The Morphology and Origin of Salt Marshes along the Glaciated Coastline of Maine, USA

• Published in: Journal of coastal research Vol. 4; no. 4; pp. 649 - 666
• Main Authors: Kelley, Joseph T., Belknap, Daniel F., Jacobson, George L., Heather A. Jacobson
• Format: Journal Article
• Language: English
• Published: Lawrence, KS Coastal Education and Research Foundation (CERF) 1988; Coastal Education and Research Foundation
• Subjects: Coasts; Earth sciences; Earth, ocean, space; Erosion; Exact sciences and technology; Geology; Geomorphology, landform evolution; Glacial landforms; Marine; Marshes; Peat; Salt marshes; Sea level rise; Sediments; Shorelines; Surficial geology; ANW, USA, Maine; United States; Shore features; Maine; Changes of level; Salt marshes; North America; Landform evolution
• ISSN: 0749-0208; 1551-5036

Systematic map and photo surveys of the abundance of tidal marshes, beaches, mudflats, bed- rock outcrops, and other physical characteristics of the coastal environments of Maine show that four types of salt marsh can be differentiated on the basis of their origins and geomorphic settings: (1) Back-barrier Marshes; (2) Transitional Marshes; (3) Fluvial Marshes; and (4) Blufftoe Marshes. Transitional Marshes, which form as the ocean breaches freshwater bogs, and Bluff-toe Marshes, which form as the ocean erodes bluffs of glaciomarine sediment, have not previously been described in the literature. The differential development of these various types of marshes depends on sediment availability and exposure to wave energy; consequently, they are unevenly distributed along Maine's bedrock-defined coastal compartments. Tidal marshes are relatively scarce in areas of high (> 6m) tidal range that are experiencing rapid rates of sea-level rise, and more common in areas where tidal range and rate of sea-level rise are low. Maine's salt marshes may contribute large quantities of peat to nearshore environments today, as they erode on their seaward margins. However, their future is uncertain because coastal development and other human activities may influence their landward displacement and alter the tidal regime of the Gulf of Maine. /// La regla de Bruun de erosion, denominada asi por geomofologos americanos (Schwartz, 1967) fue publicada por primera vez en 1962 (Bruun, 1962) y, en breve, se refiere al balance de sedimentos transversal de un perfil de playa a largo plazo. La regla se basa en la hipotesis de la existencia de un balance de sedimentos entre: (1) playa y (2) perfil del fondo del mar (exterior a la playa). La figura 1 es una representacion esquematica del efecto, una traslacion del perfil una distancia s despues de una elevacion de a del nivel del mar, produce una erosion de la linea de costa y un deposit0 de sedimentos. Este tema ha sido tratado teoricamente (Hallermeier, 1972; Allison, 1980; Bruun, 1980, 1983) y experimentalmente en la naturaleza (Bruun, 1954a,b, 1962, 1980, 1983,; Dubois, 1976; Rosen, 1978, 1980; Weggel, 1979; Fisher, 1980; Hands, 1980; Schwartz, 1965, 1967, 1979). Con posterioridad la Regla ha sido utilizada en diferentes informes sobre erosion de playas en Ocean City, Maryland, "Impacto potencial de la elevacion del nivel del mar en la playa de Ocean City, MD" publicado por la EPA, Octubre 1985 y en un articulo de Everts (1985). La regla ha sido usada a veces indescriminadamente sin tener en cuenta sus limitaciones. En primer lugar debe tenerse en cuenta que la regla es basicamente bidmensional, per0 se aplica casi siempre con caracter tridimensional. Esto ha causado un gran numero de malas interpretaciones. Usada objetivamente la Regla ofrece una linea de referencia sobre todos 10s desarrollos que ocurren en el perfil basico en relacion con el nivel del mar observado. En este articulo se discuten condiciones de contorno, desviaciones y ajustes que hacen la Regla util para interpretar 10s fenomenos observados de una manera cuantitativa.-Department of Water Sciences, University of Cantrabria, Santander, Spain