Building the future by doing more together

MURANO - Saltpans Walls of Aveiro Lagoon
Coordinator - Carlos Daniel Borges Coelho
Programme - PTDC/ECM/65589/2006
Execution dates - 2008-01-01 - 2011-06-30 (42 Months)
Funding Entity - Fundação para a Ciência e a Tecnologia (FCT)
Funding for CESAM - 81240 €
Total Funding - 90000 €
Proponent Institution - Universidade de Aveiro
Participating Institutions
Laboratório Nacional de Engenharia Civil (LNEC)

In the XV century there were about 500 saltpans in the Aveiro lagoon. About 50 years ago, the saltpans producing salt were near 270 and nowadays only 8 are exploited. The artesian salt activity is in decadence, conducting to the existence of many abandoned fields. The degradation process and abandonment of the saltpans is accelerated by the intense currents during the flood tide that penetrate inside the lagoon, destroying the protection walls of the saltpans (motas) and digging the bottoms of the channels. The motas are small rudimentary dikes, built by the farmers, with low top quotas and constituted by the consolidation of mud with stones and organic material. The absence of the traditional craft maintenance of the motas also contributes to it progressive degradation. These motas guaranteed the defence of the lagoon against the progress of the salt water and controlled, with the support of floodgates, the hydrodynamic of the lagoon. On current days, motas do not protect in an effective way the lands, due to the deficient conservation state, to the permeability and to the reduced top quota. This situation allows the water skip the walls, conducting to no definition of cross sections of lagoon channels, generating big water reservoirs supplied in high tide situation. As presented, the impact of walls destruction is important on the hydrodynamic and morphologic behaviour of the lagoon, with consequences on neighbourhood population. Some land owners already tried to stop this tendency, by applying different materials to reduce the degradation process (they used foundation stones or waste material, tyre, concrete and wood piles). The results of these interventions are apparently unsatisfactory, with important settlements of the walls and negative impacts on an environment with unique characteristics, which should be preserved. Therefore, this project will characterize the sediments, the hydrodynamic and the sediment transport conditions of the lagoon near the saltpans. It is objective of the project to analyse the behaviour of traditional walls when exposed to the characteristic hydrodynamic conditions and propose new and friendly solutions for the saltpan walls and to analyse the impact of saltpan degradation in the lagoon dynamics. To reach the proposed objectives, the methodology that is intended to follow require the definition of a study area in the lagoon, to allow the field works in a compatible dimension with the development of the project. The field work will allow to characterize the sediments properties, the hydrodynamic regime and to analyze the existent solutions for the saltpans walls. Sediment samples will be collected for analysis in laboratory and for definition of properties necessary to the evaluation of the cohesive sediment transport. The field measurements will also allow the calibration of hydrodynamic and sediment transport numeric models. The evaluation of the causes of degradation should help on the definition of a new model of mota, that results more economic for the farmer, effective in the defence of the saltpans and allowing some mechanization in its reconstruction and monitoring, while mitigating negative environmental impacts.


http://murano.web.ua.pt/index.htm

Members on this project

Main Researcher
João Miguel Dias
Researcher
Paulo A. Silva
Researcher

CESAM Funding: