Uppvärmningen av klimatet resulterar i att havsnivån stiger globalt. Detta riskerar att få omfattande sociala, ekonomiska och ekologiska konsekvenser, i synnerhet för områden som angränsar mot kusten. I Sverige har kommunerna planmonopol och förväntas ta ett stort ansvar för klimatanpassning. I Stockholm antas havet stiga cirka 0,5 meter till år 2100 och det kommer troligtvis att fortsätta stiga efter det. Denna studie bygger främst på intervjuer i syftet att utreda huruvida det råder konsensus mellan stadens planerare och politikerna i Stockholms stad gällande hur hantering av en förhöjd havsnivå bör ske. Frågan är relativt ny och i ett spekulativt stadium vilket gör att det är svårt att se tydliga skiljelinjer. Samtliga personer som ingått i denna studie är dock överens om att problematiken kring ett stigande hav är en viktig fråga i behov av mer djupgående utredningar. Även att det i slutänden kommer att bli en samhällsekonomisk analys som blir avgörande för vad, när och hur något ska genomföras. / The warming of the climate will result in rising sea levels globally. This is likely to result in widespread social, economic and environmental consequences, especially for areas adjacent to the coast. In Sweden the municipalities have a monopoly for planning and the municipalities are expected to take a substantial responsibility for the city’s adaptation to the new sea levels. In Stockholm, the expected sea level rise is approximately 0.5 meters until 2100 and the sea is expected to continue to rise after 2100. This study is based on interviews with the purpose to investigate whether there is consensus between the city planners and the politicians in the City of Stockholm in how the management of the rising sea levels should be handled. The question is relatively new and rather in a speculative stage which makes it difficult to see clear dividing lines. However all interviewees in this study agreed that the problem of rising sea levels is an important issue that is in need of more in-depth investigation. Although it will ultimately become an economic analysis that will determine what, when, and how something should be implemented.

The Antarctic ice sheet is increasingly contributing to sea-level rise because of accelerated mass losses at its floating extensions -- its ice shelves. By floating while remaining attached to the grounded ice sheet, ice shelves buttress (i.e. restrain) the inland ice in such a way that ice-shelf losses lead to accelerated ice discharge in the ocean. This thesis investigates the stability of Antarctic ice shelves -- so crucial for the stability of the entire ice sheet -- using the Roi Baudouin Ice Shelf (RBIS), Dronning Maud Land, East Antarctica, as a case study. The RBIS has remained relatively stable over the last millennia and presents various kilometre-scale features (pinning point, ice-shelf channels and englacial lakes) with potential impact on its present and future stability.We first derive a horizontal velocity field, combining interferometry and speckle tracking with Synthetic Aperture Radar images from ERS 1/2 and ALOS-PALSAR, respectively. The resulting velocities and associated shear-strain rates represent the most detailed fields, currently available for the RBIS and clearly resolve small-scale features of the RBIS: significant slow-down and shearing are observed upstream of a small pinning point and ice converges at ice-shelf channels. We then combine our flow field with high-resolution elevations from TanDEM-X to infer the Basal Mass Balance (BMB) of the RBIS. This method relies on mass conservation in a Lagrangian frame and enables us to finely detect spatial variability in the BMB. We show that the BMB of the RBIS varies substantially on sub-kilometre scales. Our technique is promising and could easily be applied more widely.Additionally, the flow field is used to investigate how considering/ignoring small pinning points in observations (geometry and velocities) impacts data initialisation of poorly known parameters (e.g. basal friction, ice viscosity) and subsequent ice-sheet modelling with BISICLES. We find that overlooking the pinning point in the bathymetry leads to erroneous ice-shelf properties whereas accurately capturing the pinning point in velocities is of secondary importance. Finally, before concluding the thesis, we discuss the stability of the RBIS and its neighbouring ice shelves. Most studies agree that the ice shelf has remained stable over the last decades to millennia and would likely remain so in the absence of external forcing. We however point out to three potential triggers of instabilities: (i) large quantities of surface meltwater are formed in the