Sediment elevations were measured on an intertidal mudflat in Maine to determine the temporal and spatial changes in sediment volume. The winter and spring months were times of greatest sediment change, with erosion in winter months followed by rapid accretion in the spring. In some months erosion and deposition took place during the same time interval but on different parts of the mudflat. The data suggest that areas of erosion quickly become sites of accretion, indicating that an equilibrium surface level is being maintained. Mudflats may strongly influence the adjacent estuary by acting as sediment banks that can periodically lend sediments to the particulate pool offshore. We conclude that mudflats should not be thought of as steady accretionary environments but rather as more variable environments that respond to seasonal changes.