The Port of Seville regenerates the Doñana coastline with 62.000 m3 of sand from maintenance dredging

24 January 2022

The Port Authority of Seville (PAS) has completed the regeneration of the coastline of the Doñana Natural Area with sediments extracted during the last dredging campaign for the maintenance of the navigation channel. In total, the Port Institution has deposited 62,000 m3 of sand, which has allowed the recovery of a 275 meter-long stretch of the right bank of the Guadalquivir River where the Doñana National Park is located.

The work began last November, in agreement with the Doñana Natural Area, which requested the contribution of sand from the maintenance dredging for the regeneration of the Park's beaches. This has been developed according to the guidelines and in collaboration with the Coastal Demarcation of Andalusia-Atlantic, and with a favorable report issued by the Ministry of Agriculture, Livestock, Fisheries and Sustainable Development of the Government of Andalusia.

With this experience, the Port of Seville has restored a stretch of the Doñana coastline that was affected by the advance of erosion caused by the occurrence in recent years of storms coinciding with high tides and flooding of the Guadalquivir River.

Specifically, thanks to the material deposited as a result of the improvement of navigation, it has been possible to protect the dune ecosystem and vegetation from the entry of salt water, as well as a stretch of the Almonte-Sanlúcar road that is used by researchers, visitors, INFOCA equipment and by the brotherhoods of Cádiz on pilgrimage to the village of El Rocío, among other groups.

The works have been carried out by the company DRAVO, S.A., which was awarded the maintenance dredging of the navigation channel for the 2019 and 2020 campaigns, and with an extension for the 2021 fiscal year. These have been carried out with the Atlantic Coast suction dredge and by means of an impulsion pipe for the transfer of sediments to the coastal area. There, land resources have also been used to spread the sands and place them along the entire area that has been recovered.

This action is an example of the beneficial use of sediments as a valuable resource for the recovery of habitats and the improvement of ecosystems. For the first time, the Port Authority of Seville has launched a pilot project to improve the Doñana Natural Area. This has required coordination between the different administrations, as stated in the “Working with Nature” model, which promotes the effective participation of all parties with the aim of obtaining truly sustainable results over time.

In-depth analysis

Before transferring the sands to Doñana, the material extracted from the sections of the mouth –Broa, Puntalete and Salinas– was studied in the dredge to assess its suitability. For this purpose, a granulometric, photographic and colorimetric analysis has been carried out to determine whether the characteristics are suitable for the coastline. 

A column of sieves, a precision balance and a sample drying oven have enabled the personnel on board the dredger to set up an ad hoc laboratory to carry out particle sizing and determine the average grain size of the cargo.

Likewise, the sands used to regenerate the beaches of Doñana have been classified as Category A, according to the Guidelines for the characterization of dredged material and its relocation in waters of the maritime-terrestrial public domain, and are therefore suitable for regenerating the beaches.

Sediment as a resource

The Port Authority of Seville, as part of its environmental strategy, is committed to the circular economy and the valorization of sediments in line with the Sustainable Development Goals. The Institution bases the improvement of navigation on the philosophy “Working with Nature”, which identifies how to achieve the objectives of the Navigation Optimization Project, working with natural processes to protect, restore or even improve the environment.

The management of dredged materials and their subsequent use are priorities for the Port Institution when establishing sustainability guidelines for operations to improve navigation.

In the 2019 and 2020 campaigns, more than 100,000 m3 were destined to the regeneration of the beaches of Sanlúcar de Barrameda. The rest of the sediments were deposited in the dumps provided by the Port of Seville for this purpose; among them, the Butano dumps where the PAS has created, together with the CSIC, new wetlands for the birds of the estuary. The first experiments are also being carried out there to study the use of sediments in the ceramics industry, construction and agricultural soil improvement.

Wetlands in Lebrija

During the current campaign for the maintenance of the channel, which will end in January, the PAS will allocate part of the dredged material to the creation of new wetlands in the estuary environment, a project recognized with the Environmental Award of the Junta de Andalucía and with the “Working with Nature” certificate of the World Association for Waterborne Transport Infrastructure (PIANC).

As an innovation, the Port Authority of Seville, in coordination with the CISC Doñana Biological Station, has created new wetlands in the Horcada confined disposal facilities, in Lebrija, and has maintained the islands for waterfowl in the Butano area next to the lock. The presence and breeding of coots, grebes, ducks, brown teal, white-headed duck and the European bee-eater is enhanced in the Horcada.

Navigation of the Guadalquivir River

The navigation channel ascends almost 50 miles along the Eurovía del Guadalquivir until it reaches the city of Seville. Due to the evolution of the Guadalquivir itself, there are certain areas along the estuary where, cyclically, suspended particles settle, making it difficult to reach Seville by sea. For this reason, the PAS promotes accessibility so that maritime traffic to the capital and the municipalities bordering the estuary is assured.

The maintenance dredging works are part of the operational measures for the optimization of the waterway that guarantee safe maritime access to the Port of Seville. These works consist of carrying out precision bathymetries to determine the points of action and the subsequent suction of the accumulated sediments with a dredge.

The maintenance dredging is being carried out with the advice and scientific monitoring of the universities of Seville, Malaga, Cadiz and Huelva and the CSIC.

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