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Designing ecosystems: the Ebro Delta

Graduation work by Davide Caspani.

This is the Ebro Delta, Catalunya’s territory, with Spanish blood and Moorish roots. Likewise many other historical landscapes, the Delta is facing several transformations in its local cultural identity. At the same time, changes on the global natural assets are threatening many natural and manmade ecosystems. Evolution never stops. Davide Caspani explains about his graduation project in this area.

Delta context

Deltas are naturally dynamic coastal systems that are unique in their close links to both land-based fluvial and coastal ocean processes. They hold ecological and economic value throughout the world and are major centres of population and agriculture (Pont et al., 2002) The Delta is an ecologically rich environment made of freshwater, brackish and saline lagoons, salt marshes and small dune sandy areas. Nevertheless, most of the delta surface is devoted to rice production, conveying economic importance to a landscape which has particular relevance within the Mediterranean Basin as one of the biggest wetlands.

The Delta is a vulnerable ecosystem which is facing many environmental challenges. Urban and agriculture developments represent the most human related stress factors for the environment, along with the increasing severity of climate phenomena. Considering the scenarios for the coming years, stakeholders of the area are facing important decisions: actions are required. A Landscape architecture approach offers an holistic understanding of the delta ecosystem and merges a pragmatic engineering approach to aesthetic ecology, offering solutions at regional scale that can arise new opportunities at the human scale.

The investigation of the Delta started at the scale of the Ebro water basin and ended up at the analysis of the rice fields irrigation system. Three main issues at different scales have been identified and translated into challenges for the design: delta regression (as the result of a shortage in river sediments), disappearing of the coastal dunes and water pollution. A parallel risk analysis related to the sea level rise scenarios from today towards 2100 brought input into the design.

Design concept

The design of the new ecosystems is based on the understanding of the delta as evolving organism. Therefore, the DELTA REGENERATION concept evokes the reactivation of the Ebro Delta evolution, proposing a series of different scale designs adapting the Ebro Delta landscape to the environmental challenges of the 21th century.

The plan 2050 envisions one possible step of the Delta evolution where flood safety is guaranteed by natural infrastructures and offers opportunities for water purification, agricultural expansion and tourism development.

The proposed interventions require at first a new management of the sediments of the lower Ebro and its delta. Sediments trapped behind the closer dams must be released by flushing floods methods, increasing the supply of natural material coming to the delta which can be used for the construction of natural flood defences. Natural processes and nourishment actions will shape the sandy material and provide opportunities for nature developments. Flood defences are divided between dunes and breakwaters (hard structures parallel to the coast profile), which provide protection from storm waves by diminishing their strength and direct impact on the coastline. Water sports, aquaculture, tourism and agricultural activities will arise as part of the new programs for the Ebro Delta economic development.

Delta networks

The design of the new green Delta edge offers opportunities for the creation of a landscape ecological experience. A series of artefacts (new landmarks in the landscape) are designed and placed along the pedestrian network, mainly as resting areas and structures for birdwatchers.

Each location corresponds with a particular locality along the actual shoreline, connecting the town of Amposta to a new destination: The Ebro museum. Such elements are inspired by present and historical elements of the Delta, aiming to reinforce the place identity of the area. The design exercise of such artefacts is rooted in the belief that the understanding of nature is a culture related process. An ecological landscape experience calls for a dialogue between the design of ecological systems connected to the cultural-identity aspects of the landscape. The attention of ecological designers must not be on the form and structure of objects or environments per se, instead should focus on their interrelation for the design of human-environment systems (Koh, 1988).

Delta water

Considering the high amount of pesticide and fertilizer used for the rice agriculture, matters of improving water quality have become an important challenge for the redesign of the area according to ecological values. The water treatment system design for the Ebro Delta aims to reduce the nitrogen and phosphorus concentrations in the water.

Constructed wetlands are engineered systems designed to take advantages of the natural processes involving wetland vegetation, soils, and their associated microbial habitats to treat wastewater.The interventions on the water layer can be explained by 3 schematic landscape sections:

The Purification system (Nutrient Sediment Control System), a short term intervention for 2025, comes from the transformation of the coastal rice fields into permanent wetlands and construction of two canals parallel to the coast line. The first canal will regulated the inflow into the wetlands and provide a first step of sedimentation. A second canal will regulate the outflow into the existing bay and lately supply a new irrigation system.

The Irrigation system, a long term intervention for 2050. Considering the proposed plan for the delta evolution 2050, a new agricultural development will take place as a major transformation of the northern bay of the delta. The new irrigation system (partially supplied by the purified water through the NSCS) will provide water for the irrigation of the new rice fields which are located on a lower level.

The Drainage system, a long term intervention for 2050-2100, comes from the fact that the rice fields outflow will be collected in a central wetland which will slowly direct the water towards a major water pump for the discharge into the Mediterranean Sea.

DeltaLab resume

The task of design is to discover new possibilities, to show and to test solutions which are unexpected and might seems unlikely at first sight, but can address new opportunities for land use, spatial composition and governance. New spatial strategies might require new governance arrangements, where for instance national government agencies can collaborate with NGO’s and local communities (Meyer, 2014). The design for the Ebro delta has mainly two challenges: Delta flood proof 2050 and the improvement of the water quality of the agricultural runoff. The overall design process is based on the understanding of the Ebro Delta as an evolving system. The strategies applied in the Ebro Delta case study aims to bring knowledge and new discussions on the topic of Delta interventions.

One of the main findings of this Thesis is the necessity to operate at different landscape scales at the same time. When intervening in a Delta area, the dialogue between the inter-regional scale and the human scale (and all the steps in between) becomes an essential practice, considering that some issues at small scale can be solved just by having a wider understanding of the overall ecosystem.

Considering that common to all natural deltas is the ability of the associated fluvial system to deliver and deposit sediment more rapidly than local sea-level rise (Wells and Coleman, 1984), I argue that the major issue in Delta area it is not related to sea level rise itself, but it is associated to the way humans have been modifying hydrology and sediment transportation (especially in the last century) of river basins and the land use of such landscapes. An alternative land use, where natural ecosystems can become helpful technology for agriculture or urban developments, is needed to give back to nature the freedom to balance itself out, taking into account natural forces and human needs.

The experience at human scale of such natural ecosystems can be part of new programs (educational, cultural and tourism oriented). New network infrastructures for bikers and pedestrians can support the development of slow tourism practices connecting the existing areas along the created Natura.

Koh, J., 1988. An Ecological Aesthetic, Landscape Journal 7, pp. 177–191

Meyer Han, 2014. Urbanised Delta in transition. Han Meyer and Steffen Nijhuis. Techne Press, Amsterdam. p.7

Pont, D., Day, J.W., Hensel, P., Franquet, E., Torre, F., Rioual, P., Ibanez, C., Coulet, E., 2002. Response scenarios for the deltaic plain of the Rhone in the face of an accelerated rate of sea-level rise with special attention to Salicornia-type environments. Estuaries 25, pp. 337–358

Wells, J.T., Coleman, J.M., 1984. Deltaic morphology and sedimentology, with special reference to the Indus River Delta. In: Haq, B. U., Milliman, J.D. (Eds.), Marine Geology and Oceanography of Arabian Sea and Coastal Pakistan. Van Nostrand Reinhold Co., New York, pp. 85–100

december 3, 2014

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