scholarly journals Soil erosion, reservoir lake infill and coastal erosion in the Mediterranean coast of southern Spain.

2021 ◽  
Author(s):  
José Luis del Río ◽  
Fatima Navas ◽  
Gonzalo Malvarez
Keyword(s):  
Sediment Transport ◽  
Sediment Accumulation ◽  
Human Action ◽  
Mediterranean Coast ◽  
Coastal Protection ◽  
Dune System ◽  
Basin Scale ◽  
Remotely Piloted Aircraft ◽  
Marine System ◽  
Increasing Demand

The combination of vigorous terrain and millenary human action has produced major changes in vegetation cover, impacting soil losses from slopes and, consequently, sediment production. Increasing focus in the management of water resources led to the widespread construction of dams to generate water flows for iron production, irrigation and to satisfy the increasing demand of the massive urban development along the Costa del Sol. To investigate the connection between soil degradation and loss and river sediment transport retention at a major dam, a first-order sediment yield prediction was established by using a GIS-based model at river basin scale. A quantitative validation of model results is provided by empirical measurements of sedimentation in the main reservoir lake of La Concepción using D_GPS/Echo sounder combination and a Remotely Piloted Aircraft compared with pre-construction blue print topography aimed at documenting spot heights where sediments accumulated or eroded over 50 years. The significant erodibility that we have estimated seems matched by potentially high sediment accumulation rates along selected profiles and spot heights across the bottom of the reservoir lake. Our study discusses that Mediterranean coastal systems may no longer stay in the resilience envelope set by a critically delicate sediment transport balance and without engineering support in the form of direct sediment feeding to the marine system by the permanent nourishment works required. Due to soil loss, sediment entrapment in reservoirs and water management policies, the coastal protection offered by the natural resilience of the beach and dune system is no longer recoverable.

VARIAÇÃO MORFOSSEDIMENTAR DO SETOR EXTREMO OESTE DA PRAIA DO ICARAÍ, CAUCAIA-CE

2019 ◽  
Vol 21 (2) ◽  
pp. 364-380
Author(s):  
Antônio Emanuel dos' Santos Silva ◽  
Matheus Silveira Pinheiro ◽  
Davis Pereira de Paula
Keyword(s):  
Civil Society ◽  
Coastal Erosion ◽  
Field Experiments ◽  
Coastal Protection ◽  
Dune System ◽  
Built Heritage ◽  
General Terms ◽  
Methodological Procedures ◽  
Sociedad Civil

Ambientalmente as dunas frontais constituem estruturas verdes de proteção costeira contra o avanço do mar, em muitos casos, são responsáveis pela manutenção do equilíbrio sedimentar do sistema praia-duna, impedindo que processos como a erosão costeira e a inundação marinha se tornem danosos a sociedade civil e ao patrimônio construído. O objetivo deste estudo foi monitorar as variações morfológicas e sedimentares do sistema praia-duna entre os anos de 2016 e 2018, no trecho extremo oeste da Praia do Icaraí, através da determinação das taxas granulométricas, volumétricas e morfológicas do sistema praia-duna na Praia do Icaraí. Os procedimentos metodológicos foram divididos em três etapas principais: levantamento bibliográfico, geocartográfico e experimentos de campo. Considerou-se que as forçantes oceanográficas foram as principais responsáveis pela erosão e solapamento das dunas frontais presentes na área de estudo. Em linhas gerais, os resultados deste trabalho significam um importante instrumento de análise dos impactos das condicionantes oceanográficas e antrópicas sobre uma praia que sofre de erosão costeira acentuada. O estudo em um trecho mais preservado dessa praia indicou de forma direta os impactos sofridos em um litoral que vem passando por transformações contínuas em suas praias, como é o caso do litoral de Caucaia.Palavras-chave: Morfodinâmica; Sistema Praial; Dunas Frontais. ABSTRACTEnvironmentally the frontal dunes constitute green structures of coastal protection against the advance of the sea, in many cases, they are responsible for the maintenance of the sedimentary balance of the beach-dune system, preventing that processes such as coastal erosion and marine flooding become harmful to civil society and built heritage. The objective of this study was to monitor the morphological and sedimentary variations of the beach-dune system between the years 2016 and 2018, in the extreme west section of Icaraí Beach, by determining the granulometric, volumetric and morphological rates of the beach-dune system in Praia of Icaraí. The methodological procedures were divided into three main stages: bibliographic survey, geocartographic and field experiments. It was considered that the oceanographic forcings were the main responsible for the erosion and overlap of the frontal dunes present in the study area. In general terms, the results of this work represent an important instrument for analyzing the impacts of oceanographic and anthropogenic conditions on a beach that suffers from marked coastal erosion. The study in a more preserved stretch of this beach indicated in a direct way the impacts suffered on a coast that has undergone continuous transformations in its beaches, as is the case of the coast of Caucaia.Keywords: Morphodynamics; Praial System; Fore Dunes. RESUMENAmbientalmente, las dunas frontales son estructuras verdes de protección costera contra el avance del mar. En muchos casos, son responsables de mantener el equilibrio sedimentario del sistema de dunas de playa, evitando que procesos como la erosión costera y las inundaciones marinas dañen a la sociedad civil. y el patrimonio construido. El objetivo de este estudio fue monitorear las variaciones morfológicas y sedimentarias del sistema de dunas de playa entre 2016 y 2018, en el extremo occidental de Praia do Icaraí, determinando el tamaño de partícula, las tasas volumétricas y morfológicas del sistema de dunas de playa en Praia de Icaraí Los procedimientos metodológicos se dividieron en tres etapas principales: estudio bibliográfico, geocartográfico y experimentos de campo. El forzamiento oceanográfico se consideró el principal responsable de la erosión y el debilitamiento de las dunas frontales presentes en el área de estudio. En general, los resultados de este trabajo representan un instrumento importante para analizar los impactos de las condiciones oceanográficas y antropogénicas en una playa que sufre una severa erosión costera. El estudio en un tramo más preservado de esta playa indicó directamente los impactos sufridos en una costa que ha sufrido cambios continuos en sus playas, como es el caso de la costa de Caucaia.Palabras claves: Morfodinámica; Sistema de playa; Dunas frontales.

