scholarly journals INCREASED WATER LEVELS DUE TO MORPHODYNAMIC CHANGES; THE LIMFJORD, DENMARK

2012 ◽  
Vol 1 (33) ◽  
pp. 49 ◽  
Author(s):  
Soeren Bjerre Knudsen ◽  
Signe M. Ingvardsen ◽  
Holger Toxvig Madsen ◽  
Carlo Sorensen ◽  
Bo Brahtz Christensen
Keyword(s):  
Water Level ◽  
Cross Section ◽  
North Sea ◽  
High Water ◽  
Water Levels ◽  
Channel Cross Section ◽  
Strongly Correlated ◽  
The North ◽  
Threefold Increase ◽  
The North Sea

The Limfjord is an estuary in Denmark between The North Sea and Kattegat. The Thyboroen Channel connects the fjord with The North Sea. The water levels in the western part of the Limfjord are strongly correlated with the water level in the sea at Thyboroen. Analyses revealed a close to threefold increase in the channel cross section over the last 100 years. This has led to a detailed investigation into the effects of the channel cross section on the extreme high water levels in the Limfjord now and in the future. For Lemvig in the western part of the Limfjord the water level with a return period of 100 years would have been 1.73 m with the 1958 channel bathymetry throughout the whole period and 1.99 m with the 2005 channel bathymetry. With the extrapolated 2060-bathymetry the 100 years water level will be 2.38 m. A number of measures to counteract the consequences of this development have been evaluated.

Linking weather types to tense dewatering situations of the Kiel Canal (NOK)

2020 ◽  
Author(s):  
Corinna Jensen ◽  
Jens Möller ◽  
Peter Löwe
Keyword(s):  
Sea Level Rise ◽  
Water Level ◽  
Sea Level ◽  
North Sea ◽  
Time Windows ◽  
Water Levels ◽  
Weather Types ◽  
The North ◽  
The North Sea ◽  
Kiel Canal

<p>Within the “Network of experts” of the German Federal Ministry of Transport and Digital Infrastructure (BMVI), the effect of climate change on infrastructure is investigated. One aspect of this project is the future dewatering situation of the Kiel Canal (“Nord-Ostsee-Kanal” (NOK)). The Kiel Canal is one of the world’s busiest man-made waterways navigable by seagoing ships. It connects the North Sea to the Baltic Sea and can save the ships hundreds of kilometers of distance. With a total annual sum of transferred cargo of up to 100 million tons it is an economically very important transportation way. Additionally to the transportation of cargo, the canal is also used to discharge water from smaller rivers as well as drainage of a catchments area of about 1500 km².</p><p>The canal can only operate in a certain water level range. If its water level exceeds the maximum level, the water must be drained into the sea. In 90% of the time, the water is drained into the North Sea during time windows with low tide. If the water level outside of the canal is too high, drainage is not possible and the canal traffic has to be reduced or, in extreme cases, shut down. Due to the expected sea level rise, the potential time windows for dewatering are decreasing in the future. With a decrease in operational hours, there will be substantial economic losses as well as an increase in traffic around Denmark.</p><p>To get a better understanding of what causes tense dewatering situations other than sea level rise a linkage between high water levels on the outside of the canal and weather types is made. Weather types describe large-scale circulation patterns and can therefore give an estimate on tracks of low-pressure systems as well as the prevailing winds, which can explain surges and water levels at the coast. This analysis is conducted for one weather type classification method based solely on sea level pressure fields. Weather types derived from regionally coupled climate models as well as reanalyses are investigated.</p>

Storm surge modelling in the North Sea-Baltic sea transition zone: model inter-comparison of static wind simulations

2020 ◽  
Author(s):  
Elin Andrée ◽  
Asger Bendix Hansen ◽  
Morten Andreas Dahl Larsen ◽  
Kristine Skovgaard Madsen ◽  
Martin Drews
Keyword(s):  
Baltic Sea ◽  
Water Level ◽  
Transition Zone ◽  
North Sea ◽  
Wind Direction ◽  
Water Levels ◽  
Wind Forcing ◽  
The North ◽  
The North Sea ◽  
Peak Value

