Coastal ecosystems respond to sea level and sediment supply change according to complex, three-way interactions between vegetation, hydrology, and sediment transport. While biogeomorphic feedbacks preserve the morphology of intertidal surfaces covered by marshland, we demonstrate with numerical model and field experimentation that temporary disturbance to vegetation facilitates rapid and widespread degradation. Vertical accretion slows in disturbed areas, allowing localized submergence of the marsh platform, tidal prism enlargement, and permanent channel network expansion. Vegetated portions of an episodically disturbed platform accrete more rapidly than rates of relative sea level rise, giving submerging marshland the appearance of maintaining elevation. This feedback between vegetation disturbance and channel erosion, and its effect on platform accretion, may explain peculiar patterns of wetland loss in Europe and North America. Copyright 2008 by the American Geophysical Union.