scholarly journals Maker Buoy Variants for Water Level Monitoring and Tracking Drifting Objects in Remote Areas of Greenland

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1254
Author(s):  
Daniel F. Carlson ◽  
Wayne J. Pavalko ◽  
Dorthe Petersen ◽  
Martin Olsen ◽  
Andreas E. Hass
Keyword(s):  
Open Source ◽  
Water Level ◽  
Low Cost ◽  
Management Strategies ◽  
Greenland Ice Sheet ◽  
Water Levels ◽  
Glacial Lake ◽  
Remote Areas ◽  
The North ◽  
Meltwater Runoff

Meltwater runoff from the Greenland Ice Sheet changes water levels in glacial lakes and can lead to glacial lake outburst flooding (GLOF) events that threaten lives and property. Icebergs produced at Greenland’s marine terminating glaciers drift into Baffin Bay and the North Atlantic, where they can threaten shipping and offshore installations. Thus, monitoring glacial lake water levels and the drift of icebergs can enhance safety and aid in the scientific studies of glacial hydrology and iceberg-ocean interactions. The Maker Buoy was originally designed as a low-cost and open source sensor to monitor surface ocean currents. The open source framework, low-cost components, rugged construction and affordable satellite data transmission capabilities make it easy to customize for environmental monitoring in remote areas and under harsh conditions. Here, we present two such Maker Buoy variants that were developed to monitor water level in an ice-infested glacial lake in southern Greenland and to track drifting icebergs and moorings in the Vaigat Strait (Northwest Greenland). We describe the construction of each design variant, methods to access data in the field without an internet connection, and deployments in Greenland in summer 2019. The successful deployments of each Maker Buoy variant suggest that they may also be useful in operational iceberg management strategies and in GLOF monitoring programs.

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.

3D hydro-morphodynamic models as support tools for obtaining sustainable sediment management strategies of reservoirs

2020 ◽  
Author(s):  
Kilian Mouris ◽  
Leon Saam ◽  
Felix Beckers ◽  
Silke Wieprecht ◽  
Stefan Haun
Keyword(s):  
Sediment Transport ◽  
Water Level ◽  
Management Strategies ◽  
Sediment Management ◽  
Transport Processes ◽  
Water Levels ◽  
Hydraulic Structures ◽  
Suspended Sediment Transport ◽  
Reservoir Sedimentation ◽  
Bottom Outlets

<p>Reservoir sedimentation reduces not only the available storage volume of reservoirs, but may also create other serious problems, such as an increase of bed levels or accumulations of nutrients and contaminants, which affect the environment. An increase in bed levels at the head of the reservoir can reduce flood safety and increase the risk for the surrounding areas. Deposited sediments close to the dam may block hydraulic structures, such as the bottom outlets, or, in case they enter the intake, lead to possible abrasion of plant components (e.g. wear of turbines and pipes).</p><p>Prior to reservoir construction, a pre-evaluation of the sediment yield from the catchment is usually performed by using soil erosion and sediment delivery models. However, the trapping efficiency is often only obtained by empirical approaches, such as Brune’s or Churchill’s curve, which are based on the capacity of the reservoir and the mean annual inflow. This is still common practice, although 3D hydro-morphodynamic models became powerful tools to numerically study sediment transport and reservoir sedimentation prior to the construction of reservoirs as well as during its operation.</p><p>Within this study, a fully 3D hydro-morphodynamic numerical model, based on the Reynolds-averaged Navier-Stokes equations, is applied to a case study to simulate, on the one hand suspended sediment transport within a hydropower reservoir and on the other hand a reservoir flushing operation as potential management scenario, with the goal to remobilize already deposited sediments and to release these sediments from the reservoir. The modeled reservoir has a total storage capacity of around 14 million m³, whereby the water level can fluctuate due to pumped-storage operation by 40.5 m (difference between the maximum operation level and the operational outlet). At the head is the natural inflow of two creeks into the reservoir and a lateral transition tunnel is located on the orographic right side, which collects several headwater streams from adjacent catchments.</p><p>Simulations are performed for different operation modes of the reservoir. The results clearly show that through active reservoir management (variation of water levels as well as using the momentum of the discharge from the transition tunnel) the sediment motion in the reservoir can be affected to a certain extent. It is for instance possible to almost completely avoid reservoir sedimentation in front of the dam and the hydraulic structures (water intake and bottom outlets) during sediment-laden flows when simultaneously high discharges are provided from the laterally located transition tunnel. The conducted simulation results of reservoir flushing also show that the success of the flushing operation is strongly dependent on the water level. As expected, flushing with full drawdown of the water level is the most efficient method to release sediments.</p><p>Through the detailed results of the 3D hydro-morphodynamic model, it is feasible to receive a deeper knowledge of the ongoing sediment transport processes within the studied reservoir. The gained knowledge can further be used to derive sustainable and efficient management strategies for the sediment management of the reservoir.</p>

