# coding: utf8
# !/usr/env/python
"""terrainbento **BasicHy** model program.
Erosion model program using linear diffusion, stream-power-driven sediment
erosion and mass conservation, and discharge proportional to drainage area.
Landlab components used:
1. `FlowAccumulator <https://landlab.readthedocs.io/en/master/reference/components/flow_accum.html>`_
2. `DepressionFinderAndRouter <https://landlab.readthedocs.io/en/master/reference/components/flow_routing.html>`_ (optional)
3. `ErosionDeposition <https://landlab.readthedocs.io/en/master/reference/components/erosion_deposition.html>`_
4. `LinearDiffuser <https://landlab.readthedocs.io/en/master/reference/components/diffusion.html>`_
"""
from landlab.components import ErosionDeposition, LinearDiffuser
from terrainbento.base_class import ErosionModel
[docs]class BasicHy(ErosionModel):
r"""**BasicHy** model program.
**BasicHy** is a model program that evolves a topographic surface described
by :math:`\eta` with the following governing equation:
.. math::
\frac{\partial \eta}{\partial t} = \frac{V Q_s}
{Q}
- KQ^{m}S^{n}
+ D\nabla^2 \eta
Q_s = \int_0^A \left((1-F_f)KQ(A)^{m}S^{n}
- \frac{V Q_s}{Q(A)} \right) dA
where :math:`Q` is the local stream discharge, :math:`A` is the local
upstream drainage area,:math:`S` is the local slope, :math:`m` and
:math:`n` are the discharge and slope exponent parameters, :math:`K` is the
erodibility by water, :math:`V` is effective sediment settling velocity,
:math:`Q_s` is volumetric sediment flux, :math:`r` is a runoff rate,
and :math:`D` is the regolith transport efficiency.
Refer to
`Barnhart et al. (2019) <https://doi.org/10.5194/gmd-12-1267-2019>`_
Table 5 for full list of parameter symbols, names, and dimensions.
The following at-node fields must be specified in the grid:
- ``topographic__elevation``
"""
_required_fields = ["topographic__elevation"]
[docs] def __init__(
self,
clock,
grid,
m_sp=0.5,
n_sp=1.0,
water_erodibility=0.0001,
regolith_transport_parameter=0.1,
settling_velocity=0.001,
fraction_fines=0.5,
solver="basic",
**kwargs
):
"""
Parameters
----------
clock : terrainbento Clock instance
grid : landlab model grid instance
The grid must have all required fields.
m_sp : float, optional
Drainage area exponent (:math:`m`). Default is 0.5.
n_sp : float, optional
Slope exponent (:math:`n`). Default is 1.0.
water_erodibility : float, optional
Water erodibility (:math:`K`). Default is 0.0001.
regolith_transport_parameter : float, optional
Regolith transport efficiency (:math:`D`). Default is 0.1.
settling_velocity : float, optional
Settling velocity of entrained sediment (:math:`V`). Default
is 0.001.
fraction_fines : float, optional
Fraction of fine sediment that is permanently detached
(:math:`F_f`). Default is 0.5.
solver : str, optional
Solver option to pass to the Landlab
`ErosionDeposition <https://landlab.readthedocs.io/en/master/reference/components/erosion_deposition.html>`__
component. Default is "basic".
**kwargs :
Keyword arguments to pass to :py:class:`ErosionModel`. Importantly
these arguments specify the precipitator and the runoff generator
that control the generation of surface water discharge (:math:`Q`).
Returns
-------
BasicHy : model object
Examples
--------
This is a minimal example to demonstrate how to construct an instance
of model **BasicHy**. For more detailed examples, including
steady-state test examples, see the terrainbento tutorials.
To begin, import the model class.
>>> from landlab import RasterModelGrid
>>> from landlab.values import random
>>> from terrainbento import Clock, BasicHy
>>> clock = Clock(start=0, stop=100, step=1)
>>> grid = RasterModelGrid((5,5))
>>> _ = random(grid, "topographic__elevation")
Construct the model.
>>> model = BasicHy(clock, grid)
Running the model with ``model.run()`` would create output, so here we
will just run it one step.
>>> model.run_one_step(1.)
>>> model.model_time
1.0
"""
# If needed, issue warning on porosity
if "sediment_porosity" in kwargs:
msg = "sediment_porosity is no longer used by BasicHy."
raise ValueError(msg)
# Call ErosionModel"s init
super().__init__(clock, grid, **kwargs)
# verify correct fields are present.
self._verify_fields(self._required_fields)
# Get Parameters
self.m = m_sp
self.n = n_sp
self.K = water_erodibility
# Instantiate a Space component
self.eroder = ErosionDeposition(
self.grid,
K=self.K,
F_f=fraction_fines,
v_s=settling_velocity,
m_sp=self.m,
n_sp=self.n,
discharge_field="surface_water__discharge",
solver=solver,
)
# Instantiate a LinearDiffuser component
self.diffuser = LinearDiffuser(
self.grid, linear_diffusivity=regolith_transport_parameter
)
[docs] def run_one_step(self, step):
"""Advance model **BasicHy** for one time-step of duration step.
The **run_one_step** method does the following:
1. Creates rain and runoff, then directs and accumulates flow.
2. Assesses the location, if any, of flooded nodes where erosion should
not occur.
3. Assesses if a :py:mod:`PrecipChanger` is an active boundary handler
and if so, uses it to modify the erodibility by water.
4. Calculates erosion and deposition by water.
5. Calculates topographic change by linear diffusion.
6. Finalizes the step using the :py:mod:`ErosionModel` base class
function **finalize__run_one_step**. This function updates all
boundary handlers handlers by ``step`` and increments model time by
``step``.
Parameters
----------
step : float
Increment of time for which the model is run.
"""
# create and move water
self.create_and_move_water(step)
# Do some erosion (but not on the flooded nodes)
# (if we're varying K through time, update that first)
if "PrecipChanger" in self.boundary_handlers:
self.eroder.K = (
self.K
* self.boundary_handlers[
"PrecipChanger"
].get_erodibility_adjustment_factor()
)
self.eroder.run_one_step(step)
# Do some soil creep
self.diffuser.run_one_step(step)
# Finalize the run_one_step_method
self.finalize__run_one_step(step)
[docs]def main(): # pragma: no cover
"""Execute model."""
import sys
try:
infile = sys.argv[1]
except IndexError:
print("Must include input file name on command line")
sys.exit(1)
ha = BasicHy.from_file(infile)
ha.run()
if __name__ == "__main__":
main()