| 1. |
- Adell, Anna, et al.
(författare)
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Morphological development of a small-scale beach nourishment in a non-tidal area
- 2023
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Ingår i: The Proceedings of the Coastal Sediments 2023. - : WORLD SCIENTIFIC.
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Konferensbidrag (refereegranskat)abstract
- Combining hard and soft costal protection solutions can be an appropriate measure to enhance structure lifetime. This study aims to quantify the morphological evolution of the nourished stretch and adjacent coastlines. A small-scale beach nourishment has been performed in front of a rock revetment at site in Faxe Ladeplads in Zealand, Denmark. The overall objective is to learn more about the dynamics of small-scale nourishments in low energy environments. Monitoring techniques include repeated topographic (Trimble RTK-GPS, drone surveying) and bathymetric (single beam) measurements. To measure the hydrodynamic conditions two surface acceleration buoys deployed at -4 and -7 m water depth were used. Sediment volumes from nourishments of size 70,000 m3 and 20,000 m3 redistributed relatively quickly. The nourished material built up the cross-shore profile and a longshore bar in this area, and distributed sediments in the direction of the dominant littoral drift (SW). Results suggest that the morphological evolution of the nourishment is dependent on local hydrodynamic conditions and local geomorphology. These findings have implications for the main objectives of preventing wave overtopping onto an adjacent coastal road during extreme events and restoring a beach for recreation.
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| 2. |
- Adell, Anna, et al.
(författare)
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Multi-scale wave modelling; Field validation in Faxe Bay, Denmark
- 2023. - 37
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Ingår i: Proceedings of the Coastal Engineering Conference. - 9780989661164
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Konferensbidrag (refereegranskat)abstract
- Access to local nearshore wave climate conditions on a detailed spatial scale is important for many coastal engineering practices. These include assessing the flood risk of coastal infrastructure, designing coastal protection measures, and estimating sediment transport processes and wave run-up. The present study displays a multi-scale wave modelling approach using the numerical wave model SWAN (Booij et al., 1999) together with field data applied in the southern Baltic Sea. The main objective of the study was to investigate the possibility of employing a single wave model for seamless simulations over several scales in time and space, from offshore to nearshore, including the effects of grid size and resolution. Validation with extensive field data was a crucial part of the study.
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| 3. |
- Adell, Anna, et al.
(författare)
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Open-access portal with hindcast wave data for Skåne and Halland
- 2021
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Ingår i: Vatten: tidskrift för vattenvård /Journal of Water Management and research. - 0042-2886. ; 77:2, s. 81-90
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Wave climate data for the Swedish provinces Skane and Halland, were hindcast using SWAN, a third-generation spectral wave model. The 40-year wave dataset, from 1979 to 2019, is made available through an open-access data portal (https://gis.sgi.se/vagmodell/). The wave data has a three-hour resolution and includes significant wave height, peak wave period, and wave direction. The wave model domain encompasses the Baltic Sea, Öresund, Kattegat, and Skagerrak. Along the coast of Skane and Halland, the spatial resolution of the computational nodes, from which data can be extracted in the portal, is 250 m. In the offshore areas, the resolution of the computational grid is coarser. The simulated significant wave height was validated against observations from 25 wave gauges, operating intermittently during the simulation period. The coefficient of determination, R2, for these comparisons ranged from 0.46 to 0.93 for the different stations. For 15 wave gauges, R2 values for the comparisons exceeded 0.80. The wave model will continuously be updated and developed.
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| 4. |
- Almström, Björn, et al.
(författare)
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Decision support tool to mitigate ship-induced erosion in non-uniform, sheltered coastal fairways
- 2022
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Ingår i: Ocean and Coastal Management. - : Elsevier BV. - 0964-5691. ; 225
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Tidskriftsartikel (refereegranskat)abstract
- The negative impact of maritime traffic in terms of shore erosion in sheltered coastal fairways can be mitigated by sustainable fairway management. Mitigation measures include regulating the ship traffic in terms of speed, routes, or size of ships, but can also involve erosion protection along a fairway. For effective shoreline management of a fairway, it is essential to predict ship waves, to identify sites with potential erosion problems, and to investigate the effectiveness of different measures before implementing them. Several attempts have been made to develop site-specific criteria for managing ship waves. However, few available generic models consider primary waves generated by large ships in confined fairways. Therefore, a tool for supporting decisions in fairway management was developed. The decision support tool is based on simplified formulas for ship- and wind-wave prediction, combined in a framework that enables automatic, rapid assessments on large spatial and temporal scales. Moreover, the tool requires only readily available input data, such as data on AIS, bathymetry, shoreline geometry, wind, fairway centreline, and grain size. The output from the model includes ship and wind wave heights and potential erosion sites. The decision support tool was applied to the Furusund Fairway, Sweden, by simulating one year of ship traffic to validate its capability of identifying potential erosion sites. The simulation demonstrated that the tool was capable of identifying known erosion sites in the fairway. Additionally, scenarios with different speed regulation strategies for the Furusund Fairway were investigated using the decision support tool. Overall, it is concluded that the developed tool enables rapid assessment of ship waves, wind waves, and potential erosion over large areas in fairways.
