pyflwdir.FlwdirRaster.subgrid_rivslp#

FlwdirRaster.subgrid_rivslp(idxs_out: ndarray | None, elevtn: ndarray, length: float = 1000, direction: Literal['both', 'up', 'down'] = 'both', method: Literal['mean', 'lstsq'] = 'mean', mask: ndarray | None = None) → ndarray[source]#

Return the subgrid river slope [m/m] estimated at unit-catchment outlets.

The slope is estimated from the elevation around the outlet pixel (direction=’both’), or between the outlet pixel and the next downstream (direction=’down’) or next upstream (direction=’up’) outlet pixel.

Parameters:

  • idxs_out (2D array of int) – Linear indices of unit catchment outlets

  • elevtn (2D array of float with self.shape) – Elevation raster, required to calculate slope.

  • length (float, optional) – Subgrid river length [m] over which to calculate the slope, by default 1000 m. Only used in combination with direction = ‘both’

  • direction ({"both", "up", "down"}) – Flow direction in which river slope is measured, by default ‘both’.

  • method ({'mean', 'lstsq'}, optional) – Estimate slope from the net elevation difference divided by length (‘mean’) or by least-squares regression (‘lstsq’), by default ‘mean’.

  • mask (2D array of bool with self.shape, optional) – True for valid pixels. Can be used to mask out pixels of small rivers.

Returns:

rivslp – subgrid river slope [m/m]

Return type:

2D array of float with idxs_out.shape