Technisch rapport duinwaterkeringen en hybride keringen 2011

Technisch rapport voor de beoordeling van duinwaterkeringen en hybride keringen ten behoeve van het voorschrift toetsen op veiligheid (VTV 2011). Het rapport bevat de volgende onderdelen: inleiding duinwaterkeringen en hybride keringen, technische richtlijnen en veiligheidsbeoordeling, rekenregels voor duinafslag, erosie en overstroming, toetssoftware en bijlagen. (conceptversie)TAW/EN

Suppleties bij Egmond en Bergen

Een analyse van de morfologische processen in het kustgebied tussen IJmuiden en de Hondsbossche Zeewering en de beheeropties voor Egmond en Bergen.KWP-collectio

Simulation of a surf zone with a barred beach. Report 1. Wave heights and wave breaking

The present report describes some of the results obtained during experiments in the Large Wave Flume of the Fluid Mechanics Laboratory of the Delft University of Technology. The experiments are part of the PhD-work of M. Boers. They follow on the LIP llD-experiments, carried out in the Delta Flume of Delft Hydraulics in spring 1993. During the LIP 11D-experiments much information was obtained about physical parameters in the surf zone such as wave heights, wave set-up and velocities. The experiments have the following objectives: To add measuring data to the LIP llD-data To obtain data which can reconstruct the mass, momentum and energy balances To obtain detailed information about regions with steep gradients of wave heights and wave set-up (onshore slope of breaker bar and toe of foreshore) To obtain information about the breaking behaviour of waves To measure bed shear stresses To measure turbulence motions The objective of this report is to distribute the results of the measurements among researchers working in the field of coastal engineering. Further, it gives information about the accuracy of the measuring data. The results of the experiments are described in two reports. Report 1 (the present report) describes the experimental set-up [Chapter 2], wave height measurements and the video recordings of the wave breaking [Chapter 3]. The results of velocities and shear stress measurements are described in Report 2 [Boers, 1996]. Some of the results are already published by Boers and Van de Graaff [1995]. The results of the analysis of the measurements is presented in many figures. Data are also available in files [Enclosure A].Civil Engineering and Geoscience

Bedforms and undertow in the surf zone; an analysis of the LIP 11D-data

The present report gives the results of a study on bedforms and undertow in the surf zone. It is the objective of this study to get a better insight into the physical processes in the surf zone. In this study, we make use of the data obtained during the LIP llDexperiments (Arcilla et al. [1994] and Roelvink and Reniers [1994]). We derive the characteristics of bedforms from measured profiles. We relate these bedform characteristics to the hydraulic conditions and analyse if they can be predicted with present prediction methods. Further, we develop an inverse modelling technique, which is based on the mass and momentum balance equations. With this technique we derive values of important physical parameters, like eddy viscosity, shear stresses, friction factors, bed roughness and mass flux. The derived physical parameters are compared with present methods to describe these parameters.Civil Engineering and Geoscience

Hydraulica en morfologie van efemere rivieren met infiltratie

Het voorliggende afstudeerverslag geeft de resultaten van een onderzoek naar efemere rivieren met infiltratie. Hierbij is aandacht geschonken aan hydraulica en morfologie. Het onderzoek is onderverdeeld in achtereenvolgens een literatuurstudie, de ontwikkeling van analytische modellen en de ontwikkeling van een numeriek model. Bij het bestuderen van de literatuur bleek, dat er weinig onderzoek naar dit onderwerp is verricht. Doordat efemere rivieren maar gedurende korte tijd water bevatten, is het moeilijk om voldoende metingen te verkrijgen. Met behulp van benaderde analytische rekenmethodes zijn er modellen ontwikkeld, die een beschrijving geven van de waterstand en de snelheid van een afvoergolf. Voorwaarde hierbij is dat deze afvoergolf op het begintijdstip een rechthoekige vorm moet hebben. Met behulp van de gevonden waterstand en snelheid kan vervolgens het sedimenttransport en de bodemverandering worden berekend. De analytische modellen Zijn getoetst m.b.v. een daartoe ontwikkeld numerieke model. Dit model maakt gebruik van het MacCormack schema, dat massa en impulsie behoudend is. Er zijn vele opties aan het model toegevoegd, om voor verschillende situaties berekeningen te kunnen maken.Hydraulic EngineeringCivil Engineering and Geoscience

