Abstract
Background, Aim and Scope
The distribution of sediments in estuarine beaches is controlled by the interactions between sediment supply, hydrodynamic processes and human intervention. The main purpose of this study is to characterize the sediments of Tagus estuarine beaches in order to understand their origin and to contribute to a better knowledge of the Tagus estuary sediment budget.
Methods
Surface sediment samples were collected across beach profiles and sand grain size analysis was performed by dry sieving. Grain size statistics for the median (d50) and standard deviation (SDM) were obtained using the Moment method. This study was complemented by a qualitative evaluation of the sediment composition. Cross-shore topographic surveys were conducted for selected sampling sites.
Results
Tagus estuarine beach sediments are mainly composed of quartz sand particles which are fine-grained and well sorted near the mouth of the estuary and medium to coarse-grained and moderately sorted in the inner domain. Compositional results show evidence of active anthropogenic sediment sources, especially in the coarser fractions.
Discussion
The analysis of the textural and compositional characteristics of beach sediments in the inner estuarine domain is compatible with local sedimentary sources, while a marine signature is present at the mouth and inlet channel sediments. In the inner domain, differences in the sedimentary processes are represented by the textural characteristics of the sediments, such as the sorting degree and the gravel content. Sediment characteristics also reflect human intervention in the system, with the introduction of anthropogenic and allochthonous particles and the mixture of sediments from different sources.
Conclusions
The sediments of the inner Tagus estuarine beaches are derived from local Plio-Pleistocene outcrops while inlet and outer estuary beaches reveal a dominant marine source. Beach textural variability observed in the inner domain is not related to wave forcing gradients, but mainly to variations in the sedimentary processes along the estuarine margins and to human intervention. Results show that the Tagus estuarine beaches depended, almost exclusively, on sediment input from local sources until the last century. With increasing human occupation, sediment transfers became dominated by anthropogenically related activities mainly connected with the occupation of estuarine margins and dredging.
Recommendations and Perspectives
Further studies should extend the present level of knowledge in what concerns sand transport patterns through additional compositional and geochemical analysis, and the development of new techniques in order to allow the quantitative evaluation of the impact of human activities on the sediment budget.
Similar content being viewed by others
References
Bettencourt A, Ramos L, Gomes V, Dias JMA, Ferreira G, Silva M, Costa L (2003): Portuguese estuaries. Ed. INAG — Ministério das Cidades, Ordenamento do Território e Ambiente, Lisboa (in Portuguese)
Darlrymple R, Zaitlin B, Boyd R (1992): Estuarine Facies Models: Conceptual Basis and Stratigraphic Implications. J Sedimentary Petrology 62(6) 1130–1146
Dalrymple R, Choi K (2007): Morphologic and facies trends through the fluvial-marine transition in tide-dominated depositional systems: A schematic framework for environmental and sequence-stratigraphic interpretation. Earth-Science Reviews 81, 135–174
Fortes CJ, Capitão RP, Oliveira FSBF, Carvalho MM, Covas JA, Vaz dos Santos MA, Sancho FE (2001): A sea wave study at the entrance of the Tagus estuary. Thalassas 17(1) 11–27
Freire P (2003): Morphological and sedimentary evolution of estuarine banks (Tagus Estuary, Portugal). Ph.D. Dissertation, University of Lisbon, LNEC, TPI 28 (in Portuguese)
Freire P, Andrade C (1999): Wind-induced sand transport in Tagus estuarine beaches. First results. Aquatic Ecology 33, 225–233
Freire P, Andrade C (2000): Short-term morphological evolution of the Alfeite estuarine beach. 3° Simpósio sobre a Margem Continental Ibérica Atlântica, Universidade do Algarve, pp 39–40
Friedman G (1961): Distinction Between Dune, Beach and River Sands from their Textural Characteristics. J Sedimentary Petrology 31(4) 514–529
