97 research outputs found
Modeling the impact of climate change on sediment transport and morphology in coupled watershed-coast systems: A case study using an integrated approach
No full textClimate change is an issue of major concern nowadays. Its impact on the natural and human environment is studied intensively, as the expected shift in climate will be significant in the next few decades. Recent experience shows that the effects will be critical in coastal areas, resulting in erosion and inundation phenomena worldwide. In addition to that, coastal areas are subject to "pressures" from upstream watersheds in terms of water quality and sediment transport. The present paper studies the impact of climate change on sediment transport and morphology in the aforementioned coupled system. The study regards a sandy coast and its upstream watershed in Chalkidiki, North Greece; it is based on: (a) an integrated approach for the quantitative correlation of the two through numerical modeling, developed by the authors, and (b) a calibrated application of the relevant models Soil and Water Assessment Tool (SWAT) and PELNCON-M, applied to the watershed and the coastal zone, respectively. The examined climate change scenarios focus on a shift of the rainfall distribution towards fewer and more extreme rainfall events, and an increased frequency of occurrence of extreme wave events. Results indicate the significance of climatic pressures in wide-scale sediment dynamics, and are deemed to provide a useful perspective for researchers and policy planners involved in the study of coastal morphology evolution in a changing climate
Soft shore protection methods: The use of advanced numerical models in the evaluation of beach nourishment
No full textBeach nourishment is one of the worldwide most common soft shore protection methods. However, the design of these projects is usually based on empirical equations and rules, leaving large margins of error regarding their expected efficiency. In the present work, an advanced wave and sediment transport numerical model is developed and tested in the evaluation of beach nourishment. Non-linear wave transformation in the surf and swash zone is computed by a non-linear breaking wave model based on the higher order Boussinesq equations, for breaking and non-breaking waves. The new Camenen and Larson (2007), transport rate formula for non-cohesive sediments (involving unsteady aspects of the sand transport phenomenon) is adopted for estimating the sheet flow sediment transport rates, as well as the bed load and suspended load over ripples. Suspended sediment transport rate is incorporated by solving the 2DH depth-integrated transport equation. Model results are compared with experimental data of both profile (cross-shore) and planform morphology evolution; the agreement between the two is considered to be quite satisfactory
An integrated approach to quantify the impact of watershed management on coastal morphology
No full textCoastal areas are subject to various natural- and human-induced impacts affecting water quality and morphology evolution. Regarding the latter, its correlation with watershed processes is self-evident, as natural streams in many cases constitute the largest sediment source for the coastal environment. However, literature references that study concurrently both fields (i.e. terrestrial and coastal) and their quantitative correlation are scarce. The present paper introduces and describes in detail an integrated approach to quantify the impact of watershed management on coastal morphology using numerical modeling. The core of the proposed methodology refers to a coupled-calibration approach of the watershed and the coastal models, incorporating three scenarios of data availability regarding the parameters of interest (coastal morphology, overland sediment transport and coastal sediment transport). To support the applicability of this approach, a brief presentation of its successful application for an area in North Greece is also presented. The study retains the viewpoint of Integrated Coastal Zone Management, and is deemed to provide an operational tool for future researchers and policy planners
The impact of watershed management on coastal morphology: A case study using an integrated approach and numerical modeling.
