Hydrodynamics and equilibrium of a multiple inlet system SFRH/BD/28257/2006 Grant holder: André Pacheco Supervision: Óscar Ferreira (UALG) and Jonathan Williams (UOP) “Hydrodynamic Evolution and Sediment Fluxes of Ria Formosa Inlets” Seminário Doutorandos Dez.2009

Hydrodynamic and equilibrium of a multiple inlet system The PhD Program APPLICATION (i) Support the decision making process by giving an overview on the hydrodynamic evolution of the system; (ii) Quantify the relations of interdependency on a multi-inlet system relating tidal prism with sediment fluxes; [iii] Infer system equilibrium which can be applied to understand similar systems Worldwide PROPOSE. In-depth study of the hydrodynamic and sediment fluxes (historic/present) of Ria Formosa Inlets GOALS 1. Establish empirical relationships between the cross-sectional area (Ac) and the tidal prism (Tp); 2. Determine the sediment fluxes through the inlets, migration patterns and recent historical evolution in relation to anthrophic influence.

Hydrodynamic and equilibrium of a multiple inlet system The PhD Thesis Chapter I. Hydrodynamic evolution and sediment fluxes at Ria Formosa Inlets Objectives and Outline Chapter II. State of the art International Research on Multiple Inlet Systems Chapter III. The Ria Formosa System Recent evolution of the inlets Chapter IV. Historical sediment budgets at tidal inlets PACHECO, A., VILA-CONCEJO, A., FERREIRA, Ó., DIAS, J.A. (2008). Assessment of Tidal Inlet Evolution and Stability Using Sediment Budget Computations and Hydraulic Parameter Analysis. Marine Geology 247, Chapter V. Measuring water velocity profiles using ADCP’s PACHECO, A., FAÍSCA, L., ALMEIDA, L., FERREIRA, Ó., WILLIAMS, J.J., DIAS, J.A. (accepted). Statistical approach to the best fit model to extrapolate velocities from free stream current profiles collected with boat-mounted ADCPs. Continental Shelf Research. Chapter VI. Estimating shear stresses from high frequency data PACHECO, A., WILLIAMS, J.J., FERREIRA, Ó., DIAS, J.A. (2009). Evaluation of shear stress computation at a tidal inlet using different methods. Journal of Coastal Research 56, Proceedings of the 10th International Coastal Symposium, Chapter VII. Hydrodynamics and Equilibrium of a Multiple Inlet System PACHECO, A., FERREIRA, Ó., WILLIAMS, J.J., GAREL, E., VILA-CONCEJO, A., DIAS, J.A. (under review). Hydrodynamics and Equilibrium of a Multiple Inlet System. Marine Geology. Chapter VIII. Sediment transport at a multiple inlet system PACHECO, A., FERREIRA, Ó., WILLIAMS, J.J., GAREL, E. (in preparation). Estimates on sediment transport for a multiple Inlet system. Chapter IX. Conclusions

Hydrodynamic and equilibrium of a multiple inlet system

Fieldwork. Planning and execution BENCHMARKING/SITE VISIT Transect definition 1 Sontek/YSI 1500kHz ADP Boat Mounting 2 RTK/DGPS and ADP syncronised for navigation and data collection through Hypack®Max 4.3ª Gold and Current Surveyor v4.3 3 Topo-Bathymetric surveyaDcp Surveys (12.5h Tidal Cycle) 4 Sediment sampling Hydrodynamic and equilibrium of a multiple inlet system

aDcp characteristics (SONTEK/YSI ADP) Sensor type/frequency: 1500kHz Beam geometry: 3 Beams Slant angle: 25º Bottom tracking Compass/tilt sensor: yes Temperature sensor: yes Pressure sensor: yes Hydrodynamic and equilibrium of a multiple inlet system

HOW it WORKS? 3-dimensional hydrodynamic data (obtained during the transect) is used to compute a velocity vector cross product at each depth in a vertical profile; Cross-product is first integrated over the water depth measured by the aDcp and them integrated by time, over the width of the cross section; How subtract the boat velocity? aDcp measures the Doppler shift of reflected acoustic energy (from the bottom of the channel) to infer boat speed – bottom tracking; And the measured cross-section? aDcp also reports an averaged depth in real-time, which can be used to determined the measured cross-section. Hydrodynamic and equilibrium of a multiple inlet system

RESULTS Spring-tides TWO Hydrodynamic sub-system 90% Tidal Prism Ancão 8%, Faro-Olhão 61% Armona 23% RESIDUAL FLOW Strong interconnection

Hydrodynamic and equilibrium of a multiple inlet system Neap-tides RESULTS Inlets work more independently Reduced residual flow Inlets expand through a vast area Channels to shallow to promote important hydraulic connections Flood through Olhão and ebb through Faro Faro-Olhão and Armona 45% and 40% Tidal Prism Hydrodynamic sub-system Area of the bay that contains most of P Determines the overall ebb/flood dominance SYSTEM EQUIBRIUM (Pendleton and FitzGerald, 2005) Question: Is the system in equilibrium?

Hydrodynamic and equilibrium of a multiple inlet system On going work Cross-section 14 surveys ( ) A c,R H,C L,T w,D max 1948

Hydrodynamic and equilibrium of a multiple inlet system Escoffier (1940,1977) Combines hydraulic and sedimentary stability criteria Conservation of mass Equation of motion (Bernoulli equation) Keulegan (1967) – repletion coeffecient K 1.Ratio a b /a o 2.Tidal phase lag (ε) 3.U’ m sedimentary stability criteria Jarret 1976 for dual jettied inlets at the Atlantic Coast stable closure unstable

Minimum A c 2006 Hydrodynamic and equilibrium of a multiple inlet system Imput parameters Mean A c U cs (t) T R and MT R For any given T R

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