A model and field investigation of hydrodynamic processes and morphological change at a sand-substrate tidal inlet is presented in order to describe conditions that can lead to shoaling and channel constriction. The Coastal Modeling System (CMS) developed at the Coastal and Hydraulics Laboratory of the U.S. Army Engineer Research and Development Center (ERDC) employs a depth-integrated two-dimensional circulation and sediment transport model, CMS-Flow, coupled with a phase-averaging, steady-state wave model, CMS-Wave, to simulate hydrodynamics and morphodynamics at Moriches Inlet in Long Island, New York. Short-term model simulations were conducted with measured water surface elevation and time-varying wave forcing to examine the capability of the model to simulate storm versus typical forcing. Model calibration and verification was performed by comparing calculations to measured water surface elevation and current velocity data collected during a field study at Moriches Inlet in 2004. Shoal development and relative movement of morphological features were reproduced in the model simulations. During simulated storm conditions, a vortex with a weak velocity field off the tip of the east jetty caused sediment to accumulate on the eastern boundary of the inlet channel. The alignment of the channel prevents the shoal from being scoured clear of the jetty. These modeled results were verified by observed morphologic response of Moriches Inlet to extratropical storms consisting of shoaling and channel constriction along the flank of the entrance channel and inlet throat. A 14-month long-term simulation also reproduced observations of channel infilling on the outer channel and accretion on the ebb tidal delta.