ABSTRACT
This chapter is an introduction to the roughness, conveyance and afflux concepts and governing equations as adopted in the CES-AES in 2005/06. The topics also include the backwater calculation, the method assumptions and limitations and the numerical solution techniques. Where the science has subsequently advanced, references are given which may be used for future evolutions of the CES-AES. The issue of uncertainty is introduced and a pragmatic approach is set-out for dealing with this when estimating water levels in practice. The CES-AES software components are presented with a description of the overall modular interaction and example screen shots.