scholarly journals Morphodynamic Evolution of a Nourished Beach with Artificial Sandbars: Field Observations and Numerical Modeling

2021 ◽  
Vol 9 (3) ◽  
pp. 245
Author(s):  
Cuiping Kuang ◽  
Xuejian Han ◽  
Jiabo Zhang ◽  
Qingping Zou ◽  
Boling Dong
Keyword(s):  
Sediment Transport ◽  
Tidal Current ◽  
Model Simulation ◽  
Morphological Changes ◽  
Current Model ◽  
Beach Nourishment ◽  
Tidal Range ◽  
Coastal Protection ◽  
Field Observations ◽  
One Year

Beach nourishment, a common practice to replenish an eroded beach face with filling sand, has become increasingly popular as an environmentally friendly soft engineering measure to tackle coastal erosion. In this study, three 200 m long offshore submerged sandbars were placed about 200 m from the shore in August 2017 for both coastal protection and beach nourishment at Shanhai Pass, Bohai Sea, northeastern China. A series of 21 beach profiles were collected from August 2017 to July 2018 to monitor the morphological changes of the nourished beach. Field observations of wave and tide levels were conducted for one year and tidal current for 25 h, respectively. To investigate the spatial-temporal responses of hydrodynamics, sediment transport, and morphology to the presence of three artificial submerged sandbars, a two-dimensional depth-averaged (2DH) multi-fraction sediment transport and morphological model were coupled with wave and current model and implemented over a spatially varying nested grid. The model results compare well with the field observations of hydrodynamics and morphological changes. The tidal range was around 1.0 m and the waves predominately came from the south-south-east (SSE) direction in the study area. The observed and predicted beach profiles indicate that the sandbars moved onshore and the morphology experienced drastic changes immediately after the introduction of sandbars and reached an equilibrium state in about one year. The morphological change was mainly driven by waves. Under the influences of the prevailing waves and the longshore drift toward the northeast, the coastline on the leeside of the sandbars advanced seaward by 35 m maximally while the rest adjacent coastline retreated severely by 44 m maximally within August 2017–July 2018. The model results demonstrate that the three sandbars have little effect on the tidal current but attenuate the incoming wave significantly. As a result, the medium-coarse sand of sandbars is transported onshore and the background silt is mainly transported offshore and partly in the longshore direction toward the northeast. The 2- and 5-year model simulation results further indicate that shoreline salient may form behind the sandbars and protrude offshore enough to reach the sandbars, similar to the tombolo behind the breakwater.

