# coding: utf8
# !/usr/env/python
"""terrainbento Model **BasicHySt** program.
Erosion model program using linear diffusion for gravitational mass transport,
and an entrainment-deposition law for water erosion and deposition. Discharge
is calculated from drainage area, infiltration capacity (a parameter), and
precipitation rate, which is a stochastic variable.
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>`_
5. `PrecipitationDistribution <https://landlab.readthedocs.io/en/master/reference/components/uniform_precip.html>`_
"""
from landlab.components import ErosionDeposition, LinearDiffuser
from terrainbento.base_class import StochasticErosionModel
[docs]class BasicHySt(StochasticErosionModel):
r"""**BasicHySt** model program.
This model program that uses a stochastic treatment of runoff and
discharge, and includes an erosion threshold in the water erosion law. It
combines models :py:class:`BasicHy` and :py:class:`BasicSt`. The model
evolves a topographic surface, :math:`\eta (x,y,t)`, with the following
governing equation:
.. math::
\frac{\partial \eta}{\partial t} = \frac{V Q_s}{\hat{Q}}
- K\hat{Q}^{m}S^{n}
+ D\nabla^2 \eta
Q_s = \int_0^A \left(K(1-F_f)\hat{Q(A)}^{m}S^{n}
- \frac{V Q_s}{\hat{Q}(A)}\right) dA
where :math:`\hat{Q}` is the local stream discharge (the hat symbol
indicates that it is a random-in-time variable), :math:`S` is the local
slope, :math:`A` is the local upstream drainage area, :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,
infiltration_capacity=1.0,
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_s`). Default is 0.0001.
nfiltration_capacity: float, optional
Infiltration capacity (:math:`I_m`). Default is 1.0.
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:`StochasticErosionModel`.
These arguments control the discharge :math:`\hat{Q}`.
Returns
-------
BasicHySt : model object
Examples
--------
This is a minimal example to demonstrate how to construct an instance
of model **BasicHySt**. 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, BasicHySt
>>> clock = Clock(start=0, stop=100, step=1)
>>> grid = RasterModelGrid((5,5))
>>> _ = random(grid, "topographic__elevation")
Construct the model.
>>> model = BasicHySt(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 BasicHySt."
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
self.infilt = infiltration_capacity
# instantiate rain generator
self.instantiate_rain_generator()
# Run flow routing and lake filler
self.flow_accumulator.run_one_step()
# Instantiate an ErosionDeposition 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 **BasicHySt** 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)
# Handle water erosion
self.handle_water_erosion(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
"""Executes model."""
import sys
try:
infile = sys.argv[1]
except IndexError:
print("Must include input file name on command line")
sys.exit(1)
em = BasicHySt.from_file(infile)
em.run()
if __name__ == "__main__":
main()
