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At this moment hydraulic structures are designed based on a simple method: the Dynamic Amplification Factor (DAF) method. This method does not consider the full dynamic interaction between the wave impacts, structure and water. The research project DynaHicS focusses on the dynamic behaviour of hydraulic structures, taking into account fluid-structure interaction (FSI). The main goal of the DynaHicS project is to develop new design guidelines to identify dynamic behaviour of hydraulic structures, so that more economical designs can be made in the future. The master thesis focusses on improving the current design method, which can contribute to the development of a new design method for hydraulic structures in the future. The present design method, the DAF method, is extended in time and space. This is done by developing a method to determine the force-time signal of multiple wave impacts, whereby the results from scale model tests are no longer required. In this method the spatial variation (height and width) of the wave impact force over the structure surface is taken into account., Civil Engineering | Structural Engineering | Hydraulic Structures

Natuurorganisaties, vissers en overheden werken samen aan een wereldwijd uniek concept op de Afsluitdijk: de Vismigratierivier. Door een permanente ‘open’ verbinding tussen de zoute Waddenzee en het zoete IJsselmeer kunnen verschillende trekvissoorten weer hun paai- en leefgebieden bereiken.

At this moment hydraulic structures are designed based on a simple method: the Dynamic Amplification Factor (DAF) method. This method does not consider the full dynamic interaction between the wave impacts, structure and water. The research project DynaHicS focusses on the dynamic behaviour of hydraulic structures, taking into account fluid-structure interaction (FSI). The main goal of the DynaHicS project is to develop new design guidelines to identify dynamic behaviour of hydraulic structures, so that more economical designs can be made in the future. The master thesis focusses on improving the current design method, which can contribute to the development of a new design method for hydraulic structures in the future. The present design method, the DAF method, is extended in time and space. This is done by developing a method to determine the force-time signal of multiple wave impacts, whereby the results from scale model tests are no longer required. In this method the spatial variation (height and width) of the wave impact force over the structure surface is taken into account., Civil Engineering | Structural Engineering | Hydraulic Structures

“During the last safety assessment of Rijkswaterstaat in 2006 the Afsluitdijk failed on the current safety standards regarding flood protection. A new design was needed which ensured continuous protection against flooding in the future. Large scale and small scale tests are performed to optimize the design. Clear differences in the average wave overtopping discharge are observed between large and small scale. The new design of the Afsluitdijk has a complex geometry and consists of new types of elements of which not much information about the roughness of these elements is available. Also, the combined effect of roughness elements and berm has not been fully investigated yet. This asks for a more accurate method to predict the average wave overtopping discharge for composite slope. Various adjustments to current theories are proposed for this type of structure. “, Civil Engineering | Hydraulic Engineering

After more than 85 years, the iconic Afsluitdijk is in need of a reinforcement. During the latest safety assessment of Rijkswaterstaat the dike did not meet the standards at two components; the amount of wave overtopping (>10 l/m/s) and armour stability. This research goes into detail about the overtopping on the Afsluitdijk. In the new design a lot a of different factors influence the amount of wave overtopping: the roughness of several elements and a berm. The combination of these different factors makes it difficult to make a reliable estimation of the amount of wave overtopping. In the design new materials are used of which the effect on wave overtopping is unknown. The band width of the design is very narrow so an accurate prediction of the amount of overtopping in the prototype is necessary. Physical model tests of two different dike section are used in this research. These dike sections are tested on different scales (small to large) to validate the final design on prototype scale. Not much is known about the possible scale effects on wave overtopping so this research goes into more detail on this issue., Afsluitdijk, Civil Engineering | Hydraulic Engineering