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| 5. |
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| 6. |
- Almström, Björn, et al.
(författare)
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Experiences of nature-based solutions for mitigating ship-induced erosion in confined coastal waters
- 2022
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Ingår i: Ecological Engineering. - : Elsevier BV. - 0925-8574. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic forces from ships operating in sheltered, confined fairways can result in increased wave impact and sediment transport leading to loss of land and habitats. Nature-based solutions (NBS) offer the potential to mitigate ship-induced erosion and increase biodiversity and ecosystem services. The aim of this study is to evaluate the performance of NBS in a sheltered, confined fairway located in a cold, temperate region. The case study presents the results of a 2.5-year study of the morphologic response at two sites where NBS was implemented to mitigate bluff erosion and at one site where NBS was implemented to mitigate the retreat of a reed belt. Moreover, a qualitative assessment was made of the vegetation development at the sites. The results showed that fine sediments with planted vegetation could not withstand the hydrodynamic forces induced by the ships. However, by adding sills as stabilizing structures, the forces were sufficiently attenuated for the vegetation to establish. The vegetation, which reduced the ship-generated waves and currents, was especially important during high water-level events when the energy dissipation by the sill decreased. Moreover, a small-scale nourishment was successfully applied to mitigate bluff erosion without negatively affecting sediment supply to an adjacent sandy beach. This study demonstrates that NBS can be implemented to retain erodible sediment and favour vegetation growth in fairways experiencing primary and secondary waves produced by large, ocean-going ships.
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| 7. |
- Almström, Björn
(författare)
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Nature-based shore protection against ship waves in intra-coastal fairways
- 2022. - first
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sjötrafik har alltid haft en stor betydelse för vårt samhälle genom att transportera gods och människor mellan och inom länder. Transporter till sjöss har stora fördelar associerat till relativt låga klimatutsläpp och transportkostnader. Tyvärr medför sjötrafik även en negativ påverkan på vår miljö. Den negativa påverkan kan till exempel bestå av utsläpp av luftföroreningar, tömning av ballastvatten eller utsläpp av olja. I farleder kan fartyg även inverka på de hydrodynamiska förhållandena genom att generera strömmar och vågor. Fartygsvågor kan resultera i skador på stränder och konstruktioner vid vattnet, öka grumlingen i vattnet, eller till och med innebära en fara för människor som vistas i eller på vattnet. Särskilt stor blir påverkan från fartygsvågor i farleder som naturligt inte utsätts för vindvågor. Det gäller farleder inomskärs, i vattendrag och i sjöar. Fartygsvågor kan här utgöra ett betydande tillskott till de totala vågkrafterna som påverkar stränderna. Om vågorna är tillräckligt stora och frekventa kan de orsaka erosion av stränderna. Denna effekt kan minskas genom att sänka fartygens hastighet, ändra fartygsrutter, begränsa storleken på fartygen eller förstärka stränderna med erosionsskydd. En farled där påverkan av fartygs- och båttrafik varit påtaglig under en lång tid är Furusundsleden i Stockholms skärgård. Furusundsleden är en viktig farled med reguljär trafik av passagerarfärjor till Åland, Finland och Estland. Därutöver trafikeras farleden även av skärgårdstrafik och kryssningsfartyg under sommarhalvåret. Fartygserosionen i Furusundsleden har varit ett uppmärksammat problem ända sedan 1980-talet. Hastigheterna har begränsats för större fartyg med effekten av erosionen avtagit längs farleden. För vissa sträckor har hastighetsbegränsningen dock inte varit en tillräcklig åtgärd för att förhindra erosionen. Därför har tidigare utredningar föreslagit någon form av erosionsskydd längs med dessa stränder. Traditionellt har erosionsskydd i farleder utgjorts av att stränderna har stabiliserats med sten eller betong. Denna metod har i många fall hindrat erosionen av stränderna, men på bekostnad av natur-, landskaps- och rekreationsvärden. De traditionella skydden kräver vanligen mer material och har en hög underhållskostnad. Därför börjar traditionella erosionsskydd alltmer ersättas av naturbaserade lösningar för att motverka erosion. Naturbaserade lösningar innebär att man tar hjälp eller inspireras av naturliga processer för att skapa erosionsskydd som bevarar eller tillskapar värden för naturen och människan. Eftersom naturbaserade lösningar är en relativt ny metodik finns det liten erfarenhet av hur de fungerar som erosionsskydd mot fartygsvågor. Denna avhandling syftar till att undersöka effektiviteten av naturbaserade lösningar som erosionsskydd i farleder och metoder för att beräkna fartygsvågor i farleder med varierande djupförhållanden. För att undersökan effektiviteten av naturbaserade lösningar anlades olika typer av naturbaserade lösningar på