scholarly journals Wave model verification based on measurements in the Wadden Sea

2016 ◽  
Author(s):  
Cordula Berkenbrink ◽  
Luise Hentze ◽  
Andreas Wurpts
Keyword(s):  
Water Level ◽  
Wadden Sea ◽  
Wave Attenuation ◽  
Calculated Data ◽  
Barrier Islands ◽  
Wave Model ◽  
Water Levels ◽  
Model Verification ◽  
Coastal Protection ◽  
Lower Saxony

Abstract. The design height of coastal protection structures in Lower Saxony / Germany is determined by the design water level and the corresponding wave run up. For the calculation of these parameters several mathematical models are used which need to be verified for the conditions at the East Frisian Wadden Sea area. For this issue a wave measuring programme is operationally run, which includes various measurement locations and devices around the islands Norderney and Juist. The measurements are continuously extended and adapted in order to improve models and measurements. This paper shows a comparison between measured and calculated data for the storm surge of the 10.–11.01.2015 incorporating to new wave and water level gauges operated within COSYNA as well as a second research project dealing with wave attenuation behind barrier islands. Water levels within the investigation area were calculated by hydrodynamic models driven with a wind field originating from weather forecast and compared to water level measurements. The corresponding wave energy field was calculated by means of a third generation wave model and results compared to measurements of several devices located around the barrier Islands. The aim of the study shown here is to give a brief overview of possible error sources for model-data as well as data-data comparisons.

scholarly journals Effect of Variations in Water Level and Wave Steepness on the Robustness of Wave Overtopping Estimation

2020 ◽  
Vol 8 (2) ◽  
pp. 63
Author(s):  
Nils B. Kerpen ◽  
Karl-Friedrich Daemrich ◽  
Oliver Lojek ◽  
Torsten Schlurmann
Keyword(s):  
Water Level ◽  
Wave Spectrum ◽  
Water Environment ◽  
Physical Modelling ◽  
Storm Surges ◽  
Water Levels ◽  
Coastal Protection ◽  
Wave Steepness ◽  
Wave Overtopping

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise.

Selecting velocity fields in urban pluvial floods from pre-calculated data

2020 ◽  
Author(s):  
Robert Sämann ◽  
Thomas Graf ◽  
Insa Neuweiler
Keyword(s):  
High Resolution ◽  
Water Level ◽  
Mean Square Error ◽  
Nearest Neighbor ◽  
Calculated Data ◽  
Velocity Fields ◽  
Water Levels ◽  
Mean Square ◽  
Run Off

<p><span>Early warning systems for floods in urban areas should forecast water levels and damage estimation to protect vulnerable regions. To estimate the danger of a flood for buildings and people, the energy of the flood has to be taken into account additionally to the water level. The energy is related to the flow velocity. For directing rescue workers or trace spreading of contaminants through flooded streets, a high resolution of the water’s energy in space and time is required. Direct numerical run-off calculation is too slow for a flood forecast in time. Therefore a database with pre-calculated events is needed and a method to select the water levels and velocity fields that are similar to a forecasted rain event. </span></p><p><span>We present a method, how to create a real-time forecast based on pre-calculated data. The selection and weighting of the pre-calculated data is based on the precipitation pattern in the flood region. A nearest neighbor approach is applied to find water levels and velocity fields from a database that are similar to the forecasting event. For the ranking of similarity, different new metrics are compared against each other. The quality of the metrics is tested with a new approach of comparing velocity fields on the surface and in the pipe system. Considering both domains is crucial for understanding the complex dynamic flow paths on the surface. An urban catchment of 5 km² with high resolution (~3 m³) triangular surface mesh and connected drainage system is used for a hydrodynamic run-off simulation. The 1D-2D coupled software HYSTEM EXTRAN is used to generate the water levels and velocity fields for strong rainfall events of the past 20 years. More than 900 events with a duration between 15 minutes and 24 hours and return periods between 10 and 100 years were calculated and stored as the “pre-calculated” dataset.</span></p><p><span>For comparing two events, the mean square error is calculated between the precipitation patterns with different approaches to select the start index and number of intervals. This number depends on the hydraulic response time, the temporal resolution and the length of the reference pattern. The quality of the nearest neighbor selection is quantified using the Nash–Sutcliffe model efficiency coefficient of pipe flow and the root mean square error of water level and velocity in significant surface cells. Additionally, the transport paths of artificial contamination spills are compared between the events to show the reproducibility of velocity fields for each metric. </span></p><p><span>Results show that the reaction time and the wetting state of the surface is very important. Single cell values correspond well between a forecasted and a dataset event. However, complex transport paths have a very high variability that is not reproducible with similar events. Further research is required to clarify if this is a result of the random walk approach or of the injection time of the particles. </span></p>

