If I have a DEM as raster layer and a point with defined position in a point layer, how could I generate a line with defined slope of e.g. -1%? The end point can be anywhere and should be defined by the line length and the constant downward slope of 1%. The line should have nodes every one or two meters, so that it follows the terrain with that accuracy.
The goal is to construct an irrigation ditch that almost follows the contour, but is defined by an optimal downward slope. If I can design it this way over a DEM with resolution <1m, I can stake it out with an RTK positioning system and have it dug accordingly.
Any ideas for a workflow or code?
I'm working in QGIS 2.18.