How do storm events and fair-weather conditions affect sedimentation patterns on salt marshes?

2020 ◽  
Author(s):  
Davide Tognin ◽  
Mattia Pivato ◽  
Andrea D'Alpaos ◽  
Luca Carniello
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Weather Conditions ◽  
Marsh Surface ◽  
Sediment Traps ◽  
Vertical Accretion ◽  
Storm Events ◽  
Fair Weather ◽  
Short Term ◽  
Intense Storm

<p>Coastal salt marshes are extremely important ecosystems, occupying the transitional zone between submerged and emerged environments. Since salt marshes are based on a delicate balance between hydrodynamics and sedimentary processes, their future is heavily affected by relative sea-level rise (RSLR), caused by both subsidence and eustatism. If vertical accretion is sufficient, salt marshes can keep pace with RSLR; otherwise, lack of sediment input can eventually lead to plant death and marsh drowning, transforming these landforms into tidal flats and subtidal platforms. Resuspension driven by intense meteorological events can represent an important source of sediment for salt marsh accretion in tidal environments characterized by negligible fluvial sediment supply. However, it is not yet clear what is the mutual role and relative contribution of intense storm events and fair-weather conditions in terms of sedimentation patterns. To better understand sedimentation dynamics on salt marshes, we stared a field campaign in October 2018 to measure vertical accretion rate and sediment accumulation.</p><p>In the Venice lagoon (Italy), which is the largest lagoon in the Mediterranean sea and is characterized by a semi-diurnal, microtidal regime, we selected three study areas: the San Felice and Sant’Erasmo salt marshes in the northern lagoon and the Conche salt marsh in the southern lagoon. Subsidence at all these study sites ranges between 1.0 and 2.0 mm yr<sup>-1</sup>, and the rate of sea-level rise is of about 2.0 mm yr<sup>-1</sup>, for a total rate of RSLR of about 3.0-4.0 mm yr<sup>-1</sup>. At each study area, we considered different transects, where we installed three measurement stations located respectively at 2.5 m, 7.5 m, and 27.5 m from the salt marsh margin. We equipped each station with an artificial marker horizon laid down on the marsh surface to measure the vertical accretion, and three sediment traps for measuring the short-term sedimentation. The material deposited in two sediment traps is collected monthly or after any single storm, whereas sediment deposited in the third trap is collected once a year, in order to compare sediment deposition dynamics at short (single storm event) and annual time scales. We measure accretion rate, grain size distribution, organic and inorganic content.</p><p>Short-term sedimentation displays a very high variability (0 – 320 g d<sup>-1</sup> m<sup>-2</sup>) highlighting the importance of particularly intense storm events in resuspending and transporting sediment from tidal flats to the salt-marsh surface. In particular, during the storm events occurred in October 2018 and November 2019, sedimentation increases significantly and displays values much higher compared to fair-weather periods. According to our analysis, sedimentation grows exponentially with daily mean inundation time. Even if the inner part of the salt marsh is characterized by lower elevation and, hence, by greater inundation time, sedimentation shows smaller values compared to the salt marsh margin, since suspended material settles close to the margin and decreases towards the inner part of the marsh.</p>

scholarly journals Topological and Morphological Controls on Morphodynamics of Salt Marsh Interiors

2021 ◽  
Vol 9 (3) ◽  
pp. 311
Author(s):  
Ben R. Evans ◽  
Iris Möller ◽  
Tom Spencer
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
East Coast ◽  
Marsh Surface ◽  
Coastal Environments ◽  
Coastal System ◽  
Morphological Segmentation ◽  
The Usa ◽  
The Uk ◽  
Over Time

Salt marshes are important coastal environments and provide multiple benefits to society. They are considered to be declining in extent globally, including on the UK east coast. The dynamics and characteristics of interior parts of salt marsh systems are spatially variable and can fundamentally affect biotic distributions and the way in which the landscape delivers ecosystem services. It is therefore important to understand, and be able to predict, how these landscape configurations may evolve over time and where the greatest dynamism will occur. This study estimates morphodynamic changes in salt marsh areas for a regional domain over a multi-decadal timescale. We demonstrate at a landscape scale that relationships exist between the topology and morphology of a salt marsh and changes in its condition over time. We present an inherently scalable satellite-derived measure of change in marsh platform integrity that allows the monitoring of changes in marsh condition. We then demonstrate that easily derived geospatial and morphometric parameters can be used to determine the probability of marsh degradation. We draw comparisons with previous work conducted on the east coast of the USA, finding differences in marsh responses according to their position within the wider coastal system between the two regions, but relatively consistent in relation to the within-marsh situation. We describe the sub-pixel-scale marsh morphometry using a morphological segmentation algorithm applied to 25 cm-resolution maps of vegetated marsh surface. We also find strong relationships between morphometric indices and change in marsh platform integrity which allow for the inference of past dynamism but also suggest that current morphology may be predictive of future change. We thus provide insight into the factors governing marsh degradation that will assist the anticipation of adverse changes to the attributes and functions of these critical coastal environments and inform ongoing ecogeomorphic modelling developments.

scholarly journals Hitchhiking Halophytes in Wrack and Sediment-Laden Ice Blocks Contribute To Tidal Marsh Development in The Upper Bay of Fundy.

