AbflussbeiwertSurplus WaterКоэффициент стокаLe coefficient d´écoulement排灌系数


Surplus Water

Water Storage

It is an increasing problem in the concrete deserts of our cities, that rainwater no longer can be absorbed by the open soil. It rapidly flows away into the municipal canals and sewers, leaving the cities too dry. In fact, in Germany we have a special charge put on the percentage of area of a property - be it private or commercial - that is covered either by a building or a stone surface, like a terrace or a drive. The more ground you seal by building or plastering, the more money you must pay to the state. This is owing to the woeful realization that flood catastrophes especially along rivers like the Rhine or the Mosel are getting more and more frequent, because water has no means to seep into a natural soil environment, and that these catastrophes could be avoided by diminishing sealed surfaces. We have no means to influence the amount of percipitation over a city, but we can decide what is to become of it. With the help of green roofs we can ensure that the air is purified and water is stored and returned to its natural cycle by simple evaporation. Extensive roof cultivations can store water in 60-70 percent of their vegetation layers. The climate of towns and cities could benefit immensely from green roofs.

In addition, the roof cultivations would thrive from the exhausts of heating and vehicles using fossile energy and thus literally devour them.

Surplus water and water storage should exist in a healthy balance. This would serve to avoid a rapid filling of brooks and rivers which eventually leads to the type of flood-catastrophes that modern society has to battle with increasingly from season to season.

Please allow our XERO FLOR team to expand on the topic of "surplus water and water storage".In German, this is what we call the 'Abflussbeiwert', meaning the index determining the percentage of perticipitation that runs from your property directly into the sewage system, thus burdening the municipal water services. You will appreciate that in Germany this is a very vital index for homeowners and owners of other properties.

If you wish, we will supply you with an excerpt from the scientifical results of a long-term test of the Institute for Green-planing and Gardenarchitecture of the University of Hannover.According to DIN 1986 ("Draining Installations for Buildings and Properties") and the Guidline '95 ("Guidlines for the Planing, Realization and Maintenance of Green Roofs") of the FFL (Society for the Research of Landscape Development and Landscape Construction), green roofs with a layer of 10cm and upwards can achieve a surplus water storage of 0,3.

This is a scientifically certificated value that does not only take in account the thickness of the layers, but also the roof's incline, the pressure of wind, its reaction to temperature differences and the ability of the substratum to store water.

Gruendach Detmold GmbH offers a combination of a high-quality layer for draining and filtering and our special XERO TERR substratum. Organic substances like lava, clay minerals, pumice and tree-bark humus garantee a high capacity for water storage.

* a roof inclined at 0 degrees= flat roof

* polyester-fleece protective cover (300g/sqm) offering an additional water storage of 4 Litres/sqm. Other storage mats can hold up to 6 Litres/sqm

* fullcover drainage-layer in combination with a fleece 100g/sqm and polyamide woven material (16 mm thick)

* XERO TERR substratum by the company XERO FLOR (registered trademark) and a thickness of 10-12 cms

* Plant community of water-retaining plants like Sedum, Allium, Festuca, Bromus, Anthemis, Ceratodon, Byrum, Hieracium can achieve a water storage-value of less than or equal 0,3 without any problems

The above cited FFL-guideline does not concentrate on a certain region, but definately could positively influence the climate of your region.