Form Follows Flow

PROJECT NARRATIVE

BACKGROUND
Venice’s founded upon the management of the balance between tides and sedimentation. Such balance’s interrupted by river diverting, jetties, port and industrial area construction in past centuries. On one side, natural (long shore drift) and anthropic factors(jetties and shipping channels) cause increasing lagoon floor and littoral erosion as well as the effect of negative sediment budget which all make the lagoon become deeper and barrier islands vanishing. On the other side, because of sea level rise, Venice is exposed to more dangerous risks. Current defense, MOSE, can’t protect the city from high tide once sea level rise more than 80cm. Also, there is a small inundation(high tide between 80- 110cm) at Venice Island because MOSE is designed only to rise when high tide arrives at 110cm.

CONCEPT : FORM FOLLOWS FUNCTION
To grow the coastal resilience in Venice, I come up with four types of forms that follows flows: water driven flood defense, polder retention system, lagoon replenishment system and shoreline nourishment system. For type 1 and 2, flood flows shape the form of flood defense which cover current shortages. For type 3 and 4, sediment is transported by flows and trapped by barriers, finally building a living shoreline and a freshwater lagoon.

PRECEDENT ANALYSIS AND STRATEGIES GENERATION
To increase the likelihood of successful implementation, I made a precedent analysis that involving the natural processes to grow coastal resilience. For type 1, I study from Water Dyke project which uses shrinkable bubbles to absorb water and raise the flood gate. Then I design a water-driven flood gate and floating quayside to prevent the current inundation on the island. Pavements are elevated in some part of the quayside to prevent flood also providing rest area. Such water-driven gates can extend its threshold in the future to prevent higher tides made a precedent analysis that involving the natural processes to grow coastal resilience For type 1, I study from Water Dyke project which uses shrinkable bubbles to absorb water and raise the flood gate. Then I design a water-driven flood gate and floating quayside to prevent the current inundation on the island. Pavements are elevated in some part of the quayside to prevent the current inundation on the island. Pavements are elevated in some part of the quayside to prevent flood also providing rest area. Such water-driven gates can extend its threshold in the future to prevent higher tides. For type 2, Room for River project gives me the inspiration to take advantage of the current polders around the lagoon as retention ponds. In the future, there will be compound floods consisting of rain and high tide in Venice. Overload rain in lagoon can be stored in polders and high tides can be diverted into polders before it flood the whole lagoon. Wind pump can use natural force to pump water out and leave soil with rich nutrient for future agricultural development. For type 3, firstly, I transfer the current irrigation locks into sediment sluice which works in the same way as sediment bypass tunnel of dams. Once sediment is silted at the chamber, input drainage locks will be shut and output sluice will be opened. Then the sediment will be transported away to the whole lagoon by ebb tide. In order to trap sediment and restore salt marsh, vegetation mounds were put along the ebb tidal channels. For type 4, dredging material will be recycled to fill the foreshore and sand will be trapped by elevated houses, oyster reef and vegetation. Oyster reef can keep up with sea level rise(2cm/yr). After several decades, a new shoreline will be generated and it will grow automatically.

PHASING PLAN
There are three phases to implement the design. Flood defense are applied to the lagoon when sea level and high tides arrive at a strategic trigger point. Sediment strategies will first involve recycling dredging material then trapping natural sediments and evolve gradually. In phase 1(2020-2050), water-driven system will be applied to cover the current gap of MOSE. And sediment will be started to return in lagoon from rivers. 21,441 acre of salt marsh will be restored in this phase. In phase 1(2020-2050), water driven system will be applied to cover the current gap of MOSE. And sediment will be started to return in lagoon from rivers. 21,441 acre of salt marsh will be restored in this phase. In phase 2(2050-2075), sea level will increase 80cm and come from the north and south boundary of lagoon. To avoid this, 95,018 acre of polders belt are transferred into retention ponds to store the high tide temporarily. Also, 29 cubic kilometers of dredging material will be filled at the foreshore. Elevated house will be built for recreation and tourism while the piers of them can trap sand to extend the shoreline. In phase 3(2075-2100), sea level will increase 150cm and MOSE will be out of work. The lagoon will be closed by earth dike at the river inlet and transferred into a freshwater lake. Wetland succession can happen on the formal siltation and help clean and restored the runoff and rain in lagoon. Oyster reefs and mangrove are applied to occupy the dune. They can keep up with sea level rise. Therefore, an automatically growing dune is generated.

Venice is threatened by flooding while subsidence continues.
Venice is founded upon the management of the balance between tides and sedimentation. Such balance is interrupted by river diverting, jetties, and port and industrial area construction in past centuries. Since sea level rise (SLR) increases, Venice is exposed to more dangerous risks.

Current Subsidence
Natural (longshore drift) and anthropogenic (jetties and shipping channels) disturbances cause depth increase of lagoon floor and littoral erosion as well as the negative sediment budget and can make the lagoon become deeper and cause barrier islands to disappear.

Current Defense
MOSE is a series of mobile floodgates at the ocean inlets, isolating lagoon from the ocean to defend high tide. However, there is 30 cm of inundation MOSE cannot defend. It, also, lacks resilience to defend SLR and future high tides.

Concept: Form Follows Flow
For type 1 and 2, flood flows shape the form of flood defense which cover current shortages. For type 3 and 4, sediment is transported by flows and trapped by barriers, building a living shoreline and a freshwater lagoon over time.

Precedent Analysis & Strategies Generation
Current engineer strategies are instant but lack resilience. By involving natural processes, a long-term growth in coastal resilience can be realized.

Framework
Flood defenses are applied to the lagoon when MSL and HT arrive at a strategic trigger point. Sediment strategies will first involve recycling dredged material then trapping natural sediments, evolving gradually.

2100 Masterplan
Masterplan shows the location of each type of strategies and multifunctional nodes.

TYPE 1: Implement Water-driven Flood Defense
There are 3 strategies to defend the current inundation at Venice island (80-110cm):
1.) movable doors along the bank of canals
2.) floating quayside
3.) elevated pavement
Water-driven flood defense is more flexible to extend its threshold in the future.

TYPE 2: Replenish the Lagoon Floor with River Sediments
To avoid water flows into the lagoon from the southern and northern boundaries, rivers are diverted to polders on the other side of the lagoon before they flow over the river bank and into the lagoon. Water can be pumped back into the ocean.

TYPE 3: Replenish the Lagoon Floor with River Sediments
There are 3 steps to replenish the lagoon:
1.) increase suspended sediments in river
2.) deliver sediments to lagoon
3.) trap sediments and restore saltmarsh
The location of delivery systems and sediment targets is based on the GIS analysis.