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Multidisciplinary Integrated Analysis of the Sediment Dynamics and Fecal Contamination in Intermittent Coastal Systems
www.lnec.pt/organizacao/dha/nec/estudos_id/madycos

More:  Institute 
Acronym: MADyCOS
Period: January 2008 till December 2010
Status: Completed

Institute  Top 
  • National Laboratory of Civil Engineering; Estuaries and Coastal Zones Division (LNEC-DHA-NEC), more, co-ordinator

Abstract:
The downstream areas of coastal streams contain small estuaries and lagoons of complex nature due to the strong
morphological changes of their inlets. These morphological changes often lead to the inlet closure, as a result of the
action of waves, tides and intermittent river flows. Hydrodynamics, morphodynamics and water renewal are thus
highly variable, both at seasonal and shorter time scales, which hampers the monitoring, the forecasting and,
ultimately, the management of these systems. This strong dynamics makes the intermittent coastal streams very
sensitive to contamination/pollution, as contaminated discharges may have very different consequences depending
on the capacity of water renewal of the system at that time.
MADyCOS aims at improving the current understanding of the hydrodynamics, morphodynamics and potential for
fecal contamination of intermitent coastal streams, through an interdisciplinary study that integrates distinct but
complementing methodologies: field data acquisition, laboratory research and high-resolution numerical modeling.
The integrated use of these approaches in the relevant disciplines (long-wave hydrodynamics, short-wave
propagation, morphodynamics and fecal contamination) will allow the evaluation of the relative impact of each
forcing on the morphology of the system and its effect on the water quality.
The small dimensions of the intermitent Aljezur coastal stream system make it an ideal testbed for the proposed
methodology. This system, located in an environmentally protected area, presents a very dynamic inlet (Fig.jpg),
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which closes occasionally. Simultaneously, the Aljezur coastal system has significant importance both at ecological
and local economy (tourism, aquaculture) levels, both inside the stream and in the coastal area. Maintaining the
high standards of water quality, for both ecological and recreational purposes, has been a growing concern for the
management authorities. Indeed, any increase in antrophogenic pressure may lead to the aggravation of the
pollution loads, with potential damaging consequences for the ecosystem and the quality of bathing waters at the
two official beaches. Evaluating the impact of this antrophogenic pressure requires the detailed knowledge of the
inlet’s morphological evolution, dependent on the relative strenght of each forcing, and of the evolution of the fecal
contamination plumes for specific environmental conditions.
Field surveys provide a first cut at understanding the dependence of the hydrodynamics, morphology and fecal
contamination in the coastal stream of the relative strengths of river flow, tidal magnitude, short waves regime and
of the pollutant discharges caracteristics. These surveys will also provide additional data to validate the numerical
models. These models will be used first in diagnostic mode to define the sampling sites. Historical data and the data
collected in the scope of the project will be integrated in a multidisciplinary database.
Microbiological laboratory experiments will increase the current knowledge on the dominant processes controlling the
survival of microorganisms in fecal contamination plumes in coastal streams. Solar radiation, temperature, salinity
and organic load are among the issues to be investigated both with field samples and in controlled laboratory
conditions. The outcome of these studies will be used in the set-up of the new fecal contamination model to be
developed in MADyCOS, which will be used to simulate the evolution of fecal contamination plumes in the Ribeira de
Aljezur.
Multiple topographic and bathymetric surveys and grain size distribution of the sediments in the downstream area,
taken for several hydrodynamic conditions, will be used to characterize the inlet's morphodynamics. Relationships
between forcings and inlet morphology will be sought through the combination of the above data and the
hydrodynamic and the wave numerical simulations. These relationships will then be validated with a morphodynamic
modeling system.
The range of inlet configurations will be defined next, based on the above morphological analysis. A set of scenarios
will be set-up to represent different exchange capacities between the stream and the sea. The impact of this
variability on the hydrodynamics, residence times and potential for fecal contamination of the system's beaches will
be evaluated using the suite of mathematical models developed and applied in the project.
MADyCOS will provide valuable and inexistent knowledge on the hydrodynamics, morphodynamics, residence times
and sanitary condition in the Aljezur coastal stream, which will be vital for its adequate management, as recognised
by the local wastewater management company (Águas do Algarve S.A., Fax.jpg). The project will also advance the
state-of-the-art on the physical and microbiological processes and their interdependence and propose a new,
multidisciplinary, integrated methodology for the analysis of the dynamics of coastal systems.

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