characteristics and evolution of ebb–dominated creeks
TRANSCRIPT
Characteristics and evolution of ebb–dominated creeksC. Zarzuelo1, A. D’Alpaos2, L. Carniello3, A. López-Ruiz4 and M. Ortega-Sánchez1
1 Andalusian Institute for Earth System Research, University of Granada, Avd. del Mediterráneo, s/n, 18006, Granada,Spain. [email protected]
2 Department of Geosciences, University of Padova, Via Giotto 1, 35131 Padova, Italy. [email protected] Department ICEA, University of Padova, Via Loredan 20, 35131 Padova, Italy. [email protected]
4 Department of Aerospace Engineering and Fluid Mechanics, University of Seville, Camino de los Descubrimientos s/n,41092, Seville, Spain. [email protected]
1. IntroductionEstuaries and bays are usually fed by the small rivers,streams and tidal creeks. These tidal creeks convey thebulk of the freshwater runoff and the associated terres-trial sediments eroded from surrounding catchments. Theshallow-water systems in which these creeks evolve aremainly dominated by tidal asymmetries, generated bynonlinear processes of interaction that promote a net flowof sediment in the direction of such asymmetries (Aubreyand Speer, 1985).In this contribution, we present the hydrodynamics be-haviour of the Sancti-Petri and Carracas creeks (Fig. 1),which are influenced by the tidal hydrodynamics of CádizBay (Southern Spain). We have focused on the tidal har-monics and currents levels as well as in the effects ofthe tidal dynamics on sediment transport. The analysis isbased on water elevations, currents, and suspended sedi-ment concentrations measurements recorded during a 40-days field survey, and also on the simulation scenariosperformed with a sand-mud transport model (Carnielloet al., 2012).
2. MethodologyThe field survey consisted on 7 moorings stations de-ployed from December 22, 2011 to April 18, 2012. Theywere 4 current meters and 3 tidal gauges, denoted by I1-I4and T1-T3, respectively (Fig 1a). On the other hand, thesand-mud transport numerical model has a tidal modulecoupled to a wind-wave and a sediment transport and bedevolution modules. The model was calibrated and testednot only at the usual intratidal scale, but also at subtidaltime scale (R2 ≈ 0.99 – 0.78).
Figure 1. Panel a- Location of the Bay of CÃadiz.Shaded areas are the outer (marked as A), central (B),and inner (C) bays. Labels I1-I4 correspond to current
profile meters, and labels T1-T3 to tidal gauges. Panel b-Zoom of the field site: Carracas and Sanctri-Petri creeks.
3. Results and final remarksTo enhance the understanding of tidal creek networks,tidal dynamics in the Carraca and the Sancti-Petri creeksand its implication in the sediment evolution have beenstudied in this work. A field survey was carried out to val-idate the implementation of a numerical model. An anal-ysis of the numerical results shows that the importance ofthe Sancti-Petri and the Carraca creeks lies on the doubleconnection at the open sea where the ride wave penetratesfrom both ends with different amplitudes, phases and flowvelocity.The results show that tidal currents continually entrainand rework sediment with an enhancement during springtides (Zarzuelo et al., 2015). Furthermore, the tidal cur-rents in the Sanct-Petri creek and the Carraca creek aredistorted from the sinusoidal form of their astronomicalforcing, what implies a transfer of energy from M2 toM4. The main consequence of the overtide generationis the strengthening (weakining) of flood (ebb) currentsin the case of the Carraca (Sancti-petri) creek. Sedimentis redistributed within the tidal creek on a regular basis bytidal currents.
AcknowledgmentsThis work was funded by the Cádiz Bay Port Authority,the Department of Innovation, Science and Business ofthe Andalusian Regional Government (Projects P09-TEP-4630 and P10-RNM-6352) and Project BIA2015-65598-P (MINECO/FEDER). The work of the first author waspartially funded by the Andalusian Regional Government,Research Grant RNM-6352.
ReferencesAubrey, D. G. and Speer, P. E. (1985). A study of non lin-
ear shallow inlet estuarine system Part I: Observations.Estuarine, Coastal and Shelf Science, 21(5674):185–205.
Carniello, L., Defina, A., and D’Alpaos, L. (2012). Mod-eling sand-mud transport induced by tidal currents andwind waves in shallow microtidal basins: Applicationto the Venice Lagoon (Italy). Estuarine, Coastal andShelf Science, 102–103:105–115.
Zarzuelo, C., Díez-Minguito, M., Ortega-Sánchez, M.,López-Ruiz, A., and Losada, M. (2015). Hydrodynam-ics and response to planned human interventions in ahighly altered embayment: The example of the Bay ofCádiz (Spain). Estuarine, Coastal and Shelf Science,167:75–85.