Coastal Resilience in Poland: from Observations to Theoretical Generalization

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive

Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A

Local bathymetric quasi-periodic patterns of oscillation are identified from monthly profile surveys taken at two shore-perpendicular transects at the USACE field research facility in Duck, North Carolina, USA, spanning 24.5 years and covering the swash and surf zones. The chosen transects are the two furthest (north and south) from the pier located at the study site. Research at Duck has traditionally focused on one or more of these transects as the effects of the pier are least at these locations. The patterns are identified using singular spectrum analysis (SSA). Possible correlations with potential forcing mechanisms are discussed by 1) doing an SSA with same parameter settings to independently identify the quasi-periodic cycles embedded within three potentially linked sequences: monthly wave heights (MWH), monthly mean water levels (MWL) and the large scale atmospheric index known as the North Atlantic Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the local bathymetric patterns. The results agree well with previous patterns identified using wavelets and confirm the highly nonstationary behaviour of beach levels at Duck; the discussion of potential correlations with hydrodynamic and atmospheric phenomena is a new contribution. The study is then extended to all measured bathymetric profiles, covering an area of 1100m (alongshore) by 440m (cross-shore), to 1) analyse linear correlations between the bathymetry and the potential forcings using multivariate empirical orthogonal functions (MEOF) and linear correlation analysis and 2) identify which collective quasi-periodic bathymetric patterns are correlated with those within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure

Data-driven and hybrid coastal morphological prediction methods for mesoscale forecasting

It is now common for coastal planning to anticipate changes anywhere from 70 to 100 years into the future. The process models developed and used for scheme design or for large-scale oceanography are currently inadequate for this task. This has prompted the development of a plethora of alternative methods. Some, such as reduced complexity or hybrid models simplify the governing equations retaining processes that are considered to govern observed morphological behaviour. The computational cost of these models is low and they have proven effective in exploring morphodynamic trends and improving our understanding of mesoscale behaviour. One drawback is that there is no generally agreed set of principles on which to make the simplifying assumptions and predictions can vary considerably between models. An alternative approach is data-driven techniques that are based entirely on analysis and extrapolation of observations. Here, we discuss the application of some of the better known and emerging methods in this category to argue that with the increasing availability of observations from coastal monitoring programmes and the development of more sophisticated statistical analysis techniques data-driven models provide a valuable addition to the armoury of methods available for mesoscale prediction. The continuation of established monitoring programmes is paramount, and those that provide contemporaneous records of the driving forces and the shoreline response are the most valuable in this regard. In the second part of the paper we discuss some recent research that combining some of the hybrid techniques with data analysis methods in order to synthesise a more consistent means of predicting mesoscale coastal morphological evolution. While encouraging in certain applications a universally applicable approach has yet to be found. The route to linking different model types is highlighted as a major challenge and requires further research to establish its viability. We argue that key elements of a successful solution will need to account for dependencies between driving parameters, (such as wave height and tide level), and be able to predict step changes in the configuration of coastal systems

Performance of a data-driven technique applied to changes in wave height and its effect on beach response

AbstractIn this study the medium-term response of beach profiles was investigated at two sites: a gently sloping sandy beach and a steeper mixed sand and gravel beach. The former is the Duck site in North Carolina, on the east coast of the USA, which is exposed to Atlantic Ocean swells and storm waves, and the latter is the Milford-on-Sea site at Christchurch Bay, on the south coast of England, which is partially sheltered from Atlantic swells but has a directionally bimodal wave exposure. The data sets comprise detailed bathymetric surveys of beach profiles covering a period of more than 25 years for the Duck site and over 18 years for the Milford-on-Sea site. The structure of the data sets and the data-driven methods are described. Canonical correlation analysis (CCA) was used to find linkages between the wave characteristics and beach profiles. The sensitivity of the linkages was investigated by deploying a wave height threshold to filter out the smaller waves incrementally. The results of the analysis indicate that, for the gently sloping sandy beach, waves of all heights are important to the morphological response. For the mixed sand and gravel beach, filtering the smaller waves improves the statistical fit and it suggests that low-height waves do not play a primary role in the medium-term morphological response, which is primarily driven by the intermittent larger storm waves

