| Title: | PROMOTING EBB DOMINANCE IN COASTAL LAGOONS |
| DOI No: | 10.1142/9789812701916_0093 |
| Source: | COASTAL ENGINEERING 2004 (pp 1173-1185)
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| Author(s): | A.B. FORTUNATO
Hydraulics and Environment Department, National Civil Engineering Laboratory, Av. do Brasil, 101, 1700-066 Lisbon, Portugal
A. OLIVEIRA
Hydraulics and Environment Department, National Civil Engineering Laboratory, Av. do Brasil, 101, 1700-066 Lisbon, Portugal
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| Abstract: | In order to minimize maintenance dredging and to improve the stability of tidal inlets, methods to foster ebb dominance in coastal lagoons are investigated. A synthetic lagoon, with dimensions similar to those of the Óbidos lagoon (Portugal) is used as a testbed. An analytical and a numerical model show that ebb dominance in the inlet is maximized for a particular depth of the tidal flats. Dredging the tidal flats to mean sea level reduces ebb duration, increases the tidal prism and enhances seaward sediment fluxes. However, dredging the whole surface of tidal flats is harmful to ecosystems and technically difficult to implement. As an alternative, dredging secondary channels over the tidal flats is proposed and analyzed. Numerical tests show that this approach leads to similar gains in sediment flushing from the inlet, provided transverse channels form a 45° angle relative to the main channel. |
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