sandplover.plan.compute_shoreline_roughness_OAM

sandplover.plan.compute_shoreline_roughness_OAM(shore_mask_45, shore_mask_120, calculate_length=False, **kwargs)

Compute shoreline roughness, as ratio of shoreline lengths at different thresholds.

Computes the shoreline roughness metric:

\[R = N_{45} / N_{120} \approx L_{45} / L_{120}\]

where R is the roughness of the shoreline, N is the number of pixels in the shoreline in the shore_mask inputs, and \(L\) is the shoreline length (after [1]).

[1]

Broaddus, C. M., Vulis, L. M., Nienhuis, J. H., Tejedor, A., Brown, J., Foufoula-Georgiou, E., & Edmonds, D. A. (2022). First-order river delta morphology is explained by the sediment flux balance from rivers, waves, and tides. Geophysical Research Letters, 49, e2022GL100355. https://doi.org/10.1029/2022GL100355

Parameters:

• shore_mask_45 (ShorelineMask, ndarray) – Shoreline mask, derived from the Opening Angle Method, at the 45 degree contour. Can be a ShorelineMask object, or a binarized array.

• shore_mask_120 (ShorelineMask, ndarray) – Shoreline mask, derived from the Opening Angle Method, at the 120 degree contour. Can be a ShorelineMask object, or a binarized array.

• calculate_length (bool, optional) – If calculate_length=True, then compute_shoreline_length is used to calculate the length of the shoreline explicitly, rather than counting the pixels in shore_mask_45 and shore_mask_120. Default is False.

• **kwargs – Passed to compute_shoreline_length, if calculate_length=True.

Returns:

roughness – Shoreline roughness, computed as described above.

Return type:

float

Examples

Calculate the shoreline roughness.

from sandplover.plan import compute_shoreline_roughness_OAM

golf = spl.sample_data.golf()
origin = np.array([golf.meta["L0"].data, golf.meta["CTR"].data]) * golf.meta["dx"].data

em = spl.mask.ElevationMask(
    golf["eta"][30, :, :], elevation_threshold=0, elevation_offset=-0.1
)
em.trim_mask(length=golf.meta["L0"].data + 1, value=1)
oam = spl.plan.OpeningAnglePlanform.from_mask(em)

sm45 = spl.mask.ShorelineMask.from_Planform(oam, contour_threshold=45)
sm120 = spl.mask.ShorelineMask.from_Planform(oam, contour_threshold=120)

fig, ax = plt.subplots(1, 2)
sm45.show(ax=ax[0])
sm120.show(ax=ax[1])
plt.show(block=False)

(Source code, png, hires.png)

roughness_oam = compute_shoreline_roughness_OAM(sm45, sm120)

fig, ax = plt.subplots()
oam.show(ax=ax)
ax.contour(
    oam.opening_angles.y,
    oam.opening_angles.x,
    oam.opening_angles,
    levels=[45, 120],
    colors=["w"],
)
ax.set_title(f"roughness: {roughness_oam:.1f}")
plt.show()

(png, hires.png)

See also

See this example, which compares all of the “shoreline roughness” metrics implemented in sandplover.