Embracing Nature-based Solutions to promote resilient marine and coastal ecosystems

The world is struggling to limit greenhouse gas emissions and reduce the human footprint on nature. We therefore urgently need to think about how to achieve more with actions to address mounting challenges for human health and wellbeing from biodiversity loss, climate change effects, and unsustainable economic and social development. Nature-based Solutions (NBS) have emerged as a systemic approach and an important component of the response to these challenges. In marine and coastal spaces, NBS can contribute to improved environmental health, climate change mitigation and adaptation, and a more sustainable blue economy, if implemented to a high standard. However, NBS have been largely studied for terrestrial – particularly urban – systems, with limited uptake thus far in marine and coastal areas, despite an abundance of opportunities. Here, we provide explanations for this lag and propose the following three research priorities to advance marine and coastal NBS: (1) Improve understanding of marine and coastal biodiversity-ecosystem services relationships to support NBS better designed for rebuilding system resilience and achieving desired ecological outcomes under climate change; (2) Provide scientific guidance on how and where to implement marine and coastal NBS and better coordinate strategies and projects to facilitate their design, effectiveness, and value through innovative synergistic actions; (3) Develop ways to enhance marine and coastal NBS communication, collaboration, ocean literacy and stewardship to raise awareness, co-create solutions with stakeholders, boost public and policy buy-in, and potentially drive a more sustained investment. Research effort in these three areas will help practitioners, policy-makers and society embrace NBS for managing marine and coastal ecosystems for tangible benefits to people and marine life.The study received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement MaCoBioS (contract no 869710), FutureMARES (contract no 869300) and REST-COAST (contract no 101037097).info:eu-repo/semantics/publishedVersio

Wave Climate in the Gulf of Gdańsk vs. Open Baltic Sea near Lubiatowo, Poland

The paper analyses long-term variability in the wave climate near Lubiatowo, ca. 15 km east of Łeba harbor, and in the Gulf of Gdańsk, near the Vistula river mouth. The wave climate was reconstructed for the 1958-2001 period by the German Institute for Coastal Research (GKSS). Using basic statistical tools - empirical mean values of significant wave height, estimation of the number of threshold crossings above a prescribed value of that height and conditional empirical probability density functions of wave approach directions - a comparison of wave height at the two locations was executed. A substantial reduction in wave height inside the Gulf (sheltering effect) was measured. Further, the increased storminess over the winter season was estimated for the open sea location. Finally, the analysis of wave approach direction in the open sea location revealed substantial growth in extreme waves from the western sector. Given the geographic configuration of the Gulf and the combined rise in storminess and evolution in extreme wave direction, it can be inferred that the sheltering effect of the Gulf can vary depending on locations within the Gulf. Identification of sheltering patterns in the Gulf emerges as obvious follow-up research. This study could also prove useful in analyses aiming at integrated management of coastal zones in the Gulf, mainly in the implementation of Coastal Protection Law (Apr. 2003), which postulates maintenance of the 2001 shoreline configuration along the entire Polish coast

Co-variability of bars in a multi-bar nearshore zone determined with canonical correlation analysis (CCA)

Nearshore bed variations of the southem Baltic shore were investigated with the aim of detecting co-variability among bed forms of a multi-bar system. The studied area is located at IBW PAN Coastal Research Station at Lubiatowo. The beach consists of fine sand of median grain equal to 0.22 mm, is mildly sloping and boasts multiple (usually 4) bars, which is typical for the coast in the southem Baltic. Data on bed topography were collected along 27 lines, equally spanned every 100 m, since 1987 to 1999, usually twice a year. Fairly high alongshore bed homogeneity made it possible to choose one representative profile for which the CCA method was employed. The method demonstrated considerable potential for detecting co-variability of bed features in the nearshore zone. The results show that some 80% of variability in the region of the offshore slope of the outermost bar can be attributed to variations of Dean equilibrium profiles. The portion of variability of the two innermost bars due to variations of equilibrium profiles equals 40%. Horizontal counter-movements of outer and inner bars can be responsible for same 20%. The remaining 40% should be related to highly variable short time scale phenomena like breakers and wave driven currents in the vicinity of inner bars