<p>Extreme water levels in the micro-tidal transition zone between the North Sea and the semi-enclosed Baltic sea are predominantly determined by wind forcing associated with synoptic-scale weather systems. This connection between the two seas is partly blocked by low-lying islands, and the bathymetry comprises a complex mixture of narrow, deep channels and shallow sills. Coastlines in the Southern Kattegat and the Western Baltic Sea are therefore exposed to wind forcing from a large range of directions, and the extent of water build-up varies strongly between locations.</p><p>In the present study, we aim to determine the most critical wind direction for most of the Danish coastlines by employing numerical modelling experiments. The simulations are conducted with two different regional 3D ocean models to enable model inter-comparison. The DMI-HBM model implements a structured grid with fully dynamic 2-way nesting, while the MIKE 3 FM invokes an unstructured mesh. Both models have grid resolutions of ~0.5–1 km within the Danish Straits and 4–6 km in the offshore Baltic Sea. The models are forced by synthetic wind fields, where both wind speed and wind direction are maintained at fixed levels over the entire model domains. Pairs of model simulations are then obtained by varying the angle from which the wind is blowing.</p><p>From the model outputs, we describe the temporal evolution of the water level by the site-specific peak water level, and the time required for the response to reach its peak value. Our results show a steady rise of the water level up until the peak value. The peak water level significantly overshoots the final equilibrium water level, which develops further into the simulations. Our study facilitates a better understanding of the sea level's response to extreme and persistent winds in a region with highly complex geometry.</p>

Lake and inland dunes as interconnected Systems: The story of Lake Tresssee and an adjacent dune field (Schleswig-Holstein, North Germany)

The Holocene ◽  
2020 ◽  
pp. 095968362098168
Author(s):  
Christian Stolz ◽  
Magdalena Suchora ◽  
Irena A Pidek ◽  
Alexander Fülling
Keyword(s):  
Water Level ◽  
Bronze Age ◽  
Environmental Changes ◽  
High Water ◽  
Alluvial Fan ◽  
Water Levels ◽  
Lake Area ◽  
Dune Field ◽  
The North ◽  
Sand Drift

The specific aim of the study was to investigate how four adjacent geomorphological systems – a lake, a dune field, a small alluvial fan and a slope system – responded to the same impacts. Lake Tresssee is a shallow lake in the North of Germany (Schleswig-Holstein). During the Holocene, the lake’s water surface declined drastically, predominately as a consequence of human impact. The adjacent inland dune field shows several traces of former sand drift events. Using 30 new radiocarbon ages and the results of 16 OSL samples, this study aims to create a new timeline tracing the interaction between lake and dunes, as well, as how both the lake and the dunes reacted to environmental changes. The water level of the lake is presumed to have peaked during the period before the Younger Dryas (YD; start at 10.73 ka BC). After the Boreal period (OSL age 8050 ± 690 BC) the level must have undergone fluctuations triggered by climatic events and the first human influences. The last demonstrable high water level was during the Late Bronze Age (1003–844 cal. BC). The first to the 9th century AD saw slightly shrinking water levels, and more significant ones thereafter. In the 19th century, the lake area was artificially reduced to a minimum by the human population. In the dunes, a total of seven different phases of sand drift were demonstrated for the last 13,000 years. It is one of the most precisely dated inland-dune chronologies of Central Europe. The small alluvial fan took shape mainly between the 13th and 17th centuries AD. After 1700 cal. BC (Middle Bronze Age), and again during the sixth and seventh centuries AD, we find enhanced slope activity with the formation of Holocene colluvia.

What can idealized storm surge simulations tell us about worst case scenarios?

