Creates an indicator grid (1, 0) that evaluates A >= (M)(Ly) based on upslope path length, D8 contributing area grid inputs, and parameters M and y. This grid indicates likely stream source grid cells. This is an experimental method with theoretical basis in Hack’s law which states that for streams L ~ A 0.6. However for hillslopes with parallel flow L ~ A. So a transition from hillslopes to streams may be represented by L ~ A 0.8 suggesting identifying grid cells as stream cells if A > M (L (1/0.8)).
The multiplier threshold (M) parameter which is used in the formula: A > (M)(Ly), to identify the beginning of streams.
Default: 0.03
The exponent (y) parameter which is used in the formula: A > (M)(Ly), to identify the beginning of streams. In branching systems, Hack’s law uggests that L = 1/M A(1/y) with 1/y = 0.6 (or 0.56) (y about 1.7). In parallel flow systems L is proportional to A (y about 1). This method tries to identify the transition between these two paradigms by using an exponent y somewhere in between (y about 1.3).
Default: 1.3
processing.runalg('taudem:lengthareastreamsource', length_grid, contrib_area_grid, threshold, exponent, stream_source_grid)