Ecotone Equilibrium

PROJECT NARRATIVE

VENICE IS SINKING.
Twenty-three centimeters (23 cm) of relative sinking occurred in the twentieth century thanks to rising sea levels coinciding with land subsidence. Both of these natural phenomena were accelerated during the twentieth century due to human activities and land-use alterations. The sinking feeling deepened after a 1966 brought flood waters to an unprecedented height of 194 cm. This spurred the development of new flood defenses that would eventually become the MOSE project of mobile tidal barriers. MOSE represents a massive investment by Venice in securing the lagoon against high tides. However, the project only protects the city from tides between 110 and 300 cm above normal sea level. Significant damages are incurred below 110 cm, and 300 cm sea level rise is expected before 2200. The floods are only getting worse, as it stands. In 2018 Venice sustained massive flooding around November 1st, costing billions, razing millions of trees, and killing several people. In 2019 Venice sustained massive flooding around November 10th that cost billions and killed several people. This trend projects to continue, given sea level rise and an intensifying climate. Drastic interventions are necessary to protect Venice and preserve its treasured way of life. Yet Venice has been constructed and sustained since birth by radical interventions in the local lagoon. Indeed, the Lagoon of Venice today exists as a novel ecosystem in which the influence of man and the expression of the lagoon are inseparable. We halted the natural evolution of the lagoon centuries ago, when the Venetian Republic undertook massive river diversion projects to prevent flooding and the infill of the lagoon. The Venetian Republic, La Serenissima, was constructed entirely on wooden pilings driven into the soft soil, and rose to power with on the strength of its wooden navy. Deforestation and timber shortages ultimately contributed to her decline. However, some vernacular interventions in lagoon ecology provide insight we can leverage to serve our modern purposes. Vallicoltura is a fish farming method first mentioned in the 11th century, where a section of the lagoon is from the waterbody at -large and used to cultivate desired fish species. The Valle da Pesca, as these sub-compartments of the lagoon are called, are sustained by metered inputs of freshwater and a main gate, or Chiavone that connects to the lagoon and permits salt-water input and permits the seasonal migration of fish. The farmers capitalize on these migrations by trapping the fish over winter in the relatively warm lagoon waters, where they are protected by vegetated embankments called Argini. In the Spring, salt water is allowed into the lagoon, prompting the fish to attempt an outward migration, where they are trapped. While the Valle da Pesca are considered heavily modified water-bodies, they present highly diverse trophic chains and realize considerable ecosystem services in water treatment and biodiversity support. The control of freshwater and saltwater inputs to maintain desired conditions shown in the Valle da Pesca implies that a similar approach may be scaled to protect Venice from flooding while maintaining a healthy lagoon dynamic. Eutrophication and sediment build-up pose major threats in a closed lagoon, put with careful control of inputs and aggressive development of upstream treatment services, we can save Venice from flooding without altering its treasured way of life. This proposal focuses on approaches to protect Venice from flooding while providing the additional ecosystem services across the Venetian ecotone mandated by the flood control projects. The concept of the ecotone, a region of transition between two ecological communities, is central to our approach. The lagoon of Venice sits squarely in a transitional zone between a mainland community historically called Terra Firma and the sea, the Mare Adriatco. To resist flooding without compromising the character of the Venetian lagoon, this project calls for a network of dikes, tidal gates, and treatment interventions both upstream and throughout the lagoon to form an integrated ecosystem management framework. Our goal: Ecotone Equilibrium. Technological development since MOSE was designed has been rapid, and several compelling alternatives have taken shape. BayARC, designed by SOM architects and winner of the 2016 Architect R&D Award, provides a lightweight alternative to MOSE. This project incorporates these tidally responsive barriers to temporarily seal off Venice in flood conditions, and calls for research and development to scale the technology as a future replacement for MOSE. For ecosystem services, the proposal embraces floating technology in the form of floating treatment wetlands, bio-habitats, and breakwaters. Floating islands provide impactful services with minimal footprint, and are relatively low-cost. In order to better connect Venetians and their surroundings, and foster engagement with the lagoon environment, the floating theme is extended to public causeways across the lagoon. These provide a novel experience as well as multi-modal route across the lagoon, and are connected with chairlifts over sensitive areas and ship channels. Upstream, a network of urban storm water wetlands along riparian corridors improves water treatment and soil storage capacity. Amenity parks are developed along-side these treatment areas where possible, and all this connects to the lagoon and Venice as part of a new regional trail network. Taken together, the design seeks to PROTECT Venice, PROVIDE ecosystem services, CONNECT Venice, Venetians, and the lagoon, and ATTRACT tourists and residents to areas beyond the old city.

The modern Venetian lagoon ecotone is the product of centuries of human intervention in the ecosystem’s natural evolution. Impacts associated with historical interventions have been exacerbated by 20th century development, driving modern flooding concerns and regional vulnerability.

MOSE will protect the Lagoon from tides of 110-300 cm, but will not mitigate high tides below110 cm and offer no recourse in extreme scenarios. The land’s water capacity also decreased dramatically, creating more flooding as the climate intensifies.

Protecting Venice from flooding will require increased upstream regulating services along 12 waterways supplying freshwater. 10 distinct waterbodies vary in characteristics and ecosystem services. Protections must address ES & water quality deficits in impaired bodies.

Acqua Alta driven by sea level rise threatens the Lagoon, while land-use changes drive increased mainland flooding. November 2018 floods at 156 cm caused €2,000,000,000 in damage. November 2019 brought the worst floods since 1966: 187 cm.

The proposal embraces integrated ecosystem management along the ecotone to achieve needed flood protections while providing essential ecosystem services, engaging humans with nature, improving residential quality of life, and enhancing tourist appeal. These comprise the design objectives: Protect, Provide, Connect, Attract.

Coastal protection and water treatment projects provide a blueprint for protecting Venice from floods while achieving supply and demand equilibrium for ecosystem services across the ecotone.

Relevant factors were analyzed for each strategy, providing specific suitability outputs to inform placement of design interventions. Siting of interventions is calibrated to eliminate flooding from historical Venice, provide critical ecosystem services, and renew the mainland residential core.

The design plan retains the character and charm of Venice while protecting against flooding, providing ecosystem services and habitat, improving access around the lagoon, engaging people with the lagoon, and creating new attractions and recreational opportunities.

The MOSE barriers protect Venice from tides in the 110-300 cm range. This proposal will eliminate flooding in Venice below the MOSE threshold, but also germinate a scalable solution for managing tides in extreme scenarios. The Causeway project will provide pedestrian connectivity between Venice and a renewed, resilient mainland Veneto.

Projected costs of flooding below the MOSE threshold by 2050 are € 2.25 billion. Lagoon closure would require currently unrealized levels of water treatment and management integration across the ecotone, making commitment to research and development critical to securing Veneto’s future.

This proposal recognizes that the lagoon of Venice ceased to exist in a purely natural state centuries ago, and today presents a dynamic marriage of Man, Mare, and Terra Firma. This proposal suggests that we assume ownership of that dynamic, in a way that respects the Sea while guaranteeing the health of the land.

Valle da Venezia is a tidal flooding defense for Old Venice. A network of barrier islands linked by BayArc tidal gates can seal off the city during Acqua Alta. Otherwise, the lagoon is open and offers new multimodal routes to explore.

Even best-case sea-level projections imply lagoon closure frequency by 2050 demanding world-class upstream water-treatment to maintain a healthy lagoon. Mass reforesting in combination with urban storm water wetlands offers the required services and opportunities for recreation and engagement with nature.