Summary: The ADCIRC hydrodynamic model has been used extensively to predict the effects of storm surge in coastal regions. In an effort to create a more holistic representation of coastal inundation (i.e., the total water level), some recent applications of ADCIRC have focused on modeling coastal river systems. Initial attempts to model river systems with ADCIRC have encountered complications associated with mass balance (artificial increase in mass in the downstream direction) and model instabilities when flow leaves the main channel, which suggests that complications may be attributed to the current treatment of the wet/dry boundary in CG ADCIRC. A new wetting/drying framework has been developed for, and implemented in, the 1D continuous Galerkin ADCIRC code, which is based on the generalized wave continuity equation (GWCE) formulation of the shallow water equations. The new algorithm allows for the inclusion of partially wet elements within the computational domain of ADCIRC, and the focus of this manuscript is flooding-type wetting/drying processes (e.g., tidal fluctuations and storm surge inundation). The new framework uses a scaling factor, \(\eta\), placed on the time derivative term in the primitive continuity equation, prior to formulation of the GWCE. Benefits of the new approach include better mass balance and more accurate tracking of the location of the wet/dry interface, compared with the current wetting and drying algorithm.