Climate change raises serious concerns for policymakers that want to ensure the success of long-term policies. To guarantee satisfactory decisions in the face of deep uncertainties, adaptive policy pathways might be used. Adaptive policy pathways are designed to take actions according to how the future will actually unfold. In adaptive pathways, a monitoring system collects the evidence required for activating the next adaptive action. This monitoring system is made of signposts and triggers. Signposts are indicators that track the performance of the pathway. When signposts reach pre-specified trigger values, the next action on the pathway is implemented. The effectiveness of the monitoring system is pivotal to the success of adaptive policy pathways, therefore the decision-makers would like to have sufficient confidence about the future capacity to adapt on time. "On time" means activating the next action on a pathway neither so early that it incurs unnecessary costs, nor so late that it incurs avoidable damages. In this paper, we show how mapping the relations between triggers and the probability of misclassification errors inform the level of confidence that a monitoring system for adaptive policy pathways can provide. Specifically, we present the "trigger-probability" mapping and the "trigger-consequences" mappings. The former mapping displays the interplay between trigger values for a given signpost and the level of confidence regarding whether change occurs and adaptation is needed. The latter mapping displays the interplay between trigger values for a given signpost and the consequences of misclassification errors for both adapting the policy or not. In a case study, we illustrate how these mappings can be used to test the effectiveness of a monitoring system, and how they can be integrated into the process of designing an adaptive policy., Policy Analysis

Climate change raises serious concerns for policymakers that want to ensure the success of long-term policies. To guarantee satisfactory decisions in the face of deep uncertainties, adaptive policy pathways might be used. Adaptive policy pathways are designed to take actions according to how the future will actually unfold. In adaptive pathways, a monitoring system collects the evidence required for activating the next adaptive action. This monitoring system is made of signposts and triggers. Signposts are indicators that track the performance of the pathway. When signposts reach pre-specified trigger values, the next action on the pathway is implemented. The effectiveness of the monitoring system is pivotal to the success of adaptive policy pathways, therefore the decision-makers would like to have sufficient confidence about the future capacity to adapt on time. "On time" means activating the next action on a pathway neither so early that it incurs unnecessary costs, nor so late that it incurs avoidable damages. In this paper, we show how mapping the relations between triggers and the probability of misclassification errors inform the level of confidence that a monitoring system for adaptive policy pathways can provide. Specifically, we present the "trigger-probability" mapping and the "trigger-consequences" mappings. The former mapping displays the interplay between trigger values for a given signpost and the level of confidence regarding whether change occurs and adaptation is needed. The latter mapping displays the interplay between trigger values for a given signpost and the consequences of misclassification errors for both adapting the policy or not. In a case study, we illustrate how these mappings can be used to test the effectiveness of a monitoring system, and how they can be integrated into the process of designing an adaptive policy., Policy Analysis

After more than 85 years, the iconic Afsluitdijk is in need of a reinforcement. During the latest safety assessment of Rijkswaterstaat the dike did not meet the standards at two components; the amount of wave overtopping (>10 l/m/s) and armour stability. This research goes into detail about the overtopping on the Afsluitdijk. In the new design a lot a of different factors influence the amount of wave overtopping: the roughness of several elements and a berm. The combination of these different factors makes it difficult to make a reliable estimation of the amount of wave overtopping. In the design new materials are used of which the effect on wave overtopping is unknown. The band width of the design is very narrow so an accurate prediction of the amount of overtopping in the prototype is necessary. Physical model tests of two different dike section are used in this research. These dike sections are tested on different scales (small to large) to validate the final design on prototype scale. Not much is known about the possible scale effects on wave overtopping so this research goes into more detail on this issue., Afsluitdijk, Civil Engineering | Hydraulic Engineering

“During the last safety assessment of Rijkswaterstaat in 2006 the Afsluitdijk failed on the current safety standards regarding flood protection. A new design was needed which ensured continuous protection against flooding in the future. Large scale and small scale tests are performed to optimize the design. Clear differences in the average wave overtopping discharge are observed between large and small scale. The new design of the Afsluitdijk has a complex geometry and consists of new types of elements of which not much information about the roughness of these elements is available. Also, the combined effect of roughness elements and berm has not been fully investigated yet. This asks for a more accurate method to predict the average wave overtopping discharge for composite slope. Various adjustments to current theories are proposed for this type of structure. “, Civil Engineering | Hydraulic Engineering

