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Research Project
Resilience-Increasing Strategies for Coasts - toolKIT
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Publications
Introduction to RISC-KIT: resilience-increasing strategies for coasts
Publication . Van Dongeren, Ap; Ciavola, Paolo; Martinez, Grit; Viavattene, Christophe; Bogaard, Tom; Ferreira, Óscar; Higgins, Ruth; McCall, Robert
In this paper an introduction is provided to the RISC-KIT project’s goals, products and applications,
which is the subject of this Special Issue. Subsequent papers provide the details on the developed
tools and their application on ten case study sites in Europe.
Coastal lagoons and rising sea level: a review
Publication . Carrasco, A. Rita; Ferreira, Óscar; Roelvink, D.
Sea-level rise (SLR) poses a particularly ominous threat to human habitations and infrastructure in the coastal
zone because 10% of the world's population lives in low-lying coastal regions within 10 m elevation of present
sea level. There has been much discussion about projected (and the sources of projection) vs. measured SLR
rates. Which rates should coastal scientists and managers apply in their studies, and what is the degree of confi-
dence of such forecasts, are still open questions.
This paper reviews the patterns and effects of relative SLR (RSLR) in coastal lagoons. Three main components are
presented in the review: (a) a summary of the main approaches used in predicting medium- to long-term trends
in RSLR, (b) a summary of the main evolutionary trends of coastal lagoons and the tools used to examine such
trends, and (c) an identification of future research needs.
The review reveals that the major source of uncertainty is how and when RSLR will manifest itself at different
spatio-temporal scales in coastal lagoon systems, and how its effects can be mitigated. Most of the studies
reviewed herein articulate a natural ‘defence’ mechanism of barriers in coastal lagoons by landward barrier retreat
through continuous migration, and a gradual change in basin hypsometry during the retreat process. So
far, only a relatively small number of detailed studies have integrated and quantified human impacts and coastal
lagoon evolution induced by RSLR. We conclude that much more research about adaptation measures is needed,
taking into consideration not only the physical and ecological systems but also social, cultural, and economic impacts.
Future challenges include a downscaling of SLR approaches from the global level to regional and local
levels, with a detailed application of coastal evolution prediction to individual coastal lagoon systems
Regional assessment of storm related overwash and breaching hazards on coastal barriers
Publication . Plomaritis, Theocharis A.; Ferreira, Óscar; Costas, Susana
Coastal communities are threatened by the impact of severe storms that may cause significant loss of life and damage to properties. Among the main processes behind such impacts on coastal barriers are the occurrence of overwash and breaching during storm events. In order to estimate potential losses associated with a particular event, the above processes must be properly parameterized. Here, we propose a novel methodology to estimate overwash and breaching hazards suitable for a regional scale analysis (Ø 100 km). For the overwash hazard assessment, the method is based on the application of the approach developed by Donnelly (2008) that allows the parametrisation of the overwash hazard considering both flow velocity and flow depth. Moreover, the inland extension of the associated hazard, which is critical to assess subsequent vulnerability, can also be estimated following this methodology. The proposed method requires the selection of a runup formula validated for the study area, a storm beach profile, a runup lens angle, and a percolation constant for infiltration. To assess the breaching, hazard, a new multivariable evaluation is proposed that allows ranking the potential of breaching. The multivariable evaluation combines overwash and erosion hazards as well as their extensions with the main morphological characteristics of the barrier, resulting in the breaching hazard index, that ranks from 0 to 5 (no breaching to inlet formation). Inland breaching extension is also relevant for the vulnerability assessment. The breaching extension can be estimated using historical or contemporary analogues of the nearest flood deltas. The developed approaches were applied to Ancão Peninsula (Algarve, Portugal) as a demonstration example. The advantages of the present approach are: adaptability to various environments where overwash and/or breaching processes are important, time efficiency on evaluating overwash and breaching hazards, and the assessment of hotspot areas at a regional scale.
Field measurements and hydrodynamic modelling to evaluate the importance of factors controlling overwash
Publication . Matias, Ana; Carrasco, A.R.; Loureiro, Carlos; Masselink, Gerd; Andriolo, Umberto; McCall, Robert; Ferreira, Oscar; Plomaritis, Theocharis; Pacheco, André; Guerreiro, Martha
Overwash hydrodynamic datasets are mixed in quality and scope, being difficult to obtain due to fieldwork experimental limitations. Nevertheless, these measurements are crucial to develop reliable models to predict overwash. Aiming to overcome such limitations, this work presents accurate fieldwork data on overwash hydrodynamics, further exploring it to model overwash on a low-lying barrier island. Fieldwork was undertaken on Barreta Island (Portugal) in December 2013, during neap tides and under energetic conditions, with significant wave height reaching 2.6 m. During approximately 4 h, more than 120 shallow overwash events were measured with a video-camera, a pressure transducer and a current-meter. This high-frequency fieldwork dataset includes runup, overwash number, depth and velocity. Fieldwork data along with information from literature were used to implement XBeach model in non-hydrostatic mode (wave-resolving). The baseline model was tested for six verification cases; and the model was able to predict overwash in five. Based in performance metrics and the verification cases, it was considered that the Barreta baseline overwash model is a reliable tool for the prediction of overwash hydrodynamics. The baseline model was then forced to simulate overwash under different hydrodynamic conditions (waves and lagoon water level) and morpho-sedimentary settings (nearshore topography and beach grain-size), within the characteristic range of values for the study area. According to the results, the order of importance of factors controlling overwash predictability in the study area are: 1st) wave height (more than wave period) can promote overwash 3–4 times more intense than the one recorded during fieldwork; 2nd) nearshore bathymetry, particularly shallow submerged bars, can promote an average decrease of about 30% in overwash; 3rd) grain-size, finer sediment produced an 11% increase in overwash due to reduced infiltration; and 4th) lagoon water level, only negligible differences were evidenced by changes in the lagoon level. This implies that for model predictions to be reliable, accurate wave forecasts are necessary and topo-bathymetric configuration needs to be monitored frequently.
Historical analysis of storm events: case studies in France, England, Portugal and Italy
Publication . Garnier, E.; Ciavola, P.; Spencer, T.; Ferreira, Óscar; Armaroli, C.; McIvor, A.
An historical analysis of the occurrence of storms and their damage intensity is presented. The work analysed historical large-scale events from The Middle Ages to the 1960s at case study sites along the coasts of North Norfolk (UK); Charente-Maritime and Vendée (France); Cinque Terre-Liguria coast (Italy); Emilia-Romagna coast (Italy) and Ria Formosa (Portugal). The work presented here used a database of events built by the RISC-KIT project, including the characteristics of the storms as well as recorded human impacts. Historical records can provide an important test bed to complement the statistical analysis of the return period of events based on measurements and provide important indicators of past events and their impact that are no longer within the historical memories of resident populations and coastal managers.
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Funding agency
European Commission
Funding programme
FP7
Funding Award Number
603458