Assessing the relation between the distribution of salt-marsh communities and the sediment budget of the North Norfolk coast

2002 ◽  
Vol 8 (1) ◽  
pp. 55-60
Author(s):  
N. J. Brown ◽  
R. Cox ◽  
R. Pakeman ◽  
A. G. Thomson ◽  
R. A. Wadsworth ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sediment Budget ◽  
The North

Assessing the relation between the distribution of salt-marsh communities and the sediment budget of the North Norfolk coast

2002 ◽  
Vol 8 (1) ◽  
pp. 55 ◽  
Author(s):  
N.J. Brown ◽  
R. Cox ◽  
R. Pakeman ◽  
A.G. Thomson ◽  
R.A. Wadsworth ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sediment Budget ◽  
The North

Wave, Tide and Morphological Controls on Embayment Circulation and Headland Sand Bypassing

2020 ◽  
Author(s):  
Erin King ◽  
Daniel Conley ◽  
Gerd Masselink ◽  
Nicoletta Leonardi ◽  
Robert McCarroll ◽  
...  
Keyword(s):  
Surf Zone ◽  
Accurate Determination ◽  
Circulation Pattern ◽  
Sediment Budget ◽  
Tidal Currents ◽  
Sand Transport ◽  
Tidal Elevation ◽  
Zone Width ◽  
Wave Forcing ◽  
The North

<p>Embayed beaches separated by irregular rocky headlands represent around 50% of the world’s shoreline and are important zones ecologically and commercially. Accurate determination of sediment budgets is necessary for prediction of coastal change over long timescales in these zones. Some headlands have been shown to permit sediment bypassing under particular forcing conditions, therefore knowledge of sediment inputs and outflows via headland bypassing are important for sediment budget closure. Recent modelling work demonstrates bypassing rates are predictable for an isolated headland, however, it remains to test this predictability using a range of real headland morphologies, and to examine the influence of embayment morphology, sediment availability and tidal effects.</p><p>We show that bypassing rates are strongly influenced by the relative proximity between adjacent headlands, and the degree of embaymentisation. Tidal currents are secondary to wave forcing, mildly moderating bypass rates, whereas tidal elevation strongly influences bypassing rates largely through variations in apparent headland and embayment morphology.</p><p>A fully coupled (3D hydrodynamics and waves) numerical model was used to simulate sand transport along a 75 km long macrotidal, embayed coast in the north of Cornwall, UK. Twenty-five embayments were included in the analysis. Nine wave conditions were simulated and bypass rates were analysed for three tidal elevations. Simulations were performed with both uniform sediment availability and a realistic spatial distribution of sediment, and both including and excluding tidal currents. It is shown that many of the embayments along this stretch of coast exhibit headland bypassing under energetic wave forcing, highlighting the need for accurate bypass rate predictions for sediment budget determination on embayed coasts.</p><p>Headland extent relative to surf-zone width was a critical control on sand bypass rates in line with previous work. Predictive expressions were accurate to within a factor of 4 for beaches exhibiting a ‘normal’ circulation pattern (embayment length long relative to surf zone width), however, they did not predict well cases where embayment cellular circulation was dominant (embayment length short relative to surf zone width).  Tidal currents exhibited a secondary control relative to wave forcing, moderating bypass rates by up to 20% in this macrotidal environment. Large differences in the apparent morphology of the embayments between high and low tide strongly impact bypassing rates, with greatest bypassing occurring at low-tide when headland cross-shore length is smallest. Bypass rates were reduced for realistic sediment distributions versus uniform sediment availability, due to larger transport magnitudes when sediment is available off the headland toe.</p><p>This work highlights the extent to which headland bypassing occurs along this embayed coast with implications for similar coasts worldwide. It also emphasises the need for accurate predictions of headland bypassing in these regions and suggests areas for further efforts to focus to refine future predictive parameterisations.</p>

Impact of salt marsh and seagrass beds on the sediemnt buget and resilience of coatsal areas