Climate change is likely to affect our infrastructures in the Netherlands and seems to accelerate: sooner, faster, stronger. This stresses the need for adaptable infrastructure. Asset owners cannot assume a certain final situation of the infrastructure and the impacts on it due to climate change. This report answers the following research question: How can existing infrastructural asset designs in the Netherlands be adapted to anticipated current and future expected climate change effects? A method is developed to explore what the effects of climate change are on infrastructure and what further steps can be taken to make the infrastructure adaptable. The Afsluitdijk is used as a case study and has five embedded sub-assets: the dam, motorway, outlet sluices, ship locks and bridges. Nine climate change effects are distinguished for the Netherlands in the scenario WH of the KNMI in 2085. The climate change effects are combined with the asset parts and all combinations are assessed separately. An expert reflects on the combination of climate change impacts and asset part and elaborates on how the climate change effect impacts the reliability, safety or maintenance of the asset. This resulted in 21 identified possible problems for the 2020 design of the Afsluitdijk. In this report is looked at foreign situations that are comparable to the Afsluitdijk’s circumstances. Some of the 21 identified problems can easily be solved. A structured approach on how to assess the impact of climate change on infrastructure is lacking so far. The method makes sure all aspects are considered and helps the expert to think of all theoretical problems that have not occurred yet but are in the future a possible problem. Assets that are an integral system are preferred. The Afsluitdijk is interconnected to its environment and hard boundaries are difficult to determine. This makes the Afsluitdijk not an ideal case study, but this interconnectedness is typical for large scale infrastructural pro, Civil Engineering | Construction Management and Engineering

Climate change is likely to affect our infrastructures in the Netherlands and seems to accelerate: sooner, faster, stronger. This stresses the need for adaptable infrastructure. Asset owners cannot assume a certain final situation of the infrastructure and the impacts on it due to climate change. This report answers the following research question: How can existing infrastructural asset designs in the Netherlands be adapted to anticipated current and future expected climate change effects? A method is developed to explore what the effects of climate change are on infrastructure and what further steps can be taken to make the infrastructure adaptable. The Afsluitdijk is used as a case study and has five embedded sub-assets: the dam, motorway, outlet sluices, ship locks and bridges. Nine climate change effects are distinguished for the Netherlands in the scenario WH of the KNMI in 2085. The climate change effects are combined with the asset parts and all combinations are assessed separately. An expert reflects on the combination of climate change impacts and asset part and elaborates on how the climate change effect impacts the reliability, safety or maintenance of the asset. This resulted in 21 identified possible problems for the 2020 design of the Afsluitdijk. In this report is looked at foreign situations that are comparable to the Afsluitdijk’s circumstances. Some of the 21 identified problems can easily be solved. A structured approach on how to assess the impact of climate change on infrastructure is lacking so far. The method makes sure all aspects are considered and helps the expert to think of all theoretical problems that have not occurred yet but are in the future a possible problem. Assets that are an integral system are preferred. The Afsluitdijk is interconnected to its environment and hard boundaries are difficult to determine. This makes the Afsluitdijk not an ideal case study, but this interconnectedness is typical for large scale infrastructural pro, Civil Engineering | Construction Management and Engineering

This report drafts a monitoring program aiming at determining and optimizing the effectiveness of restoring fish migration at Kornwerderzand with the ‘Fish Migration River’ (FMR.) For an adaptive management of the operation of the FMR, monitoring and evaluation are key aspects. The main research questions underlying the monitoring program will be outlined. The proposed research and monitoring approach describes which monitoring techniques can be applied, what set-up and schedule of different research components involved.