Duinen als Waterkering: Inventarisatie van kennisvragen bij waterschappen, provincies en rijk

Binnen het programma Sterkte en Belastingen van Waterkeringen (SBW) van het Ministerie van Verkeer en Waterstaat wordt kennis ontwikkeld ten behoeve van de periodieke toets van de waterkeringen in Nederland. Een onderdeel van dit programma betreft de ontwikkeling van een nieuw toetsinstrumentarium voor de duinwaterkeringen aan de Noordzeekust. Voordat een start gemaakt wordt met de ontwikkeling van nieuwe kennis is een inventarisatie gemaakt van kennisvragen bij de gebruikers afkomstig van waterschappen, provincies en rijk. Dit rapport geeft hiervan een verslag. Achtereenvolgens wordt in dit rapport aandacht geschonken aan de bestuurlijke verantwoordelijkheden van de overheden aangaande de duinwaterkering, een gebiedsgerichte beschrijving van de duinwaterkeringen in de 13 betreffende dijkringgebieden, een overzicht van programma's en projecten die gericht zijn op de veiligheid van duinwaterkeringen en een overzicht van de gebruikerswensen ten aanzien van een nieuw duintoetsinstrumentarium. Uit deze gebruikerswensen worden kennisvragen afgeleid voor onderzoek binnen het programma SBW. In de bijlagen zijn verslagen opgenomen van interviews met medewerkers van waterschappen, provincies en rijk. Verder zijn kaarten gemaakt waarin de eigenschappen van de Nederlandse duinwaterkeringen worden geïllustreerd.SB

Turbulentie in de brandingszone

Civil Engineering and Geoscience

Effects of a deep sand extraction pit: Final report of the PUTMOR measurements at the Lowered Dump Site