grounding zone and subsequently stored on the ice shelf, thereby providing fuel for hydrofracturing; (ii) ice-shelf channels are found to significantly incise the ice inland and (iii) a bathymetric trough beneath the RBIS forms a potential gateway for warm water intrusions the ice-shelf cavity, which could destabilise the ice shelf from below. We close with a short essay on the importance of outreach, where we argue that public engagement as a scientist should be considered as being part of science and should be valued for its worth. This chapter gives us the opportunity to present outreach activities undertaken in the frame of this thesis. We conclude that, just like ice shelves control Antarctic ice losses, science communication determines transfers of scientific expertise to public knowledge. / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

The increasing rate of global sea mean level rise, one of many effects of climate change, will most likelyproduce heightened risk of coastal flooding. Cities located along coastlines have to adapt to thesecircumstances that otherwise will increase the magnitude and frequency of coastal flooding. The purposeof this study is to evaluate the current and future risk of coastal flooding in central Stockholm in relationto global sea level rise. The overall coastal flood risk of central Stockholm is assessed using the currentsea level as well as with possible future sea level rise. Wave modelling is carried out in Saltsjön toestimate the possible addition to extreme sea levels from wave action. The wave characteristics isdetermined according to the physical properties of inner Saltsjön and local meteorological conditions.In-depth case studies regarding flood risk and flood prevention measures are carried out on Stadsholmenand Hammarby Sjöstad, two areas with very different physical characteristics. Areas most prone toflooding in these districts are identified using flood vulnerability maps. Suggestions for flood defencemeasures for the identified vulnerable areas are presented. It is evident that implementation of flooddefence should be adapted after the physical and social properties of the locality. Results of this studycorrelates with well with similar research claiming that there is a small risk of significant coastalflooding in central Stockholm. The flood risk will not increase significantly in the near future, primarilydue to the effect of regional uplift counteracting the global sea level rise. The accelerating rate of globalsea level rise in combination with possible trend changes of meteorological extremes will however mostlikely generate larger problems with coastal flooding in a longer time span. / En av de mest påtagliga effekterna av pågående klimatförändringar är global havsnivåhöjning. Ökademedel- samt extremnivåer kommer innebära ökad risk för översvämningar längs med kuststräckor.Städer belägna längs med kuster behöver anpassa sig efter dessa framtida förhållanden för att undvikaomfattande skador och förluster. Syftet med denna studie är att utvärdera den nuvarande och framtidarisken för kustöversvämning i centrala Stockholm med koppling till global havsnivåhöjning. Dengenerella risken för kustöversvämning i centrala Stockholm bedöms för den nuvarande havsnivån såvälsom för möjliga framtida havsnivåer. Modellering och beräkning av möjliga våghöjder för Saltsjönutförs för att uppskatta det potentiella tillägget till extrema havsnivåer från vågeffekter. Den potentiellavåghöjden i inre Saltsjön kontrolleras främst av de rådande meteorologiska och fysiskaförutsättningarna, så som vindens styrka och riktning. Mer ingående fallstudier gällandeöversvämningsrisk och åtgärder för att förhindra översvämningar utförs för Stadsholmen (Gamla Stan)och Hammarby Sjöstad, två områden med distinkt olika stadsbild och förutsättningar. Områden mestsårbara för kustöversvämning i dessa distrikt identifieras med hjälp av översvämningssårbarhetskartor.Förslag till åtgärder för att förhindra översvämningar i dessa områden presenteras. Hur och vad för typav översvämningsskydd som anläggs bör anpassas efter den specifika plats fysiska och estetiskaförutsättningar. Resultaten i denna studie stämmer överens med tidigare forskning vad gällande den lågarisk för kustöversvämning som finns i centrala Stockholm. Översvämningsrisken kommer inte ökanämnvärt i den närmaste framtiden, främst på grund av den regionala landhöjningens motverkandeeffekt till den globala havsnivåhöjningen. Däremot kommer hastigheten hos den globalahavsnivåhöjningen att öka. Detta i kombination med möjliga förändringar i meteorologiska extremerkommer troligtvis utgöra större risk för kustöversvämningar i ett längre tidsperspektiv.