Precise ground-based GNSS-reflectometry water level measurements using multiple low-cost antennas

2020 ◽  
Author(s):  
David Purnell ◽  
Natalya Gomez ◽  
William Minarik ◽  
Gregory Langston
Keyword(s):  
Water Level ◽  
Low Cost ◽  
Multiple Antennas ◽  
Random Noise ◽  
Water Levels ◽  
Tropospheric Delay ◽  
Sources Of Error ◽  
Gnss Reflectometry ◽  
Water Level Measurements ◽  
Level Sensors

<p>GNSS-Reflectometry (GNSS-R) is a promising new technique to monitor water levels due to easier and cheaper installation of instruments in remote environments compared to traditional acoustic sensors or pressure gauges. GNSS stations that have been used for reflectometry purposes thus far are designed for monitoring land motion and may cost more than 10,000 USD each. We have found that a low-cost GNSS antenna and receiver (10 USD) can be used to make equally precise water level measurements, with an RMSE of a few centimeters when compared to a collocated acoustic sensor. However, an RMSE of less than one centimeter is typical for water level sensors and this level of accuracy is desired for research purposes. Two of the dominant sources of error in GNSS-R measurements are the effects of random noise in the Signal-to-Noise Ratio (SNR) data and tropospheric delay. Modelling work suggests that these sources of error can be reduced by using multiple low-cost antennas in the same location. In light of this, we have installed an experimental setup of antennas at various locations along the Saint Lawrence River and Initial results show that multiple antennas can be used to provide more precise measurements than a single antenna. Our installations of multiple antennas are less than 5% of the cost of stations that have been used in previous GNSS-R literature. Hence this approach could be applied to install a dense network of water level sensors along rivers, lakes or coastlines at a relatively low cost. We expect that this approach could also be applied to GNSS-R soil moisture or snow depth measurements.</p>

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>

Low-cost river discharge measurements using a transparent velocity-head rod

2020 ◽  
Author(s):  
Aurélien Despax ◽  
Jérôme Le Coz ◽  
Francis Pernot ◽  
Alexis Buffet ◽  
Céline Berni
Keyword(s):  
Water Level ◽  
Low Cost ◽  
Electrical Contact ◽  
Field Tests ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Velocity Head ◽  
Low Velocity ◽  
Average Deviation ◽  
The Difference

