Tidal Prism Control on Cross-Sectional Geometry and Incision Extent of Marsh Creeks

Salt marshes are coastal ecosystems influenced by tidal cycles, sediment transport, and vegetation. These environments are dissected by a network of tidal creeks, which drain and flood the marsh platform. To describe tidal channel morphology, the O'Brien–Jarrett–Marchi (OBJM) law relates the tidal prism to the channel cross-sectional area. While this law has been validated for submerged tidal channels, its applicability to small intertidal creeks that dry during ebb tides remains uncertain. In Chapter 1, this knowledge gap is addressed through a field-based study at Little Sapelo Island (Georgia, USA), using numerical modeling to test the OBJM law in small intertidal channels. Building on this, Chapter 2 presents a numerical modeling approach based on a simplified salt marsh, inspired by the dimensions of Sapelo Island, to simulate tidal channel evolution and provide preliminary validation of the OBJM relationship. The model also explores how varying biomass levels influence headward erosion rates. This thesis provides new insights into the morphodynamic behavior of tidal creeks, emphasizing the key role of vegetation, erosion processes, and tidal forcing in determining salt marsh stability under changing environmental conditions.

SSalt marshes are coastal ecosystems influenced by tidal cycles, sediment transport, and vegetation. These environments are dissected by a network of tidal creeks, which drain and flood the marsh platform. To describe tidal channel morphology, the O'Brien–Jarrett–Marchi (OBJM) law relates the tidal prism to the channel cross-sectional area. While this law has been validated for submerged tidal channels, its applicability to small intertidal creeks that dry during ebb tides remains uncertain. In Chapter 1, this knowledge gap is addressed through a field-based study at Little Sapelo Island (Georgia, USA), using numerical modeling to test the OBJM law in small intertidal channels. Building on this, Chapter 2 presents a numerical modeling approach based on a simplified salt marsh, inspired by the dimensions of Sapelo Island, to simulate tidal channel evolution and provide preliminary validation of the OBJM relationship. The model also explores how varying biomass levels influence headward erosion rates. This thesis provides new insights into the morphodynamic behavior of tidal creeks, emphasizing the key role of vegetation, erosion processes, and tidal forcing in determining salt marsh stability under changing environmental conditions.