2021 ◽  
Author(s):  
Jeremy Lundholm ◽  
Tasha R.M. Rabinowitz ◽  
Lyndsay Greene ◽  
Alisha D. Glogowski ◽  
Tony Bowron ◽  
...  
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Coastal Wetland ◽  
Marsh Surface ◽  
Plant Colonization ◽  
Bay Of Fundy ◽  
Plant Debris ◽  
Salt Marsh Restoration ◽  
Potential Source ◽  
Total Sediment

Abstract Salt marshes are a type of coastal wetland that are affected by dynamic coastal processes. Ice blocks and wrack (mats of plant debris) regularly float onto northern marshes and become stranded, affecting vegetation and soil accretion. There is little research regarding the capacity of ice and wrack to transport viable plant propagules onto marshes where they can colonize, which may be particularly important at barren new salt marsh restoration sites. Contributions of sediment by ice may also be important at restoration sites to raise the marsh platform to elevations appropriate for plant colonization. We collected ice (n = 27) and wrack (n = 18) samples at marshes in the Bay of Fundy, ran germination trials with the contents, and measured the quantity of sediment in the ice. We found viable propagules from halophytic and non-halophytic species in wrack, and viable propagules of Sporobolus pumilus in ice. Additionally, we found sediment densities between 0.01 and 4.75 g·cm−3 in ice blocks that translated to 26.61 – 21,483.59 kg of total sediment per block, representing a large source of sediment. We found that the number of germinating propagules could not be predicted by wrack size, and that pH, sediment density, sediment weight in ice blocks were variable across the marsh surface, while ice salinity was negatively correlated with elevation and distance from creek. Our results indicate that ice and wrack represent a potential source for vegetation colonization at salt marsh sites and highlights their contributions to facilitating vegetation colonization through building marsh soils.

scholarly journals GEOTECHNICAL PROPERTIES OF SALT MARSH AND TIDAL FLAT SUBSTRATES AT TILLINGHAM, ESSEX, UK.

2018 ◽  
pp. 55
Author(s):  
Helen Brooks ◽  
Iris Möller ◽  
Tom Spencer ◽  
Kate Royse ◽  
Simon James Price
Keyword(s):  
Salt Marsh ◽  
Systematic Study ◽  
Salt Marshes ◽  
Tidal Flat ◽  
Marsh Surface ◽  
Geotechnical Properties ◽  
Surface Erosion ◽  
Marsh Edge ◽  
Erosion Risk ◽  
Erosion Processes

Salt marshes and, to a lesser extent, tidal flats, attenuate incoming hydrodynamic energy, thus reducing flood and erosion risk in the coastal hinterland. However, marshes are declining both globally and regionally (the Northwest European region). Salt marsh resistance to incoming hydrodynamic forcing depends on marsh biological, geochemical and geotechnical properties. However, there currently exists no systematic study of marsh geotechnical properties and how these may impact both marsh edge and marsh surface erosion processes (e.g. surface removal, cliff undercutting, gravitational slumping). This has led to poor parameterization of marsh evolution models. Here, we present a systematic study of salt marsh and tidal flat geotechnical properties (shear strength, bulk density, compressibility, plasticity and particle size) at Tillingham, Essex, UK.

scholarly journals 14C Wiggle-Match Dating in High-Resolution Sea-Level Research

Radiocarbon ◽  
2001 ◽  
Vol 43 (2A) ◽  
pp. 391-402 ◽  
Author(s):  
O van de Plassche ◽  
R J Edwards ◽  
K van der Borg ◽  
A F M de Jong
Keyword(s):  
Salt Marsh ◽  
High Resolution ◽  
Sea Level ◽  
Time Scales ◽  
Calibration Curve ◽  
Salt Marshes ◽  
Accumulation Rate ◽  
The Other ◽  
Short Term ◽  
Radiocarbon Dates

