The average slope length describes the distance that sheet flow is the dominant surface runoff flow process. It should be measured to the point where flow begins to concentrate. It is easily observable after a heavy rain on a fallow field when the rills are well developed. In this situation, the slope length is the distance from the micro-watershed divide to the origin of the rill. The average slope length can also be determined from topographic maps.

The average slope length is used to compute soil erosion using the MUSLE.

This parameter is used to compute the sediment transport capacity of surface runoff across an HRU. A large coefficient will result in a high transport capacity and thus a larger amount of sediment leaving the HRU.

The name of the topography record is a primary key referenced by topo in hru-data.hru and topo in rout_unit.rtu.

The average slope length for lateral flow is typically longer than the surface slope length.

The average slope steepness of the HRUs is calculated based on the DEM.