What drains into a pixel?

What drains into this pixel?

Finding what drains into a point normally means walking the network: step upstream, follow every branch, keep going until the branches run out. The cost grows with the catchment. Here it is a lookup. Every land pixel stores two numbers, dfs_in and dfs_out — the positions at which a depth-first walk of the flow network enters and leaves that pixel. Pixel p is upstream of pixel q when dfs_in(q) ≤ dfs_in(p) ≤ dfs_out(q) — one integer comparison, the same at a headwater and at the mouth of the Amazon. Nothing is traced.

Click a pixel on the map. The panel chooses what is drawn and gives the formula behind that choice, and the result appears beside the map.

Base layer dfs_in dfs_out upstream area none

What to draw The catchmentevery pixel that drains to the one you click Its dividethe ridge line that encloses that catchment Its streamsthe channels inside it, each one a separate colour

This site runs on a basic hosting plan with a fixed number of requests a day. If a map stops loading, it is most likely that a lot of people are using it at once — try again in a few minutes. We will raise the budget as the traffic grows. The archived files on Zenodo are never affected.

Interval query · basin 8595

Click anywhere inside the basin. The click moves to the pixel with the largest drainage area nearby, marked with a star, so a click on a hillslope still returns a catchment. Everything upstream of that pixel is found by one interval test on dfs_in and dfs_out.

The interactive examples run on a small hosting plan and can be briefly unavailable if its request limit is reached; The archived files on Zenodo are unaffected.