In rainfall-runoff modelling, loss models are methods or procedures that determine the 'losses' from rainfall that do not contribute to runoff. They are abstractions from the rainfall, producing rainfall excess, equal to rainfall minus losses.

The most popular models are:

• the initial loss - continuing loss model,
  

• the initial loss - proportional loss model,
  

• the Horton infiltration model, as used in DRAINS for pervious surfaces.
  

These models can be mixed and combined with other losses such as depression storages.