Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales
This Thesis conducts the study of bedform development and dynamics in the inner shelf integrating observations at different spatial and temporal scales. An initial assumption is that different scales of sedimentary processes strongly interact between them and small-scale sedimentary processes intend...
| Autor: | |
|---|---|
| Tipo de recurso: | tesis doctoral |
| Fecha de publicación: | 2019 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/129263 |
| Acceso en línea: | https://hdl.handle.net/2117/129263 https://dx.doi.org/10.5821/dissertation-2117-129263 |
| Access Level: | acceso abierto |
| Palabra clave: | Sediments fluvials Sediments marins Àrees temàtiques de la UPC::Enginyeria civil |
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Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| title |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| spellingShingle |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales Guerrero Sánchez, Queralt Sediments fluvials Sediments marins Àrees temàtiques de la UPC::Enginyeria civil |
| title_short |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| title_full |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| title_fullStr |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| title_full_unstemmed |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| title_sort |
Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scales |
| dc.creator.none.fl_str_mv |
Guerrero Sánchez, Queralt |
| author |
Guerrero Sánchez, Queralt |
| author_facet |
Guerrero Sánchez, Queralt |
| author_role |
author |
| dc.contributor.none.fl_str_mv |
Guillen Aranda, Jorge |
| dc.subject.none.fl_str_mv |
Sediments fluvials Sediments marins Àrees temàtiques de la UPC::Enginyeria civil |
| topic |
Sediments fluvials Sediments marins Àrees temàtiques de la UPC::Enginyeria civil |
| description |
This Thesis conducts the study of bedform development and dynamics in the inner shelf integrating observations at different spatial and temporal scales. An initial assumption is that different scales of sedimentary processes strongly interact between them and small-scale sedimentary processes intended to foster those of larger scale. The potential contribution of small-scale bedforms to the sediment transport is particularly addressed. The study includes the monitoring and analysis of sand ridges, ripples and near-bottom suspended sediment variations at the Ebro Delta (NW Mediterranean Sea) and Perranporth (Atlantic Ocean) inner shelves. A sand ridge field with maximum ridges heights of 2.5 m and 400 m spaced is located over a retreating lobe in the Ebro Delta. Ridges are mostly symmetric arranging obliquely to the shoreline. The change of the main Ebro River channel led to the progressive abandonment of the former river mouth and to the severe coastal retreatment, providing large amount of sediment available in the coastal zone. NW winds induce strong near-bottom currents flowing towards the SE, which are able to transport sediment and produce ridge formation and migration towards the SE at ~10 m/y. The characteristics of the Ebro sand ridges match well with those of shoreface-connected sand ridges and, particularly, with the initial stages of sand ridge development on storm-dominated continental shelves. Time-scales related to their genesis can be within a few decades. The presence of ripples on the different inner shelves is the most usual situation under low- to moderate-energetic conditions. In the wave-dominated and tideless coast (Ebro Delta) ripples were observed superimposed on sand ridges. Four types were identified: small undulations that were the precursor ripples, 2D wave-ripples, current-dominated 2D-3D-ripples, and combined wave-current 3D-ripples. The wave-ripples were static while the current-dominated ripples migrated. In a macro-tidal sandy beach exposed to high-energetic Atlantic storms (Perranporth), only wave-ripples were developed arranging orthogonal to wave approach and they were static. The size of ripples changed from larger (developed in equilibrium conditions) to smaller ripples, the latter interpreted as degraded ripples in wash-out conditions. The ripple prediction did not well-adjust to neither ripple appearance nor dimension. However, if the observed thresholds of seabed states are applied the model improves ripple appearance forecast. The near-bottom suspended sediment variability from seconds to months in the Ebro Delta is described distinguishing between waves, currents, and combined wave-currents conditions. In general, waves dominated the sediment resuspensions although strong currents also have an important contribution in the suspended sediment concentration (SSC) increases. The time-averaged SSC usually showed redundant structure by forming three layers with different patterns. In the lower and intermediate layers the SSC oscillated at gravity and infragravity wave frequencies. Time-varying and instantaneous profiles exhibit sediment patterns potentially related to ripples. The potential role of ripple migration as an additional long-term mechanism of sediment transport was analysed. In Perranporth, wave ripples are stationary and did not contribute to beach recovery because of wave orbital symmetry. The sediment transport is alongshore during low-energetic regimes and cross-shore during more energetic regimes when ripples are washed-out. In the Ebro Delta, 3D-ripples migration agrees with sand ridges migration direction towards the SE. The respective migration rates and their differences in size, support that a subordinate part of sand ridge migration can be the result of ripple migration contribution under low-, moderate-regimes, suggesting that in specific environments, dynamics of small-scale bedforms can play a subordinate but not negligible role in the evolution of larger bedforms |