Local Wave Energy Dissipation and Morphological Beach Characteristics along a Northernmost Segment of the Polish Coast

This paper analyses cross-shore bathymetric profiles between Władysławowo (km 125 of the Polish coastal chainage) and Lake Sarbsko (km 174) done in 2005 and 2011. Spaced every 500 m, they cover beach topography from dune/cliff crests to a seabed depth of about 15 m. They were decomposed by signal processing techniques to extract the monotonic component of beach topography and to perform a straightforward assessment of wave energy dissipation rates. Three characteristic dissipation patterns were identified: one associated with large nearshore bars and 2–3 zones of wave breaking; a second, to which the equilibrium beach profile concept can be applied; and a third, characterized by mixed behaviour. An attempt was then made to interpret these types of wave energy dissipation in terms of local coastal morphological features and the underlying sedimentary characteristics

Some characteristic wave energy dissipation patterns along the Polish coast

Summary: The paper analyses cross-shore bathymetric profiles between Władysławowo (km 125 of the national coastal chainage) and Lake Sarbsko (km 174) commissioned in 2005 and 2011 by coastal authorities for monitoring purposes. The profiles, spaced every 500 m, cover beach topography from dune/cliff tops through the emerged beach to a seabed depth of about 15 m. They were decomposed by signal processing techniques to extract their monotonic components containing all major modes of the variability of beach topography. They are termed empirical equilibrium profiles and can be used for straightforward assessment of wave energy dissipation rates. Three characteristic patterns of wave energy dissipation were thus identified: one associated with large nearshore bars and several zones of wave breaking; a second, to which the equilibrium beach profile concept can be applied; and a third, characterized by mixed behaviour. Interestingly, most profiles showed significant seabed variations beyond the nearshore depth of closure – this phenomenon requires comprehensive studies in future. Keywords: Coastal morphology, Wave energy dissipation, Equilibrium profiles, Data-driven modelling, Signal processin

Megascale rhythmic shoreline forms on a beach with multiple bars

The study, carried out in 2003 and 2006 at the Lubiatowo Coastal ResearchStation (Poland), located on the non-tidal southern Baltic coast(tidal range &#x003C; 0.06 m), focused on larger rhythmic forms (mega-cusps) withwavelengths in the interval 500 m &#x003E; L_c &#x003E; 20 m. Statistical analyses of detailed shoreline configurations were performed mostly with the Discrete Wavelet Transformmethod (DWT). The beach is composed of fine sand with grain diameter D₅₀ &asymp; 0.22 mm, which produces 4 longshore sandbars and a gently sloping seabed with <i>&beta;</i> = 0.015. The analysis confirms the key role of bars in hydro- and morphodynamic surf zone processes.The hypothesis was therefore set up that, in a surf zone with multiple bars, the bars and mega-scale shoreline rhythmic forms form one integrated physical system; experimental evidence to substantiate this hypothesis was also sought.In such a system not only do self-regulation processes include swash zone phenomena, they also incorporate processes in offshore surf zone locations.The longshore dimensions of large cusps are thus related to the distances between periodically active large bed forms (bars). The spatial dimension of bar system activity (number of active bars) depends, at a given time scale, on the associated hydrodynamic conditions. It was assumed that such a time scale could include either the development and duration of a storm, or a period of stable, yet distinct waves, capable of remodelling the beach configuration.The indentation to wavelength ratio of mega-cusps for the studied non-tidal dissipative environment may be one order of magnitude greater than for mesotidal, reflective beaches