scholarly journals Sediment budget and morphological development of the Dutch Wadden Sea: impact of accelerated sea-level rise and subsidence until 2100

2018 ◽  
Vol 97 (3) ◽  
pp. 183-214 ◽  
Author(s):  
Zheng Bing Wang ◽  
Edwin P.L. Elias ◽  
Ad J.F. van der Spek ◽  
Quirijn J. Lodder
Keyword(s):  
Sea Level ◽  
Wadden Sea ◽  
Barrier Islands ◽  
Tidal Flats ◽  
Morphological Development ◽  
Tidal Channels ◽  
The North ◽  
Tidal Basins ◽  
The North Sea

AbstractThe Wadden Sea is a unique coastal wetland containing an uninterrupted stretch of tidal flats that span a distance of nearly 500km along the North Sea coast from the Netherlands to Denmark. The development of this system is under pressure of climate change and especially the associated acceleration in sea-level rise (SLR). Sustainable management of the system to ensure safety against flooding of the hinterland, to protect the environmental value and to optimise the economic activities in the area requires predictions of the future morphological development.The Dutch Wadden Sea has been accreting by importing sediment from the ebb-tidal deltas and the North Sea coasts of the barrier islands. The average accretion rate since 1926 has been higher than that of the local relative SLR. The large sediment imports are predominantly caused by the damming of the Zuiderzee and Lauwerszee rather than due to response to this rise in sea level. The intertidal flats in all tidal basins increased in height to compensate for SLR.The barrier islands, the ebb-tidal deltas and the tidal basins that comprise tidal channels and flats together form a sediment-sharing system. The residual sediment transport between a tidal basin and its ebb-tidal delta through the tidal inlet is influenced by different processes and mechanisms. In the Dutch Wadden Sea, residual flow, tidal asymmetry and dispersion are dominant. The interaction between tidal channels and tidal flats is governed by both tides and waves. The height of the tidal flats is the result of the balance between sand supply by the tide and resuspension by waves.At present, long-term modelling for evaluating the effects of accelerated SLR mainly relies on aggregated models. These models are used to evaluate the maximum rates of sediment import into the tidal basins in the Dutch Wadden Sea. These maximum rates are compared to the combined scenarios of SLR and extraction-induced subsidence, in order to explore the future state of the Dutch Wadden Sea.For the near future, up to 2030, the effect of accelerated SLR will be limited and hardly noticeable. Over the long term, by the year 2100, the effect depends on the SLR scenarios. According to the low-end scenario, there will be hardly any effect due to SLR until 2100, whereas according to the high-end scenario the effect will be noticeable already in 2050.

scholarly journals Editorial

2018 ◽  
Vol 97 (3) ◽  
pp. 69-70
Author(s):  
Ad J.F. van der Spek ◽  
Niels van den Berg
Keyword(s):  
Salt Marshes ◽  
Wadden Sea ◽  
Barrier Islands ◽  
Natural Process ◽  
Tidal Channels ◽  
Ecological Value ◽  
The North ◽  
Wide Range ◽  
The North Sea ◽  
A Chain

The Wadden Sea region spans a distance of nearly 500km along the North Sea coast from the Netherlands to Denmark. It consists of a chain of barrier islands which shelter an area of extensive intertidal flats and salt marshes that are dissected by tidal channels and creeks. Moreover, several estuaries are part of this area which is known for its intriguing morphodynamics. The natural process of continuous erosion, transport and deposition of sediment shapes the morphology of the area, which has a high ecological value, especially the intertidal morphology that supports a wide range of wildlife.

Inter-annual and long-term mean sea level changes along the North Sea coastline

2013 ◽  
Vol 165 ◽  
pp. 1987-1992 ◽  
Author(s):  
Thomas Wahl ◽  
Ivan D. Haigh ◽  
Sönke Dangendorf ◽  
Jürgen Jensen
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Sea Level Changes ◽  
Mean Sea Level ◽  
The North ◽  
The North Sea

scholarly journals EXTREME LEVELS ARISING FROM METEOROLOGICAL SURGES

1974 ◽  
Vol 1 (14) ◽  
pp. 1 ◽  
Author(s):  
P. Ackers ◽  
T.D. Ruxton
Keyword(s):  
Sea Level ◽  
North Sea ◽  
High Tide ◽  
Water Levels ◽  
Return Periods ◽  
The North ◽  
Extreme Water Levels ◽  
Independent Events ◽  
The North Sea

