Longest flow path in Watershed

JospehM

Hi GM forum

I want to automatically join the longest flow path from the various drainage network to use on hydrological calculations, but the catchment areas are too larg with too many flow paths. I was hoping there is a way of joining lines from end to end to create the longest flow path within a selected polygon. I don't eant to disgard streams as they are equally important. Please assist.

Also, can GM delineate only the catchment area and drainage flow paths to the selected point or line without analysing the entire DEM.

hennie

As for your last question, load your catchment area on top of the DEM.

Select the watershed with the digitizer tool. From the terrain analysis menu, choose create watershed. Choose watershed bounds as the selected catchment area. It will then only analyse the DEM within your watershed.

JospehM

Thank you for your response.

This method will require that i first have to create a watershed to get the catchment area. I'm looking for a methos where it will create the catchment area and water shed without considering areas that do not contribute to that catchment.

I'm thinking it might be hard but If the delineation starts from the point going in reverse order, it will be able to capture only the contributing area.

hennie

Not possible in GM at present. I know this feature has been requested in the past.

I have the same need an look forward to implememtation.

JospehM

It would be supper. Also starting to learn software development to be able to do such because such features are pretty.

Thank you very much.