Nearest neighbour analysis with higher elevation using QGIS

Question

How do I calculate the flow that goes through the rainfall drainage points under a railway?

I have two layers:

DT: Point layer with drainage information: DT_id and elevation.

ACA: Point layer with de flowrate information: ACA_id, flowrate and elevation.

I need the flowrate that is upstream of each drainage point. Therefore I want to get the nearest ACA point to each DT point. But I need to add the condition that the nearest neibour has to be more elevated than the related DT point, in order to be sure that we selected the point that is upstream and not the one that is downstream.

I have tried using the "distance matrix" but I can't find how to impose this condition.

Answer 1

You can use ProcessX Plug-In and run the algorithm Join attributes by nearest with condition from processing toolbox. Set it up the following:

Disclaimer: I am the author of this Plug-In.