Pond nodes:
- allow variable infiltration at different levels (up to 3 different rates)
- allow variable perimeter with level i.e. plan area through which side infiltration can occurs can vary
- no porosity function

Storage nodes:
- 1 porosity value (which only works below ground, above ground it is assumed to be 100%)
- fixed perimeter for infiltration i.e. assumes cylindrical shape for infiltration (despite the plan area changing with level)
- fixed infiltration rate (no change with height)

It is not possible to model both porosity and a change in infiltration with height.

I propose that pond and storage nodes are merged into 1 unit (they are effectively the same thing anyway).
Within the storage-plan area array allow extra columns for: perimeter, porosity and infiltration.
There should be a simple tick box to say whether to allow infiltration through the base and/or/neither sides.

This functionality would be essential for modelling SuDS for example a biorientation SuDS unit with variable medium at different layers, or a lined infiltration system with no base, but side infiltration etc.
At present modelling SuDS units is quite a 'fudge'.