The objective of this thesis was to establish how, in an emerging era of sinking islands andincreasing environmental degradation, ideas concerning climate justice have been developedin pacific small island states. These ideas have been analysed from a framework of southernand justice theory and, hence, been put in comparison to the global framework of climatejustice and the notion that sovereign states, no matter location or historical circumstances, areleft alone to deal with the worst effects of climate change.The research questions used to achieve the objective were: what ideas of climate justiceare produced in Kiribati, Fiji and the Maldives; in what way do these ideas affect their local adaptation strategies and how can these ideas be understood in light of southern theory? Thedata consisted of three national policies from the countries of interest in this thesis – Kiribati,Fiji and the Maldives – and manifest each country’s approach to dealing with the impacts of achanging climate and, especially, rising seas. These were analysed through a qualitativecontent analysis where an abductive approach was used to establish the themes that guided theanalysis. The result was that ideas of climate justice in the three countries are affected by thechanging tides, both by nature and the international community, but differ depending onnational leadership. It was also found that the adaptation strategies, while being nationalpolicies, all emphasise the need for international solidarity if being able to solve the issue ofdisappearing islands. This is something that has yet to take place within the global frameworkof climate change, where the global North do not want to acknowledge any responsibility forthe fate of small island states but rather aids affected countries based on goodwill and not oflaw.

Coastal socio-ecological systems face unprecedented challenges due to climate change, with impacts encompassing long-term, chronic changes and short-term extreme events. These events will impact society in many ways and prompt human responses that are extremely challenging to predict. This dissertation employs complex systems methods of agent-based modeling and machine learning to simulate the interactions between climatic stressors such as increased flooding and extreme weather and socio-economic aspects of coastal human systems. Escalating sea-level rise and intensified flooding has the potential to prompt relocation from flood-prone coastal areas. This can reduce flood exposure but also disconnect people from their homes and communities, sever longstanding social ties, and lower the tax base leading to difficulties in providing government services. Chapter 2 demonstrates a stochastic agent-based model to simulate human relocation influenced by flooding events, particularly focusing on the responses of rural and urban communities in coastal Virginia and Maryland. The findings indicate that a stochastic, bottom-up social system simulator is able to replicate top-down population projections and provide a baseline for assessing the impact of increasingly intense flooding. Chapter 3 leverages this model to assess how incorporating heterogeneity in relocation decisions across socio-economic groups impacts flood-induced relocation patterns. The results demonstrate how this heterogeneity leads to a decrease in low-income households, yet a rise in the proportion of elderly individuals in flood-prone regions by the end of the simulation period. Flood-prone areas also exhibit distinct income clusters at the end of simulation time horizon compared to simulations with a homogenous relocation likelihood. Lastly, Chapter 4 explores relationships between extreme weather and agricultural losses in the Delmarva Peninsula. Existing research on climatic impacts to agriculture largely focuses on changes to major crop yields, providing limited insights into impacts on diverse regional agricultural systems where human management and adaptation play a large role. By comparing various multistep modeling configurations and machine learning techniques, this work demonstrates that machine learning methods can accurately simulate and predict agricultural losses across the complex agricultural landscape that exists on the Delmarva peninsula. The multistep configurations developed in this work are able to address data imbalance and improve models' capacity to classify and estimate damage occurrence, which depends on multiple geographical, seasonal, and climatic factors. Collectively, this work demonstrates the potential for advanced modeling techniques to accurately replicate and simulate the impacts of climate on complex socio-ecological systems, providing insights that can ultimately support coastal adaptation. / Doctor of Philosophy / Coastal areas are facing increasing challenges from climate change, including rising sea levels and extreme weather conditions. This dissertation explores socio-economic consequences of these adverse environmental changes for coastal communities. Disruptive repetitive flooding due to exacerbated rise in sea levels is one of these consequences that may eventually leave some highly exposed coastal communities no alternative but migrating from their residences. Focusing on coastal Virginia and Maryland, Chapter 2 develops a data-informed model that can simulate individual relocation decisions and assess how they impact population changes and migration patterns. Chapter 3 employs this model to investigate how future changes in sea levels affect diverse socio-economic groups, their relocation decisions, and the resulting collective migration flows in flood-prone areas. We found that considering demographic differences leaves highly flood-prone areas with less low-income households, higher elderly individuals, and more economic clusters compared to simulations where these differences are not accounted for. Chapter 4 uses machine learning models to simulate the economic impact of extreme weather events as another manifestation of climate change on the agriculture in the Delmarva Peninsula. Through data-based modeling techniques, we identify the climatic conditions most responsible for agricultural losses and recognize modeling choices that enhance our predictive ability. Collectively, this dissertation demonstrates how sophisticated modeling techniques can be used to better understand the complex ways in which climate change will impact human society, with the ultimate goal of supporting adaptation strategies that can better address these impacts.

