class CapturedNodeBaselevelHandler

# Captured Node Baselevel Handler¶

CaptureNodeBaselevelHandler implements “external” stream capture.

class CaptureNodeBaselevelHandler(grid, capture_node=None, capture_start_time=0, capture_stop_time=None, capture_incision_rate=- 0.01, post_capture_incision_rate=None, **kwargs)[source]

Bases: object

Turn a closed boundary node into an open, lowering, boundary node.

A CaptureNodeBaselevelHandler turns a given node into an open boundary and lowers its elevation over time. This is meant as a simple approach to model stream capture external to the modeled basin.

Note that CaptureNodeBaselevelHandler increments time at the end of the run_one_step method.

__init__(grid, capture_node=None, capture_start_time=0, capture_stop_time=None, capture_incision_rate=- 0.01, post_capture_incision_rate=None, **kwargs)[source]
Parameters
• grid (landlab model grid) –

• capture_node (int) – Node id of the model grid node that should be captured.

• capture_start_time (float, optional) – Time at which capture should begin. Default is at onset of model run.

• capture_stop_time (float, optional) – Time at which capture ceases. Default is the entire duration of model run.

• capture_incision_rate (float, optional) – Rate of capture node elevation change. Units are implied by the model grids spatial scale and the time units of step. Negative values mean the outlet lowers. Default value is -0.01.

• post_capture_incision_rate (float, optional) – Rate of captured node elevation change after capture ceases. Units are implied by the model grids spatial scale and the time units of step. Negative values mean the outlet lowers. Default value is 0.

Examples

Start by creating a landlab model grid and set its boundary conditions.

>>> from landlab import RasterModelGrid
>>> mg = RasterModelGrid((5, 5))
>>> mg.set_closed_boundaries_at_grid_edges(bottom_is_closed=True,
...                                        left_is_closed=True,
...                                        right_is_closed=True,
...                                        top_is_closed=True)
>>> mg.set_watershed_boundary_condition_outlet_id(
...     0, mg.at_node["topographic__elevation"], -9999.)
>>> print(z.reshape(mg.shape))
[[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]]


Now import the CaptureNodeBaselevelHandler and instantiate.

>>> from terrainbento.boundary_handlers import (
...                                       CaptureNodeBaselevelHandler)
>>> bh = CaptureNodeBaselevelHandler(mg,
...                                  capture_node = 3,
...                                  capture_incision_rate = -3.0,
...                                  capture_start_time = 10,
...                                  capture_stop_time = 20,
...                                  post_capture_incision_rate = -0.1)
>>> for _ in range(10):
...     bh.run_one_step(1)


The capture has not yet started, so we should expect that the topography is still all zeros.

>>> print(z.reshape(mg.shape))
[[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]
[ 0.  0.  0.  0.  0.]]


Running forward another 10 time units, we should see node 3 lower by 30.

>>> for _ in range(10):
...     bh.run_one_step(1)
>>> print(z.reshape(mg.shape))
[[  0.   0.   0. -30.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]]
>>> bh.model_time
20.0


Now that model time has reached 20, lowering will occur at the post- capture incision rate. The node should lower by 1 to -31 in the next 10 time units.

>>> for _ in range(10):
...     bh.run_one_step(1)
>>> print(z.reshape(mg.shape))
[[  0.   0.   0. -31.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]
[  0.   0.   0.   0.   0.]]

run_one_step(step)[source]

Run CaptureNodeBaselevelHandler to update captured node elevation.

The run_one_step method provides a consistent interface to update the terrainbento boundary condition handlers.

In the run_one_step routine, the CaptureNodeBaselevelHandler will determine if capture is occuring and change the elevation of the captured node based on the amount specified in instantiation.

Note that CaptureNodeBaselevelHandler increments time at the end of the run_one_step method.

Parameters

step (float) – Duration of model time to advance forward.