Private adaptation of buildings to coastal flooding in the historic centre (Venice, Italy)
The Climate Challenge
The historic centre of Venice, Italy is built inside a coastal lagoon that is directly connected to the Adriatic Sea. Sea level rise related to climate change will make flooding events more frequent and more intense and high waters are projected to exceed the historic range of tidal excursion.
The occasional flooding of urban areas has significant economic and social impacts, which increase with the level reached by the flood event and its duration. Although much of the city is adapted to high waters, flooding and humidity rising from the ground brings higher, non-adapted parts of the buildings into closer and/or more frequent contact with salt water. These damages are expressed mainly in terms of increases in maintenance costs, where plaster and bricks need to be replaced more frequently, and building elements such as doors or floors may have a shortened lifetime.
The Adaptation Response
Spontaneous adaptation is already being undertaken by private and public actors - about 42% of residential buildings and 36% of commercial buildings surveyed – to adapt their premises to rising sea levels in the historic centre. The city has historically adapted to periodic flooding events with water-sensitive urban and building design, e.g. choosing building materials resistant to salt water intrusion or humidity rising from the ground, such as impermeable limestome (pietra d’Istria). Raising floor levels, installing vascas (complete waterproofing of the floor and the walls of the unit) or pumps and cutting of walls to insert impermeable barriers are all widespread measures. Most of the measures employed do not interfere with the visual aspect of the building and can be employed also on cultural heritage buildings of special value.
A survey conducted by municipal authorities in the early 2000s indicated that the majority of measures implemented were those preventing less costly damages. According to calculations made in the BASE case study, these present adaptation measures would only help avoid some 5% of the potential damage costs under a sea level rise scenario of 30 cm. Under a scenario of dry flood proofing, this rate would go up to approx. 64%.
The People and Institutions Involved
This case study examines spontaneous adaptation as undertaken by public and private actors in residential or commercial residencies.
The Outcome of Action
According to the calculations made in the BASE case study; measures actually in place are able to avoid only a small potential damages under present day conditions, with benefits corresponding to approx. 5% of the costs (investment and net present value of residual damages) under a sea level rise scenario of 30 cm. Under a scenario of the most expensive protection measures being applied in all residential units, (full impermeabilization or dry flood proofing) the relation between costs and benefits would be slightly above 25%, with only very small changes under different scenarios of sea level rise. The study concludes that private flood adaptation for buildings can considerably reduce damages but will not prevent them totally. Furthermore, most options come with a considerable investment cost that may not be feasible for all households.
Margaretha Breil, firstname.lastname@example.org
The full report of this case study can be read here.
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