Coastal Cliff Exposure and Management

[Abstract:] Coastal cliffs cover about 75% of the world's coastlines. Many of these cliffs suffer severe erosion problems, which are mainly caused by wave action and lead to important damages. The main objective of this work is to propose and apply a methodology to characterize and map wave exposure levels for the management of cliff coasts. The methodology proposed consists of a number of steps. First, a statistical characterization of the wave climate in deep water is performed. Second, relevant sea states are propagated towards the cliff by means of a numerical model. Then, the results are used to assess the distribution of significant wave heights and wave power along the cliff toe. Finally, four exposure levels are defined based on the wave power values at the cliff, and exposure zones are mapped accordingly along the cliff. This approach is illustrated with a case study – the Catedrales Cliffs and Beach, a tourism hotspot in Galicia (NW Spain) where erosion caused loss of human life. We find that exposure levels are primarily influenced by the nearshore bed morphology, which controls wave refraction, shoaling and breaking, as well as by the geometry and orientation of the cliff, with some parts more exposed than others to the prevailing wave direction. On the islets off the cliff the windward faces have a greater level of exposure, since the leeward faces are protected by the islets themselves and lower water depths. The rocky outcrops that occur at the cliff toe in some sections act as emerged (submerged) breakwaters under low (high) tide conditions, dissipating wave power and thus reducing wave exposure. The methodology proposed in this work enables coastal managers to prevent the personal and material damages derived from cliff erosion by focusing remedial measures where they are most needed.Ministerio de Ciencia, Innovación y Universidades; FJCI-2017-3178

Towards an optimum design of wave energy converter arrays through an integrated approach of life cycle performance and operational capacity

Premio ETSI al mejor artículo científico del trimestre. 3a ed. Junio 2018 -Artículo subido a idUS con permiso de su primer autor (López-Ruiz, Alejandro), que proporciona las versiones preprint y postprint.Over the last few decades, several efforts have been made to develop an alternative and sustainable energy source from wind waves. To achieve financial sustainability of this technology, most of the research has focused on analyzing facilities composed of several wave energy converters (WECs) arrays instead of isolated ones. Although the interaction between devices and its implications on the performance of the facilities have been studied previously, these works considered only certain combinations of sea states, limiting the applicability of the results. This work applies a new methodology based on statistical methods to assess the performance of different WEC array distributions during their entire life-cycle in an efficient way, using downscaling techniques and advanced numerical modeling to propagate the wave climate. The results obtained during the hindcasting life-cycle are used to analyze the maintenance and operation capabilities of the different alternatives of arrays defined for the WEC facility. The interactions between devices and their efficiency considering the associated impact are also quantified. The assessment of these efficiencies during the complete life-cycle of the devices is highly valuable tool for promoters and coastal managers to evaluate different WEC array alternatives. The entire process was applied to a hypothetical array location in the Gulf of Cádiz (southwestern Spain), where three different array distributions were defined. The results show that the distance between WECs is a key parameter that controls the potential energy production, the efficiency of the facility and the interactions between several devices.Ministerio de Economía y Competitividad BES-2013-062617Universidad de Sevill

Towards an optimum design of wave energy converter arrays through an integrated approach of life cycle performance and operational capacity

Premio ETSI al mejor artículo científico del trimestre. 3a ed. Junio 2018 -Artículo subido a idUS con permiso de su primer autor (López-Ruiz, Alejandro), que proporciona las versiones preprint y postprint.Over the last few decades, several efforts have been made to develop an alternative and sustainable energy source from wind waves. To achieve financial sustainability of this technology, most of the research has focused on analyzing facilities composed of several wave energy converters (WECs) arrays instead of isolated ones. Although the interaction between devices and its implications on the performance of the facilities have been studied previously, these works considered only certain combinations of sea states, limiting the applicability of the results. This work applies a new methodology based on statistical methods to assess the performance of different WEC array distributions during their entire life-cycle in an efficient way, using downscaling techniques and advanced numerical modeling to propagate the wave climate. The results obtained during the hindcasting life-cycle are used to analyze the maintenance and operation capabilities of the different alternatives of arrays defined for the WEC facility. The interactions between devices and their efficiency considering the associated impact are also quantified. The assessment of these efficiencies during the complete life-cycle of the devices is highly valuable tool for promoters and coastal managers to evaluate different WEC array alternatives. The entire process was applied to a hypothetical array location in the Gulf of Cádiz (southwestern Spain), where three different array distributions were defined. The results show that the distance between WECs is a key parameter that controls the potential energy production, the efficiency of the facility and the interactions between several devices.Ministerio de Economía y Competitividad BES-2013-062617Universidad de Sevill

