Salt-marsh accretion and sea-level movement in the inner Severn Estuary, southwest Britain: the archaeological and historical contribution

1991 ◽  
Vol 148 (3) ◽  
pp. 485-494 ◽  
Author(s):  
J. R. L. ALLEN
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Severn Estuary ◽  
Historical Contribution ◽  
Marsh Accretion ◽  
And Sea Level

Historical rates of salt marsh accretion on the outer Bay of Fundy

2001 ◽  
Vol 38 (7) ◽  
pp. 1081-1092 ◽  
Author(s):  
Gail L Chmura ◽  
Laurie L Helmer ◽  
C Beth Beecher ◽  
Elsie M Sunderland
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Sea Level Change ◽  
Bay Of Fundy ◽  
Relative Sea Level ◽  
Early 19Th Century ◽  
Level Change ◽  
Pollen Stratigraphy ◽  
Accretion Rates ◽  
Marsh Accretion

We examine rates of salt marsh accumulation in three marshes of the outer Bay of Fundy. At each marsh we selected a site in the high marsh with similar vegetation, and thus similar elevation. Accretion rates were estimated by 137Cs, 210Pb, and pollen stratigraphy to estimate rates of change over periods of 30, 100, and ~170 years, respectively. These rates are compared with records from the two closest tide gauges (Saint John, New Brunswick, and Eastport, Maine) to assess the balance of recent marsh accretion and sea-level change. Averaged marsh accretion rates have ranged from 1.3 ± 0.4 to 4.4 ± 1.6 mm·year–1 over the last two centuries. Recent rates are similar to the rate of sea-level change recorded at Eastport, Maine, suggesting that they are in step with recent sea-level change but very sensitive to short-term variation in relative sea level. Based on the pollen stratigraphy in the marsh sediments, the marsh accretion rate was higher during the late 18th to early 19th century. Higher rates probably were due to local increases in relative sea level as a result of neotectonic activity and may have been enhanced by increased sediment deposition through ice rafting.

Salt marsh resilience to sea-level rise and increased storm intensity

2021 ◽  
Author(s):  
Natascia Pannozzo ◽  
Nicoletta Leonardi ◽  
Iacopo Carnacina ◽  
Rachel Smedley
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Storm Surge ◽  
Salt Marshes ◽  
Sediment Budget ◽  
Geophysical Research ◽  
Storm Intensity ◽  
Combined Impact ◽  
And Sea Level

<p>Salt marshes are widely recognised as ecosystems with high economic and environmental value. However, it is still unclear how salt marshes will respond to the combined impact of future sea-level rise and possible increases in storm intensity (Schuerch et al. 2013). This study investigates marsh resilience under the combined impact of various storm surge and sea-level scenarios by using a sediment budget approach. The current paradigm is that a positive sediment budget supports the accretion of salt marshes and, therefore, its survival, while a negative sediment budget causes marsh degradation (Ganju et al. 2015). The Ribble Estuary, North-West England, was used as test case, and the hydrodynamic model Delft3D was used to simulate the response of the salt marsh system to the above scenarios. We conclude that the resilience of salt marshes and estuarine systems is enhanced under the effect of storm surges, as they promote flood dominance and trigger a net import of sediment.  Conversely, sea-level rise threatens marsh stability, by promoting ebb dominance and triggering a net export of sediment. Ultimately, when storm surge and sea-level scenarios are combined, results show that storms with the highest intensities have the potential to counteract the negative impact of sea-level rise by masking its effects on the sediment budget.</p><p><strong>Acknowledgements</strong></p><p>We acknowledge the support of the School of Environmental Sciences, University of Liverpool.</p><p><strong>References</strong></p><p>Ganju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. “Sediment transport-based metrics of wetland stability”. Geophysical Research Letters, 42(19), 7992-8000.</p><p>Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. “Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise”. Journal of Geophysical Research-Earth Surface, 118(1),<strong> </strong>84-96.</p>

