I am a hydrologist and there are 2 important pieces of information I need for modeling. I need to know the longest flow path for each sub catchment in my area of interest and I need to know the elevations of point specific distances along those paths.
As an example, I have a shapefile with specific boundaries that represent my catchment and an elevation raster. I would like to be able to determine the longest path that water flows in each of these defined areas. Once I have a shapefile containing the longest flow paths for each catchment, I would like to find the elevation at 10% and 90% the length of each flow path and the distance between each point.
I have not found either of these functions in anything except the Arc Hydro tool bar for ArcGIS. I know that the individual tools for creating these things exist in QGIS ( through SAGA and GRASS ) but I am new to Python and not a programmer in any respect. I am hoping these tools are in an existing package and I am just too new to QGIS/GRAS/SAGA to find them.
I have been using QGIS for about 18 months.