Sediment transport modifications induced by submerged artificial reef systems: a case study for the Gulf of Venice

2014 ◽  
Vol 43 (1) ◽  
Author(s):  
Davide Bonaldo ◽  
Alvise Benetazzo ◽  
Andrea Bergamasco ◽  
Francesco Falcieri ◽  
Sandro Carniel ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Coastal Zone Management ◽  
Artificial Reef ◽  
Sediment Concentration ◽  
Quantitative Information ◽  
Small Scale ◽  
Zone Management ◽  
Basin Scale ◽  
Scale Modelling ◽  
Maritime Spatial Planning

AbstractThe shallow, gently sloping, sandy-silty seabed of the Venetian coast (Italy) is studded by a number of outcropping rocky systems of different size encouraging the development of peculiar zoobenthic biocenoses with considerably higher biodiversity indexes compared to neighbouring areas. In order to protect and enhance the growth of settling communities, artificial monolithic reefs were deployed close to the most important formations, providing further nesting sites and mechanical hindrance to illegal trawl fishing.In this framework, a multi-step and multi-scale numerical modelling activity was carried out to predict the perturbations induced by the presence of artificial structures on sediment transport over the outcroppings and their implications on turbidity and water quality. After having characterized wave and current circulation climate at the sub-basin scale over a reference year, a set of small scale simulations was carried out to describe the effects of a single monolith under different geometries and hydrodynamic forcings, encompassing the conditions likely occurring at the study sites. A dedicated tool was then developed to compose the information contained in the small-scale database into realistic deployment configurations, and applied in four protected outcroppings identified as test sites. With reference to these cases, under current meteomarine climate the application highlighted a small and localised increase in suspended sediment concentration, suggesting that the implemented deployment strategy is not likely to produce harmful effects on turbidity close to the outcroppings.In a broader context, the activity is oriented at the tuning of a flexible instrument for supporting the decision-making process in benthic environments of outstanding environmental relevance, especially in the Integrated Coastal Zone Management or Maritime Spatial Planning applications. The dissemination of sub-basin scale modelling results via the THREDDS Data Server, together with an user-friendly software for composing single-monolith runs and a graphical interface for exploring the available data, significantly improves the quantitative information collection and sharing among scientists, stakeholders and policy-makers.

scholarly journals The role of the reef–dune system in coastal protection in Puerto Morelos (Mexico)

2018 ◽  
Vol 18 (4) ◽  
pp. 1247-1260 ◽  
Author(s):  
Gemma L. Franklin ◽  
Alec Torres-Freyermuth ◽  
Gabriela Medellin ◽  
María Eugenia Allende-Arandia ◽  
Christian M. Appendini
Keyword(s):  
Sand Dunes ◽  
Coastal Flooding ◽  
Water Levels ◽  
Coastal Protection ◽  
Dune System ◽  
Fore Reef ◽  
Extreme Water Levels ◽  
Reef Environments ◽  
Storm Impact

Abstract. Reefs and sand dunes are critical morphological features providing natural coastal protection. Reefs dissipate around 90 % of the incident wave energy through wave breaking, whereas sand dunes provide the final natural barrier against coastal flooding. The storm impact on coastal areas with these features depends on the relative elevation of the extreme water levels with respect to the sand dune morphology. However, despite the importance of barrier reefs and dunes in coastal protection, poor management practices have degraded these ecosystems, increasing their vulnerability to coastal flooding. The present study aims to theoretically investigate the role of the reef–dune system in coastal protection under current climatic conditions at Puerto Morelos, located in the Mexican Caribbean Sea, using a widely validated nonlinear non-hydrostatic numerical model (SWASH). Wave hindcast information, tidal level, and a measured beach profile of the reef–dune system in Puerto Morelos are employed to estimate extreme runup and the storm impact scale for current and theoretical scenarios. The numerical results show the importance of including the storm surge when predicting extreme water levels and also show that ecosystem degradation has important implications for coastal protection against storms with return periods of less than 10 years. The latter highlights the importance of conservation of the system as a mitigation measure to decrease coastal vulnerability and infrastructure losses in coastal areas in the short to medium term. Furthermore, the results are used to evaluate the applicability of runup parameterisations for beaches to reef environments. Numerical analysis of runup dynamics suggests that runup parameterisations for reef environments can be improved by including the fore reef slope. Therefore, future research to develop runup parameterisations incorporating reef geometry features (e.g. reef crest elevation, reef lagoon width, fore reef slope) is warranted.

