Dear Arham Mansoor,
There are two main options for defining the dambreak.
1) user defined geometry: The breach of the dam is defined through a timeseries defining the breach development
2) erosion based: The breach development is based on erosion calculted through a sediment transport formula.
For the former you typically need to consider historical data with regards to the developoment of a breach in a similar dam. For the erosion based approach you need to have some insight into the dams composition to set the grain dimater, porosity etc.
Regards
Johan