<p>The common streamgauging methods (ADCP, current-meter or tracer dilution) generally require expensive equipment, with the notable exception of volumetric gaugings and floats, which are however often difficult to implement and limited to specific conditions. The following work aims at testing and validating a reliable, easy-to-deploy and low-cost gauging method, at a cost typically below 40 € each.<br><br>The “velocity-head rod” firstly described by Wilm and Storey (1944), made transparent by Fonstad et al. (2005) and improved by Pike et al. (2016) meets these objectives, for wading gauging with velocities greater than 20 cm/s typically. The 9.85 cm wide clear plastic rod is placed vertically across the stream to identify upstream and downstream water levels using adjustable rulers. The difference in level (or velocity head) makes it possible to calculate the average velocity over the vertical, using a semi-empirical calibration relationship.<br><br>Experiments carried out in INRAE’s hydraulic laboratory and in the field have enabled us to find a calibration relationship similar to that proposed by Pike et al. (2016) and confirm the optimal conditions of use. The average deviation to a reference discharge has been found to be close to 5 % except for very slow-flow conditions. The influence of the width of the rod on the velocity-head was studied in the laboratory. The uncertainty of the velocity due to the reading of water levels has been estimated. It increases at low velocity due to decreasing sensitivity, and increases at high velocities due to water level fluctuations that are difficult to average.<br><br>Several improvements were tested in order to facilitate and improve the measurement operations, without increasing the cost too much: magnetic ruler, removal of a graduated steel rule (expensive), plastic ruler with water level and velocity graduations, reading the depth with another ruler, spirit level, electrical contact (so the operator has not to bend to the surface of the water). An operational procedure and a spreadsheet for computing discharge are proposed. The method being extremely simple and quick to apply is well suited for rapid estimates of flow (instead of floats), training or demonstrations, citizen science programs or cooperation with services with limited resources.</p><p>Acknowledgments<strong>: </strong>The authors thank Q. Morice, J. Cousseau, Y. Longefay (DREAL) who were involved in this study by carrying out field tests.</p>

scholarly journals Pembangunan Sistem Pengukuran Muka Air Otomatis (Automatic Water Level Recorder) Berbasis Gelombang Akustik Untuk Pengamatan Pasang Surut Laut

2019 ◽  
Vol 2019 (1) ◽  
Author(s):  
Agung Pandi Nugroho ◽  
Nirmawana Simarmata ◽  
Irdam Adil
Keyword(s):  
Open Source ◽  
Water Level ◽  
Acoustic Waves ◽  
Lower Cost ◽  
Water Levels ◽  
Tide Gauges ◽  
Field Scale ◽  
Hardware System ◽  
Level Recorder ◽  
Water Level Recorder

AbstrakPasang surut adalah fenomena naik turunnya muka air. Pasut dapat diukur dengan berbagai macam metode, baik manual maupu otomatis. Pengukuran otomatis dengan menggunakan alat pengukur pasut, khususnya untuk pengukuran jangka panjang dinilai relatif lebih berbiaya rendah dibandingkan dengan pengukuran manual, akan tetapi alat pengukur pasut otomatis hampir semuanya memiliki harga yang relatif mahal sehingga diperlukan peralatan yang lebih terjangkau dan andal. Pengembangan sistem automatic water level recorder (AWLR) berbasis gelombang akustik dilakukan dengan membangun dan merancang sistem perangkat lunak maupun perangkat keras alat dengan berbasiskan perangkat open source Arduino. Alat yang dihasilkan dapat mengukur dengan baik di skala laboratorium maupun lapangan. Pengukuran skala lapangan menunjukkan RMSE 36,6 cm di daerah terpencil dan RMSE 11 cm untuk daerah yang memungkinkan alat dipasang dengan stabil.Kata Kunci : AWLR, pengukur pasut otomatis, skala lapangan, skala laboratorium.AbstractTides were phenomenon of  rising water levels. Tides could be measured by various methods, manual or automatic way. Measurements using automatic tide gauges, especially for long-term measurements, usually needed lower cost compared to manual ones, but in facts automatic tide gauges were relatively more expensive prices, so it was worthy to develop the reliable equipment with lower cost. This automatic water level recorder (AWLR) system using acoustic waves was developed by building and designing a software and hardware system based on an open source device named Arduino. The builded equipment had could reached well level in scales, laboratory or field scales. Field scale measurements showed that RMSE in outlying areas reached 36.6 centimeters and could be better for areas where tide gauges could be installed stably (11 centimeters).Keywords: AWLR, automatic tide gauges, field scale, laboratory scale

Detecting coastal change around the North Sea from open-source satellite images

2021 ◽  
Author(s):  
Freya Fenwick ◽  
Timothy Price ◽  
Gerben Ruessink
Keyword(s):  
Open Source ◽  
Satellite Imagery ◽  
North Sea ◽  
Morphological Evolution ◽  
Google Earth ◽  
Water Levels ◽  
The North ◽  
The North Sea ◽  
Google Earth Engine ◽  
Wave Conditions

