xrspatial.hydro.flow_length_mfd.flow_length_mfd#

xrspatial.hydro.flow_length_mfd.flow_length_mfd(flow_dir_mfd: DataArray, direction: str = 'downstream', name: str = 'flow_length_mfd') → DataArray[source]#

Compute flow length from an MFD flow direction grid.

Parameters:

  • flow_dir_mfd (xarray.DataArray or xr.Dataset) – 3-D MFD flow direction array of shape (8, H, W) as returned by flow_direction_mfd. Values are flow fractions in [0, 1] that sum to 1.0 at each cell (0.0 at pits/flats, NaN at edges or nodata cells). Supported backends: NumPy, CuPy, NumPy-backed Dask, CuPy-backed Dask. If a Dataset is passed, the operation is applied to each data variable independently.

  • direction (str, default 'downstream') – 'downstream': proportion-weighted average distance from each cell to its outlet. Each cell gets the expected distance across all MFD flow paths. 'upstream': longest path from any divide to each cell.

  • name (str, default 'flow_length_mfd') – Name of output DataArray.

Returns:

2-D float64 array of flow length values in coordinate units. NaN where the input has NaN.

Return type:

xarray.DataArray or xr.Dataset

References

Qin, C., Zhu, A.X., Pei, T., Li, B., Zhou, C., and Yang, L. (2007). An adaptive approach to selecting a flow-partition exponent for a multiple-flow-direction algorithm. International Journal of Geographical Information Science, 21(4), 443-458.

Quinn, P., Beven, K., Chevallier, P., and Planchon, O. (1991). The prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models. Hydrological Processes, 5(1), 59-79.