Tidal wetlands including salt marshes and mangroves tend to move inland with sea level rise as they have done in the past. In North America geological records from salt marsh deposits showed early evidence of marsh inland migration as far back as 3,000 years ago when rates of eustatic sea levels decreased (Lambeck and Bard 2000). Where this decrease was accompanied by a slow in isostatic adjustments, marsh vegetation was able to establish and enhance sediment deposition as described by FitzGerald et al. (2008). As the elevation of marshes increased, they migrated seaward and inland (Redfield 1972). At these historically low rates of sea-level rise and stable sediment supply, the rate of marsh migration inland is controlled by the slope of the hinterland. Brinson et al. (1995) noted that, if bordered by steeply sloping hinterlands, marsh migration would be “stalled.” In the Gulf Coast of Florida, Raabe and Stumpf (2016) used historical maps and satellite imagery to show that, despite retreat of marsh seaward edge with increased rates of sea level rise, the low slopes of the hinterland allowed extensive inland migration that compensated for that loss. In Chesapeake Bay, Hussein (2009) found that in low-relief submerging areas, coastal marshes accrete vertically and migrate laterally over adjacent forest soils to keep pace with sea-level rise. We are unaware of any studies that have determined the maximum slope required to prevent stalling of marsh migration under any scenario of sediment supply or sea level rise.