The strong impact of human activities with the consequent climate change that is generating increasingly intense environmental phenomena and the high waterproofing of land in urban areas are the cause of increasingly frequent localized flooding.

The Rain Gardens or Gardens of the Rain are gardens made up of:

• bushes,
• perennial herbs
• other plant species.

All able to resist temporary flooding planted in a depression or depression (natural or artificial) on particularly absorbent soil to collect rainwater or runoff.

Through the Gardens of the Rain it is possible to reduce the risks related to the uncontrolled flow of water. At the same time these gardens perform an ecological function as they are able to promote biodiversity, becoming new habitats for pollinating insects, butterflies and birdlife. Through the use of specific plants they are able to reduce the pollutants that end up in the groundwater through the bioretention process.

This type of garden falls within those interventions defined as Low Impact Development (LID – Low Impact Development) which aim to preserve, restore and recreate the characteristics of the natural landscape with the aim of minimizing impermeability, while creating a drainage system that attracts rainwater, transforming it from a waste product into a resource.

The design of the Rain Gardens consists in recreating a stratigraphic structure of the accumulation basin such as to allow the gradual outflow into the ground of the water conveyed therein, guaranteeing a slow and continuous absorption.

To allow for complete absorption, it is preferable to create Rain Gardens in sunny areas. The project vegetation will consist of wetland species in the central part of the valley (area more prone to flooding), mesophilous species in the intermediate part and plant species with less water requirements in the outer part. An estimate of the times for emptying the reservoir helps, in the design phase, to refine the choice of plant species to be included in the garden.