The design of coastal works depends on estimating the probabilities of extreme water levels, as well as of waves Previous studies of surge-affected levels have extrapolated observed annual maxima or the n highest levels in n years to predict rarer events In addition to using these well-established methods, m this study of tide levels on the Essex coast of Britain a long term record of extreme levels was synthesised by adding surge residuals at the time of predicted HW to predicted HW levels, treating them as statistically independent events Many more large surge residuals have been measured than extreme water levels as many surges are associated with small tides Events with return periods up to 1000 years may be estimated without extrapolating beyond the range of observed surge residuals and predicted tides This method is assessed in relation to previous methods and information relevant to the design of coastal works in the south western part of the North Sea was obtained In addition to forecasting the probabilities of high tide levels, the study included wave forecasts and the encounter probabilities of combinations of sea level and wave height for various aspects of coastal developments.

scholarly journals The long-term variability of extreme sea levels in the German Bight

2019 ◽  
Author(s):  
Andreas Lang ◽  
Uwe Mikolajewicz
Keyword(s):  
Sea Level ◽  
North Sea ◽  
German Bight ◽  
Large Scale ◽  
Climate System ◽  
Tide Gauge Record ◽  
Sea Levels ◽  
The North ◽  
The North Sea

Abstract. We investigate the long-term variability of extreme high sea levels (ESL) in the southern German Bight and associated large-scale forcing mechanisms in the climate system using simulations covering the last 1000 years. To this end, global MPI-ESM simulations from the PMIP3 past1000 project are dynamically scaled-down with a regionally coupled climate system model focusing on the North Sea. We find that the statistics of simulated ESL compare well with observations from the tide gauge record at Cuxhaven but show large variations on interannual to centennial timescales. ESL arise independent of preferred systematic oscillations and are to a large extent decoupled from variations of the background sea level (BSL). Large scale circulation regimes associated with periods of high ESL are regionally consistent and similar to those associated with elevated BSL, but the location of the respective centers of action of the governing sea level pressure (SLP) dipole differs. While BSL variations correlate well with the wintertime North Atlantic Oscillation (NAO), ESL variations are rather associated with a dipole between northeastern Scandinavia and the Gulf of Biscay, leading to a stronger local north-westerly wind component in the North Sea. Potential links with solar or volcanic forcing are masked due to the high ESL variability. The high internal variability stresses the irreducible uncertainties related to traditional extreme value estimates based on shorter subsets which fail to account for long-term variations. Existing estimates of future changes in ESL may be dominated by natural variability rather than climate change signals, thus requiring larger ensemble simulations to assess future flood risks.

scholarly journals Projected Responses of Tidal Dynamics in the North Sea to Sea-Level Rise and Morphological Changes in the Wadden Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Christian Jordan ◽  
Jan Visscher ◽  
Torsten Schlurmann
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
North Sea ◽  
Wadden Sea ◽  
Morphological Changes ◽  
Vertical Accretion ◽  
Tidal Dynamics ◽  
Intertidal Flats ◽  
The North ◽  
The North Sea

This study explores the projected responses of tidal dynamics in the North Sea induced by the interplay between plausible projections of sea-level rise (SLR) and morphological changes in the Wadden Sea. This is done in order to gain insight into the casual relationships between physical drivers and hydro-morphodynamic processes. To achieve this goal, a hydronumerical model of the northwest European shelf seas (NWES) was set-up and validated. By implementing a plausible set of projections for global SLR (SLRRCP8.5 of 0.8 m and SLRhigh−end of 2.0 m) by the end of this century and beyond, the model was run to assess the responses of the regional tidal dynamics. In addition, for each considered SLR, various projections for cumulative rates of vertical accretion were applied to the intertidal flats in the Wadden Sea (ranging from 0 to 100% of projected SLR). Independent of the rate of vertical accretion, the spatial pattern of M2 amplitude changes remains relatively stable throughout most of the model domain for a SLR of 0.8 m. However, the model shows a substantial sensitivity toward the different rates of vertical accretion along the coasts of the Wadden Sea, but also in remote regions like the Skagerrak. If no vertical accretion is assumed in the intertidal flats of the Wadden Sea, the German Bight and the Danish west coast are subject to decreases in M2 amplitudes. In contrast, those regions experience increases in M2 amplitudes if the local intertidal flats are able to keep up with the projected SLR of 0.8 m. Between the different scenarios, the North Frisian Wadden Sea shows the largest differences in M2 amplitudes, locally varying by up to 14 cm. For a SLR of 2.0 m, the M2 amplitude changes are even more amplified. Again, the differences between the various rates of vertical accretion are largest in the North Frisian Wadden Sea (> 20 cm). The local distortion of the tidal wave is also significantly different between the scenarios. In the case of no vertical accretion, tidal asymmetry in the German estuaries increases, leading to a potentially enhanced sediment import. The presented results have strong implications for local coastal protection strategies and navigation in adjacent estuaries.