2020 ◽  
Author(s):  
Nicoletta Leonardi ◽  
Carmine Donatelli ◽  
Xiahoe Zhang ◽  
Neil Ganju ◽  
Sergio Fagherazzi
Keyword(s):  
Salt Marsh ◽  
Water Resources ◽  
Salt Marshes ◽  
Numerical Models ◽  
Sediment Budget ◽  
Coastal Protection ◽  
Seagrass Beds ◽  
Geophysical Research ◽  
Coastal System ◽  
Depositional Patterns

<p>Salt marshes and seagrass beds can offer sustainable coastal protection solutions and several ecosystem co-benefits. The delicate balance regulating salt marsh stability depends on several factors including the sediment added to and removed from the coastal system (<em>Donatelli et al., 2018, 2019; Zhang et al., 2019</em>).  Despite the importance of these sediment budget dynamics, many feedbacks between salt marsh presence and sediment availability are still unclear. Here, we use numerical models to simulate changes in depositional patterns of six estuaries along the U.S. coastline to investigate how salt marsh and seagrass beds removal and restoration can alter the sediment budget and resilience of coastal environments. </p><p><em>Donatelli, C., Ganju, N.K., Kalra, T.S., Fagherazzi, S. and Leonardi, N., 2019. Changes in hydrodynamics and wave energy as a result of seagrass decline along the shoreline of a microtidal back-barrier estuary. Advances in Water Resources, 128, pp.183-192.</em></p><p><em>Zhang, X., Leonardi, N., Donatelli, C. and Fagherazzi, S., 2019. Fate of cohesive sediments in a marsh-dominated estuary. Advances in water resources, 125, pp.32-40.</em></p><p><em>Donatelli, C., Ganju, N.K., Fagherazzi, S. and Leonardi, N., 2018. Seagrass impact on sediment exchange between tidal flats and salt marsh, and the sediment budget of shallow bays. Geophysical Research Letters, 45(10), pp.4933-4943.</em></p>

scholarly journals Salt-marsh reconstructions of relative sea-level change in the North Atlantic during the last 2000 years

2014 ◽  
Vol 99 ◽  
pp. 1-16 ◽  
Author(s):  
Natasha L.M. Barlow ◽  
Antony J. Long ◽  
Margot H. Saher ◽  
W. Roland Gehrels ◽  
Mark H. Garnett ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
North Atlantic ◽  
Sea Level Change ◽  
Relative Sea Level ◽  
Level Change ◽  
The North ◽  
The North Atlantic

scholarly journals The saline Interface of a Shallow Unconfined Aquifer, Rangitikei Delta

2021 ◽  
Author(s):  
◽  
Desiree S A Craig
Keyword(s):  
Salt Marsh ◽  
River Estuary ◽  
Shallow Groundwater ◽  
Cumulative Effect ◽  
High Volume ◽  
Unconfined Aquifer ◽  
Saline Intrusion ◽  
Groundwater System ◽  
The North ◽  
Groundwater Aquifer

<p>The coastal communities of Tangimoana and Scott's Ferry have a long history of using shallow groundwater bores. The cumulative effect of pumping over decades could influence the saline interface given the close proximity of the communities to the seashore and river estuary. It is important to quantify the effects of pumping on both the shallow groundwater system and the dynamics of the saline interface. This is necessary to protect the groundwater system against saline intrusion especially given the increasing number of high volume groundwater consents to support dairying. Resistivity soundings and traverses, coupled with chemical analyses of groundwater samples, were found to be an effective method for defining the saline interface of the shallow groundwater aquifer under the Rangitikei delta. The saline interface extends from the salt marsh to beneath the farmland north of Tangimoana. The interface is a zone of diffusion with freshwater and brackish water mixing from the estuary. The interface is currently located on the outskirts of Tangimoana, and it is likely to extend beneath the township. The infiltration of brackish surface waters into sediments of the salt marsh form a surficial mixing zone that decreases with distance from the salt marsh. There is no indication of salinity in the area to the north of the Rangitikei delta. This area is most at risk of contamination from saline intrusion because of high volume groundwater abstractions, even though these abstractions are from deeper aquifers. The shallow groundwater beneath Tangimoana showed high concentrations of Ca and HCO3 ions. This may be a result of carbonate dissolution, which can occur when saline and freshwater mix. This creates groundwater that is under-saturated with calcium. The mixing water dissolves carbonates and increases the concentrations of Ca and HCO3. The major source of sodium and chloride was likely rainwater with evaporated solutes from seawater. The saline interface near Tangimoana appears to be relatively static, but the estuary and salt marsh are areas of low relief. There are preferential flows paths across the salt marsh to the farmland. These factors make the shallow groundwater in the Rangitikei delta vulnerable to saline intrusion.</p>