DEEP SAND EXTRACTION ON THE NETHERLANDS CONTINENTAL SHELF (NCS) In the \u93Nota Ruimte\u94 (=National Spatial Strategy) the Dutch Government has announced to allow for deep sand extraction on the NCS, where former legislation only allowed for extraction till a depth of 2 m below the initial seabed. This new legislation has been worked out in the \u93Regionaal Ontgrondingenplan Noordzee 2\u94 (= Regional Extraction Plan North Sea 2). It prescribes that for sand extractions with an extraction volume exceeding 10 million m3 or an extraction area exceeding 500 hectares an environmental impact assessment is required, and that an ecological study is required when the intended extraction depth exceeds 2 m below the initial seabed. It appears that there is little experience with the effects of deep sand extraction pits on existing values and user functions, due to the legislation prior to 2004. Since it is the responsibility of the Dutch Government to develop legislation on sand extraction, and to judge the proposals for sand extraction before granting an extraction license, Rijkswaterstaat, North Sea Directorate has asked Rijkswaterstaat, The National Institute of Coast and Sea/RIKZ to study the hydraulic and morphological responses of a deep sand pit and the risks of oxygen depletion and deposition of fines inside such a pit. The general conclusion is that there are no indications that a deep sand extraction pit with a final water depth of 40 meter necessarily leads to unacceptable effects on existing values and user functions, and therefore it is expected that deep sand extraction will be an interesting alternative for shallow sand pits with a volume of more than 10 million m3. For the environmental impact assessment of a proposed deep sand extraction pit, numerical models are available for useful predictions of the hydraulic and morphological response of such a pit. THE PUTMOR MEASURING CAMPAIGN From autumn 1999 till summer 2000 there was an opportunity to carry out measurements at a temporary deep sand pit (referred to as the PUTMOR pit) of the Lowered Dump Site (LDS) near Hook of Holland [Figures 1.1 and 1.3]. The PUTMOR pit was located at an initial water depth of 23 m and was left open for a period of 10 months, after which it was refilled with dredged material from the Port of Rotterdam. The pit had a content of about 4.5 million m3, a length of 1300 m, a width of 500 m and an extraction depth varying between 5 and 12 m. Within a period of 10 months, Rijkswaterstaat gathered data about the hydraulic conditions, the water quality and the morphological changes. THE IMPACT OF A DEEP SAND EXTRACTION PIT ON VALUES AND USER FUNCTIONS There are two major concerns related to deep sand extraction. The first concern is that benthic communities cannot re-establish on the bottom of a deep sand pit due to oxygen depletion and deposition of fines. The second concern is that a deep sand pit will harm existing cables, pipelines and offshore constructions, and the coastal defence system. To address these concerns, we have formulated the following questions: \u95 What effects has a deep sand pit on the flow conditions, stratification, oxygen depletion deposition of fines and bottom changes? \u95 Can the original benthic communities recover on the sand pit bottom? \u95 Is there a risk of damage to cables, pipelines and offshore structures? \u95 What is the effect on the sand budget of the coastal system? \u95 Is it possible to judge a sand pit design with an extraction depth of more than 2 metres below the initial seabed using hydraulic and morphodynamic models? With the help of the PUTMOR measurements, which was made up with other measuring data from the NCS, we came to the following conclusions: \u95 The PUTMOR measurements showed an increase of the flow rate (discharge per meter width) inside the pit with one-third, but the flow velocity near the bottom of the pit has a decrease of one-third compared to the measured flow velocities outside the pit. \u95 The PUTMOR measurements did not show stratification and oxygen depletion inside the pit, below the initial seabed. In the upper ten metres of the water column, the usual haline stratification was measured, resulting from the fresh water discharge from the river Rhine. On the NCS, there are no records of oxygen depletion due to this haline stratification, which is probably the result of the temporal presence of a halocline during the tidal period and the upwelling of oxygen rich water from the offshore. Thermal stratification is not expected since the water depth inside the pit is less than 40 m, which is the minimum water depth for thermal stratification found at the NCS. Besides, the water inside the PUTMOR pit was refreshed four times a day due to the tide. In general, there is no chance on long-term haline or thermal stratification within a deep sand pit on the NCS with a final water depth less than 40 m pit, and we expect that the risk of oxygen depletion in such a pit is negligible. \u95 When there is a large deposition of fines, there may be a negative impact on the recovery of benthos communities. In the PUTMOR pit, we did not measure a large deposition if fines. However, the deposition of fines is very site-specific, depending on the local flow velocities, the suspended concentrations of fines and the characteristics of the sand extraction pit. \u95 We expect that recovery of benthic communities on the new seabed within a deep sand extraction pit is possible. \u95 The morphological changes of a large pit in deep water are very slow, although they depend on the local conditions. The backfilling of a deep sand pit at an initial water depth of more than 20 m is expected to take a period of centuries. The risks on offshore infrastructure and coast at a distance of more than half a kilometre away from the sand pit seem very small. \u95 There are numerical models available to judge the hydraulic and morphological responses of a deep sand pit. Calculations with the numerical model DELFT3D showed that flow velocities were predicted at a satisfactory level. This model also gives a good qualitative prediction of the backfilling/flattening and migration of a pit, a trench or a dump site under various environmental conditions, although the modelling of the magnitude of migration and backfilling or flattening in time should be further improved.KUST200

