HEC-RAS allows the user to model ice-covered channels at two levels. The first level is an ice cover with known geometry. In this case, the user specifies the ice cover thickness and roughness at each cross section. Different ice cover thicknesses and roughness can be specified for the main channel and for each overbank and both can vary along the channel. The second level is a wide-river ice jam. In this case, the ice jam thickness is determined at each section by balancing the forces on it. The ice jam can be confined to the main channel or can include both the main channel and the overbanks. The material properties of the wide-river jam can be selected by the user and can vary from cross section to cross section. The user can specify the hydraulic roughness of the ice jam or HEC-RAS will estimate the hydraulic roughness on the basis of empirical data.
This chapter describes the general guidelines for modeling ice-covered channels with HEC-RAS. It contains background material and the equations used. For information on how to enter ice cover data and to view results, see "Modeling Culverts" and "Modeling Gated Spillways, Weirs and Drop Structures" of the HEC-RAS User's Manual.