Comparison of two sets of marsh-accumulation records from each of three Connecticut (USA) salt marshes, one based on individually calibrated dates and the other on wiggle-match dating of the same series of dates, shows that wiggle-match dating results in more precise and objective reconstructions of longer-term (102–103 yr) changes in accumulation rate. On (sub-)century time scales, wiggle-match dating can reveal steps in the calibrated marsh-accumulation envelope as artefacts of the calibration curve, but may also leave real short-term changes in accumulation rate undetected. Wiggle-matches are non-unique, being dependent on the number, quality and distribution of radiocarbon dates in a sequence, how a series of dates is subdivided into groups (representing intervals of uniform accumulation rate), and what is considered a “best match”. Samples from the studied salt-marsh deposits required no correction for reservoir effects prior to calibration.

scholarly journals Sediment and carbon deposition vary among vegetation assemblages in a coastal salt marsh

2017 ◽  
Vol 14 (16) ◽  
pp. 3763-3779 ◽  
Author(s):  
Jeffrey J. Kelleway ◽  
Neil Saintilan ◽  
Peter I. Macreadie ◽  
Jeffrey A. Baldock ◽  
Peter J. Ralph
Keyword(s):  
Salt Marsh ◽  
Sea Level ◽  
Salt Marshes ◽  
Salt Marsh Vegetation ◽  
Medium Term ◽  
Short Term ◽  
Marsh Vegetation ◽  
Tidal Period ◽  
13C Nuclear Magnetic Resonance ◽  
Accretion Rates

Abstract. Coastal salt marshes are dynamic, intertidal ecosystems that are increasingly being recognised for their contributions to ecosystem services, including carbon (C) accumulation and storage. The survival of salt marshes and their capacity to store C under rising sea levels, however, is partially reliant upon sedimentation rates and influenced by a combination of physical and biological factors. In this study, we use several complementary methods to assess short-term (days) deposition and medium-term (months) accretion dynamics within a single marsh that contains three salt marsh vegetation types common throughout southeastern (SE) Australia.We found that surface accretion varies among vegetation assemblages, with medium-term (19 months) bulk accretion rates in the upper marsh rush (Juncus) assemblage (1.74 ± 0.13 mm yr−1) consistently in excess of estimated local sea-level rise (1.15 mm yr−1). Accretion rates were lower and less consistent in both the succulent (Sarcocornia, 0.78 ± 0.18 mm yr−1) and grass (Sporobolus, 0.88 ± 0.22 mm yr−1) assemblages located lower in the tidal frame. Short-term (6 days) experiments showed deposition within Juncus plots to be dominated by autochthonous organic inputs with C deposition rates ranging from 1.14 ± 0.41 mg C cm−2 d−1 (neap tidal period) to 2.37 ± 0.44 mg C cm−2 d−1 (spring tidal period), while minerogenic inputs and lower C deposition dominated Sarcocornia (0.10 ± 0.02 to 0.62 ± 0.08 mg C cm−2 d−1) and Sporobolus (0.17 ± 0.04 to 0.40 ± 0.07 mg C cm−2 d−1) assemblages.Elemental (C : N), isotopic (δ13C), mid-infrared (MIR) and 13C nuclear magnetic resonance (NMR) analyses revealed little difference in either the source or character of materials being deposited among neap versus spring tidal periods. Instead, these analyses point to substantial redistribution of materials within the Sarcocornia and Sporobolus assemblages, compared to high retention and preservation of organic inputs in the Juncus assemblage. By combining medium-term accretion quantification with short-term deposition measurements and chemical analyses, we have gained novel insights into above-ground biophysical processes that may explain previously observed regional differences in surface dynamics among key salt marsh vegetation assemblages. Our results suggest that Sarcocornia and Sporobolus assemblages may be particularly susceptible to changes in sea level, though quantification of below-ground processes (e.g. root production, compaction) is needed to confirm this.

Urbanization impacts on production and recruitment of Fundulus heteroclitus in salt marsh creeks

2020 ◽  
Vol 645 ◽  
pp. 187-204
Author(s):  
PJ Rudershausen ◽  
JA Buckel
Keyword(s):  
Salt Marsh ◽  
Salt Marshes ◽  
Fundulus Heteroclitus ◽  
Multiple Factor Analysis ◽  
Southeastern Usa ◽  
Density Dependent ◽  
Dependent Relationship ◽  
Juvenile Abundance ◽  
The Relationship ◽  
Throw Trap