Physical Effects of Sea Sand Extraction / Fysische effecten van zeezandwinning

FRAMEWORK OF EXISTING POLICY Several Dutch policy documents are relevant with respect to sea sand extraction on the Netherlands Continental Shelf (NCS), ie: - the government directive on shallow mineral reserves SOD (Structuurschema Oppervlakte Delfstoffen= Master Plan Surface Minerals), - the regional directive on extraction at the NCS RON/MER (Regionaal Ontgrondingsplan Noordzee = Regional Extraction Plan North Sea), linked to an Environmental Impact Assessment (MER = EIA), - the policy document 4e Nota Waterhuishouding (= 4th Note on Water Management), - and the government directive on rural areas SGR (Structuurschema Groene Ruimte = Master Plan Green Areas). Core principles are to use shallow mineral reserves as economically as possible, to achieve an optimal gearing to other user functions in the North Sea, and to maintain sustainable functioning of the North Sea water system. Several sea sand extraction guidelines have been adopted to realize these core principles. Since 1993, a number of developments have occurred which are not included in the RON/MER. A revised version (RON2) could give these developments their due. Partly for this reason it is desirable to examine the physical effects of temporary sand extraction in the nearshore coastal zone, of large-scale sand extraction by means of navigation channel overdimensioning, and of largescale sand extraction in designated extraction areas. TEMPORARY SAND EXTRACTION IN THE NEARSHORE COASTAL ZONE In the execution of beach nourishment operations, it may be desirable to construct a transhipment station in the nearshore coastal zone in the form of a temporary sand pit. A delivery pipe then extracts beach nourishment sand from the sand pit, after which dredgers refill the sand pit with sea sand. The maximum volume of such a sand pit is in the order of 1 million m3. Data from previous sand extraction operations in the nearshore coastal zone show that the characteristic time scale on which the pit is filled to about two-thirds of its capacity, is approximately six to twelve months. Model calculations indicate that an unfilled sand pit in the nearshore coastal zone causes the coastline to recede a maximum of several metres in one year. The direct consequences of a temporary sand pit for coastal safety are negligible if the sand pit is constructed at a depth of the coastal profile below NAP1 \u96 7m. Calculations with dune erosion model DUROSTA show that in that case the increase in dune erosion volume is less than 5%. LARGE-SCALE SAND EXTRACTION BY OVERDIMENSIONING OF NAVIGATION CHANNELS Overdimensioning, ie widening and deepening of the Euro-Maas Channel and the IJ Channel is one of the options for large-scale sand extraction. If the \u91Zero-Plus option\u92 in the present RON/MER is executed, the maximum mineable amount is estimated to be 320 million m3 for the Euro-Maas Channel and 200 million m3 for the IJ Channel. The consequences for shipping are generally positive: the width and depth increase and flow velocity crossing the channel decreases. However, depending on the design of the overdimensioning, around the jetty heads a complex flow pattern can occur which could hinder the shipping through the channel. Larger wave heights could furthermore occur, due to the fact that waves can penetrate further inshore through the navigation channels. Widening and deepening the navigation channels postpones the need for maintenance for an certain period of time. It increases the dredging margin, ie the difference between the actual depth and the target depth, as well as the distance between shipping traffic and slopes. Estuarine circulation, causing a shoreward flow of the salt seawater near the bottom, while the lighter, fresh river water near the surface flows offshore, may strengthen. This could result in an increase of silt transport towards the harbours. Erosion of the navigation channel banks could result in nearby existing cables and pipelines getting exposed, with risk of breach. Furthermore, erosion of the (deeper parts of the) coastal zone has a negative influence on the total sand budget of the Dutch coast. Over a period of 50 years, the erosion zone can expand over a distance of 6 to 20 kilometres along the deeper section of the coast. It\u92s influence on the nearshore coastal zone adjacent to the shipping channels is expected to be small, as a result of the dominating influence of the harbour jetties, resulting in sedimentation. The effect of navigation channel overdimensioning on coastal safety is of importance only with respect to the seawall around the jetties. This effect is not investigated in this report. LARGE-SCALE SAND EXTRACTION IN DESIGNATED EXTRACTION AREAS Large-scale sand extraction in designated extraction areas exceeding 100 million m3 could affect ecology, cables and pipelines, coastline maintenance and coastal safety. Sand extraction causes the entire bottom fauna of the extraction pit to disappear. The bottom fauna can recover only if the water residence time in the extraction pit is less than approximately 10 days, as a result of which the oxygen content remains at the same level. It is important, therefore, that vortices down the sand pit slope and stratification underneath the original seabed are avoided. By positioning the length of the sand designated extraction areas parallel to the flow direction, a process occurs which causes the designated extraction area to accelerate the flow, which in turn results in quicker water refreshment. The presence of a large-scale sand designated extraction area also has morphological consequences, the most important of which is orientation towards the tidal current and the length/width ratio. Model calculations show that continued deepening after construction is possible, depending on the geometry of the sand designated extraction area. Within a period of 50 years, banks caving in and the extraction pit being moved could cause problems with respect to cables and pipelines within a zone of several kilometres around the extraction pit. If the extraction pit is located near the seaward boundary of