deltametrics.mobility.calculate_channel_decay

deltametrics.mobility.calculate_channel_decay(chmap, landmap, basevalues=None, basevalues_idx=None, window=None, window_idx=None)

Calculate channel decay (reduction in dry fraction).

Uses a method similar to that in Cazanacli et al 2002 [1] to measure the dry fraction of a delta over time. This requires providing an input channel map, an input land map, choosing a set of base maps to use, and a time lag/time window over which to do the analysis.

The dry fraction is calculated as the fraction of the land map that is not channelized (per the channel map) at a given time. The dry fraction is calculated as it changes relative to a base time. Multiple base times can be used, and the resulting 2-D array provides the decay of the dry fraction relative to each base time along each row of the array. Each column of the array represents the decay of the dry fraction at a given time lag relative to the base time. Consistent with Cazanacli et al 2002, the dry fraction is not normalized, and thus the initial dry fraction at the base time is not fixed at 1.0 (and likely should not be 1.0 unless starting with an entirely dry surface).

[1]

Cazanacli, Dan, Chris Paola, and Gary Parker. “Experimental steep, braided flow: application to flooding risk on fans.” Journal of Hydraulic Engineering 128, no. 3 (2002): 322-330.

Parameters:

• chmap (list, xarray.DataArray, numpy.ndarray) – Either a list of 2-D deltametrics.mask, xarray.DataArray, or numpy.ndarray objects, or a t-x-y 3-D xarray.DataArray or numpy.ndarray with channel mask values.

• landmap (list, xarray.DataArray, numpy.ndarray) – Either a list of 2-D deltametrics.mask, xarray.DataArray, or numpy.ndarray objects, or a t-x-y 3-D xarray.DataArray or numpy.ndarray with land mask values.

• basevalues (list, int, float, optional) – List of time values to use as the base channel map. (or single value)

• basevalues_idx (list, optional) – List of time indices to use as the base channel map. (or single value)

• window (int, float, optional) – Duration of time to use as the time lag (aka how far from the basemap will be analyzed).

• window_idx (int, float, optional) – Duration of time in terms of indices (# of save states) to use as the time lag.

Returns:

dryfrac – len(basevalues) x time_window 2-D array with each row representing the dry fraction (aka number of pixels not visited by a channel) in reference to a given base value at a certain time lag (column)

Return type:

ndarray