scholarly journals A PROBABILISTIC MODEL FOR THE DETERMINATION OF HYDRAULIC BOUNDARY CONDITIONS IN A DYNAMIC COASTAL SYSTEM

2011 ◽  
Vol 1 (32) ◽  
pp. 38 ◽  
Author(s):  
Jacco Groeneweg ◽  
Joost Beckers ◽  
Caroline Gautier
Keyword(s):  
Wind Speed ◽  
Boundary Conditions ◽  
Water Level ◽  
Wind Direction ◽  
Wadden Sea ◽  
Water Levels ◽  
Tidal Basin ◽  
Wind Fields ◽  
Coastal System ◽  
Advanced Method

In 2011 new Hydraulic Boundary Conditions must be established for the statutory assessment of flood protection in the Wadden Sea area, which is a complex tidal system in the northern part of the Netherlands. The aim is to base these normative wave conditions on the wave simulation model SWAN and the probabilistic method Hydra-K, to be consistent with other systems as the Holland Coast and the Zeeland Delta. Assumptions made for the latter water systems, like steady state wind forcing, uniform water levels and neglect of currents, are not valid in the tidal basin of the Wadden Sea. A schematic temporal variation of both wind direction and wind speed is applied to define wind fields that drive the hydrodynamic computations. Both wind fields and resulting water level and current fields form the input of SWAN computations for a large number of combinations of basic wind speed and wind direction, offshore surge level and phase difference between tide and maximum wind speed. The result is a large database of SWAN results that is used as a look-up table in Hydra-K to transform the offshore statistics to the load on the primary sea defenses. In general the more advanced method leads to wave heights that are up to 10% lower and wave periods that are 10-20% smaller than those obtained with the method that is presently applied for the Holland Coast and the Zeeland Delta. These differences can be ascribed to the inclusion of currents and positive shoreward tilt in water level. The inclusion of relevant physics in the hydrodynamic computations increases the accuracy of the resulting HBC. Therefore, the more advanced method will be applied to determine the HBC for 2011.

scholarly journals INVESTIGATION OF WAVE INDUCED STORM SURGE WITHIN A LARGE COASTAL EMBAYMENT - MORETON BAY (AUSTRALIA)

2011 ◽  
Vol 1 (32) ◽  
pp. 22 ◽  
Author(s):  
Philip Treloar ◽  
David Taylor ◽  
Paul Prenzler
Keyword(s):  
Water Level ◽  
Tropical Cyclones ◽  
Storm Surge ◽  
Wave Model ◽  
Water Levels ◽  
Residual Water ◽  
Storm Tide ◽  
Moreton Bay ◽  
Coastal Embayment ◽  
Set Up