the coastal foundation zone, this could cause sand loss in the coastal zone. (At the time of publication of this report, the seaward boundary of the coastal foundation zone was not formally established. This will probably be the established NAP \u9620m depth contour.) The effects of large-scale sand extraction on coastline maintenance and coastal safety seem to be limited. Based on a limited number of numerical model calculations to predict the effect of a future Second Maasvlakte, the conclusion is drawn that there is no significant increase in hydraulic boundary conditions (water levels, wave heights and wave periods), and that structural receding of the coastline position is not to be expected within a period of 5 years. However, the effect on the coastline position over a longer period, for example 50 years, has not been clearly mapped out as yet. RECOMMENDATIONS For temporary sand extraction in the nearshore coastal zone along the straight Dutch coastline and the central coastal sections of the islands, the following recommendations are given: \u95 It is recommended in any case that after the sand nourishment the temporary sand pit be filled to the original sea bed elevation. \u95 It is furthermore recommended to demand compensation for the loss of sand transported to the pit from the surrounding area during the use of the temporary sand pit. This compensation can be achieved by overdimensioning the sand nourishment or by creating an extra sand buffer at the temporary sand pit. The volume of this compensation can be estimated by means of a formula presented in this report. \u95 To prevent any adverse consequences of the temporary sand pit to coastal safety, it is recommended to carry out the extraction operations seaward of the NAP \u967m line with a surface area under 10 ha. For the Zeeland and South Holland islands and for the heads of the Wadden Islands, further conditions need to be determined for temporary sand pits in the nearshore coastal zone. For large-scale sand extraction by means of overdimensioning of the navigation channels, the following recommendations are given: \u95 To prevent wave reflection on the navigation channel banks it is recommended that the slopes be at least as gentle as 1:7. \u95 With respect to cables and pipelines, it is recommended that an influence zone of 6 to 20 kilometres, running parallel to the navigation channels, be taken into account over a period of 50 years. Possible measures are the creation of a 1,000 metre buffer zone, deeper digging in of cables and pipelines, and periodical checks for possibly exposed cables and pipelines. \u95 As a result of the complex flow pattern around the jetty heads, it is recommended that navigation channel entrance design be studied using a numerical model. \u95 It is recommended to investigate beforehand if navigation channel overdimensioning results in estuarine circulation changes, and if this is the case, to indicate whether an increase in sedimentation of the harbours may be expected. \u95 It is recommended to chart the positive and negative effects on the sand budget of adjoining coastal sections. It is furthermore recommended to define the boundaries of this coastal zone parallel to the navigation channels where an influence of the navigation channel is accepted, taking into account a maximum overdimensioning and expected expansion of the morphological influence area in the longer term. \u95 It is recommended to carry out further studies into the effect of navigation channels on wave conditions in the nearshore coastal zone and to examine how overdimensioning affects wave conditions during extreme conditions. \u95 It is recommended to examine the effects of large-scale sand extraction by navigation channel overdimensioning in connection with the effects of other large-scale interventions in the North Sea, eg during future Environmental Impact Assessment (EIA) studies. For large-scale sand extraction in designated extraction areas the following recommendations are given: \u95 With respect to cables and pipelines, it is recommended that influence zones of several kilometres around the large-scale sand designated extraction areas be taken into account over a period of 50 years. Possible measures are the creation a 1,000 metre buffer zone, deeper digging in of cables and pipelines, and periodical checks for possibly exposed cables and pipelines. \u95 It is recommended to create a buffer zone of several kilometres between large-scale extraction pits and the coastal zone. \u95 Despite the fact that large-scale sand extraction in designated extraction areas does not seem to have any significant adverse effect on coastal safety, it is recommended to include this aspect when considering large-scale sand extraction in designated extraction areas. \u95 If considering large-scale sand extraction in a sand designated extraction area, it is recommended to carry out a study of the oxygen concentration at the bottom by means of a water quality model. \u95 With respect to the geometry of the sand designated extraction area, it is recommended not to draw up quantitative guidelines. Instead it is recommended to examine the effects on the relevant user functions beforehand for every large-scale sand extraction operation, for example by means of a Milieu Effect Rapportage. \u95 It is recommended to examine the effects of large-scale sand extraction in designated extraction areas in connection with the effects of other large-scale interventions in the North Sea, eg during EIA studies. NOTE ALSO A DUTCH VERSION IS ADDED TO THE FILE

WTI 2017 Beschrijving Faalmechanisme Duinafslag

Dit document bevat een fenomenologische beschrijving van het faalmechanisme duinafslag. Er wordt beschreven welke belasting en welke sterkte er onder maatgevende omstandigheden aanwezig zijn. Vervolgens wordt beschreven hoe het faalmechanisme duinafslag plaatsvindt, hoe dit kan leiden tot falen van de primaire waterkering en hoe de waterkeringbeheerder dit faalmechanisme kan beoordelen. Vervolgens wordt aan de hand van een gebeurtenissenboom beschreven wat er gebeurt indien een waterkering faalt als gevolg van het faalmechanisme duinafslag.WTI201