| publishDate |
2019 |
| dc.date.none.fl_str_mv |
2019 2019-02-08 2019 2019-02-12 |
| dc.type.none.fl_str_mv |
doctoral thesis http://purl.org/coar/resource_type/c_db06 VoR http://purl.org/coar/version/c_970fb48d4fbd8a85 |
| dc.type.openaire.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
| format |
doctoralThesis |
| dc.identifier.none.fl_str_mv |
https://hdl.handle.net/2117/129263 https://dx.doi.org/10.5821/dissertation-2117-129263 |
| url |
https://hdl.handle.net/2117/129263 https://dx.doi.org/10.5821/dissertation-2117-129263 |
| dc.language.none.fl_str_mv |
Inglés eng |
| language_invalid_str_mv |
Inglés |
| language |
eng |
| dc.rights.none.fl_str_mv |
open access http://purl.org/coar/access_right/c_abf2 |
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info:eu-repo/semantics/openAccess |
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open access http://purl.org/coar/access_right/c_abf2 |
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openAccess |
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application/pdf |
| dc.publisher.none.fl_str_mv |
Universitat Politècnica de Catalunya |
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Universitat Politècnica de Catalunya |
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reponame:UPCommons. Portal del coneixement obert de la UPC instname:Universitat Politècnica de Catalunya (UPC) |
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Universitat Politècnica de Catalunya (UPC) |
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UPCommons. Portal del coneixement obert de la UPC |
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UPCommons. Portal del coneixement obert de la UPC |
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1869420804943380480 |
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Bedforms and associated sediment dynamics on the inner shelves at different spatio-temporal scalesGuerrero Sánchez, QueraltSediments fluvialsSediments marinsÀrees temàtiques de la UPC::Enginyeria civilThis Thesis conducts the study of bedform development and dynamics in the inner shelf integrating observations at different spatial and temporal scales. An initial assumption is that different scales of sedimentary processes strongly interact between them and small-scale sedimentary processes intended to foster those of larger scale. The potential contribution of small-scale bedforms to the sediment transport is particularly addressed. The study includes the monitoring and analysis of sand ridges, ripples and near-bottom suspended sediment variations at the Ebro Delta (NW Mediterranean Sea) and Perranporth (Atlantic Ocean) inner shelves. A sand ridge field with maximum ridges heights of 2.5 m and 400 m spaced is located over a retreating lobe in the Ebro Delta. Ridges are mostly symmetric arranging obliquely to the shoreline. The change of the main Ebro River channel led to the progressive abandonment of the former river mouth and to the severe coastal retreatment, providing large amount of sediment available in the coastal zone. NW winds induce strong near-bottom currents flowing towards the SE, which are able to transport sediment and produce ridge formation and migration towards the SE at ~10 m/y. The characteristics of the Ebro sand ridges match well with those of shoreface-connected sand ridges and, particularly, with the initial stages of sand ridge development on storm-dominated continental shelves. Time-scales related to their genesis can be within a few decades. The presence of ripples on the different inner shelves is the most usual situation under low- to moderate-energetic conditions. In the wave-dominated and tideless coast (Ebro Delta) ripples were observed superimposed on sand ridges. Four types were identified: small undulations that were the precursor ripples, 2D wave-ripples, current-dominated 2D-3D-ripples, and combined wave-current 3D-ripples. The wave-ripples were static while the current-dominated ripples migrated. In a macro-tidal sandy beach exposed to high-energetic Atlantic storms (Perranporth), only wave-ripples were developed arranging orthogonal to wave approach and they were static. The size of ripples changed from larger (developed in equilibrium conditions) to smaller ripples, the latter interpreted as degraded ripples in wash-out conditions. The ripple prediction did not well-adjust to neither ripple appearance nor dimension. However, if the observed thresholds of seabed states are applied the model improves ripple appearance forecast. The near-bottom suspended sediment variability from seconds to months in the Ebro Delta is described distinguishing between waves, currents, and combined wave-currents conditions. In general, waves dominated the sediment resuspensions although strong currents also have an important contribution in the suspended sediment concentration (SSC) increases. The time-averaged SSC usually showed redundant structure by forming three