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Denne rapport består af en række uafhængige kapitler vedrørende klapning og klapningspraksis samt anbefalinger til Best Practice ved større klapninger typisk i forbindelse med anlægsarbejder. Den aktuelle forvaltningspraksis i en række europæiske lande er gennemgået med udgangspunkt i anbefalinger vedrørende praksis for klapning udarbejdet af HELCOM og OSPAR. Anbefalingerne fra HELCOM/OSPAR omfattes i rapporten af følgende emner: a) Hierarki for placering af opgravet marint materiale; b) Krav til ansøgninger om klapning; c) Plan for prøvetagning i forbindelse med klapninger både før og under klapningen; d) Krav til karakterisering af det opgravede materiale i relation til fysiske, biologiske og miljøkemiske parametre; e) Procedurer for udstedelse af klaptilladelse; f) Håndtering af klapningen herunder angivelse af ”Best Practice”; g) Iværksættelse af overvågning/monitering af klapningen; h) Krav til afrapportering til HELCOM og OSPAR. De enkelte landes praksis er vurderet i forhold til HELCOM/OSPARs anbefalinger med særligt fokus på den danske forvaltning, som den er beskrevet i Klapbekendtgørelsen. I tilhørende bilag til rapporten er angivet diverse krav til tilladelser til klapning i danske farvande samt internationale kriterier for tålegrænser for miljøfremmede stoffer. I Danmark er den foretrukne metode til dumpning af opgravet sedimentært materiale klapning. Det opgravede materiale placeres i en splitpram, og frigives ved åbning af klapperne i bunden af splitprammen, deraf navnet. Materialet synker straks efter klapning mod bunden forårsaget af materialets højere densitet. Der findes en række alternative metoder til klapning fra splitpram, som i dag anvendes forskellige steder i verden. Pumpning af det opgravede materiale til bunden evt. i kombination med en diffusor ved overgangen fra pumperør til bund er et alternativ, der vil fjerne spredning af finkornet materiale og frigivelse af næringsstoffer m.m. under transporten fra splitprammen til

This paper describes a new morpho-dynamic 3D surf-zone model. The hydrodynamic model used for this purpose is the MIKE 3 Wave FM Model. This model solves the 3D Navier-Stokes equations on a 2D horizontal unstructured mesh with a sigma transformation describing the vertical coordinate. A recent solution to the well-known over-production of turbulence outside the surf-zone in RANS models has been applied and is shown to improve the predicted undertow profiles. The sediment transport is modelled using an advection-diffusion equation for the suspended load, together with a bed-load formulation. In the present paper the predicted surf zone hydrodynamics and sea bed evolutions are compared against experimental laboratory data.

The construction of hard protection measures along the northeast coast of Sealand, Denmark, has gradually led to profile steepening, loss of beaches, and increased storm erosion. Although the problem has been addressed for decades no common solutions have been implemented yet. However, the impact of cyclone Xaver in December 2013 with severe coastal erosion led to collaboration between the involved municipalities to work on a coherent solution for the entire coastline that involves sand nourishments, renovation and optimization of hard protection structures, and the restoration of recreational values. We present a concept of 'erosion pressure' as a simple method to estimate potential chronic (longshore) and acute (cross-shore) erosion on protected coasts. The erosion pressure estimates are reliable at the investigated coast and the concept has proved useful for dissemination to stakeholders about coastal dynamics.

