Schorre

Un schorre ou pré-salé est une étendue naturelle plane à végétation basse située à proximité du bord de mer, inondée par les eaux salées uniquement lors des hautes marées. Il correspond à la partie de l'estran qui va de la partie supérieure de l'étage médiolittoral à la partie inférieure de l'étage supralittoral et forme ainsi la frange haute des marais maritimes. Les schorres se développent en amont de la zone de vasière littorale qui reste généralement nue en région tempérée (la slikke) ou qui est colonisée par des palétuviers en région tropicale (la mangrove). Les schorres sont au contact des slikkes dont ils sont séparés par un talus ou, lorsque le matériel sédimentaire est moins fin et le site moins abrité, par une microfalaise. Selon les secteurs, ils peuvent régresser par érosion latérale, ou progresser (selon deux modes : extension par vagues rétrogressives ou extension progressive simple). Le schorre est caractérisé par une prairie de végétation halophile répartie en éta

Tide-induced surface water and groundwater interactions in coastal wetlands

David Andrew Barry

Intertidal wetlands such as salt marshes are complex hydrological systems characterized by strong, dynamic interactions between coastal surface water and groundwater, driven particularly by tides. We simulated such interactions with a focus on 3D, variably saturated pore water flow in a salt marsh with a two-layer soil configuration (with a low-permeability mud layer overlying a high-permeability sandy-loam layer), which is commonly found in natural marshes. Simulated intra-tidal groundwater dynamics exhibited significant flow asymmetry with non-zero mean flow velocities over the tidal period. The tidally averaged flow led to 3D pore water circulation linked strongly to the marsh topography, over a range of spatial scales: near the creek bank, around the creek meander and over long marsh sections inclined towards the main channel. Time scales associated with these circulations differed by orders of magnitude. Under the simulated conditions, the creek served as the main outlet of the pore water circulation paths, especially those with infiltration taking place in the upper marsh surface areas away from the main channel. Water infiltrating the soil in the lower marsh surface areas away from the creek tended to discharge to the main channel directly. These flow characteristics have important implications for mass and nutrient transport and transformations in the marsh soil. Since the origin of pore water in the marsh soil is largely the coastal surface water, the travel paths and times revealed by the particle tracking are key factors that determine the (modified) chemical composition of the recycling water at the circulation outlet, which in turn affects the net exchange between the marsh and coastal surface water. Our study highlights the hydrological complexity of intertidal marshes and the need for further research on interactions among marsh morphology, hydrology and ecology, which underpin the functionalities of these wetland systems.

2011

Tidal influence on soil conditions in an intertidal creek-marsh system

David Andrew Barry

To understand better how tides affect the soil conditions of salt marshes, pore-water flow in a modeled 3-D creek-marsh system was simulated under the influence of both monochromatic and spring-neap tides. In analyzing the simulation results, we examined six indices, viz., marsh surface elevation, hydroperiod, shortest distance to creeks, mean soil water saturation, soil saturation index and net water flux across the marsh surface. The results demonstrated that mean soil water saturation, soil saturation index and net water flux exhibited corresponding patterns of spatial variations, which were related to marsh surface elevation, hydroperiod, shortest distance to creeks and tidal regime. While the relationships could be described by a simple function under monochromatic tides, under spring-neap tides it was more complex with different behaviors in the lower and upper marsh areas. The shortest distance to creeks was a critically important factor affecting soil conditions. Well aerated and drained zones co-existed near the creek under both monochromatic and spring-neap tides. Spring-neap tides led to improved soil aeration in the upper marsh, including the interior section (away from the creek) where the hydroperiod and inundation frequency were reduced during neap tides. However, the local flushing condition did not improve correspondingly. The study suggests that single morphological index cannot describe the soil conditions adequately. A proper representation of the soil conditions for plant growth and distribution should take into account not only the aeration condition but also the flushing condition. For that purpose, a composite index is needed to combine the soil water saturation index and the net flux index.

American Geophysical Union2013

Tide-induced surface water and groundwater interactions in coastal wetlands

David Andrew Barry

2011

Sulfate reduction processes in salt marshes affected by phosphogypsum: Geochemical influences on contaminant mobility

Tide-induced surface water and groundwater interactions in coastal wetlands

Tidal influence on soil conditions in an intertidal creek-marsh system

Sulfate reduction processes in salt marshes affected by phosphogypsum: Geochemical influences on contaminant mobility

Tide-induced surface water and groundwater interactions in coastal wetlands

Tidal influence on soil conditions in an intertidal creek-marsh system