This Python 3 module implements the Multiple Flow Direction (MFD) flow accumulation as proposed by Freeman (1991). As suggested by Freeman the free parameter p, the exponent that scales the fractions of flows, is tuned to the divergent flows of cones with p = 1.1, but can optionally be specified. It is written in C and based on the code by Pelletier (2008).

git clone https://github.com/UP-RS-ESP/mfdrouting.git
cd mfdrouting
sudo python3 setup.py install

Alternatively, use the Cython version in the cython folder.

import numpy as np
import mfdrouting
help(mfdrouting)

will show:

SCA(z, cellwidth, exponent = 1.1)
Returns the specific catchment area of the topography (DEM) in z.

Parameters
----------
z : array_like
    A 2-D array containing the elevations of the topography (DEM).
cellwidth : float
    The cell width of the grid in meters.
exponent : float, optional
    The exponent determining the flow divergence in relation to the slope.
    See http://dx.doi.org/10.1016/0098-3004(91)90048-i.

Returns
-------
a : ndarray
    The specific catchment area matrix on the same grid as z (DEM).

The in-build sink-filling routine is not able to handle NaN values or negative elevations. However, the Cython version converts all elevations so that the lowest is zero and converts NaN values to zeros. After flow accumulation NaN values are filled back in.

In case you receive a segmentation fault it is likely that the cause is a stack overflow. Please try running your Python scripts in a shell with an unlimited stack size. On Linux run

$ ulimit -s unlimited

in your shell of choice.