Friedman G (1967): Dynamic Processes and Statistical Parameters Compared for Size Frequency Distribution of Beach and River Sands. J Sedimentary Petrology 37(2) 327–354
Hegge B, Eliot I, Hsu J (1999): Sheltered Sandy Beaches of Southwestern Australia. J Coastal Research 12, 748–760
Hurdle DP, Stive RJH (1989): Revision of SPM 1984 Wave Hindcast Model to Avoid Inconsistencies in Engineering Applications. Coastal Eng 12, 339–351
Jackson N (1995): Wind and waves: Influence of local and non-local waves on mesoscale beach behaviour in estuarine environments. Annals of the Assoc of American Geographers 85(1) 21–37
Jackson N, Nordstrom K (1992): Site specific controls on wind and wave processes and beach mobility on estuarine beaches in New Jersey, USA. J Coastal Research 8(1) 88–98
Jackson N, Nordstrom K (1993): Depth of activation of sediment by plunging breakers on a steep sand beach. Marine Geology 115, 143–151
Jackson N, Nordstrom K, Eliot I, Masselink G (2002): Low energy sandy beaches in marine and estuarine environments: A review. Geomorphology 48, 147–162
Kennedy D (2002): Estuarine beach morphology in microtidal Middle Harbour, Sydney. Australian Geog Studies 40(2) 231–240
Louzada C (1995): Contribution for the sand sediments provenance of Tagus estuary left embankment beaches. University of Lisbon, unpublished report (in Portuguese)
MacLaren P (1981): An interpretation of trends in grain size measures. J Sedimentary Petrology 51(2) 0611–0624
Maretec (2001): Definition of the downstream limit of Portuguese estuaries [accessed on 20th November 2006]. Available at: http://www.maretec.mohid.com/Estuarios/Inicio/Introducao.htm (in Portuguese)
Nichols MM, Biggs RB (1985): Estuaries. In: Davis RA (ed), Coastal Sedimentary Environments. Springer-Verlag, New York, pp 77–187
Nordstrom K (1977): The Use of Grain Size Statistics to Distinguish Between High-and-Moderate-Energy Beach Environments. J Sedimentary Petrology 47(3) 1287–1294
Nordstrom K (1980): Cyclic and Seasonal Beach Response: A Comparison of Oceanside and Bayside Beaches. Physical Geography 1(2) 177–196
Nordstrom K (1992): Estuarine beaches. An introduction to the physical and human factors affecting use and management of beaches in estuaries, lagoons, bays and fjords. Elsevier Science Publishers Ltd, New York
Nordstrom K, Jackson N (1992): Two-dimensional Change on Sandy Beaches in Meso-tidal Estuaries. Zeits Geomorph N F 34(4) 465–478
Nordstrom K, Jackson N (1993): Distribution of surface pebbles with changes in wave energy on a sandy estuarine beach. J Sedimentary Petrology 63(6) 1152–1159
Nordstrom K, Jackson N, Allen J, Sherman D (1996): Wave and current processes and beach changes on a microtidal lagoonal beach at Fire Island, New York. In: Nordstrom KF, Roman CT (eds), Estuarine Shores. Evolution, Environments and Human Alterations. Wiley, pp 213–232
Nordstrom K, Jackson N, Pranzini E (2004): Beach sediment alteration by natural processes and human actions: Elba Island, Italy. Annals of the Assoc of American Geographers 94(4) 794–806
Nordstrom K, Sten H, Jackson N (1991): Comparison of estuarine beaches in Germany and USA. Proceedings of Coastal Zone’91, Long Beach, pp 2409–2420
Oliveira R (1967): Contribution to the study of Tagus estuary. Sedimentology. Memória 296, LNEC, Lisboa (in Portuguese)
Portela L (2004): An Approximate Sediment Budget for the Tagus Estuary. 3rd International SedNet Conference: The future of sediment management in Europe, Conference Documents, European Sediment Research Network, pp 3
Roman C, Nordstrom K (1996): Environments, processes and interactions of estuarine shores. In: Nordstrom KF, Roman CT (eds), Estuarine Shores. Evolution, Environments and Human Alterations. Wiley, pp 1–12
Valente C (2006): Morphological and sedimentary evolution of estuarine beaches. University of Lisbon, unpublished report (in Portuguese)
Valente C, Freire P, Taborda R (2006): Mesoscale morphological evolution of Alfeite beach. VII Congresso Nacional de Geologia, Universidade de Évora, pp 437–440 (in Portuguese)
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Freire, P., Taborda, R. & Silva, A.M. Sedimentary characterization of Tagus estuarine beaches (Portugal). J Soils Sediments 7, 296–302 (2007). https://doi.org/10.1065/jss2007.08.243
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1065/jss2007.08.243