Late Flandrian shoreline oscillations in the Severn Estuary: change and reclamation at Arlingham, Gloucestershire

1990 ◽  
Vol 330 (1613) ◽  
pp. 315-334 ◽  
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Salt Marshes ◽  
Medieval Period ◽  
Relative Sea Level ◽  
Severn Estuary ◽  
The Past ◽  
Wetland Reclamation ◽  
Geomorphic Surfaces ◽  
Past 300 Years

Five morphostratigraphic units of estuarine alluvium in an erosively off-lapping relationship underlie the now almost totally reclaimed post-glacial wetland enclosed by the great bend in the upper Severn Estuary at Arlingham. The oldest unit is mud-dominated and includes peats, but the next, probably spanning the Medieval Period, sees the beginning of a substantial influx of sand into the upper estuary. The three youngest units are identifiable with the estuary-wide Rumney, Awre and Northwick Formations, which formed within the past 300 years in response to the repetition of a regional cycle of coastal movement that involved cliff cutting on the salt marshes and then the upbuilding of further mudflats and wetlands. The trend of relative sea level in the area has meanwhile continued upward. Piecemeal wetland reclamation, commencing not later than the Medieval Period, and possibly beginning in Romano-British times, has complicated the development of these morphostratigraphic elements. The reclaimed part of the salt marsh now has the form of an upward and outward flight of geomorphic surfaces that increase in elevation with declining age. Locally, where sea defences have been either abandoned or eroded in response to changes in the pattern of estuarine currents, renewed tidal siltation had led to the burial of soils formed on the reclamations.

scholarly journals Salt Marsh Accretion With and Without Deep Soil Subsidence as a Proxy for Sea-Level Rise

2022 ◽  
Author(s):  
Han F. van Dobben ◽  
Alma V. de Groot ◽  
Jan P. Bakker
Keyword(s):  
Salt Marsh ◽  
Sea Level Rise ◽  
Sea Level ◽  
Water Depth ◽  
Salt Marshes ◽  
Small Scale ◽  
Deep Soil ◽  
Flooding Regime ◽  
Soil Subsidence ◽  
Marsh Accretion

AbstractThe relation between salt marsh accretion and flooding regime was quantified by statistical analysis of a unique dataset of accretion measurements using sedimentation-erosion bars, on three barrier islands in the Dutch Wadden Sea over a period of c. 15 years. On one of the islands, natural gas extraction caused deep soil subsidence, which resulted in gradually increasing flooding frequency, duration, and depth, and can thus be seen as a proxy for sea-level rise. Special attention was paid to effects of small-scale variation e.g., in distance to tidal creeks or marsh edges, elevation of the marsh surface, and presence of livestock. Overall mean accretion rate was 0.44 ± 0.0005 cm year−1, which significantly exceeded the local rate of sea-level rise of 0.25 ± 0.009 cm year−1. A multiple regression approach was used to detect the combined effect of flooding regime and the local environment. The most important flooding-related factors that enhance accretion are mean water depth during flooding and overall mean water depth, but local accretion strongly decreases with increasing distance to the nearest creek or to the salt marsh edge. Mean water depth during flooding can be seen as an indicator for storm intensity, while overall mean water depth is a better indicator for storm frequency. The regression parameters were used to run a simple model simulating the effect of various sea-level scenarios on accretion and show that, even under extreme scenarios of sea-level rise, these salt marshes can probably persist for the next 100 years, although the higher parts may experience more frequent inundation.

Accretion of a New England (U.S.A.) Salt Marsh in Response to Inlet Migration, Storms, and Sea-level Rise

1997 ◽  
Vol 45 (6) ◽  
pp. 717-727 ◽  
Author(s):  
C.T. Roman ◽  
J.A. Peck ◽  
J.R. Allen ◽  
J.W. King ◽  
P.G. Appleby
Keyword(s):  
Salt Marsh ◽  
New England ◽  
Sea Level Rise ◽  
Sea Level ◽  
And Sea Level
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