RichDEM

RichDEM, by Richard Barnes, packages his influential terrain-analysis algorithms — Priority-Flood depression filling, depression breaching, flow accumulation across eight flow metrics (D8, D-infinity, Freeman, Quinn and more) — as a C++ library with clean Python bindings. The algorithms are the ones his widely-cited papers describe, and the implementations are built for very large DEMs, with parallel variants that have processed continent-scale terrain.

Development has slowed in recent years, but the library remains sound and widely used; every routine cites the paper it implements, which makes methods sections easy. For interactive workflows WhiteboxTools offers more breadth; RichDEM wins when raw conditioning speed inside a Python pipeline is the requirement.