Coastal flooding on gravel-dominated beaches under global warming

This work analyses the effects of sea-level rise on flooding events for 3 different scenarios: present situation (S0), optimistic projection (RCP4.5) and pessimistic projection (RCP8.5). The study area is a gravel-dominated beach in southern Spain (Playa Granada), where the SWAN and XBeach-G models are applied to assess wave propagation patterns, total run-up and flooded dry beach area. The results indicate that sea-level rise modifies wave propagation patterns, with alongshore-averaged increases in breaking wave height equal to 1.2% (1.9%) un-der westerly (easterly) storms in the optimistic scenario and 2.6% (2.4%) in the pessimistic scenario. These increments lead to maximum increases in total run-up greater than 13% (14%) for westerly (easterly) storms in the optimistic scenario and 16% (20%) in the pessimistic scenario. Finally, the increases in flooded dry beach area induced by sea-level rise under westerly (easterly) storms are equal to 1.6% (5.9%) and 1.8% (7.7%) in scenarios RCP4.5 and RCP8.5, respectively, and the maximum increments in flooded cross-shore distances exceed 8% in all cases. The methodology proposed in the present work can be extended to other coasts worldwide for assessing the influence of sea-level rise on coastal flooding events

Improving Indicators of Hydrological Alteration in Regulated and Complex Water Resources Systems: A Case Study in the Duero River Basin

[EN] Assessing the health of hydrological systems is vital for the conservation of river ecosystems. The indicators of hydrologic alteration are among the most widely used parameters. They have been traditionally assessed at the scale of river reaches. However, the use of such indicators at the basin scale is relevant for water resource management since there is an urgent need to meet environmental objectives to mitigate the effects of present and future climatic conditions. This work proposes a methodology to estimate the indicators of hydrological alteration at the basin scale in regulated systems based on simulations with a water allocation model. The methodology is illustrated through a case study in the Iberian Peninsula (the Duero River basin), where different minimum flow scenarios were defined, assessing their effects on both the hydrological alteration and the demand guarantees. The results indicate that it is possible to improve the hydrological status of some subsystems of the basin without affecting the water demand supplies. Thus, the methodology presented in this work will help decision makers to optimize water management while improving the hydrological status of the river basins.This research was funded by the Spanish Research Agency (AEI), grant number PID2019-106322RB-100; AEI/10.13039/501100011033. R.J.B. was partly funded by the Spanish Ministry of Science and Innovation through the research contract IJC2019-038848-I.Pardo-Loaiza, J.; Solera Solera, A.; Bergillos, RJ.; Paredes Arquiola, J.; Andreu Álvarez, J. (2021). Improving Indicators of Hydrological Alteration in Regulated and Complex Water Resources Systems: A Case Study in the Duero River Basin. Water. 13(19):1-18. https://doi.org/10.3390/w13192676118131

Coastal cliff exposure and management

Coastal cliffs cover about 75% of the world's coastlines. Many of these cliffs suffer severe erosion problems, which are mainly caused by wave action and lead to important damages. The main objective of this work is to propose and apply a methodology to characterize and map wave exposure levels for the management of cliff coasts. The methodology proposed consists of a number of steps. First, a statistical characterization of the wave climate in deep water is performed. Second, relevant sea states are propagated towards the cliff by means of a numerical model. Then, the results are used to assess the distribution of significant wave heights and wave power along the cliff toe. Finally, four exposure levels are defined based on the wave power values at the cliff, and exposure zones are mapped accordingly along the cliff. This approach is illustrated with a case study - the Catedrales Cliffs and Beach, a tourism hotspot in Galicia (NW Spain) where erosion caused loss of human life. We find that exposure levels are primarily influenced by the nearshore bed morphology, which controls wave refraction, shoaling and breaking, as well as by the geometry and orientation of the cliff, with some parts more exposed than others to the prevailing wave direction. On the islets off the cliff the windward faces have a greater level of exposure, since the leeward faces are protected by the islets themselves and lower water depths. The rocky outcrops that occur at the cliff toe in some sections act as emerged (submerged) breakwaters under low (high) tide conditions, dissipating wave power and thus reducing wave exposure. The methodology proposed in this work enables coastal managers to prevent the personal and material damages derived from cliff erosion by focusing remedial measures where they are most needed