Les zones côtières ont depuis longtemps été attractives pour leur potentiel économique, et leur intérêt touristique et résidentiel. Elles ont fait l’objet d’une implantation massive dans tous les pays du monde. Or, les littoraux sont non seulement fragilisés par cette anthropisation, mais sont également sujet à des dégradations liées au changement climatique. À l’élévation du niveau de la mer souvent mise en avant dans les médias s’ajoute l’érosion intensifiée par les tempêtes et ouragans à répétition. Alors qu’émerge depuis plusieurs années la question des déplacés environnementaux ne disposant d’aucun statut protecteur, et dont le symbole le plus extrême est la situation de certains petits États insulaires dont le territoire est menacé de disparition par la montée des eaux, la question de la gestion de cette problématique dans le respect des droits humains se pose de manière accrue. L’enjeu de ce travail, s’appuyant sur des pays au profil différent : Bangladesh, États-Unis, France, petits États insulaires (notamment les Maldives, Kiribati, Tuvalu), est de rechercher les causes profondes de cette contrainte devenue tellement intense qu’elle conduit au déplacement, pour favoriser l’adaptation sur place ou mettre en œuvre un déplacement non plus conçu comme un échec mais comme une stratégie d’adaptation. Ce changement de perspective impliquera de mobiliser des outils juridiques issus de branches variées du droit (urbanisme, assurance, responsabilité et droit humanitaire, etc.) et surtout de respecter certains principes afin d’assurer l’anticipation et l’acceptation de la démarche par les populations. Fort de l’étude de ces exemples, il s’agira d’identifier ces éléments communs tout en mettant en lumière et en tenant compte des spécificités de chaque pays, de chaque communauté. / Coastal areas have always been attractive for their economic potential and their touristic and residential interest. They have been massively settled in countries all over the world. However, while coastlines are weakened by human impact, they are also subject to degradations due to climate change. Besides the sea-level rise, often emphasized by the media, we must consider the erosion caused by storms and hurricanes. The current context is strongly marked by the question of the environmental displaced persons who do not have any status. This situation can be illustrated by the small island states whose territory is threatened by the sea-level rise. Thus, the issue of managing these problems in respect with human rights arises to an increased extent. The challenge of this work, supported by different country profiles: Bangladesh, USA, France, Small Island States (including the Maldives, Kiribati, Tuvalu), is to seek the root causes of this dilemma that has become so intense that it leads to displacement, and then to promote and facilitate adaptation in-situ or adopt new displacement policies that are no longer perceived as a failure but as an adaptation strategy towards risks. This change of perspective intends to mobilize legal tools from various branches of law (Urbanism, Insurance, Liability and humanitarian law, etc.). It also intends to respect principles to ensure anticipation and acceptance of the approach by the people. With the study of these examples, we must identify these commons elements and take into account the specificities of each country and each community.

