## Stochastic Simulation

REBEKA II calculates the frequency distribution of model outputs (i.e.
number of critical events for ammonia toxicity, riverbed erosion and
turbidity, TSS load and time of critical TSS immission) by means of a
Monte Carlo simulation. The number of runs can be chosen by the user.

For each run a deterministic simulation
over 10 years is performed. In each run, the
program determines for each rain event if it is critical or not with
regard to the different criteria (erosion, ammonia toxicity, turbidity)
and calculates the fraction of time while critical densities of TSS
accumulation on the riverbed are exceeded. At the end of each run
average numbers of critical events per year are calculated.

After
proceeding of all runs frequency distributions of the number of
critical events are plotted as results. The parameters are randomly
varied between consecutive runs according to the chosen
upper and lower
limits and the probability distribution.

## Examples of Results

The results are divided into three charts: