natcap.invest.sdr.sdr_core¶
-
natcap.invest.sdr.sdr_core.
calculate_average_aspect
()¶ Calculate the Weighted Average Aspect Ratio from MFD.
Calculates the average aspect ratio weighted by proportional flow direction.
- Parameters
mfd_flow_direction_path (string) – The path to an MFD flow direction raster.
target_average_aspect_path (string) – The path to where the calculated weighted average aspect raster should be written.
- Returns
None
.
-
natcap.invest.sdr.sdr_core.
calculate_sediment_deposition
()¶ Calculate sediment deposition layer.
This algorithm outputs both sediment deposition (r_i) and flux (f_i):
r_i = dr_i * (sum over j ∈ J of f_j * p(i,j)) + E'_i f_i = (1 - dr_i) * (sum over j ∈ J of f_j * p(i,j)) + E'_i (sum over k ∈ K of SDR_k * p(i,k)) - SDR_i dr_i = -------------------------------------------- (1 - SDR_i)
where:
p(i,j)
is the proportion of flow from pixeli
into pixelj
J
is the set of pixels that are immediate upstream neighbors of pixeli
K
is the set of pixels that are immediate downstream neighbors of pixeli
E'
isUSLE * (1 - SDR)
, the amount of sediment loss from pixeli
that doesn’t reach a stream (e_prime_path
)SDR
is the sediment delivery ratio (sdr_path
)
f_i
is recursively defined in terms ofi
’s upstream neighbors. The algorithm begins from seed pixels that are local high points and so have no upstream neighbors. It works downstream from each seed pixel, only adding a pixel to the stack when all its upstream neighbors are already calculated.Note that this function is designed to be used in the context of the SDR model. Because the algorithm is recursive upstream and downstream of each pixel, nodata values in the SDR input would propagate along the flow path. This case is not handled because we assume the SDR and flow dir inputs will come from the SDR model and have nodata in the same places.
- Parameters
mfd_flow_direction_path (string) – a path to a raster with pygeoprocessing.routing MFD flow direction values.
e_prime_path (string) – path to a raster that shows sources of sediment that wash off a pixel but do not reach the stream.
f_path (string) – path to a raster that shows the sediment flux on a pixel for sediment that does not reach the stream.
sdr_path (string) – path to Sediment Delivery Ratio raster.
target_sediment_deposition_path (string) – path to created that shows where the E’ sources end up across the landscape.
- Returns
None.