This thesis investigates the effectiveness of Low Impact Development Infrastructure (LIDI) and Green Infrastructure (GI) in reducing flooding resulting from heavy rainfall events and sea-level rise, and in improving stormwater quality in the City of Miami Beach (CMB). InfoSWMM was used to simulate the 5, 10, and 100-year, 24-hour storm events, total suspended solids (TSS), biochemical oxygen demand (BOD), and chemical oxygen demand (COD) loadings, and in evaluating the potential of selected LIDI and GI solutions in North Shore neighborhood. Post-development results revealed a decrease of 48%, 46%, and 39% in runoff, a decrease of 57%, 60%, and 62% in TSS, a decrease of 82%, 82%, and 84% in BOD, and a decrease of 69%, 69%, and 70% in COD loadings. SWMM 5.1 was also used to simulate the king tide effect in a cross section in Indian Creek Drive. The proposed design simulations successfully demonstrated the potential to control flooding, showing that innovative technologies offer the city opportunities to cope with climate impacts. This study should be most helpful to the CMB to support its management of flooding under any adaptation scenarios that may possibly result from climate changes. Flooding could be again caused as a result of changes in inland flooding from precipitation patterns or from sea-level rise or both.

IPCC於第四次報告書中，模擬氣候持續暖化預測未來海平面上升之情形，而海平面上升對於人口集中的台北都會區將產生莫大之衝擊，同時亦會造成土地利用變遷。本研究目的在於探討海平面上升對台北都會區土地利用變遷之影響，以及受淹沒地區之人口未來可能之遷移區位，主要係從社會經濟發展層面進行分析。運用二元羅吉斯迴歸模式並結合土地利用轉換與影響模型（CLUE-s），以四種不同情境模擬土地利用變遷之情況，其情境分別為海平面上升59公分管制農林地與不管制，以及海平面上升100公分管制農林地與不管制。 　　研究結果顯示，海平面上升之情形越嚴重，未來的都市建地發展會越趨向擴張的形式，對農林地產生變遷之壓力；而於同一海平面上升水平下，針對農林地進行管制，其建地之發展會較為集中於都市計畫地區範圍內，且多數人口亦將遷移至此，容易形成人口壓力。此外，土地利用變遷模擬所得之新增建地部分，於情境A、C下足以容納受影響之人口，但情境B、D則不足以容納，皆會對台北都會區產生容受力之問題，產生累計人口超過計畫人口之現象。因此，建議未來政府於都市發展上，可調整都市計畫內之土地使用強度或都市範圍，也可利用都市更新之方式減少新的土地開發；此外，從國家層級分析，未來的國土計畫法於立法上，亦可將更多氣候變遷相關影響因子納入四大功能分區，透過適宜性分析進行分類分級，以做為未來土地利用發展之引導。 / The 4th IPCC report simulated climate warming and predicted future sea-level rise scenarios. A sea level rise will have a great impact on the population of the Taipei metropolitan area, and it will also produce land-use changes. The purpose of this study is to research the impact of sea level change on land use changes and population migration in Taipei metropolitan, and the areas that will be immigrated by the flooded areas. The method used includes binary logistic regression model combined with Conversion of Land Use and its Effects Model (CLUE-s). Setting the sea-level rise and regulating agricultural land, forest land of the four simulated situations. The results show that the higher sea level rises, the more transformation towards urban development in the future, and the higher sea level will also pressure agriculture and forestry changes. As a result of population pressure on Taipei metropolitan area, the same level of sea-level rise for the regulation of agriculture and forestry land, the development of building sites and population migration will be more concentrated on urban planning areas. In addition, the simulation of land use change generated new building sites, sufficient enough to accommodate the affected population under A and C simulated situations, but B and D couldn’t generate such results. Instead, it will generate a carrying capacity issue. Therefore, this thesis suggests that the government adjust the intensity of land use in urban development, urban areas and urban renewal of urban planning. In addition, the analysis from the national level, the future legislation of Land Planning Act should include the relation of climate change impact factors as a consideration of future land use development.