It is unclear how urbanization affects secondary biological production in estuaries in the southeastern USA. We estimated production of larval/juvenile Fundulus heteroclitus in salt marsh areas of North Carolina tidal creeks and tested for factors influencing production. F. heteroclitus were collected with a throw trap in salt marshes of 5 creeks subjected to a range of urbanization intensities. Multiple factor analysis (MFA) was used to reduce dimensionality of habitat and urbanization effects in the creeks and their watersheds. Production was then related to the first 2 dimensions of the MFA, month, and year. Lastly, we determined the relationship between creek-wide larval/juvenile production and abundance from spring and abundance of adults from autumn of the same year. Production in marsh (g m-2 d-1) varied between years and was negatively related to the MFA dimension that indexed salt marsh; higher rates of production were related to creeks with higher percentages of marsh. An asymptotic relationship was found between abundance of adults and creek-wide production of larvae/juveniles and an even stronger density-dependent relationship was found between abundance of adults and creek-wide larval/juvenile abundance. Results demonstrate (1) the ability of F. heteroclitus to maintain production within salt marsh in creeks with a lesser percentage of marsh as long as this habitat is not removed altogether and (2) a density-dependent link between age-0 production/abundance and subsequent adult recruitment. Given the relationship between production and marsh area, natural resource agencies should consider impacts of development on production when permitting construction in the southeastern USA.

scholarly journals The Relevance of Grated Inlets within Surface Drainage Systems in the Field of Urban Flood Resilience. A Review of Several Experimental and Numerical Simulation Approaches

2021 ◽  
Vol 13 (13) ◽  
pp. 7189
Author(s):  
Beniamino Russo ◽  
Manuel Gómez Valentín ◽  
Jackson Tellez-Álvarez
Keyword(s):  
Overland Flow ◽  
Drainage System ◽  
Critical Conditions ◽  
Hydraulic Efficiency ◽  
Storm Events ◽  
Urban Resilience ◽  
Urban Flood ◽  
Drainage Systems ◽  
Surface Drainage ◽  
Intense Storm

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

scholarly journals Performance Evaluation of Neural Network-Based Short-Term Solar Irradiation Forecasts

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3030
Author(s):  
Simon Liebermann ◽  
Jung-Sup Um ◽  
YoungSeok Hwang ◽  
Stephan Schlüter
Keyword(s):  
Neural Network ◽  
Goodness Of Fit ◽  
Renewable Energy Sources ◽  
Weather Conditions ◽  
Solar Irradiation ◽  
Weather Data ◽  
Short Term ◽  
Climate Conditions ◽  
Lstm Network ◽  
The Time Domain

Due to the globally increasing share of renewable energy sources like wind and solar power, precise forecasts for weather data are becoming more and more important. To compute such forecasts numerous authors apply neural networks (NN), whereby models became ever more complex recently. Using solar irradiation as an example, we verify if this additional complexity is required in terms of forecasting precision. Different NN models, namely the long-short term (LSTM) neural network, a convolutional neural network (CNN), and combinations of both are benchmarked against each other. The naive forecast is included as a baseline. Various locations across Europe are tested to analyze the models’ performance under different climate conditions. Forecasts up to 24 h in advance are generated and compared using different goodness of fit (GoF) measures. Besides, errors are analyzed in the time domain. As expected, the error of all models increases with rising forecasting horizon. Over all test stations it shows that combining an LSTM network with a CNN yields the best performance. However, regarding the chosen GoF measures, differences to the alternative approaches are fairly small. The hybrid model’s advantage lies not in the improved GoF but in its versatility: contrary to an LSTM or a CNN, it produces good results under all tested weather conditions.

scholarly journals A Study of the Effects of Rain, Snow and Hail on the Atmospheric Electric Field near Ground

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 996
Author(s):  
Athanasios Karagioras ◽  
Konstantinos Kourtidis
Keyword(s):  
Frequency Distribution ◽  
Complex Structure ◽  
Potential Gradient ◽  
Weather Conditions ◽  
The Other ◽  
Fair Weather ◽  
Northern Greece ◽  
Rain Events ◽  
The Impact ◽  
Bounce Back

The purpose of the present study is to investigate the impact of rain, snow and hail on potential gradient (PG), as observed in a period of ten years in Xanthi, northern Greece. An anticorrelation between PG and rainfall was observed for rain events that lasted several hours. When the precipitation rate was up to 2 mm/h, the decrease in PG was between 200 and 1300 V/m, in most cases being around 500 V/m. An event with rainfall rates up to 11 mm/h produced the largest drop in PG, of 2 kV/m. Shortly after rain, PG appeared to bounce back to somewhat higher values than the ones of fair-weather conditions. A decrease in mean hourly PG was observed, which was around 2–4 kV/m during the hail events which occurred concurrently with rain and from 0 to 3.5 kV/m for hail events with no rain. In the case of no drop, no concurrent drop in temperature was observed, while, for the other cases, it appeared that, for each degree drop in temperature, the drop in hourly mean PG was 1000 V/m; hence, we assume that the intensity of the hail event regulates the drop in PG. The frequency distribution of 1-minute PG exhibits a complex structure during hail events and extend from −18 to 11 kV/m, with most of the values in the negative range. During snow events, 1-minute PG exhibited rapid fluctuations between high positive and high negative values, its frequency distribution extending from −10 to 18 kV/m, with peaks at −10 and 3 kV/m.

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