In februari 2016 is door Alterra, onderdeel van Wageningen Universiteit en Researchcentrum, een quickscan uitgevoerd om de kwaliteit van de zode van de Afsluitdijk te bepalen. Gegevens over de doorworteling van de zode, het graslandtype en de vegetatiebedekking vormen de basis om tot een kwaliteitsoordeel van de zode te komen. Daarnaast is een korte vergelijking gemaakt tussen de huidige uitkomst en de situatie van 2010. Afsluitend wordt een beheeradvies gegeven.

As part of the Afsluitdijk project the discharge capacity, which is currently facilitated by two sluice complexes, is increased to cope with future sea level rise. It was decided to realise this by an innovative solution: the pump gate. The steel lifting gates, each containing three pumps, will be implemented in the existing sluice complex in phases, expecting a total of thirteen by the year 2050. This concept provides the possibility of pumping when necessary without hampering the discharge capacity during gravity flow, in which case the gates are lifted. The gates were designed to withstand quasi-static loads. Mainly due to the presence of the pumps, which have a high weight and require limited vibrations, the dynamic behaviour of the gate may lead to more strict design requirements. Two reference designs are investigated: the regular, and flood defence pump gate. The latter is designed to act as part of the primary flood defence, and is therefore significantly more robust. The analysis of the pump gate is limited to three components: the gate structure with its supports, pumps, and fluid. Standard expressions for the hydrodynamic pressures do not apply to the pump gate and surrounding fluid, mainly due to the three-dimensional vibration shape of the gate and the presence of the pumps. General methods or numeric models to quantify vibrations are not readily available for a continuous system with interacting gate, pumps, and fluid. In this thesis, a method is developed to determine the dynamic behaviour of gate-fluid systems confined by sluices. This method is based on a frequency domain semi-analytical coupled modal analysis, able to directly solve the behaviour of gate and fluid for the linearized equations. Several fluid schematizations are found in literature taking surface waves, compressibility, or neither into consideration. The validity of these schematizations was investigated for a wide range of water depths and excitation frequencies. Distinct regions we, Hydraulic Structures and Flood Risk, Hydraulic Engineering, Civil Engineering and Geosciences

Eelco Brandenburg beschrijft een opvallende ontmoeting met Tapuiten

As part of the Afsluitdijk project the discharge capacity, which is currently facilitated by two sluice complexes, is increased to cope with future sea level rise. It was decided to realise this by an innovative solution: the pump gate. The steel lifting gates, each containing three pumps, will be implemented in the existing sluice complex in phases, expecting a total of thirteen by the year 2050. This concept provides the possibility of pumping when necessary without hampering the discharge capacity during gravity flow, in which case the gates are lifted. The gates were designed to withstand quasi-static loads. Mainly due to the presence of the pumps, which have a high weight and require limited vibrations, the dynamic behaviour of the gate may lead to more strict design requirements. Two reference designs are investigated: the regular, and flood defence pump gate. The latter is designed to act as part of the primary flood defence, and is therefore significantly more robust. The analysis of the pump gate is limited to three components: the gate structure with its supports, pumps, and fluid. Standard expressions for the hydrodynamic pressures do not apply to the pump gate and surrounding fluid, mainly due to the three-dimensional vibration shape of the gate and the presence of the pumps. General methods or numeric models to quantify vibrations are not readily available for a continuous system with interacting gate, pumps, and fluid. In this thesis, a method is developed to determine the dynamic behaviour of gate-fluid systems confined by sluices. This method is based on a frequency domain semi-analytical coupled modal analysis, able to directly solve the behaviour of gate and fluid for the linearized equations. Several fluid schematizations are found in literature taking surface waves, compressibility, or neither into consideration. The validity of these schematizations was investigated for a wide range of water depths and excitation frequencies. Distinct regions we, Hydraulic Structures and Flood Risk, Hydraulic Engineering, Civil Engineering and Geosciences