Wave energy converter configuration in dual wave farms

Wave farms, i.e., arrays of Wave Energy Converters (WECs), have recently been proven to be effective in fulfilling the dual function of carbon-free energy generation and coastal protection. In this paper these dual-function wave farms are referred as dual wave farms. The objective of this work is to investigate the influence of the WEC configuration on the performance of these dual wave farms through a case study: a dual wave farm consisting of WaveCat WECs deployed off an eroding beach. WaveCat is a floating overtopping WEC consisting of two hulls joined by their stern, forming a wedge. Two configurations are considered, with wedge angles of 30° and 60°. To characterize wave-WEC interaction, laboratory tests of a 1:30 WaveCat model are conducted using the two configurations and low-, mid- and high-energy sea states characteristic of the study area. The reflection and transmission coefficients obtained from the laboratory tests are inputted into a suite of numerical models to investigate the hydro- and morphodynamics of the beach. We find that the smaller wedge angle (30°) WECs afford more (less) coastal protection - quantified in terms of dry beach area availability - for short (long) peak periods than WECs with . These results allow us to conclude that, for optimum performance of dual wave farms, WEC geometry should be adapted dynamically to the sea state

Multi-criteria characterization and mapping of coastal cliff environments: A case study in NW Spain

This paper presents a novel approach to characterize cliff exposure to marine action that combines wave power and biology. This multidisciplinary approach is illustrated through a case study on a coastal stretch in NW Spain – the Catedrales Natural Monument. The engineering perspective is based on quantifying the wave power acting on the cliff. To this end, a statistical characterization of the wave climate in deep water is carried out, and relevant sea states are propagated numerically from deep water to the cliff. Four levels of cliff exposure, from sheltered to exposed, are defined based on wave power and mapped onto the study area. As for the biological perspective, ecological factors, bioindicated variables and biological indicators characterized through field observations are considered and, on this basis, also four levels of cliff exposure are established and mapped. In general, there is good agreement between the exposure patterns obtained through the engineering and biological perspectives; however, there are some differences in certain areas. The upshot is that the engineering and biological points of view should be regarded as complementary. The multi-criteria characterization performed in this paper may be used as a management tool to establish different degrees of exposure to marine action on cliff coasts elsewhere

Morpho-sedimentary dynamics of a micro-tidal mixed sand and gravel beach, Playa Granada, southern Spain

publisher: Elsevier articletitle: Morpho-sedimentary dynamics of a micro-tidal mixed sand and gravel beach, Playa Granada, southern Spain journaltitle: Marine Geology articlelink: http://dx.doi.org/10.1016/j.margeo.2016.05.003 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved

Coastal infrastructure operativity against flooding - A methodology

The operativity of the transport infrastructures and urban developments protected by coastal structures is conditioned by flooding events and the resulting wave overtopping. This work presents a methodology to assess the operational conditions of infrastructures located in coastal areas based on the combination of advanced statistical techniques, laboratory experiments and state-of-the-art numerical models properly validated. It is applied to a case study in the SW coast of England, the railway seawall at Dawlish, which was subjected to recurrent wave overtopping until its dramatic collapse in February 2014. To quantify the increase in overtopping discharges with wave height and water level, we define an ad hoc variable, the effective overtopping forcing, which explains 98% of the variability of the overtopping discharge. The return periods associated to the operational thresholds for coastal structures protecting people and railways are also obtained. The proposed methodology enables the assessment of the overtopping discharge induced by a given sea state and, thus, check if a coastal infrastructure will be or not operational under any expected marine condition. This innovative methodology can also be used to analyse the flooding event consequences on urban areas protected by coastal infrastructures