Moreton Bay is a large coastal embayment on the south-east Queensland coast which is surrounded by the urbanised areas of greater Brisbane on its western and southern shorelines. It is protected from the open coast by a number of islands, including South Stradbroke, North Stradbroke and Moreton Islands. Tropical cyclones occasionally track far enough south to cause significant damage to south-east Queensland due to flooding, winds, waves and elevated ocean water levels. Distant tropical cyclones which may be several hundred kilometres north of Moreton Bay have been known to cause storm surge, high waves and erosion inside Moreton Bay. These events generally do not generate gale force winds within Moreton Bay, but can generate large ocean swell waves. It has been identified that the wave conditions generated from distant cyclones can cause a variation in water levels inside Moreton Bay. A detailed study was undertaken to investigate the regional wave set-up process which affects Moreton Bay. The simulation of the residual water levels within Moreton Bay using a coupled hydrodynamic and wave model system developed for this study is considerably more accurate than applying a hydrodynamic model alone and explains water level anomalies that have a tidal frequency. The paper discusses the physical process of regional wave set-up inside a large embayment, analysis of observed residual water level and also the modelling study undertaken to quantify the influence of waves on storm tide levels inside Moreton Bay. The storm tide hazard study for the Moreton Bay Councils included the effects of regional wave set-up in the specification of design water levels.

Generation of Multivariate Wave Conditions as Input for a Probabilistic Level III Breakwater Design

2014 ◽  
Author(s):  
Peter Mercelis ◽  
Marc Dufour ◽  
Ariel Alvarez Gebelin ◽  
Vincent Gruwez ◽  
Sarah Doorme ◽  
...  
Keyword(s):  
Water Level ◽  
Wind Velocity ◽  
Regression Function ◽  
Wave Model ◽  
Water Levels ◽  
Spectral Wave Model ◽  
Navigation Channel ◽  
Extreme Wind ◽  
Wave Conditions ◽  
Area Of Concern

For an offshore LNG project situated in the estuary of the Rio de la Plata nearby Montevideo, Uruguay, it was required to verify the deterministic design of the protective rubble mound breakwater and the jetty infrastructure with a level three probabilistic design. Therefore, in first instance extreme site conditions were required both in front of and behind the breakwater. To obtain these conditions, the first step is to extrapolate the offshore variables in order to translate them to the breakwater location. All the possible combinations of extreme wind, water level and waves are quantified with a probability of occurrence. A combination of univariate extreme value distributions, copula’s and regression is used to describe the multivariate statistical behaviour of the offshore variables. The main variable is the wind velocity, as in the area of concern extreme wave conditions are wind driven. The secondary variable is water level. Wind velocity and water levels are only correlated for some wind directions. For these directions, wind velocity and water level extreme value distributions are linked through a multivariate Gumbel Copula. The wave height at the model boundaries was taken into account by a regression function with the extreme wind velocity at the offshore location and the wave period by a regression function with the wave height. This way 1515 synthetic events were selected and simulated with the spectral wave model SWAN, each of which a frequency of occurrence is calculated for. However, due to refraction and diffraction effects of the approach channel (in the area of concern water depths are limited to about 7 m and the navigation channel has a depth of about 14 m), the port basin and the breakwater itself, the spectral wave model SWAN is not sufficient to accurately calculate the local wave conditions in the entire area of interest. Therefore a non-linear Boussinesq wave model (i.e. Mike 21 BW) was set up in addition, using input from the spectral model at the boundary and including the navigation channel of more than 12 km long. Combining both models, significant wave heights are obtained on both the seaward side and the leeside of the breakwater with corresponding frequencies of occurrence. This approach allows the determination of conditional return periods and generates the site conditions required for a probabilistic level three design of the breakwater and the jetty infrastructure taking for example the joint probabilities between waves and water levels fully into account as needed for overtopping or failure calculations.

scholarly journals Wave-attenuation characteristics of combined-vegetation wave break forests for big rivers with large flood water level changes

2021 ◽  
Vol 83 (4) ◽  
pp. 831-840
Author(s):  
Jie Ren ◽  
Zengchuan Dong ◽  
Dawei Jin ◽  
Yue Zhou ◽  
Wei Xu ◽  
...  
Keyword(s):  
Water Level ◽  
Water Depth ◽  
Water Surface ◽  
Wave Attenuation ◽  
Water Levels ◽  
Large Rivers ◽  
Attenuation Effect ◽  
Practical Applications ◽  
Different Types ◽  
Wave Break

