
class
BasicHySt
¶
Model BasicHySt¶
terrainbento Model BasicHySt program.
Erosion model program using linear diffusion for gravitational mass transport, and an entrainmentdeposition 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:

class
BasicHySt
(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)[source]¶ Bases:
terrainbento.base_class.stochastic_erosion_model.StochasticErosionModel
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
BasicHy
andBasicSt
. The model evolves a topographic surface, \(\eta (x,y,t)\), with the following governing equation:\[ \begin{align}\begin{aligned}\frac{\partial \eta}{\partial t} = \frac{V Q_s}{\hat{Q}}  K\hat{Q}^{m}S^{n} + D\nabla^2 \eta\\Q_s = \int_0^A \left(K(1F_f)\hat{Q(A)}^{m}S^{n}  \frac{V Q_s}{\hat{Q}(A)}\right) dA\end{aligned}\end{align} \]where \(\hat{Q}\) is the local stream discharge (the hat symbol indicates that it is a randomintime variable), \(S\) is the local slope, \(A\) is the local upstream drainage area, \(m\) and \(n\) are the discharge and slope exponent parameters, \(K\) is the erodibility by water, \(V\) is effective sediment settling velocity, \(Q_s\) is volumetric sediment flux, \(r\) is a runoff rate, and \(D\) is the regolith transport efficiency.
Refer to Barnhart et al. (2019) Table 5 for full list of parameter symbols, names, and dimensions.
 The following atnode fields must be specified in the grid:
topographic__elevation

__init__
(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)[source]¶  Parameters
clock (terrainbento Clock instance) –
grid (landlab model grid instance) – The grid must have all required fields.
m_sp (float, optional) – Drainage area exponent (\(m\)). Default is 0.5.
n_sp (float, optional) – Slope exponent (\(n\)). Default is 1.0.
water_erodibility (float, optional) – Water erodibility (\(K_s\)). Default is 0.0001.
nfiltration_capacity (float, optional) – Infiltration capacity (\(I_m\)). Default is 1.0.
regolith_transport_parameter (float, optional) – Regolith transport efficiency (\(D\)). Default is 0.1.
settling_velocity (float, optional) – Settling velocity of entrained sediment (\(V\)). Default is 0.001.
fraction_fines (float, optional) – Fraction of fine sediment that is permanently detached (\(F_f\)). Default is 0.5.
solver (str, optional) – Solver option to pass to the Landlab ErosionDeposition component. Default is “basic”.
**kwargs – Keyword arguments to pass to
StochasticErosionModel
. These arguments control the discharge \(\hat{Q}\).
 Returns
BasicHySt
 Return type
model object
Examples
This is a minimal example to demonstrate how to construct an instance of model BasicHySt. For more detailed examples, including steadystate 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

run_one_step
(step)[source]¶ Advance model BasicHySt for one timestep of duration step.
The run_one_step method does the following:
Creates rain and runoff, then directs and accumulates flow.
Assesses the location, if any, of flooded nodes where erosion should not occur.
Assesses if a
PrecipChanger
is an active boundary handler and if so, uses it to modify the erodibility by water.Calculates erosion and deposition by water.
Calculates topographic change by linear diffusion.
Finalizes the step using the
ErosionModel
base class function finalize__run_one_step. This function updates all boundary handlers handlers bystep
and increments model time bystep
.
 Parameters
step (float) – Increment of time for which the model is run.