Er zijn plannen om in zes van de tien spuikokers van het spuisluiscomplex van Kornwerderzand in totaal 18 Tocardo getijturbines turbines te installeren. Deze turbines zullen energie winnen uit de sterke stroming die bij het spuien van overtollig water vanuit het IJsselmeer naar de Waddenzee in de spuikokers ontstaat. Deze turbines vormen door potentieel botsingsgevaar en verstoring mogelijk een risico voor vissen, vogels en zeezoogdieren en zouden wellicht een verandering in het habitat teweeg kunnen brengen. De risico’s en belemmeringen voor vissen worden groter ingeschat dan die voor vogels en zeezoogdieren. Sterfte (direct) door de turbines kan zowel stroomopwaarts als stroomafwaarts optreden door fenomenen als: botsing met de bladen en structuren, drukverschillen, cavitatie, turbulentie en ‘shear stress’. In stroomopwaartse richting vormen de turbines voor de sterkere zwemmers, zalm, zeeforel, zeeprik, rivierprik, fint en houting een risico of belemmering.

Vergroening van kustverdediging (VGK) is een nieuwe trend in waterveiligheidsbeleid. In plaats van harde constructies voor de bescherming tegen overstromingen, worden zachte en meer natuurvriendelijke oplossingen ontwikkeld om golven te dempen, erosie tegen te gaan en sedimentatie processen te ondersteunen. Toch is het realiseren van vergroening in nationale en internationale waterveiligheidsprojecten allesbehalve vanzelfsprekend. Kennis is een essentieel onderdeel van VGK besluitvorming, maar daar is tot nu toe weinig aandacht aan besteed. Het doel van deze studie is daarom zowel het vergroten van inzicht in kennis in VGK besluitvorming als het verbeteren van kennis om VGK in waterveiligheidsprojecten mogelijk te maken. Aan de hand van bestaande projecten is deze studie beschreven. Zijnde zandmotor, Afsluitdijk en Markermeerdijken.

At the moment, for determining the safety of the dike ring areas around the IJsselmeer a possible failure of the Afsluitdijk is assumed to have no influence on loads occurring on the IJsselmeer dikes. As failure of the Afsluitdijk is always possible, the consequences of such a failure should be investigated. The objective of this thesis is to investigate these consequences of a possible failure of the Afsluitdijk. What happens with the water level of the IJsselmeer if during extreme conditions the Afsluitdijk breaches? This objective is achieved by first defining 4 different possible breach scenarios. Then, the effect of such a breach on the water level of the IJsselmeer is investigated. Subsequently, the consequences of this increase in water level on the probability of failure of the dikes of the Noordoostpolder is studied by using the program PC-Ring. For both cases, failure and no failure of the Afsluitdijk, the risks and consequences are combined to see the change in the risks of flooding of the Noordoostpolder., Hydraulic Engineering, Civil Engineering and Geosciences

The most famous dam of the Netherlands, the Afsluitdijk, is in need of renovation. Hydraulic conditions for the year 2050, for some aspects even 2100, must be considered during the renovation of the dam originally constructed 1927-1933. A combination of sea level rise due to climate change and a change in the applied statistical methods result in design conditions that are, at some locations, meters higher than those used a century ago. In a mission to retain the required level of safety while keeping expenses at a minimum, several innovative designs are considered; one of which is to allow very large overtopping discharges by making the dam resilient to erosion. However, calculations have shown that the overtopping values can be over 10 litres per second per meter dam, and the effect of this overtopping on the Afsluitdijk is unknown. In Dutch national design guidelines for dikes, schematizations are proposed for the phreatic surface in dikes during storm conditions. Wave overtopping is mentioned to have a rising effect on the phreatic surface, but clear methods to determine the magnitude of this effect are not prescribed. The guidelines suggest assuming full saturation of the dam in severe overtopping conditions, which has a detrimental effect on the slope stability. Recent studies and large scale infiltration tests on the Afsluitdijk show that only a very limited amount of water infiltrates in the dam and that the assumption of full saturation is much too conservative in case of the Afsluitdijk. In the present study, a finite-element model (Plaxflow) is used to model the phreatic surface in the Afsluitdijk during storm conditions, taking into account the effect of wave overtopping on the phreatic line. Parameters were determined by in-situ and laboratory investigations. To verify the model, calculations were calibrated on standpipe measurements. Wave overtopping is modelled by defining infiltration boundaries based on experiments and sensitivity analyses are condu