layers with different patterns. In the lower and intermediate layers the SSC oscillated at gravity and infragravity wave frequencies. Time-varying and instantaneous profiles exhibit sediment patterns potentially related to ripples. The potential role of ripple migration as an additional long-term mechanism of sediment transport was analysed. In Perranporth, wave ripples are stationary and did not contribute to beach recovery because of wave orbital symmetry. The sediment transport is alongshore during low-energetic regimes and cross-shore during more energetic regimes when ripples are washed-out. In the Ebro Delta, 3D-ripples migration agrees with sand ridges migration direction towards the SE. The respective migration rates and their differences in size, support that a subordinate part of sand ridge migration can be the result of ripple migration contribution under low-, moderate-regimes, suggesting that in specific environments, dynamics of small-scale bedforms can play a subordinate but not negligible role in the evolution of larger bedformsLa Tesi estudia el desenvolupament i dinàmica de les formes de fons a la plataforma continental somera mitjançant la integració d’observacions a diferents escales espacials i temporals. Es parteix de la hipòtesi en què els processos sedimentaris a diferents escales estan relacionats i que els de petita escala fomenten als majors, fent especial èmfasi a la contribució de les formes de fons petites al transport de sediments. L’estudi inclou la monitorització i anàlisi de sand ridges, ripples i de les variacions de concentració de sediment en suspensió (CSS) prop del fons a la zona somera de les plataformes continentals del Delta de l’Ebre (NO Mar Mediterrània) i a Perranporth (oceà Atlàntic). Un camp de sand ridges amb crestes de fins 2.5 m d’alçada i 400 m espaiades es troba en un antic lòbul al Delta de l’Ebre. Les crestes són simètriques i obliqües respecte a la línia de costa. El canvi del canal principal del riu va suscitar l’abandonament progressiu de l’antiga desembocadura amb el retrocés sever de la línia de costa, proporcionant gran quantitat de sediments per formar els sand ridges que actualment migren ~10 m/any. Les característiques dels sand ridges de l’Ebre son anàlogues a les de sand ridges connectats a la costa i especialment a les seves etapes inicials a plataformes continentals dominades per tempestes. Les escales temporals relacionades amb la seva formació poden comprendre dècades. Les petites formes de fons observades inclouen: ripples superposats als sand ridges a la costa amb marees ínfimes dominada per tempestes de l’Ebre i ripples a la costa macro-mareal esposada a tempestes atlàntiques de Perranporth. Ambdues àrees, la presència de ripples és la situació habitual en condicions de baixa i mitja energia. A l’Ebre, es van diferenciar quatre morfologies: petites ondulacions precursores de 2D-ripples d’onatge, 2D-3D-ripples de corrents i 3D-ripples de la combinació d’onatge i corrents. Els ripples d’onatge eren estàtics mentre que els dominats per corrents migraven ~10 cm/h. A Perranporth, es van observar dues mides de ripples d’onatge amb crestes perpendiculars a la direcció de l’onatge i també estàtics. Els ripples més petits s’interpreten com la degradació dels grans. El model de predicció de ripples no s’ajusta ni per la seva formació ni dimensions. Tanmateix, quan els llindars d’estat de fons observats s’apliquen, el model millora el seu pronòstic. Les CSS prop del fons al Delta de l’Ebre es distingeix entre condicions d’onatge, corrents i la combinació d’onatge i corrents. En general, l’onatge domina la resuspensió de sediments tot i que els corrents també hi contribueixen de forma important. Les estimacions d’estrès total de cisallament és un bon indicador de pics de CSS i assenyala llindars d’inici de resuspensió de sediments. Les CSS van oscil·lar entre freqüències d’onatge gravitacional i infragravitacional. Les mitjanes dels perfils de CSS mostren una estructura vertical de tres capes mentre que els perfils instantanis mostren patrons en els CSS potencialment relacionats amb la presència de ripples. La migració de ripples en direcció a la costa com a mecanisme addicional a la recuperació de la platja a llarg termini a Perranporth va ser descartat degut a la estacionalitat del ripples i a la simetria de les velocitats orbitals de l’onatge. El transport de sediment és paral·lel a la costa durant condicions de baixa energia i perpendicular en condicions d’alta energia quan els ripples són erosionats. A l’Ebre, els sand ridges i de ripples migren cap a la mateixa direcció (SE). La relació entre velocitat de migració i dimensions entre les dues morfologies refermen que una part subordinada de la migració dels sand ridges podria ser conseqüència de la migració de ripples durant períodes de baixa i mitja energia. Llavors, en entorns específics, la dinàmica de les formes de fons petites podrien tenir un paper subordinat, però no menyspreable, en l’evolució de les formes més gransUniversitat Politècnica de CatalunyaGuillen Aranda, Jorge20192019-02-0820192019-02-12doctoral thesishttp://purl.org/coar/resource_type/c_db06VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/doctoralThesisapplication/pdfhttps://hdl.handle.net/2117/129263https://dx.doi.org/10.5821/dissertation-2117-129263reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/1292632026-05-27T15:37:01Z |
| score |
15,300719 |