<p>Wave-dominated sandy coastlines worldwide are susceptible to change under the expected climate-change induced developments in sea level rise, mean wave conditions and storm events. For coastal management it remains important to observe and quantify these coastal changes, especially in low-lying developed coastal areas susceptible to flooding. The beaches surrounding an ocean basin have a variety of orientations, tidal ranges and management strategies, to name a few, which will lead to a range of morphological responses to future changes in hydrodynamic conditions within the basin. In addition, the conditions under which these varied responses mainly occur (e.g., under regular conditions or only during storm conditions) is not clear. Here, we used satellite imagery to compare the morphological response of a selection of beaches surrounding the North Sea.</p><p>The position of the shoreline is generally considered as a key variable to monitor the morphological evolution of sandy coasts. This research used the open-source software toolkit CoastSat (Vos et al., 2019) to automatically map shorelines from publicly available satellite imagery from 1984 to present, which are retrieved via Google Earth Engine (Gorelick et al., 2017). We selected five long, sandy beaches around the North Sea with varying tidal ranges, orientations and wave exposure for our analysis: (1) Skallingen in Denmark, (2) Egmond aan Zee and (3) the barrier island of Schiermonnikoog, both in the Netherlands, (4) Groenendijk in Belgium, and (5), Theddlethorpe in the UK. Approximately 2000 images per site were used for the shoreline extraction. Offshore wave buoy measurements and numerical model output provided the tidal water levels and wave conditions for the different sites. To account for tidal correction of the shoreline to a reference elevation, we used the dataset of Athanasiou et al. (2019) to estimate characteristic beach face slopes. At the conference we will present our analysis of the shoreline responses around the North Sea over the last few decades.</p><p>Athanasiou, P., Van Dongeren, A., Giardino, A., Vousdoukas, M., Gaytan-Aguilar, S., & Ranasinghe, R. (2019). Global distribution of nearshore slopes with implications for coastal retreat. Earth system science data, 11(4).</p><p>Gorelick, N., Hancher, M., Dixon, M., Ilyushchenko, S., Thau, D., & Moore, R. (2017). Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote sensing of Environment, 202, 18-27.</p><p>Vos, K., Splinter, K. D., Harley, M. D., Simmons, J. A., & Turner, I. L. (2019). CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery. Environmental Modelling & Software, 122, 104528.</p>

scholarly journals Very severe storm tides in the German Bight (North Sea) and their potential for enhancement

2019 ◽  
Author(s):  
Iris Grabemann ◽  
Lidia Gaslikova ◽  
Tabea Brodhagen ◽  
Elisabeth Rudolph
Keyword(s):  
Sea Level Rise ◽  
Water Level ◽  
Sea Level ◽  
North Sea ◽  
German Bight ◽  
Water Levels ◽  
Atmospheric Conditions ◽  
Ems Estuary ◽  
Data Set ◽  
The North

Abstract. Storm tides are an essential hazard for the German North Sea coasts. For coastal protection and economic activities, planning information on probability and magnitude of extreme storm tides and their possible future changes is important. This study focuses on the most extreme events and examines whether they could have become more severe under slightly different conditions still remaining within the physical plausibility. In the face of limited amount of observational data on very severe events, an extensive set of model data is used to extract most extreme storm tide events for locations in the German Bight, in particular Borkum and the Ems estuary. The data set includes water levels and respective atmospheric conditions from a hindcast and future climate realizations without sea level rise describing today's and possible future conditions. A number of very severe events with water levels exceeding those measured near Borkum since 1906 has been identified in the data set. A possible further amplification of the highest events is investigated by simulating these events for the North Sea with different phase lags between the astronomical tide given at the open model boundaries and the wind forcing. It was found that superposition of spring tide conditions, different timing of the astronomical high water and atmospheric conditions during the highest storm event would cause an enhancement of the highest water level up to about 50 cm. The amplified water levels of the two highest events from the data set are used to analyse the effects in the Ems estuary using a high-resolution model of the German Bight. Additionally, the influence of an extreme river runoff and of sea level rise is studied. The extreme river runoff of 1200 m3 s−1 increases the highest water levels by several decimeters in the narrow upstream part of the Ems estuary. This effect diminishes downstream. The sea level rise increases the water level in the downstream part of the Ems estuary by the amount applied at the model boundary to the North Sea. In the upstream part, its influence on the water level decreases. This study may serve as a first step towards an impact assessment for severe storm tides and their implications for coastal areas and activities.

