priority_flow.slope_calc_upwind

Calculate slopes from a DEM using upwinding.

Translated line-by-line from PriorityFlow R package Slope_Calc_Upwind.R. This function calculates slopes using standard or upwinding options and applies a range of smoothing options, consistent with ParFlow OverlandFlow BC.

Functions

slope_calc_upwind(, minslope, maxslope, secondary_th, ...)

Calculate slopes from a DEM.

Module Contents

priority_flow.slope_calc_upwind.slope_calc_upwind(dem: numpy.ndarray, direction: numpy.ndarray, dx: float, dy: float, mask: numpy.ndarray | None = None, borders: numpy.ndarray | None = None, borderdir: int = 1, d4: tuple[int, int, int, int] = (1, 2, 3, 4), minslope: float = 1e-05, maxslope: float = -1, secondary_th: float = -1, river_method: int = 0, river_secondary_th: float = 0, rivermask: numpy.ndarray | None = None, subbasins: numpy.ndarray | None = None, printflag: bool = False, upflag: bool = True) → dict[str, numpy.ndarray][source]

Calculate slopes from a DEM.

This function will calculate slopes using standard or upwinding options and apply a range of smoothing options.

Parameters:

  • dem (np.ndarray) – Digital elevation model (nx x ny) in HydroFrame layout.

  • direction (np.ndarray) – Flow direction (1=down, 2=left, 3=up, 4=right). May be modified in place for borders.

  • dx (float) – Lateral grid cell resolution.

  • dy (float) – Lateral grid cell resolution.

  • mask (np.ndarray or None) – Domain mask (1=active, 0=inactive). If None, full rectangular domain is used.

  • borders (np.ndarray or None) – Matrix with 1 for border cells default out, 2 default in, 0 for non-border. Built from mask if None.

  • borderdir (int) – Default for border cells: 1=point out, 2=point in.

  • d4 (tuple) – Direction codes (down, left, up, right). Default (1, 2, 3, 4).

  • minslope (float) – Minimum absolute slope for flat cells. Use -1 to disable minimum enforcement.

  • maxslope (float) – Maximum absolute slope. Use -1 to disable.

  • secondary_th (float) – Max ratio |secondary|/|primary|. Use -1 to disable.

  • river_method (int) – 0=none, 1=scale secondary along river, 2=watershed mean slope, 3=stream mean slope.

  • river_secondary_th (float) – Secondary ratio for river cells when river_method 1-3.

  • rivermask (np.ndarray or None) – River mask (1=river). Required for river_method 1, 2, 3.

  • subbasins (np.ndarray or None) – Subbasin ids. Required for river_method 2, 3.

  • printflag (bool) – Print progress.

  • upflag (bool) – If True, downwind slopes for OverlandFlow; if False, standard [i+1]-[i] (OverlandKin).

Notes

River methods:

  • 0: default value, no special treatment for river cells.

  • 1: scale secondary slopes along the river (requires a river mask and a river-specific secondary threshold).

  • 2: apply watershed mean slope to each river reach (requires river mask and subbasins).

  • 3: apply the stream mean slope to each reach (requires river mask and subbasins).

NOTE: The river mask can differ from the rivers used to create the subbasins (for example, using a higher threshold to define subbasins and a lower threshold to define river cells).

Returns:

“slopex”, “slopey”, “direction” (nx x ny arrays).

Return type:

dict