This master thesis examines the morphodynamics of two coastal barriers: a barrier spit and a barrier island, located in a micro-tidal low to moderate energetic coastal system, Rødsand, Denmark. The purpose is to improve the understanding of the morphodynamic processes in this system. The study encompasses three research areas: background morphology, hydrodynamics and sediment transport. A variety of research methods have been applied to investigate the barrier morphodynamics such as side-scan sonar, dGPS, sediment deposits and samples, and simulating sediment dynamics with numerical models like LITPACK and MIKE 21. The background morphology studies conclude that the barrier spit is more developed in terms of barrier volumes and dune crest heights than the barrier island. Furthermore, the analysis of sediment deposits showed that the beach is composed of five sediment layers. The hydrodynamic results are that waves and water levels are partially dependent variables and often opposite correlated and that the wave climate is multi-energetic and multi-directional. Also, a storm impact model showed that collision regimes occur regularly on the barrier spit and the barrier island is recurrently overwashed and inundated under present hydrodynamic conditions. Moreover, under a predicted rise in sea-levels and storm-surges the collision regimes increase significantly at the barrier spit and the barrier island is constantly exposed to overwashes and inundations. The simulation of the sand transport in a longshore direction revealed a net littoral drift to the east and erosion/accretion patterns on both barriers, which resonates with the morphological findings. Lastly, a simulated overwash event uncovered how much waves and water levels contribute to the transport of sand and water across the barrier island. On the basis of these findings a conceptual model has been created to improve the understanding of how this coastal system evolves and behaves., This master thesis examines the morphodynamics of two coastal barriers: a barrier spit and a barrier island, located in a micro-tidal low to moderate energetic coastal system, Rødsand, Denmark. The purpose is to improve the understanding of the morphodynamic processes in this system. The study encompasses three research areas: background morphology, hydrodynamics and sediment transport. A variety of research methods have been applied to investigate the barrier morphodynamics such as side-scan sonar, dGPS, sediment deposits and samples, and simulating sediment dynamics with numerical models like LITPACK and MIKE 21. The background morphology studies conclude that the barrier spit is more developed in terms of barrier volumes and dune crest heights than the barrier island. Furthermore, the analysis of sediment deposits showed that the beach is composed of five sediment layers. The hydrodynamic results are that waves and water levels are partially dependent variables and often opposite correlated and that the wave climate is multi-energetic and multi-directional. Also, a storm impact model showed that collision regimes occur regularly on the barrier spit and the barrier island is recurrently overwashed and inundated under present hydrodynamic conditions. Moreover, under a predicted rise in sea-levels and storm-surges the collision regimes increase significantly at the barrier spit and the barrier island is constantly exposed to overwashes and inundations. The simulation of the sand transport in a longshore direction revealed a net littoral drift to the east and erosion/accretion patterns on both barriers, which resonates with the morphological findings. Lastly, a simulated overwash event uncovered how much waves and water levels contribute to the transport of sand and water across the barrier island. On the basis of these findings a conceptual model has been created to improve the understanding of how this coastal system evolves and behaves.

Coastlines around the world are receding due to coastal erosion.With rising sea levels and a potential climatic deterioration due to climate change, erosion rates are likely to increase at many locations in the future.Together with the current preference of people to settle near or directly by the ocean, coastal erosion issues become increasingly more important to the human values at risk. Along many Danish coastlines, hard structures already act as coastal protection in the form of groins, breakwaters, revetments etc. These eroding coasts however still lack sand and where the public, in general, neglects the need for sand replenishment i.e. in the form of repeated sand nourishments. Here we present a conceptual model and method for dividing coastal erosion into acute and chronic erosion pressure, respectively. We focus on the model use for management and climate change adaptation purposes and on how to make coastal processes and the impacts of climate change on the coasts more comprehendible to the public.

This study focuses on one distinct feature to be found on coasts exposed to a very oblique wave incidence, namely an accumulating spit. That is a spit where no retreat of the shoreline is going on along the spit. This requires a monotonically decreasing sediment transport capacity from the updrift stretch of coast, along the spit as the coast curves away from the approaching waves towards the tip of the spit. A one-line model for the coastline development predicts that accumulating spits can exist on coasts exposed to waves approaching at angles larger than 45 degree only. It is suggested that such a spit grows without changing its shape i.e. an equilibrium form emerge if the coast is exposed to a constant wave climate. During experiments conducted in a wave tank where a uniform stretch of coast was exposed to waves approaching at a very oblique angle an accumulating spit was formed at the down-drift end of the coast. The spits approached equilibrium forms when constant wave climates were applied. The sediment transport around the spit has been investigated by two-dimensional models. The characteristic length scale for the equilibrium form depends linearly on the width of the surf zone for constant wave incidence at the updrift stretch of coast. The factor of proportionality is in reasonable agreement with the experimentally found.