Before we begin, let’s clarify something. There is really little to nothing that you can do to prevent your property from severe rains and disastrous floods. You can only prepare so much and be ready for a quick recovery. But frequent smaller rains are quite manageable and having a garden on your roof is one of the things that might easily help.
It is not a new concept and people have been dealing with floods for centuries. But modern urban development has pushed away most of the landscape in favour of the concrete jungle. That makes rainwater’s travel distance much longer since there are no greens to absorb it, thus bypassing elements from the natural hydrological cycle. The idea of roof gardens is to substitute some of the missing trees, grass and wetlands most of the big cities lack.
There is already a movement aiming to manage the rainwater naturally and it is known as Sustainable Urban Drainage Systems (SUDS). SUDS are ideal for managing small but frequent floods from rain, something London is quite familiar with. The system has three main points:
- to slow down and partially catch the flow of water
- to improve the quality of our water sources by not allowing any pollutants reach them trough flooding
- to provide the local community with a green space that people may enjoy and relax at
The main aspect of roof greens is to manage water exactly where it lands, reducing water runoff in the process. This way the city’s drainage pipes will be less loaded and the risk of flooded streets and houses will become significantly smaller. The principle of roof gardens is to work exactly as ponds and wetlands in un-urbanised areas.
Of course, this is a practice mostly for commercial buildings with large roofs. But that doesn’t mean individual roof gardens should be neglected. Although they might seem small in scale, if done in big enough numbers their contribution might be substantial. Another option for home owners is to have a small pond or wetland in their yard.
Sometimes floods can not be stopped. Record-breaking rainfalls are the landscape engineer’s worst nightmares and can not be tackled so easily. SUDS can’t really handle them, they are effective only against smaller, frequent floods. But they can deliver us a healthier urban look, more livable neighbourhoods, and cleaner rivers and streams. Besides, having a green roof looks awesome.