Blue Energy, het opwekken van energie door de menging van zoet en zout water, is veel in het nieuws. De gekozen technologie staat bekend als RED, voluit Reverse Electro Dialysis. Eind vorig jaar opende koning Willem-Alexander een proefinstallatie op de Afsluitdijk, maar ook het buitenland heeft volop belangstelling. Blue Energy: hoe werkt het precies, wat zijn de mogelijke toepassingen en wat is interessant voor de watersector?

The most famous dam of the Netherlands, the Afsluitdijk, is in need of renovation. Hydraulic conditions for the year 2050, for some aspects even 2100, must be considered during the renovation of the dam originally constructed 1927-1933. A combination of sea level rise due to climate change and a change in the applied statistical methods result in design conditions that are, at some locations, meters higher than those used a century ago. In a mission to retain the required level of safety while keeping expenses at a minimum, several innovative designs are considered; one of which is to allow very large overtopping discharges by making the dam resilient to erosion. However, calculations have shown that the overtopping values can be over 10 litres per second per meter dam, and the effect of this overtopping on the Afsluitdijk is unknown. In Dutch national design guidelines for dikes, schematizations are proposed for the phreatic surface in dikes during storm conditions. Wave overtopping is mentioned to have a rising effect on the phreatic surface, but clear methods to determine the magnitude of this effect are not prescribed. The guidelines suggest assuming full saturation of the dam in severe overtopping conditions, which has a detrimental effect on the slope stability. Recent studies and large scale infiltration tests on the Afsluitdijk show that only a very limited amount of water infiltrates in the dam and that the assumption of full saturation is much too conservative in case of the Afsluitdijk. In the present study, a finite-element model (Plaxflow) is used to model the phreatic surface in the Afsluitdijk during storm conditions, taking into account the effect of wave overtopping on the phreatic line. Parameters were determined by in-situ and laboratory investigations. To verify the model, calculations were calibrated on standpipe measurements. Wave overtopping is modelled by defining infiltration boundaries based on experiments and sensitivity analyses are condu

At the moment, for determining the safety of the dike ring areas around the IJsselmeer a possible failure of the Afsluitdijk is assumed to have no influence on loads occurring on the IJsselmeer dikes. As failure of the Afsluitdijk is always possible, the consequences of such a failure should be investigated. The objective of this thesis is to investigate these consequences of a possible failure of the Afsluitdijk. What happens with the water level of the IJsselmeer if during extreme conditions the Afsluitdijk breaches? This objective is achieved by first defining 4 different possible breach scenarios. Then, the effect of such a breach on the water level of the IJsselmeer is investigated. Subsequently, the consequences of this increase in water level on the probability of failure of the dikes of the Noordoostpolder is studied by using the program PC-Ring. For both cases, failure and no failure of the Afsluitdijk, the risks and consequences are combined to see the change in the risks of flooding of the Noordoostpolder., Hydraulic Engineering, Civil Engineering and Geosciences

De “Vismigratierivier Afsluitdijk” is een uniek project om het Nederlandse icoon de Afsluitdijk te vernieuwen. Het project heeft als doel om de ecologische barrière, die de Afsluitdijk voor trekvissen is, te verzachten. De Vismigratierivier (VMR) zorgt er voor dat een brede groep trekvissen, zoals de spiering, houting, aal (paling) en zalm, weer de ruimte krijgt om hun paai-, leef- en opgroeigebieden in het IJsselmeer, de Friese Meren, de Overijsselse Vecht, de IJssel en verder te bereiken. Voordat er een gedetailleerd werkplan voor de uitvoering van de Vismigratierivier bij Kornwerderzand kan worden uitgevoerd, moeten er een aantal cruciale vismigratieprocessen onderzocht worden. Voor dit programma worden zeven fuiken in het voor- en najaar twee keer per week gelicht. Deze monitoring heeft als doel jaarlijkse trends waar te nemen van diadrome vissen.

