able to open the network analyst window, set parameters for closest facility by loading your facilities and testing sites, and then solve for closest facilities. Others might have more succinct answer but hopefully this helps..