scholarly journals PIONEER: open wireless sensor network for smart environmental monitoring of remote areas

2020 ◽  
Author(s):  
Federico Dallo ◽  
Daniele Zannoni ◽  
Fabrizio de Blasi ◽  
Jacopo Gabrieli ◽  
Carlo Barbante ◽  
...  
Keyword(s):  
Climate Change ◽  
Wireless Sensor Network ◽  
Open Source ◽  
Human Health ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Crucial Role ◽  
Low Cost ◽  
Wireless Sensor ◽  
Remote Areas

<p>Atmospheric observatories in the remote areas represent the primary infrastructure for the state-of-the-art meteorological and climate research and play a crucial role in Climate Change comprehension. However, the World Meteorological Organization Global Atmosphere Watch (WMO-GAW) states in their 2018 final report that “the fate of the next generation of monitoring stations will be dramatically modified by the breakthroughs of new low-cost sensor (LCS) technologies.”. The development and improvement of low-cost technologies are proving notable applications and today LCSs are already playing a crucial role in fields such as model or emission validation and spatial variability of pollution[1]. Upcoming earth observation programmes, applications, services and support in citizen inclusion in earth monitoring are pushing the European Union (EU) in funding R&D to assess low-cost technologies, thus making the introduction of basic and applied research imperative.<br>PIONEER* aims at establishing a low-cost wireless sensor network (LCS-WSN) for the study of transboundary transport phenomena of air pollutants. Given its highly relevance for the Earth climate, ecosystems, and human health, primary endeavor will be directed towards the study of tropospheric ozone to obtain quantitative, reproducible in-situ measurements. Tropospheric ozone is one of the most important atmospheric gases involved in photochemical reactions[2], it plays a central role in the radiative budget of the atmosphere and it is the third greenhouse gas in the troposphere[3]. Also, surface ozone is a dangerous secondary pollutant causing harm to human health and ecosystems[4]. Since the troposphere is a very complex system the goal is to develop and deploy a reliable LCS-WSN, along the trail Munich-Venice, to be used by scientists as well as citizen engineers in remote areas, where the needs of reliable dense spatial data to model the transport phenomena and Climate Change effects is decisive. <br>PIONEER will exploit the existing open source technologies and commercial low-cost sensors to provide a LCS-WSN systems for long term climate data collection, a cloud-assisted database for time series collection and management, a web portal for uploading, displaying, performing statistical analysis and downloading records and metadata in a fully open access fashion, a comprehensive open source repository with tools, guidelines and application developed. The software will be open-source and released under copyleft license, thus allowing the complete reproducibility of all the developed devices and tools. </p><p>*Individual Global Fellowships granted by the Research Executive Agency. <br>Grant Agreement number: 844526 — PIONEER — H2020-MSCA-IF-2018</p><p>[1] Lewis, Alastair, W. Richard Peltier, and Erika von Schneidemesser. "Low-cost sensors for the measurement of atmospheric composition: overview of topic and future applications." (2018).</p><p>[2] Crutzen, P.J., Lawrence, M.G., Poschl, U.,“On the background photochemistry of tropospheric ozone”, Tellus AB 51, 123–146 (1999).</p><p>[3] Forster, Piers, et al. "Changes in atmospheric constituents and in radiative forcing. Chapter 2." Climate Change 2007. The Physical Science Basis. 2007.</p><p>[4] Cooper, Owen R., et al. "Global distribution and trends of tropospheric ozone: An observation-based review." (2014).</p><p>[5] Young, P. J., et al. "Pre-industrial to end 21st century projections of tropospheric ozone from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP)." Atmospheric Chemistry and Physics 13.4 (2013): 2063-2090.</p>

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.

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