Radiative forcing by increased atmospheric levels of greenhouse gases (GHGs) produced by human activities could lead to strongly undesirable effects on oceans and their dependent human systems in the coming centuries. Such dangerous anthropogenic interference with the climate system is a possibility the UN Framework Convention on Climate Change (UNFCCC) calls on nations to avoid. Unacceptable consequences of such interference could include inundation of coastal areas and low-lying islands by rising sea level, the rate of which could exceed natural and human ability to adapt, and ocean acidification contributing to widespread disruption of marine and human food systems. Such consequences pose daunting socioeconomic costs, for developing nations in particular. Drawing on existing literature, we define example levels of acceptable global marine change in terms of global mean temperature rise, sea level rise and ocean acidification. A global-mean climate model (ACC2), is implemented in an optimizing environment, GAMS, and coupled to an economic model (DICE). Using cost-effectiveness analysis and the tolerable windows approach (TWA) allows for the computation of both economically optimal carbon dioxide emissions pathways as well as a range in carbon dioxide emissions (the so-called ``emissions corridor'') which respect the predetermined ceilings and take into account the socio-economically acceptable pace of emissions reductions. The German Advisory Council on Global Change (WBGU) has issued several guardrails focused on marine changes, of which we find the rate and absolute rise in global mean temperature to be the most restrictive (0.2 degrees Celsius per decade, 2 degrees Celsius total). Respecting these guardrails will require large reductions in both carbon and non-carbon GHGs over the next century, regardless of equilibrium climate sensitivity. WBGU sea level rise and rate of rise guardrails (1 meter absolute, 5 cm per decade) are substantially less restrictive, and respecting them does not require deviation from a business-as-usual path in the next couple hundred of years, provided common assumptions of Antarctic ice mass balance sensitivity are correct. The ocean acidification guardrail (0.2 unit decline relative to the pre-industrial value) is less restrictive than those for temperature, but does require emissions reductions into the coming century.

Die Anpassung von Küstenniederungen, Seemarschen und Inseln an klimatische Veränderungen und einen steigenden Meeresspiegel ist eine der großen Herausforderungen des 21. Jahrhunderts. Im Gegensatz zu eingedeichten Küstenmarschen und Inseln besitzen tidebeeinflusste Seemarschen ein natürliches Anpassungspotential an sich verändernde hydrologische Rahmenbedingungen. Überflutungsabhängige Sedimenteinträge führen zu einem Anwachsen der Marschoberfläche und kompensieren somit einen Anstieg des Meeresspiegels. Die 10 verbliebenen nordfriesischen Halligen (Schleswig-Holstein, Deutschland) (Kapitel 1) sind bewohnte Inselmarschen, welche aufgrund ihrer anthropogenen Überprägung von naturbelassenen Seemarschen unterschieden werden müssen. Diese umfasst z.B. den Bau von flachen Sommerdeichen und Sielanlagen. Inwiefern sich diese Veränderungen auf die Sedimentdynamik der Marschen auswirken, ist bislang unzureichend belegt, was eine fundierte Diskussion bezüglich zukünftiger Entwicklungsperspektiven der Halligmarschen verhindert. Die vorliegende Arbeit ist dazu angelegt, diese Wissenslücke zu schließen. Sie untersucht das