The natural way to protect the Ebro Delta from drowning

The delta of the Ebro River has been hit hard by last week’s storm Gloria. One of the most important coastal delta’s of the Mediterranean basin, the Ebro delta provides a particularly important wetland habitat for biodiversity and encompasses over 20,000 hectares of rice fields. However, coastal erosion is threatening ecosystems and livelihoods in the delta. The erosion has been aggravated on the one side by dams on the Ebro river and on the other by the rising sea level. Calls for more ‘grey’ infrastructure to defend the coast line may provide short term relief but are not a long term solution to protect the delta. The Iberian Center for River Restoration and Wetlands International Europe call upon the Spanish authorities to favor an alternative approach to the management of the Ebro: one that restores the river’s natural dynamics and helps combat coastal erosion to protect the delta from drowning.

Protected wetland habitat

The Ebro delta’s ecosystems include salt marshes, freshwater springs and lagoons and provide a habitat for a large biodiversity including 77 protected species. The wetlands’ high ecological values are of national and international significance, and a heaven for birdwatchers. The area is a designated Natural Park in Spain and protected under the EU Birds and Habitats Directives, the Ramsar Convention and UNESCO (Rodríguez-Santalla e.a., 2011).

Gloria

On January 22^nd, a storm surge caused by storm Gloria flooded Spain’s largest delta and important wetland area up to 3 kilometer inland. The sea water left huge damage to 1000s of hectares of rice fields which form part of the Ebro delta’s primary economic activity. The storm caused the flooding of buildings and homes and put another 1000s of hectares of the natural park at risk.

Dams

Storm events like Gloria accelerate the gradual coastal erosion and retreat of the delta which are caused by its subsidence and a lack of sediment supply by the river Ebro. Dams constructed on the river in the 1960’s resulted in a 95% reduction of sediment transport by the river due to sediment trapping, as compared to the situation prior to dam construction (Rodríguez-Santalla e.a., 2011). This problematic context is exacerbated by the planning of new irrigated crops upstream and the absence of environmental flow in the river.

Nature-based solutions

After major events like the flooding caused by storm Gloria, plans for new works to control erosion and floods are often proposed and adopted with urgency. They usually include dredging, channelization and construction of flood defenses and water storage reservoirs. However, the cost of such interventions in a vulnerable coastline as the Ebro delta and in the actual context of climate change, is likely both economically unviable and unsustainable. Hard infrastructures can be costly to build and maintain, have negative impacts on coastal habitats and biodiversity, reduce fishery production and have unintended consequences that worsen or create new erosion issues.

These negative impacts can be exacerbated when structures are designed or developed without a strong understanding of fluvial and coastal dynamics. Such solutions are in need of an integrated long term vision aiming to lower the risk for people and nature by restoring the functionality of the river and the delta respecting natural processes and functions. These so called Nature-based solutions are largely encouraged by the European Union through its environmental policies and all over the world.

Integral vision

To reverse ongoing trends and try to save the Ebro delta from drowning and sustain its ecological and economic values, the Iberian Center for River Restoration and Wetlands International propose to the Spanish authorities to adopt a new integral vision and management planning of the river-sea system of the Ebro. We envision the conservation and restoration of the Ebro’s unique hydrogeomorphological and ecological functioning as far as possible. Such management planning should include:

the application of Nature-based solutions for building up the shoreline, such as the restoration of coastal dunes and inter-tidal habitats, and in general adoption of a strategy that prioritises the implementation of natural water retention and green infrastructure measures as part of the Ebro basin management plan which allows for the restoration of the river’s natural dynamics and increased mobility of the river;
an improved sediment regime based on adequate measures – avoiding dredging of the river – to address the sediment deficit as a consequence of major regulation works in the basin, integrated in a sediment management plan. This includes addressing the problem of river discontinuity created by the Mequinenza and Ribarroja dams which cause sediment retention and impede fauna migration. A sediment by-pass would restore the flow of sediment from the Ebro river to the sea and help reverse the coastal erosion and sustain habitats for e.g. fish and benthic fauna;
the accelerated implementation of an improved ecological flow regime which takes into account seasonal variations to ensure a dynamic fluvial system and the minimal maintenance of the estuary;
avoiding new irrigated crops upstream to improve water availability in Ebro basin;
proper accounting of the ecosystem services delivered by the river Ebro, quantifying the benefits from achieving the Water Framework Directive objectives as compared to the benefits of any proposed new water infrastructure projects, not to forget the assessment of the cumulative impacts of those projects;
limit erosion control works and dredging activities to very specific zones justified from the point of view of the protection of urban areas and critical infrastructure.

This approach should be reflected in the 3^rd River Basin Management Plan and 2^nd Flood Risk Management Plan for the Ebro and should be coupled with the necessary funds to carry out the measures. These measures will contribute to achieving the objectives of the EU Water Framework Directive (2000/60/EC), Floods Directive (2007/60/EC), and Birds and Habitats Directives (2009/147/EC and 92/43/CEE).

Sources:

Brils, J. (2018). SOS – Save our Sediments. Paper presented at The 8^th Global FRIEND-Water Conference, Beijing, China, 2018.

Commission Staff Working Document (2019). Second River Basin Management Plans – Member State: Spain. SWD(2019) 42 final.

Commission Staff Working Document (2015). Report on the implementation of the Water Framework Directive River Basin Management Plans, Member State: SPAIN. SWD(2015) 56 final.

Letter by CIREF to the Confederación Hidrográfica del Ebro (30-06-2015). Alegaciónes del Centro Ibérico de Restauración Fluvial – CIREF – a la propuesta del plan hidrológico de la Cuenca del Ebro 2015-2021.

Ollero, Alfredo. (2011). Crecidas e inundaciones en la Ribera Alta del Ebro. 10.13140/RG.2.2.33930.67528.

Rodríguez-Santalla, Inmaculada & Serra-Raventós, J. & Montoya-Montes, Isabel & Sánchez, María. (2011). The Ebro Delta: From its origin to present uncertainty. River Deltas: Types, Structures and Ecology. 161-171.

El mar se come el delta del Ebro: https://elpais.com/ccaa/2020/01/21/catalunya/1579619649_057372.html

Powerful Winter Storm in Spain Kills at Least 10: https://www.nytimes.com/2020/01/23/world/europe/storm-gloria-spain-floods.html

Ebre Delta shell shocked by effects of Storm Gloria: https://www.catalannews.com/society-science/item/ebre-delta-shell-shocked-by-effects-of-storm-gloria