Europe: Reducing flooding by storing water on top of greenhouses

From FreshPlaza.com: Westland, The Netherlands, the largest continuous glass greenhouse area in Europe, has been having problems with flooding for years. A consulting and engineering company called DHV was commissioned by the Westland municipality and the Delfland Water Board to conduct a study on storing water on top of greenhouses. DHV developed, in cooperation with TNO, a 'water storage warehouse'. Existing gutters on the greenhouses were strategically blocked to temporarily store water. The findings will be tested in a practical setting which will start after the summer. 

In urban areas, 50 percent of the ground consists of hard surfaces. In Westland that amount is upwards of 85 percent. This causes the rain water to flow easily into surface water which increases the risk of flooding. Hans van Leeuwen, project manager at DHV: "The chance of flooding occurring is once every ten years in some places, which according to the norm, this should only be happening once every fifty years."