Sand transport rates in the Troia-Sines Arc, southwest Portugal
Gomes, N.; Andrade, C.; Romariz, C. (1992). Sand transport rates in the Troia-Sines Arc, southwest Portugal, in: Carter, R.W.G. et al. (Ed.) Coastal dunes: geomorphology, ecology and management for conservation: Proceedings of the 3rd European Dune Congress Galway, Ireland, 17-21 June 1992. pp. 33-43
In: Carter, R.W.G.; Curtis, T.G.F.; Sheehy-Skeffington, M.J. (Ed.) (1992). Coastal dunes: Geomorphology, ecology and management for conservation: Proceedings of the 3rd European Dune Congress Galway, Ireland, 17-21 June 1992. A.A. Balkema [etc.]: Rotterdam. ISBN 90-5410-058-3. 533 pp., more
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| Keywords |
Management > Ecosystem management > Coastal zone management
Sand dunes
Marine/Coastal |
| Author keywords |
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| Authors | | Top |
- Gomes, N.
- Andrade, C.
- Romariz, C.
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| Abstract |
The Troia-Sines littoral arc is located in the southwest coast of Portugal, 50km south of Lisbon. The 65km study area is essentially a continuous sand beach bordered by vegetated sand dunes, extending from the Troia peninsula (flanking the Sado estuary to the north) to the cape of Sines at its southern margin. Beach sediments are clean quartz sand, moderately sorted to well sorted with the mean diameter increasing irregularly from north to south. Sand from the beach face is always finer than that from the berm and back beach area. Mean diameter of foredune sand within the Troia peninsula increases steadily from north to south (0.3mm to 0.6mm) and varies between 0.4mm and 0.6mm in the rest of the arc. All foredune sands are clean and moderately sorted. North and northwest winds dominate both in frequency and intensity in the study area. However, on the northern edge of the Troia sand spit NW winds are not as influential as in the southern half, probably because of the sheltering effect of the Serra da Arràbida. Easterly winds have low frequencies but highest intensities. Gross and net potential aeolian sand transport rates at both end of the study area were estimated using Bagnold's formulae. Within the Troia peninsula, results are much more sensitive to increases mean grain diameter than further south. The rates of gross and net potential sand transport by wind at Troia (north) are respectively 50m³/m/year and 15m³/m/year (Gomes et al., 1990),8.3% to 12.6% and 4.4% to 7.2% of figures obtained at Sines (south). Thus it is expected that there will be greater sand dune activity in the south. Field observations suggest that these rates may differ because of morphology, vegetation and moisture controls which are being evaluated at the moment. However, potential transport rates suggest that (l) the exposed beach is the major sand source for the dune system and that beach nourishment from dune sands is an occasional and exceptional event; 2) sand volume stored in the foredune system increases according to the potential gross transport rate; and 3) the rate of growth of a newly forming embryo foredune is at least twice the rate of growth of an established and fully vegetated foredune. |
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