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

&lt;p&gt;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.&amp;#160; 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.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Acknowledgements&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;We acknowledge the support of the School of Environmental Sciences, University of Liverpool.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;References&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Ganju, N.K., Kirwan, M.L., Dickhudt, P.J., Guntenspergen, G.R., Cahoon, D.R. and Kroeger, K.D. 2015. &amp;#8220;Sediment transport-based metrics of wetland stability&amp;#8221;. Geophysical Research Letters, 42(19), 7992-8000.&lt;/p&gt;&lt;p&gt;Schuerch, M., Vafeidis, A., Slawig, T. and Temmerman, S. 2013. &amp;#8220;Modeling the influence of changing storm patterns on the ability of a salt marsh to keep pace with sea level rise&amp;#8221;.&amp;#160;Journal of Geophysical Research-Earth Surface, 118(1),&lt;strong&gt;&amp;#160;&lt;/strong&gt;84-96.&lt;/p&gt;

scholarly journals The ‘Voordelta’, the contiguous ebb-tidal deltas in the SW Netherlands: large-scale morphological changes and sediment budget 1965–2013; impacts of large-scale engineering

2016 ◽  
Vol 96 (3) ◽  
pp. 233-259 ◽  
Author(s):  
Edwin P.L. Elias ◽  
Ad J.F. van der Spek ◽  
Marian Lazar
Keyword(s):  
Large Scale ◽  
Morphological Changes ◽  
Tidal Flow ◽  
Sediment Budget ◽  
Delta Front ◽  
Knowledge Based ◽  
The North ◽  
Sediment Volume ◽  
Ebb Tidal Delta ◽  
The Individual

AbstractThe estuaries in the SW Netherlands, a series of distributaries of the rivers Rhine, Meuse and Scheldt known as the Dutch Delta, have been engineered to a large extent as part of the Delta Project. The Voordelta, a coalescing system of the ebb-tidal deltas of these estuaries, extendsc.10 km offshore and coversc.90 km of the coast. The complete or partial damming of the estuaries had an enormous impact on the ebb-tidal deltas. The strong reduction of the cross-shore directed tidal flow triggered a series of morphological changes that continue until today. This paper aims to give a concise overview of half a century of morphological changes and a sediment budget, both for the individual ebb-tidal deltas and the Voordelta as a whole, based on the analysis of a unique series of frequent bathymetric surveys. The well-monitored changes in the Voordelta, showing the differences in responses of the ebb-tidal deltas, provide clear insight into the underlying processes. Despite anthropogenic dominance, knowledge based on natural inlets can still explain the observed developments. Complete damming of the three northern estuaries Brielse Maas, Haringvliet and Grevelingen resulted in a regime shift, from mixed-energy to wave-dominated, and sediments are transported in landward and downdrift direction. This results in large morphodynamic changes – sediments are redistributed from the delta front landward – but small net volume changes – a 0.1–0.2 × 106m3a−1increase in volume over the period 1965–2010 – since the dams block sediment transport into the estuaries. Sediment volume losses of 106m3a−1are observed on the ebb-tidal delta of the partially closed Eastern Scheldt and still open Western Scheldt estuary. As a result of a reduction of the estuarine tide in the mouth of the Eastern Scheldt, the north–south-running North Sea tidal wave has gained impact on its ebb-tidal delta, which causes morphological adjustments and erosion of the Banjaard shoal area. Moreover, the Eastern Scheldt ebb-tidal delta delivers sediment to its neighbours. The stable ebb-tidal delta configuration in the Western Scheldt, despite major dredging activities, illustrates that these large inlet systems are robust and resilient to significant anthropogenic change, as long as the balance between the dominant hydrodynamic processes (tides and waves) does not alter significantly.

Sign in / Sign up

Export Citation Format

Share Document