vertikale Marschwachstum exemplarisch auf den Halligen Hooge, Langeneß und Nordstrandischmoor und beurteilt deren Anpassungsvermögen an einen steigenden Meeresspiegel. Darüber hinaus werden zukünftige Entwicklungsperspektiven diskutiert. Um Faktoren und Prozesse, welche maßgeblich die Sedimentdynamik der Halligen beeinflussen, messbar zu machen, musstengeeignete Methoden entwickelt und angewendet werden. Zur Berechnung jährlicher Überflutungshäufigkeiten wurden Pegelschwellenwerte für Überflutungsereignisse auf Basis von digitalen Geländemodellen (DGMs) und d-GPS (differential global positioning system) Messungen errechnet und auf die verfügbaren, regionalen Pegeldaten angewendet (Kapitel 2). Sedimentfallen, bestehend aus LDPE (low density polyethylene) Flaschen (1 Liter) und Kunstrasenmatten (20 x 30 cm), bilden die Grundlage einer dreijährigen (November 2010 – März 2013) Feld- und Laborstudie zur zeitlichen und räumlichen Erfassung der sturmflutabhängigen Sedimentdeposition (Kapitel 3). Durch die Verwendung regionaler bodenphysikalischer Parameter (Lagerungsdichte und Gehalt an organischer Bodensubstanz) können Depositionsraten in eine vertikale Wachstumskomponente transformiert werden. Dazu werden Ergebnisse einer Rammkernsondierung genutzt, welche 12 Sedimentkerne mit einer Länge von maximal 100 cm umfasst. Die Sedimentbohrkerne sind weiterhin die Grundlage für eine 137Cs- und 210Pb-Datierung. Die Kombination beider Datensätze (Kapitel 4) ermöglicht einen schlüssigen Vergleich der Marschentwicklung seit dem Jahr 1915 mit regionalen Pegeldaten und Projektionen des zukünftigen Meeresspiegelanstiegs. Die Analyse der verfügbaren Pegeldaten (Kapitel 2) zeigt eine hohe Variabilität der jährlichen Überflutungshäufigkeiten. Das zehnjährige Mittel eintretender Ereignisse beträgt 2 Überflutungen auf Hooge, 9 – 10 Überflutungen auf Langeneß und 15 Überflutungen auf Nordstrandischmoor. Aufgrund der künstlichen Überhöhung der Marschkante durch Sommerdeiche mit + 1.54 m ü. mittlerem Tidehochwasser (MThw) auf Hooge und + 0.98 m ü. MThw auf Langeneß werden die betreffenden Halligen lediglich bei selten eintretenden Sturmflutereignissen überflutet. Die Höhe des wasser- und sedimentundurchlässigen Steinpflasters auf Nordstrandischmoor beträgt lediglich + 0.7 m ü. MThw. Die methodischen Untersuchungen bezüglich der Nutzung von Sedimentfallen (Kapitel 3) zeigen, dass beide Typen von Sedimentfallen vergleichbare Ergebnisse liefern. Oberhalb einer Depositionsrate von ~ 2.0 kg/m2 sinkt das Rückhaltevermögen der Kunstrasenmatte im Vergleich zur LDPE Flasche deutlich ab. Die parallele Nutzung beider Fallentypen, insbesondere wenn die Depositionsraten den Schwellenwert (~ 2.0 kg/m2) nicht überschreiten, erlaubt: (1) Die Überprüfung, ob beide Datensätze konsistent sind. (2) Die Identifizierung von Ausreißern. (3) Eine Abschätzung, ob Sediment auf oder in der Sedimentfalle nach der Überflutung remobilisiert wird. Um die Sedimentdeposition in eine vertikale Wachstumsrate zu übersetzen, muss die mittlere Bodendichte als auch der Gehalt an organischer Bodensubstanz des Marschbodens berücksichtigt werden. Die Bohrkernuntersuchungen zeigen, dass diese bodenphysikalischen Parameter auf den unterschiedlichen Halligen stark variieren. Marschen, die häufig überflutet werden lagern weniger organisches Material im Oberboden ein als selten überflutete Marschen. Niedrige Gehalte an leichten organischen Materialien geringer Dichte resultieren wiederum in einer höheren Lagerungsdichte des Marschbodens (Hooge 0.64 g/cm3, Langeneß 0.67 g/cm3, Nordstrandischmoor 0.83 g/cm3). Autochthones organisches Material (welches primär von der Halligvegetation stammt) trägt mit einem Anteil von 9.0 ± 1.4 % (Hooge) bis 21.4 ± 6.6 % (Nordstrandischmoor) zum Marschwachstum bei. Die Ergebnisse der Sedimentfallenuntersuchungen als auch der Datierungen zeigen deutlich ein Ungleichgewicht zwischen Marschwachstum und Meeresspiegelanstieg seit Beginn des 20. Jahrhunderts. Die langjährigen Wachstumsraten, basierend auf der 210Pb-Datierung, liegen mit 1.0 ± 0.3 mm/a auf Hooge, 1.2 ± 0.3 mm/a auf Langeneß und 2.6 ± 0.9 mm/a auf Nordstrandischmoor deutlich unterhalb des MThw-Anstiegs von 5.0 ± 0.3 mm/a (1951 – 2011, Wyk auf Föhr). Projektionen des Meeresspiegelanstiegs bis zum Jahr 2100 (Berechnet durch das fwu, Siegen) weisen darauf hin, dass extreme Wasserstände (höchste, jährliche Tidehochwasserstände, HThw, 6.6 ± 3.8 mm/a) deutlich schneller ansteigen werden als das MThw oder der mittlere Meeresspiegel (2.6 ± 0.4 mm/a). Aufgrund dieser Beobachtungen ist von einem zukünftigen Anstieg des Gefährdungspotentials für die Halligen auszugehen, wenn es nicht gelingt, ein sedimentologisches Gelichgewicht zwischen Meeresspiegel und Marschwachstum herzu stellen. Der Anstieg der Wellenhöhe und Periode, aufgrund von steigender Wassertiefe und einer geringeren Wellentransmissionsrate an den Sommerdeichen, resultiert in einer steigenden hydrodynamischen Belastung der Warften und der Marschoberfläche. Das sedimentäre Ungleichgewicht, besonders auf Hooge und Langeneß, kann eindeutig auf das hydrologische Management der Halligen zurückgeführt werden. Aus sedimentologischer Sicht sind die beiden Hauptkritikpunkte (1) die geringe Anzahl an Überflutungen aufgrund der Deichanlagen und (2) der eingeschränkte Transport suspendierter Feststoffe über die Binnenpriele. Letzteres resultiert aus der Blockade der Binnenpriele durch Sielanlagen und führt zu einer Abnahme der Sedimentdeposition mit zunehmender Entfernung zur Uferlinie. Um dem Ungleichgewicht zwischen Marschwachstum und Meeresspiegelanstieg entgegenzuwirken, ist es dringend erforderlich, neue Managementstrategien für die Halligen zu entwickeln (Kapitel 6), welche sedimentologische/geomorphologische Aspekte sowie die speziellen Bedürfnisse der Halligbevölkerung gleichermaßen berücksichtigen. Letztere beinhalten die Minimierung ökonomischer Schäden wie etwa Einschränkungen der landwirtschaftlichen Nutzung oder des Tourismus. Mögliche Szenarien können ein Abflachen der bestehenden Deiche oder deren Rückbau und Erneuerung durch wasser- und sedimentdurchlässige Rauhstreifen (z.B. Elastocoast®, BASF) beinhalten. Weiterhin erscheint die Reaktivierung der blockierten Binnenpriele eine plausible Maßnahme zu sein. Erste Freilandexperimente auf Hallig Langeneß (Kapitel 5) belegen einen erhöhten Sedimenttransport in die Binnenmarsch aufgrund geöffneter Sielanlagen in Verbindung mit Windstau (Thw-Ereignisse über Springtideniveau). Ob die generelle Umsetzung derartiger Maßnahmen möglich ist, ist in erster Linie davon abhängig, ob die Halligbevölkerung derartigen Veränderungen ihrer Umwelt aufgeschlossen gegenübersteht und diese lokalpolitisch getragen werden. Auf jeden Fall ist ein Umdenken dahingehend erforderlich, die halligtypischen Überflutungen (Land-Unter) nicht ausschließlich als Bedrohung zu verstehen. Sie sind ein natürliches Phänomen, welches notwendig ist, um das Gleichgewicht zwischen Meeresspiegelanstieg und Sedimentdeposition aufrechtzuerhalten.