topic Questions on delineating catchments in Water Resources Questions

Questions on delineating catchments

RonMan — Mon, 22 Jan 2018 17:55:52 GMT

I do have a problem delineating watershed/catchment areas and i have a questions as a arcgis beginner. I am given existing road alignment and a dem. I was able to do flow distribution, flow accumulation and stream. For the pour points, do i have to put pour points where my road alignment intersects the stream? Is that a correct practice? I did the watershed tool but unfortunately it gives me a big watershed. Could someone be able to point me how i could derive the catchment for each of the river crossings in my alignment? Thanks.

If i post to the wrong group, kindly point me to the right one.

Best Regards,

Ron

Re: Questions on delineating catchments

ChrisDonohue__GISP — Mon, 22 Jan 2018 18:16:52 GMT

If it is desired to create the watershed at each road alignment where it crosses a stream, then one would need a pour point at each of these locations.

How Watershed works—Help | ArcGIS Desktop

Deriving runoff characteristics—Help | ArcGIS Desktop

Image source: Understanding drainage systems—Help | ArcGIS Desktop

Chris Donohue, GISP

Re: Questions on delineating catchments

RonMan — Tue, 23 Jan 2018 01:22:56 GMT

Thanks and i appreciate your response Chris. I placed pour point at each road/stream crossing unfortunately it gives big watersheds and not as i expected. I shall read first your given links and see if i can achieve my goal and be back if i'm still not able to delineate properly.

Re: Questions on delineating catchments

ChrisDonohue__GISP — Tue, 23 Jan 2018 15:42:52 GMT

Can you post an image of the output?

Also, if you have not already done it, one thing you may want to try is running Snap Pour Point tool to ensure that the Pour Points get located in the flow areas.

Snap Pour Point—Help | ArcGIS for Desktop

Chris Donohue, GISP

Re: Questions on delineating catchments

RonMan — Wed, 24 Jan 2018 05:22:02 GMT

Hi Chris,

I think it is resolved now. Here is an overall screenshot.

Here is more zoomed:

I just have to increase the streams to fill the white area gaps between watersheds and then redo the pour points and watersheds.

I have found the solution which is to use the FID as the pour point field (optional) in the snap pour point tool. This will create separate watersheds for each pour point.

And also i have to ensure that i have a snap raster set to Flow accumulation raster before running the snap pour point tool.

Best Regards,

Ron

(U.A.E.)