scholarly journals Interconnected Accommodation Space Controls Between Sand-Charged Shallow Tidal Channels and Wind-Wave Truncated Tidal Flats During Latest-Holocene Sea Level Rise (~3.0 m) in a Large Mesotidal Wave-Dominated Estuary, Grays Harbor, Washington, USA

2018 ◽  
Vol 10 (3) ◽  
pp. 26 ◽  
Author(s):  
Curt D Peterson ◽  
Sandy Vanderburgh
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tidal Flat ◽  
Wind Wave ◽  
Tidal Flats ◽  
Tidal Channel ◽  
Tidal Channels ◽  
Accommodation Space ◽  
Global Sea Level

The late-Holocene (5–0 ka) record of accommodation space controls of tidal channel and tidal flat deposition in the shallow mesotidal wave-dominated Grays Harbor estuary (236 km2 surface area) was investigated in previously reported drill cores (n=15) and new vibracores (n=20), reaching 3–10 m depth subsurface. Continuous vibracore facies sequences (3–4 m depth subsurface) discriminate between tidal channel and tidal flat deposition and demonstrate responses of both depositional settings to interseismic uplift and coseismic subsidence (1±0.5 m vertical) from cyclic neotectonic forcing (200–800 yr recurrence intervals) in the Cascadia subduction zone. Vibracore channel samples, at 0.5 m or 1.0 m depth intervals, were analyzed for sediment grain size (sample n=124) and sand source mineralogy (sample n=67). The mean and standard deviation of sand size in the sand fraction is 175±x34 1σ µm. Sediment 14C dates (n=29) range from 376 to 6,579 median calyrBP and establish long-term sedimentation rates in subtidal channel accretionary banks (average 4.2 m ka-1), intertidal channel accretionary banks (average 3.7 m ka-1), and tidal flats (average 1.1 m ka-1). Tidal channel accretionary bank deposition largely reflects reworking of pre-existing estuary deposits. Long-term total basin sediment accumulation rates (232x106 m3 ka-1) are tied to rates of net sea level rise (1.0 m ka-1) or increasing basin accommodation space. In latest Holocene time (3–0 ka) littoral sand import (117x106 m3 ka-1) was about twice as large as the retention of river sand and mud in the estuary. The selective export of winnowed mud from the estuary provided the necessary accommodation space for the import of littoral sand in latest-Holocene time. Shallow intertidal settings in Grays Harbor (60% by surface area) are maintained by self-regulating conditions of channelized sediment import, wind-wave erosion of tidal flats, and tidal prism forcing of tidal channel discharge. Hind-casted wind-wave bottom orbital velocities (>20 cm sec-1) are sufficient to truncate tidal flat elevations to lower-intertidal levels, which maintain substantial tidal prism volumes (modern MLLW-MHHW ~6.1 x 108 m3) and associated tidal channel discharge in the shallow estuary. Net sediment deposition in the estuary is controlled by the interaction of limiting accommodation space controls in the tidal flats and tidal channels. The balance between sediment supply, energy of sediment transport/resuspension, and sediment export has survived small changes in relative sea level (1±0.5 m) from cyclic neotectonic forcing. However, the prehistoric (natural) balance could be altered by future anthropogenic impacts from sustained global sea level rise (> 1.5 m during the next century) or diminished wind-wave fetch distances, which could result from tidal flat diking/filling or uncontrolled spread of non-native invasive stabilizing sea grass (Spartina). In this regard, the susceptibilities of prehistorically-balanced sediment dynamics in Grays Harbor serve as warning for other similar mesotidal wave-dominated estuaries that could be impacted by future global sea level rise, changing sediment inputs, and/or tidal flat diking/filling, which could reduce intertidal habitat and associated ecosystem functions. 

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