priority_flow.fix_drainage

Walk upstream from a point ensuring DEM is increasing by a minimum epsilon.

Line-by-line translation of Fix_Drainage.R (FixDrainage) from the R PriorityFlow package. R uses 1-based indexing; we use 0-based. startpoint is (row, col) 0-based.

Functions

fix_drainage() → Dict[str, numpy.ndarray])

Walk upstream from a point ensuring DEM is increasing by a minum epsilon.

Module Contents

priority_flow.fix_drainage.fix_drainage(dem: numpy.ndarray, direction: numpy.ndarray, mask: numpy.ndarray, bank_epsilon: float, startpoint: Tuple[int, int] | list | numpy.ndarray, d4: Tuple[int, int, int, int] = (1, 2, 3, 4)) → Dict[str, numpy.ndarray][source]

Walk upstream from a point ensuring DEM is increasing by a minum epsilon.

This walks upstream from a point following a flow direction file and checks that the elevation upstream is greater than or equal to the elvation at the point + epsilon Once the function reaches a point where upstream cells pass it stops

NOTE: this is only processing the immediate neigborhood and does not recurse over the entire domain, For example if you did the entire overal prioirty flow processing with an espilon of 0 then ran this functon starting at a river point with an epsilon of 0.1 this function will traverse upstream from the river bottom checking that every cell conneting to the river cell is higher by at least this ammout but once it reaches a point where every connected cell passes this test it will stop. Therefore there could still be locations higher up on the hillslope with the original epsilon of zero still. This is on purpose and this script is not intended to gobally ensure a given epsilon.

Parameters:

  • dem (np.ndarray) – 2D array of elevations for the domain (nx, ny).

  • direction (np.ndarray) – 2D array of D4 flow directions for each cell. Direction codes follow the d4 numbering scheme.

  • mask (np.ndarray) – 2D mask with ones for cells that are allowed to be processed and zeros elsewhere. Only neighbors within the mask can be adjusted.

  • bank_epsilon (float) – Minimum elevation difference that upstream cells must have relative to the current cell. If an upstream neighbor is lower than current + bank_epsilon, its elevation is raised to current + bank_epsilon.

  • startpoint (tuple[int, int] or list or np.ndarray) – Starting grid cell given as (row, col) indices (0-based) from which to begin walking upstream.

  • d4 (tuple of int, optional) – Direction numbering system for the D4 neighbors, given as (down, left, up, right). Defaults to (1, 2, 3, 4) to match the original R implementation.

Returns:

Dictionary containing:

  • "dem.adj": 2D elevation array after local adjustments.

  • "processed": 2D array marking cells that were adjusted (1) or visited during processing, and 0 elsewhere.

Return type:

Dict[str, np.ndarray]