The basic principles in urban rain water management and retention is to mimic nature, meaning to stay as close as possible to the natural water cycle. In an ideal case, infiltration can store water and then release it as needed. However, in urban environments this is not always possible, therefore, rainwater should be stored in a buffer and gradually released to the natural environment .
Alternative solutions for rainwater management and retention are for example :
Infiltration reservoir roadway runs alongside the road and stores excess water from the road.
Infiltration trenches are areas close to roads or parking areas allowing rainwater run and preventing road flooding.
Swales collect storm water from roads, driveways, parking lots and other hard surfaces.
Soakaways are pits in the ground into which rainwater drainage runs.
Infiltration basins, vegetated depressions storing runoff on the surface and infiltrating it gradually into the ground. They are dry except in periods of heavy rainfall.
Permeable surfaces let the rainwater penetrate the surface.
Green roofs are roof structures with vegetation.
Retention ponds are used to hold and distribute rain runoff, which in turn helps prevent flooding.
Infiltration reservoir roadway 
Infiltration trenches 
Basins, detention pond 
Permeable surfaces 
Well-functioning rainwater management prevents water concentration and runoff. The water concentration can be harmful for the building and road foundations. Runoff can cause road flooding and difficulties in road traffic. In addition, runoff water can damage agriculture and spoil the harvest. The runoff can be easily avoided with water buffers. The integration of the water into urban areas can have both recreational and functional purposes.
Water management platforms collect the information about the water use of irrigation, water distribution and water consumption. In addition, the platforms enable a holistic analysis of all water use and where the water use is located in the city or region. The water management platforms serve the whole water system, and the rainwater system is a part of it. Water management systems provide better situation awareness and real-time information of the water system functions .
Most rainwater management and retention solutions are already available on the market or very close to commercial deployment. Some examples are:
Rainwater management systems are often part of urban water management systems. Some water management systems are already in commercial deployment, but there are also further developments, e.g., in wireless monitoring of water amounts.
UNaLab piloted water management systems and water management platforms. The water management platform collects information, and monitors and analyses urban water management.
The identification of risks and co-development of an all-hazards risk management framework for physical and cyber protection of critical water infrastructures is piloted in Stop-IT.