All methods are based on the FHWA HEC-18 scour equations with additional design procedures to account for complex pier geometry. The User should read and understand the discussion on the HEC-18 pier scour equations. This program computes the HEC-18 pier scour equations based on the input provided by the user.
The User can also analyze pier scour using the Florida Method. See HEC-18, Section 7.3.
The HEC-18 pier scour equation computes the same scour depth regardless of the size of the bed material; it is unaffected by the D50 grain size.
The Florida pier scour equation includes a factor for grain size but its use should be limited to soils with a D50 between 0.1 mm (0.0003 feet) to 100 mm (0.3 feet). The equation may provide unrealistic answers for bed materials with a D50 outside of these limits.
The FHWA Manual HEC-18 Fifth Edition, April 2012 does not include a comprehensive methodology for computing local pier scour that includes consideration of the effect of the D50 grain size of the bed material. The User of ABSCOUR 10 is referred to the method on Pier Scour in Coarse Bed Materials in the Utilities Module for insight into the effect of larger bed materials in reducing the extent of pier scour.