2021 ◽  
Author(s):  
Elin Andrée ◽  
Jian Su ◽  
Martin Drews ◽  
Morten Andreas Dahl Larsen ◽  
Asger Bendix Hansen ◽  
...  
Keyword(s):  
Wind Speed ◽  
Sea Level ◽  
North Sea ◽  
Wind Direction ◽  
Water Levels ◽  
Sea Levels ◽  
The North ◽  
The North Sea ◽  
Sea Coast ◽  
North Sea Coast

<p>The potential impacts of extreme sea level events are becoming more apparent to the public and policy makers alike. As the magnitude of these events are expected to increase due to climate change, and increased coastal urbanization results in ever increasing stakes in the coastal zones, the need for risk assessments is growing too.</p><p>The physical conditions that generate extreme sea levels are highly dependent on site specific conditions, such as bathymetry, tidal regime, wind fetch and the shape of the coastline. For a low-lying country like Denmark, which consists of a peninsula and islands that partition off the semi-enclosed Baltic Sea from the North Sea, a better understanding of how the local sea level responds to wind forcing is urgently called for.</p><p>We here present a map for Denmark that shows the most efficient wind directions for generating extreme sea levels, for a total of 70 locations distributed all over the country’s coastlines. The maps are produced by conducting simulations with a high resolution, 3D-ocean model, which is used for operational storm surge modelling at the Danish Meteorological Institute. We force the model with idealized wind fields that maintain a fixed wind speed and wind direction over the entire model domain. Simulations are conducted for one wind speed and one wind direction at a time, generating ensembles of a set of wind directions for a fixed wind speed, as well as a set of wind speeds for a fixed wind direction, respectively.</p><p>For each wind direction, we find that the maximum water level at a given location increases linearly with the wind speed, and the slope values show clear spatial patterns, for example distinguishing the Danish southern North Sea coast from the central or northern North Sea Coast. The slope values are highest along the southwestern North Sea coast, where the passage of North Atlantic low pressure systems over the shallow North Sea, as well as the large tidal range, result in a much larger range of variability than in the more sheltered Inner Danish Waters. However, in our simulations the large fetch of the Baltic Sea, in combination with the funneling effect of the Danish Straits, result in almost as high water levels as along the North Sea coast.</p><p>Although the wind forcing is completely synthetic with no spatial and temporal structure of a real storm, this idealized approach allows us to systematically investigate the sea level response at the boundaries of what is physically plausible. We evaluate the results from these simulations by comparison to peak water levels from a 58 year long, high resolution ocean hindcast, with promising agreement.</p>

scholarly journals An ensemble study of extreme storm surge related water levels in the North Sea in a changing climate

Ocean Science ◽  
2009 ◽  
Vol 5 (3) ◽  
pp. 369-378 ◽  
Author(s):  
A. Sterl ◽  
H. van den Brink ◽  
H. de Vries ◽  
R. Haarsma ◽  
E. van Meijgaard
Keyword(s):  
North Sea ◽  
Climate Model ◽  
Sea Water ◽  
Global Climate ◽  
Global Climate Model ◽  
Storm Surges ◽  
Water Levels ◽  
The North ◽  
Extreme Storm ◽  
The North Sea

Abstract. The height of storm surges is extremely important for a low-lying country like The Netherlands. By law, part of the coastal defence system has to withstand a water level that on average occurs only once every 10 000 years. The question then arises whether and how climate change affects the heights of extreme storm surges. Published research points to only small changes. However, due to the limited amount of data available results are usually limited to relatively frequent extremes like the annual 99%-ile. We here report on results from a 17-member ensemble of North Sea water levels spaning the period 1950–2100. It was created by forcing a surge model of the North Sea with meteorological output from a state-of-the-art global climate model which has been driven by greenhouse gas emissions following the SRES A1b scenario. The large ensemble size enables us to calculate 10 000 year return water levels with a low statistical uncertainty. In the one model used in this study, we find no statistically significant change in the 10 000 year return values of surge heights along the Dutch during the 21st century. Also a higher sea level resulting from global warming does not impact the height of the storm surges. As a side effect of our simulations we also obtain results on the interplay between surge and tide.

