The storm surge event that affected the coastal margins of the southern North Sea on 5-6 December 2013 produced the highest still water levels on record at several tide gauges on the UK east coast. On east-facing coasts south of the Humber estuary and north-facing Norfolk, water levels were higher than in the twentieth century benchmark surge event of 31 January-1 February 1953. Maximum significant wave heights were highest off the North Norfolk coast (peak H s = 3.8 m offshore, 2.9 m inshore) and lowest off the Suffolk coast (H s = 1.5-1.8 m inshore); comparable offshore wave heights in 1953 were 7-8 m and ca. 3 m. The lower wave heights, and their short duration, in 2013 explain both localised breaching, overtopping, and back-barrier flooding associated with gravel ridges and relatively low earthen banks as well as the lack of failure in more highly-engineered coastal defences. On barrier coasts and within estuaries, the signal of maximum runup was highly variable, reflecting the modification of the tide-surge-wave signal by inshore bathymetry and the presence of a range of coastal ecosystems. The landscape impacts of the December 2013 surge included the notching of soft rock cliffs and cliffline retreat; erosion of coastal dunes; and the augmentation or re-activation of barrier island washover deposits. Whilst surge event-related cliff retreat on the rapidly eroding cliffs of the Suffolk coast lay within the natural variability in inter-annual rates of retreat, the impact of the surge on upper beach/sand dune margins produced a pulse of shoreline translation landwards equivalent to about 10 years of 'normal' shoreline retreat. The study of east coast surges over the last 60 years, and the identification of significant phases of landscape change -such as periods of rapid soft rock cliff retreat and the formation of new gravel washovers on barrier islands -points to the importance of high water levels being accompanied by high wave activity. Future developments in early warning systems and evacuation planning require information on the variable impacts of such extreme events.
The three-dimensional structure of salt marsh plant canopies, amongst other marsh surface characteristics, is of critical importance to the functioning and persistence of coastal salt marshes. Together with plant flexibility it controls the contribution of vegetation to the tidal flow and wave energy dissipation potential of marshes. However detailed information on these two key biophysical properties of salt marsh canopies is scarce. In this paper we present biophysical properties of four plants commonly occurring in NW European salt marshes. We measured stem flexibility, diameter and height of the grasses Spartina anglica, Puccinellia maritima and Elymus athericus and above ground biomass and canopy height in stands of Elymus athericus and the dwarf shrub Atriplex portulacoides. Further we compared the performance of two methods for the non-destructive assessment of above ground biomass, such that they may be used during field assessments of marsh surface vegetation structure (i) Measurement of light availability within the canopy and (ii) side-on photography of vegetation. All data were collected on a salt marsh on the Dengie Peninsula, eastern England, UK, in summer (July). We found significant differences in stem flexibility both between species and between the different parts of their stems. P. maritima was found to be the species with the most flexible stems, and, as a result of their relatively large stem diameter, S. anglica the species with the stiffest stems. Above ground biomass and hence potential canopy resistance to water flow could be estimated more accurately by side-on photography of vegetation than from measurement of light availability within the canopy. Our results extend the existing knowledge base on plant properties with relevance to studies of habitat structure and ecosystem functioning as well as wave energy dissipation in salt marsh environments and can be used for the development of a more realistic representation of vegetation in numerical models and laboratory flume studies of plant-flow interactions. Highlights Paper reports quantitative data on plant flexibility and above ground biomass (a proxy for vegetation structure), in salt marsh canopies. Both these biophysical properties of salt marsh canopies need to feed into flow and wave dissipation models, if the predictive capacity of such models is to be improved. Stem flexibility of salt marsh plants differs significantly both between different species and between the different stem parts of specimens of one species. Side-on photography of vegetation is an appropriate technique for non-destructive assessment of above ground biomass and vegetation structure in structurally complex salt marsh canopies. Above ground biomass and its vertical distribution within the canopy can be estimated more accurately by side-on photography than by measurement of light availability in the canopy.
Bed level dynamics at the interface of the salt marsh and tidal flat have been highlighted as a key factor connecting the long‐term biogeomorphological development of the marsh to large‐scale physical forcing. Hence, we aim to obtain insight into the factors confining the location of the marsh edge (i.e., boundary between tidal flat and salt marsh). A unique data set was collected, containing measurements of daily bed level changes (i.e., integrative result of physical forcing and sediment properties) at six intertidal transects in the North Sea area. Moreover, various biophysical parameters were measured, such as sediment characteristics, waves, inundation time, and chlorophyll‐a levels. The data show that both bed level change and waves decreased from the lower intertidal flat toward the marsh edge and further diminished inside the marsh. However, no direct general relation was found between waves and bed level change. Bed level change inside the marsh was always small, regardless of wave energy. By combining the data sets, we demonstrate that the location of the lower marsh edge is restricted by two interacting factors: inundation time and bed level change. For vegetation establishment to withstand longer inundation stress, which slows down plant growth, more stable bed levels are required so that plants are not heavily disturbed. Conversely, to withstand more dynamic bed levels that disturbs plant growth, lower inundation stress is needed, so that plants grow fast enough to recover from the stress. The results suggest that bed level change is important in determining the position of the marsh edge.
Working across U.S. federal agencies, international agencies, and multiple worldwide data centers, and spanning seven international network organizations, the Earth System Grid Federation (ESGF) allows users to access, analyze, and visualize data using a globally federated collection of networks, computers, and software. Its architecture employs a system of geographically distributed peer nodes that are independently administered yet united by common federation protocols and application programming interfaces (APIs). The full ESGF infrastructure has now been adopted by multiple Earth science projects and allows access to petabytes of geophysical data, including the Coupled Model Intercomparison Project (CMIP)—output used by the Intergovernmental Panel on Climate Change assessment reports. Data served by ESGF not only include model output (i.e., CMIP simulation runs) but also include observational data from satellites and instruments, reanalyses, and generated images. Metadata summarize basic information about the data for fast and easy data discovery.
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