Littoral drift, or shore drift, is the process by which beach sediment is moved along the shoreline. Drift results primarily from the oblique approach of wind-generated waves and can therefore change in response to short-term (daily, weekly, or seasonally) shifts in wind direction. Over the long term, however, many shorelines exhibit a single direction of net shore drift. Net shore-drift is determined through geomorphologic analysis of beach sediment patterns and of coastal landforms. Many shorelines can be divided into discrete littoral, or drift, cells, which are independent of one another and for which distinct sediment sources and sinks can be identified. This coverage denotes the extent of individual littoral cells and the direction of net shore-drift within each.