scholarly journals Storm Tilo over Europe in November 2007: storm surge and impacts on societal and energy infrastructure

2019 ◽  
Vol 49 ◽  
pp. 187-196 ◽  
Author(s):  
Anthony James Kettle
Keyword(s):  
Water Level ◽  
Storm Surge ◽  
North Sea ◽  
Tide Gauge ◽  
Winter Storms ◽  
Energy Infrastructure ◽  
The North ◽  
Short Period ◽  
Pressure Centre ◽  
The North Sea

Abstract. Storm Tilo on 8–9 November 2007 ranks among the serious winter storms in northern Europe over the past 30 years. Its low pressure centre passed across the northern North Sea, and this led to a cold air outbreak in northwest Europe. Strong north winds across the North Sea contributed to a high storm surge that was serious for coastal regions in eastern England, the Netherlands and Germany. Storm winds and unusually high waves caused shipping accidents and damage to some offshore energy infrastructure. This report presents an outline of the met-ocean conditions and a short overview of storm impacts on societal and energy infrastructure. The progress of the storm surge around the North Sea is analysed using data from the national tide gauge networks. A spectral analysis of the water level data is used to isolate the long period storm surge and short period oscillations (i.e., <4.8 h) from the tidal signal. The calculated skew surge is compared with literature reports for this storm and also with another serious North Sea storm from 31 October–1 November 2006 (Storm Britta). The short period oscillations are compared with the platform and shipping incident reports for the 2 d storm period. The results support previous reports of unusual wave and water level dynamics during some severe regional winter storms.

scholarly journals THE DUTCH PROGRAM OF INVESTIGATIONS ON STORM SURGES IN THE NORTH SEA

2011 ◽  
Vol 1 (5) ◽  
pp. 34
Author(s):  
J. B. Schijf
Keyword(s):  
The Netherlands ◽  
North Sea ◽  
Storm Surges ◽  
Water Levels ◽  
Wind Effects ◽  
Shallow Sea ◽  
The North ◽  
The North Sea ◽  
Western Germany ◽  
North Western

The North Sea is a shallow sea and therefore it is very sensitive to wind effects. As a result the water levels along the coasts are, in addition to the tidal oscillations subject to a considerable wind setup and exceptionally severe gales throughout history have been accompanied by inundations of the low-lying regions bordering the North Sea, in particular its southern part. No stretch of coast has suffered more than that belonging to the Netherlands and the adjacent parts of Belgium and North Western Germany. Several factors combine to bestow on us this doubtful privilege.

Model-based hydrodynamic leveling; a power full tool to enhance the quality of the geodetic networks

2020 ◽  
Author(s):  
Yosra Afrasteh ◽  
Cornelis Slobbe ◽  
Martin Verlaan ◽  
Martina Sacher ◽  
Roland Klees
Keyword(s):  
North Sea ◽  
Water Levels ◽  
Offshore Platforms ◽  
Tide Gauges ◽  
Data Set ◽  
Model Based ◽  
The North ◽  
Height System ◽  
The North Sea ◽  
The Impact

&lt;p&gt;Model-based hydrodynamic leveling is an efficient and flexible alternative method to connect islands and offshore tide gauges with the height system on land. The method uses a regional, high-resolution hydrodynamic model that provides total water levels. From the model, we obtain the differences in mean water level (MWL) between tide gauges at the mainland and at the islands or offshore platforms, respectively. Adding them to the MWL relative to the national height system at the mainland&amp;#8217;s tide gauges realizes a connection of the island and offshore platforms with the height system on the mainland. Usually, the geodetic leveling networks are based on spirit leveling. So, as we can not make the direct connections between coastal countries, due to the inability of the spirit leveling method to cross the water bodies, they are weak in these regions. In this study, we assessed the impact of using model-based hydrodynamic leveling connections among the North Sea countries on the quality at which the European Vertical Reference System can be realized. In doing so, we combined the model-based hydrodynamic leveling data with synthetic geopotential differences among the height markers of the Unified European Leveling Network (UELN) used to realize the European Vertical Reference Frame 2019. The uncertainties of the latter data set were provided by the BKG. The impact is assessed in terms of both precision and reliability. We will show that adding model-based hydrodynamic leveling connections lowers the standard deviations of the estimated heights in the North Sea countries significantly. In terms of reliability, no significant improvements are observed.&lt;/p&gt;

