class NotCoreNodeBaselevelHandler

# Not Core Node Baselevel Handler¶

NotCoreNodeBaselevelHandler modifies elevation for not-core nodes.

class NotCoreNodeBaselevelHandler(grid, modify_core_nodes=False, lowering_rate=None, lowering_file_path=None, model_end_elevation=None, **kwargs)[source]

Bases: object

Control the elevation of all nodes that are not core nodes.

The NotCoreNodeBaselevelHandler controls the elevation of all nodes on the model grid with status != 0 (i.e., all not-core nodes). The elevation change at these nodes is specified either as a constant rate, or through a text file that specifies the elevation change through time.

Through the parameter modify_core_nodes the user can determine if the core nodes should be moved in the direction (up or down) specified by the elevation change directive, or if the non-core nodes should be moved in the opposite direction.

The NotCoreNodeBaselevelHandler expects that topographic__elevation is an at-node model grid field. It will modify this field as well as the field bedrock__elevation, if it exists.

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

__init__(grid, modify_core_nodes=False, lowering_rate=None, lowering_file_path=None, model_end_elevation=None, **kwargs)[source]
Parameters
• grid (landlab model grid) –

• modify_core_nodes (boolean, optional) – Flag to indicate if the core nodes or the non-core nodes will be modified. Default is False, indicating that the boundary nodes will be modified.

• lowering_rate (float, optional) – Lowering rate of the outlet node. One of lowering_rate and lowering_file_path is required. Units are implied by the model grids spatial scale and the time units of step. Negative values mean that the outlet lowers.

• lowering_file_path (str, optional) – Lowering history file path. One of lowering_rate and lowering_file_path is required. Units are implied by the model grids spatial scale and the time units of step. This file should be readable with np.loadtxt(filename, skiprows=1, delimiter=",") Its first column is time and its second colum is the elevation change at the outlet since the onset of the model run. Negative values mean the outlet lowers.

• model_end_elevation (float, optional) – Average elevation of the nodes_to_lower at the end of the model run duration. When the outlet is lowered based on an lowering_file_path, a model_end_elevation can be set such that lowering is scaled based on the starting and ending outlet elevation. Default behavior is to not scale the lowering pattern.

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 NotCoreNodeBaselevelHandler and instantiate.

>>> from terrainbento.boundary_handlers import (
...                                      NotCoreNodeBaselevelHandler)
>>> bh = NotCoreNodeBaselevelHandler(mg,
...                                 modify_core_nodes = False,
...                                 lowering_rate = -0.1)
>>> bh.run_one_step(10.0)


We should expect that the boundary nodes (except for node 0) will all have lowered by -1.

>>> print(z.reshape(mg.shape))
[[-1. -1. -1. -1. -1.]
[-1.  0.  0.  0. -1.]
[-1.  0.  0.  0. -1.]
[-1.  0.  0.  0. -1.]
[-1. -1. -1. -1. -1.]]


If we wanted instead for all of the non core nodes to change their elevation, we would set modify_core_nodes = True.

>>> 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.)
>>> from terrainbento.boundary_handlers import (
...                                        NotCoreNodeBaselevelHandler)
>>> bh = NotCoreNodeBaselevelHandler(mg,
...                                 modify_core_nodes = True,
...                                 lowering_rate = -0.1)
>>> bh.run_one_step(10.0)
>>> print(z.reshape(mg.shape))
[[ 0.  0.  0.  0.  0.]
[ 0.  1.  1.  1.  0.]
[ 0.  1.  1.  1.  0.]
[ 0.  1.  1.  1.  0.]
[ 0.  0.  0.  0.  0.]]


More complex baselevel histories can be provided with a lowering_file_path.

run_one_step(step)[source]

Run NotCoreNodeBaselevelHandler forward and update elevations.

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

In the run_one_step routine, the NotCoreNodeBaselevelHandler will either lower the closed or raise the non-closed nodes based on inputs specified at instantiation.

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

Parameters

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