De sluiting van de 32 km lange Afsluitdijk heeft grote gevolgen gehad voor de migratie van vis tussen de Zuiderzee en de aangrenzende rivieren. Waar eerst een natuurlijke overgang bestond van zoet en zout water, is nu een harde scheiding tussen het IJsselmeer en de Waddenzee ontstaan. Zoet water stroomt bij afgaand tij via twee spuicomplexen richting de Waddenzee. Stroomopwaarts migrerende vis wordt - afhankelijk van de timing - geconfronteerd bij de spuicomplexen met dichte deuren, korte migratievensters, grote stroomsnelheden en een harde overgang van zoet naar zout water. Om stroomopwaarts migrerende vis te faciliteren in hun migratie naar het IJsselmeer liggen er ontwerpen voor een vismigratierivier bij het spuicomplex Kornwerderzand. Een kunstmatige ‘rivier’ van 6 km lang, waar getijwerking tussen zoet en zout meer de ruimte krijgt, langere migratie vensters geboden worden en de stroomsnelheden van het water lager zijn. De VisMigratieRivier (VMR) bestaat – in het huidige in de haalbaarheidsstudie gepresenteerde ontwerp - uit een 2 km lang deel aan de Waddenzeezijde, een koker onder de weg door en een deel in het IJsselmeer van 4 km lang. De delen van de VMR worden beheerd door afsluiters die afhankelijk van het getij worden open- of dichtgezet.

De sluiting van de 32 km lange Afsluitdijk in 1932 heeft grote gevolgen gehad voor de migratie van vis tussen de Zuiderzee en de aangrenzende rivieren. Waar eerst een natuurlijke overgang bestond van zoet en zout water, is nu een harde scheiding tussen het IJsselmeer en de Waddenzee ontstaan. Jaarlijks bieden zich, afhankelijk van de soort, enkele tientallen tot honderden miljoenen vissen aan bij het spuicomplex bij Kornwerderzand. Deze vissen willen tijdens hun stroomopwaartse migratie het IJsselmeer bereiken richting paai of opgroeigebieden, maar de Afsluitdijk vormt een barrière en veroorzaakt daarmee vertraging en of blokkering tijdens de stroomopwaartse migratie. Om deze reden zijn er plannen om een vispassage of een VismigratieRivier (VMR) te bouwen naast het spuicomplex te Kornwerderzand met als doel om de ecologische barrière, die de Afsluitdijk voor trekvissen vormt, te verzachten. Deze rapportage gaat in op de ruimtelijke verspreidingsdynamiek van kleine vis (driedoornige stekelbaars, spiering, botlarven en glasaal), het zoekgedrag en passagesucces van grotere vis (houting, zeeprik en zeeforel) en de aanwezigheid van diadrome vis buiten de spuikom.

