A blue infrastructure: from hydraulic protection to landscape design. The case study of the village of Ballao in the Flumendosa river valley

The United States Environmental Protection Agency (EPA) provides an interesting definition of ’green/blue’ infrastructure (GI): ’an approach to ecosystem management that relies on constructing landscape features that function similarly to natural systems thereby increasing the functionality of built or urbanized ecosystems. GI systems use vegetation, soils, and natural processes to manage storm water and maintain ecosystem functions. GI systems are intended to also provide social and economic benefits that enhance urban liveability. ’They typically operate alongside blue infrastructures, defined as all the systems which channel water, whether they are surface or underground streams, marine or inland waters. The synergy between green and blue infrastructures does not only produce strategic environmental value, but it also plays a central role in the management of rainwaters during floods, the collection and storage of water, the prevention of floods, the defense against sea-level rise, the mitigation of natural risks and the reduction of environmental temperature. Two aspects of green/blue parks are of notable interest: the first one consists in their potential in enhancing the resilience of territories affected by environmental critical phenomena (such as floodings), by limiting their impact and restoring rapidly their initial conditions with minimal damages. The second one consists in their dual value as infrastructures for the mitigation of hydraulic risk, designed to preserve communities that are vulnerable to that risk, and as a public space, exploitable in the time laps between the critical or disastrous events. It is therefore necessary to discuss a dual use of hydraulic protection systems, which may become -in the long run- public spaces open to collective use. The case study of Ballao (Sardinia) along the Flumendosa river offers the opportunity to test practically the approaches suggested by the international best practices.