Sediment slugs: large-scale fluctuations in fluvial sediment transport rates and storage volumes

1995 ◽  
Vol 19 (4) ◽  
pp. 500-519 ◽  
Author(s):  
A.P. Nicholas ◽  
P.J. Ashworth ◽  
M.J. Kirkby ◽  
M.G. Macklin ◽  
T. Murray
Keyword(s):  
Sediment Transport ◽  
Sediment Supply ◽  
Fluvial Systems ◽  
Event Scale ◽  
Fluvial Sediment ◽  
Sediment Routing ◽  
Basin Scale ◽  
Wide Range ◽  
And Storage ◽  
Fluvial Sediment Transport

Variations in fluvial sediment transport rates and storage volumes have been described previously as sediment waves or pulses. These features have been identified over a wide range of temporal and spatial scales and have been categorized using existing bedform classifications. Here we describe the factors controlling the generation and propagation of what we term sediment slugs. These can be defined as bodies of clastic material associated with disequilibrium conditions in fluvial systems over time periods above the event scale. Slugs range in magnitude from unit bars (Smith, 1974) up to sedimentary features generated by basin-scale sediment supply disturbances (Trimble, 1981). At lower slug magnitudes, perturbations in sediment transport are generated by local riverbank and/or bed erosion. Larger-scale features result from the occurrence of rare high- magnitude geomorphic events, and the impacts on water and sediment production of tectonics, glaciation, climate change and anthropogenic influences. Simple sediment routing functions are presented which may be used to describe the propagation of sediment slugs in fluvial systems. Attention is drawn to components of the fluvial system where future research is urgently required to improve our quantitative understanding of drainage-basin sediment dynamics.

scholarly journals Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

2020 ◽  
Vol 12 (22) ◽  
pp. 3689
Author(s):  
Iain Fairley ◽  
Jose Horrillo-Caraballo ◽  
Ian Masters ◽  
Harshinie Karunarathna ◽  
Dominic E. Reeve
Keyword(s):  
Spatial Scales ◽  
Coastal Dunes ◽  
Sediment Supply ◽  
Tidal Range ◽  
Coastal Protection ◽  
Dune System ◽  
Pressure Transducers ◽  
Significant Wave ◽  
Wave Heights ◽  
Significant Wave Heights

Coastal dunes have global importance as ecological habitats, recreational areas, and vital natural coastal protection. Dunes evolve due to variations in the supply and removal of sediment via both wind and waves, and on stabilization through vegetation colonization and growth. One aspect of dune evolution that is poorly understood is the longshore variation in dune response to morphodynamic forcing, which can occur over small spatial scales. In this paper, a fixed wing unmanned aerial vehicle (UAV), is used to measure the longshore variation in evolution of a dune system in a megatidal environment. Dune sections to the east and west of the study site are prograding whereas the central portion is static or eroding. The measured variation in dune response is compared to mesoscale intertidal bar migration and short-term measurements of longshore variation in wave characteristics during two storms. Intertidal sand bar migration is measured using satellite imagery: crescentic intertidal bars are present in front of the accreting portion of the beach to the west and migrate onshore at a rate of 0.1–0.2 m/day; episodically the eastern end of the bar detaches from the main bar and migrates eastward to attach near the eastern end of the study area; bypassing the central eroding section. Statistically significant longshore variation in intertidal wave heights were measured using beachface mounted pressure transducers: the largest significant wave heights are found in front of the dune section suffering erosion. Spectral differences were noted with more narrow-banded spectra in this area but differences are not statistically significant. These observations demonstrate the importance of three-dimensionality in intertidal beach morphology on longshore variation in dune evolution; both through longshore variation in onshore sediment supply and through causing longshore variation in near-dune significant wave heights.

scholarly journals A key source area and constraints on entrainment for basin-scale sediment transport by Arctic sea ice

2000 ◽  
Vol 27 (13) ◽  
pp. 1919-1922 ◽  
Author(s):  
Hajo Eicken ◽  
Josef Kolatschek ◽  
Johannes Freitag ◽  
Frank Lindemann ◽  
Heidemarie Kassens ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Sea Ice ◽  
Source Area ◽  
Arctic Sea Ice ◽  
Basin Scale ◽  
Arctic Sea
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