Flood Risk, Hydraulic Engineering, Civil Engineering and Geosciences

The degradation of infrastructure and sea level rise cause the existing discharge capacity of the Stevin and Lorentz sluices at the Afsluitdijk to be insufficient. This thesis focuses on the design of a new discharge facility at the Afsluitdijk with the possibility to anticipate on the changing conditions at both the IJsselmeer and Wadden Sea. The system is schematised as a closed-off estuary system within a water storage model, based on the water balance equation and a wind model from SOBEK. In contrast to previous studies, this study takes extreme conditions into account instead of only the daily conditions. The water storage system depends on the following governing parameters: the wind setup, tidal movement, target water level, sea level rise, in- and outflow conditions, in which the sea level rise is used as the function parameter. Within this schematisation three normative design conditions are considered for the acceptable water level prolongation at the inner basin: (I) the maximum acceptable height, (II) an acceptable duration of the high water level event and (III) the target water level boundaries. By means of a general sea level rise computation, the analyses showed that during daily conditions the need for pumps is inevitable from a sea level rise of +0.25m or more, because the daily discharge driven by gravity becomes limited. However, during extreme conditions discharge driven by gravity remains beneficial up to a sea level rise of +1.00m. Pumping is the only option beyond this point. Two design options are considered to be feasible for the combination of discharge driven by pumps and gravity: the open discharge sluice and the venturi culvert. The open discharge sluice is capable of discharging large volumes via gravity. In combination with the four pumps within a vertical door, the complete tidal cycle is utilised to discharge water, resulting in the most economical design option. On the other hand, there is the discharge facility made up of venturi, Hydraulic Engineering, Hydraulic Engineering, Civil Engineering and Geosciences

The Afsluitdijk is unable to withstand the future conditions that belong to an annual probability of occurrence of 1/10 000 per year for water level and wave conditions. Solution of Rijkswaterstaat is to strengthen the dike according to the principle of the wave overtopping resilient dike (NL: Overslagbestendige dijk). Therefore the Afsluitdijk has to be able to cope with large amounts of wave overtopping (>150 l/s/m). The current design methods are unsuitable to prove the resistance of the Afsluitdijk against these large amounts. The goal of this thesis is to develop design procedures in order to prove the landward slopes erosion resilience of the Afsluitdijk against large amounts of wave overtopping. Based on a theoretical study a new design procedure has been developed, this method consists of six sub-procedures, two choices and two results. The first step is to determine the wave overtopping discharge. Up to 30 l/s/m good quality grass can be applied. This average wave overtopping discharge appeared a good measure for the load below 30 l/s/m. Otherwise the load should be expressed as the front flow velocity per overtopping wave. It is important to express the velocity for each wave separately, because only waves resulting in a higher velocity than the critical velocity contribute to the damage. Damage only occurs if the critical velocity the landward slope is able to withstand is exceeded. These wave are the number of critical overtopping waves Ncow or the percentage of waves that contribute to the damage Pcow. The overtopping velocities are based on empirical relations between the overtopping velocity and volume. The volume has been determined using the probability of a certain wave volume to occur (a Weibull distribution with a freeboard dependent scale factor a and shape factor b). A categorization based on the discontinuities and objects that are present on the Afsluitdijk has been created. For each category an amplification factor for the front flow velocit, Hydraulic Engineering, Hydraulic Engineering, Civil Engineering and Geosciences

Het primaire doel van deze studie is het bepalen van de economisch optimale toetskans voor de Afsluitdijk en andere dijken. Uit de studie blijkt ook dat het welvaartsverhogend is de Afsluitdijk te versterken conform een recent kabinetsbesluit. Als daarnaast wordt uitgegaan van pompen op de Afsluitdijk en de Houtribdijk én indien alle dijkringen nu minimaal voldoen aan de huidige wettelijke normen, dan blijkt bovendien dat veel dijkringdelen in het IJsselmeergebied de komende decennia niet te hoeven worden versterkt. Sommige dijkringdelen, vooral in de IJssel- en Vechtdelta moeten nog wel worden versterkt, wat zo'n half miljard euro kost tot 2050, oftewel gemiddeld enkele tientallen miljoenen euros per jaar. Daarnaast zijn er nog een aantal open vragen over de stabiliteit van de dijken rond het'Markermeer en is niet duidelijk of de huidige dijken wel voldoen aan de huidige normen en wat de consequenties daarvan zijn. Hiervoor is nader onderzoek nodig.