# How Flood Modeller 2D solvers work

This section describes
the theory behind Flood Modeller 2D solvers: the equations it solves,
the numerical methods used in the solution, how the solutions have been
benchmarked and how the user can control the solution through advanced
parameters.

Most of this section
is for advanced users, and assumes some knowledge of numerical methods.
You can use it for

Diagnosing awkward
models

Modelling unusual
situations where the governing equations and solution methods may
not automatically be suitable

Evaluating
the accuracy of model outputs

In general, this
section gives more reasoning behind decisions. Most users should not need
to change the advanced parameters from their default values, and
should exercise caution if they do.

### More information

Shallow
water hydraulics

Flood Modeller
2D solver (ADI)

Flood Modeller
2D solver (TVD)

Flood
Modeller 2D solver (FAST)

Test
cases and benchmarks

Advanced
parameters