Horton Statistics

The Horton Statistics operation calculates for each (Strahler) stream order number and for each merged catchment:

• the number of streams,
• the average stream length (km), and
• the average area of catchments (km²), and
• expected values for these by means of a least squares fit.

The output is stored in a table which can be used to construct so-called Horton plots in a graph window.

Horton plots enable you to inspect the regularity of your extracted stream network based on the (Strahler) stream order numbers, and may serve as a quality control indicator for the entire stream network extraction process. It is expected that:

• the number of streams show a relative decrease for subsequent Strahler order numbers,
• the length of streams and the catchment areas show a relative increase for subsequent Strahler order numbers.

As input is required:

• the output of a previous Catchment extraction operation,
• the output of a previous Catchment merge operation,
• the output of a previous Drainage network ordering operation.