No full textCoastal morphology evolves as the combined result of both natural- and human- induced factors that cover a wide range of spatial and temporal scales of effect. Areas in the vicinity of natural stream mouths are of special interest, as the direct connection with the upstream watershed extends the search for drivers of morphological evolution from the coastal area to the inland as well. Although the impact of changes in watersheds on the coastal sediment budget is well established, references that study concurrently the two fields and the quantification of their connection are scarce. In the present work, the impact of land-use changes in a watershed on coastal erosion is studied for a selected site in North Greece. Applications are based on an integrated approach to quantify the impact of watershed management on coastal morphology through numerical modeling. The watershed model SWAT and a shoreline evolution model developed by the authors (PELNCON-M) are used, evaluating with the latter the performance of the three longshore sediment transport rate formulae included in the model formulation. Results document the impact of crop abandonment on coastal erosion (agricultural land decrease from 23.3% to 5.1% is accompanied by the retreat of ~ 35 m in the vicinity of the stream mouth) and show the effect of sediment transport formula selection on the evolution of coastal morphology. Analysis denotes the relative importance of the parameters involved in the dynamics of watershed–coast systems, and – through the detailed description of a case study – is deemed to provide useful insights for researchers and policy-makers involved in their study
Comparison of three longshore sediment transport rate formulae in shoreline evolution modeling near stream mouths
No full textLongshore sediment transport (LST) rate is the most essential quantity to be defined in shoreline evolution models. Intercomparisons of different formulae on the basis of laboratory or field measurements of LST rate values are commonly found in literature; however, examples of comparison based on long-term shoreline evolution observations are scarce. Moreover, applications of shoreline evolution models near stream mouths (where the sediment input affects coastal morphology) are also scarce. In the present paper, three well-known LST rate formulae are compared, as part of a model used to simulate shoreline evolution in the vicinity of a stream mouth. The model was properly adapted by the authors to provide with new capabilities regarding: (a1) the use of wind data to simulate wave climate, (b1) the description of coastal morphology and sediment transport and (c1) the introduction of sediment sources. Results show the relative efficiency of the three formulae in terms of: (a2) the stream sediment discharge needed to simulate measured shorelines, and (b2) the divergence observed between simulations and measurements; analysis is deemed to provide a useful perspective on the importance of LST rate formula selection in similar engineering applications
High-resolution wave and hydrodynamics modelling in coastal areas: operational applications for coastal planning, decision support and assessment
No full textNumerical modelling has become an essential component of today's coastal
planning, decision support and risk assessment. High-resolution modelling
offers an extensive range of capabilities regarding simulated conditions,
works and practices and provides with a wide array of data regarding
nearshore wave dynamics and hydrodynamics.
In the present work, the open-source TELEMAC suite and the commercial
software MIKE21 are applied to selected coastal areas of South Italy.
Applications follow a scenario-based approach in order to study
representative wave conditions in the coastal field; the models' results are
intercompared in order to test both their performance and capabilities and
are further evaluated on the basis of their operational use for coastal
planning and design. A multiparametric approach for the rapid assessment of
wave conditions in coastal areas is also presented and implemented in areas
of the same region. The overall approach is deemed to provide useful insights
on the tested models and the use of numerical models – in general – in the
above context, especially considering that the design of harbours, coastal
protection works and management practices in the coastal zone is based on
scenario-based approaches as well
Wave and hydrodynamics modelling in coastal areas with open-source solver: influence of the coupling mechanisms
No full textTowards improving the simulation of beaching in oil spill models
No full textOil-shoreline interaction (or “beaching” as commonly referred in literature) is an issue of major concern in oil- spill modeling, due to the significant environmental, social and economic importance of coastal areas. The amount of oil that reaches and stays at the shore, as well as the temporal characteristics of the involved processes –in short– define the oil-spill impact on a specific coastal stretch and are subsequently used to assess this impact. This paper presents and implements a methodology to improve the simulation of beaching in oil spill models, based on the parametrization of shoreline response for different oil types, coastal types and beach properties. The methodology is tested using the MEDSLIK-II model; the evaluation of the expected improvement is based on the intercomparison of model results for the Lebanon spill incident in 2006
Simulation of tsunami generation, propagation and coastal inundation in the Eastern Mediterranean
No full textIn the present work, an advanced tsunami generation, propagation and coastal
inundation 2-DH model (i.e. 2-D Horizontal model) based on the higher-order
Boussinesq equations – developed by the authors – is applied to simulate representative
earthquake-induced tsunami scenarios in the Eastern Mediterranean. Two areas
of interest were selected after evaluating tsunamigenic zones and possible
sources in the region: one at the southwest of the island of Crete in Greece
and one at the east of the island of Sicily in Italy. Model results are
presented in the form of extreme water elevation maps, sequences of
snapshots of water elevation during the propagation of the tsunamis, and
inundation maps of the studied low-lying coastal areas. This work marks one
of the first successful applications of a fully nonlinear model for the 2-DH
simulation of tsunami-induced coastal inundation; acquired results are
indicative of the model's capabilities, as well of how areas in the Eastern
Mediterranean would be affected by eventual larger events
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