Abstract For large rivers with a compound cross section, the downstream channel has a very wide water surface during the flood season. A wide water surface, high water level, and larger wind speed will cause higher waves, increasing the threat of flooding to the dike. The design of a combined-vegetation wave break forest was put forward to achieve better wave attenuation effect. The main idea of this concept is to plant different types of vegetation at different locations in front of the dike. Three single-vegetation and four combined-vegetation forest schemes were tested under seven different water depth conditions. Both physical experiments and wave numerical simulations were carried out for each scheme to study the wave attenuation effect. The results showed that the wave attenuation effect of the single-vegetation wave break forest was significantly different under different water depth conditions, and the overall effect of the combined-vegetation of wave forest was better. Combined-vegetation wave break forests combine the advantages of different types of vegetation in different water levels, which makes it more economical and reasonable to plant by rivers with large water level variation. The proposed design ideas and methods could provide theoretical support for ecological revetment engineering of large rivers and insights for practical applications.

scholarly journals Filtration reliability and safety of earth-fill dam

2021 ◽  
Vol 264 ◽  
pp. 03064
Author(s):  
Khojiakbar Khasanov ◽  
Kakhramon Babajanov ◽  
Nodira Babajanova
Keyword(s):  
Water Level ◽  
Flow Rate ◽  
Calculated Data ◽  
Water Reservoir ◽  
Drainage Water ◽  
Water Levels ◽  
The Body ◽  
Filtration Flow ◽  
Channel Water ◽  
Earth Fill

The study of the reliability and safety of the constructed earth-fill dams and the comparison with their design and calculated data makes it possible to improve the structures and methods of the calculation substantiation of these structures. This work aims to study the filtration reliability and safety of the earth-fill dam of the Channel water reservoir of the Tuyamuyun hydroelectric complex (THC) on the Amu Darya River, which was put into exploitation in 1984. Field studies were carried out according to the traditional method using results of control and measuring equipment (CME) embedded in the body of the dam. The water levels of the upper and lower reaches, piezometers, and drainage water flow were measured. The maximum water levels upstream of 130.00 were observed in July-August and November 2017, and the minimum of 117.50 at the end of March. The water levels downstream depend on the value of the discharge through the hydrosystem. The maximum level downstream for 2017 was 112.55 m (01.06.2017) with a flow rate of 2000 m3/s. The minimum level downstream of 109.15 m was observed on November 29, 2017, when the discharge into the downstream through the hydroelectric complex was 260 m3/s. A tendency to an increase in the level of the bottom downstream was found. Filling and depletion graphs of the Channel water reservoir have been built, from which it is found that they reached 2.00 m/day, and 1.60 m/day, respectively. This is 4 and 1.6 times more than the standard 0.5 m/day and 1.0 m/day. Of the 53 piezometers, 34 are working conditions; the rest do not work, require flushing. Graphs of water level changes in piezometers show that they change with an average 15-20 day delay in the water level in the Channel water reservoir. In general, the natural depression curve is below the design one. The maximum filtration flow rate was 63.3 l/s at a water level in the upper pool of 129.00.

AUTOMATIC WATER LEVEL MONITORING WITH IOT AND LPWAN

2019 ◽  
pp. 95-103
Author(s):  
Krum Videnov ◽  
Vanya Stoykova
Keyword(s):  
Water Level ◽  
Real Time ◽  
Early Warning ◽  
Water Sources ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Level Monitoring ◽  
Water Level Monitoring

Monitoring water levels of lakes, streams, rivers and other water basins is of essential importance and is a popular measurement for a number of different industries and organisations. Remote water level monitoring helps to provide an early warning feature by sending advance alerts when the water level is increased (reaches a certain threshold). The purpose of this report is to present an affordable solution for measuring water levels in water sources using IoT and LPWAN. The assembled system enables recording of water level fluctuations in real time and storing the collected data on a remote database through LoRaWAN for further processing and analysis.

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