tre platser i Furusundsleden, som är belägen i Stockholms skärgård. Två av platserna utgjordes av eroderande moränjord, där en flera meter hög erosionsbrant uppstått. Den tredje platsen utgjordes av ett område där vassen nästintill försvunnit på grund av fartygsvågorna. Olika varianter av naturbaserade erosionsskydd testades. Experimenten visade att en variant där en stenrevel, som löpte parallellt med stranden, kombinerades med vegetation innanför var mest framgångsrik att hindra erosionen. Innanför stenreveln skapades förutsättningar för finare sediment att ackumulera och vegetation att växa. Utöver fältexperimenten med de naturbaserade erosionsskydden innefattar avhandlingen även en ny matematisk modell för att identifiera platser där fartygstrafik kan ge upphov till erosion längs en farled. Modellen är i första hand tänkt att fungera som ett stöd inför beslut om åtgärder i en farled. Det kan vara åtgärder som till exempel att begränsa hastigheten eller identifiera lokaler där behov av erosionsskydd behöver utredas ytterligare.
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| 8. |
- Almström, Björn, et al.
(författare)
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Predicting ship waves in sheltered waterways – An application of XBeach to the Stockholm Archipelago, Sweden
- 2021
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Ingår i: Coastal Engineering. - : Elsevier BV. - 0378-3839. ; 170
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Tidskriftsartikel (refereegranskat)abstract
- Predicting hydrodynamic forces from ship waves along a waterway is essential for managing a sustainable shoreline in fairways. In this context, a numerical model can be a useful tool for calculating ship waves in fairways with complex geometry. XBeach is a numerical model offering the potential to be a one-tool solution for simulating ship waves from the ship to the shore. However, XBeach has not been evaluated against field measurements of ship waves. Thus, the objective of this paper is (1) to compare XBeach against high-quality field measurements of ship waves and (2) to assess its general applicability to ship wave simulations through an extensive sensitivity analysis with regard to the main input parameters. Water level measurements from 42 passages of the M/S Baltic Princess in the Furusund navigational fairway in the Stockholm Archipelago were chosen to test and evaluate XBeach. The results showed that XBeach was able to generate and propagate the primary and secondary waves. Primary waves were reproduced well with a mean absolute error (MAE) of 3 cm for the drawdown height. The overall secondary wave field pattern was represented by XBeach; however, for the largest, single divergent wave comparison for height, period, and timing showed deviation from the observations. Overall, XBeach was found to be a robust model for ship wave applications, only requiring input data typically available. Sensitivity analysis for a generic hull, derived from the type of vessel studied and with the corresponding dimensions as the real hull, showed similar results enabling robust and reliable simulations without access to detailed technical drawings.
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| 9. |
- Almström, Björn, et al.
(författare)
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Protecting intra-coastal fairways from ship waves using living shorelines techniques : A full scale experiment
- 2023
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Ingår i: Coastal Sediments 2023. - : WORLD SCIENTIFIC. - 9789811279898 ; , s. 2008-2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study evaluates the effectiveness of applying living shoreline techniques for protecting reed belts and eroding bluffs in an intra-coastal fairway with intense traffic by ocean-going vessels. The re-establishment of the reed belt can be explained by the dissipation of the hydrodynamic forces by the sill structure. There is a negative relationship between vegetation growth and wave exposure due to washout from the rhizome layer and destabilization of the reed belt fringe by excessive wave forces. A stabilizing structure in front of vegetation may reduce the washout of seeds and promote the establishment and survival of sprouts. The stabilization of the bluff can be explained by that the protective measure reducing waves attacking the bluff base. Waves attacking the bluff base are one of the dominant processes for bluff erosion. In this study, the wave forces were reduced by the sill and the vegetation on the foreshore, in combination with elevated the bluff base due to the foreshore. After reinforcing the sills in September 2019 there has been no need for maintenance of the protective measures. The results after a four-year study period indicate reed growth can be promoted by installing a sill parallel to the shore and that eroding bluffs can be stabilized by creating a vegetated foreshore in front of the bluff combined with a shore parallel sill. This study showcases the potential of using living shoreline techniques in fairways exposed to intense ship traffic from larger vessels to promote reed growth and reduce bluff erosion.
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| 10. |
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