What are wadis? Example of Green Infrastructure

Wadis are a Dutch term used for temporary water retention areas as a form of green infrastructure. You can see a famous example from Enschede in the video below. This is part of the main ring road surrounding Enschede's center. You can see the retention area is quite deep, but the number of plant species is quite monotonous. During heavy rainfall it can fill up, but it is also connected underground to prevent overflowing.

Ideally, wadis are made by disconnecting the streets and roofs of buildings from the sewage system in order to collect the water in natural areas. This helps prevent the sewer from overflowing, prevents clean water from entering the sewer, and helps restore the ground water level. You can see this disconnected system where water flows from roofs, down the center of the street, and into a nearby pond in the video below.