Transport and Water Quality Modelling in the Southern North Sea in Relation to Coastal Pollution Research and Control

1986 ◽  
Vol 18 (4-5) ◽  
pp. 245-256 ◽  
Author(s):  
J. A. van Pagee ◽  
H. Gerritsen ◽  
W P. M. de Ruijter
Keyword(s):  
Heavy Metals ◽  
Water Quality ◽  
Coastal Zone ◽  
North Sea ◽  
Water Levels ◽  
Coastal Pollution ◽  
The North ◽  
Pollution Research ◽  
The North Sea ◽  
And Control

Mathematical modelling techniques are used to quantify the transport in the southern part of the North Sea of pollutants originating from various inputs. Special attention was given to the anthropogenic increase in local concentrations of nutrients (N, P) and heavy metals (Cd, Hg, Cu, Pb, Zn, Cr) and their potential impact on marine organisms. A depth-averaged hydrodynamic model is used to calculate tidal and wind driven velocities and water levels. By averaging, residual flows are calculated, forming the basis for advective transports in a water quality model. Dispersive transports are derived from a comparison of simulated and observed salinity distributions. Water mass distributions and age functions for various inflowing water types are determined with the model. Transports of nutrients and heavy metals in the southern part of the North Sea are calculated using annual pollution inputs for 1980. Although interactions with bottom sediments are not considered, the calculated and measured concentrations show good similarities. The water quality in the Dutch coastal zone and German Bight area is shown to be highly determined by local pollution loads from the rivers Rhine, Weser and Elbe respectively. Comparison of simulated concentrations for 1980 with those resulting from simulations with estimated natural river inputs, shows that more than 50% of nutrients and heavy metal concentrations originate from human activities in large coastal zone areas. From toxicological information and standards, it is concluded that Cd, Hg and Cu are substances that need special attention in pollution research and control for the Dutch coastal waters.

Uncertainties and constraints on breaching and their implications for flood loss estimation

2005 ◽  
Vol 363 (1831) ◽  
pp. 1423-1430 ◽  
Author(s):  
Robert Muir Wood ◽  
William Bateman
Keyword(s):  
North Sea ◽  
Storm Surges ◽  
Maximum Size ◽  
Water Levels ◽  
The North ◽  
Sensitivity Tests ◽  
The North Sea ◽  
Pass Through ◽  
Inland Flooding ◽  
Crest Height

Around the coasts of the southern North Sea, flood risk is mediated everywhere by the performance of natural and man-made flood defences. Under the conditions of extreme surge with tide water levels, the performance of the defences determines the extent of inland flooding. Sensitivity tests reveal the enormous increase in the volume of water that can pass through a defence once breaching is initiated, with a 1 m reduction in sill elevation doubling the loss. Empirical observations of defence performance in major storm surges around the North Sea reveal some of the principal controls on breaching. For the same defence type, the maximum size and depth of a breach is a function of the integral of the hydraulic gradient across the defence, which is in turn determined by the elevation of the floodplain and the degree to which water can continue to flow inland away from the breach. The most extensive and lowest floodplains thereby ‘generate’ the largest breaches. For surges that approach the crest height, the weaker the protection of the defence, the greater the number of breaches. Defence reinforcement reduces both the number and size of the breaches.

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