The Stormwater Experts

Concept of decentralized stormwater management

The idea

The idea is to try to replicate natural systems by using cost effective solutions with low environmental impact to manage polluted surface water run-off through collection, storage, and cleaning before allowing it to be released slowly back into the environment. The main concept is to:

  •  Retain water on site

  •  Re-use stormwater as a drinking water alternative, toilet flushing, irrigation…

  •  Improve the local climate and promote evaporative cooling

  •  Recharge groundwater by promoting infiltration

  •  Filter and clean through natural soil filtration

  •  If necessary throttled to a water body or discharged through a drain.


Building blocks of stormwater management

Ideally, these individual components are combined in accordance with local conditions for an optimized overall system. It may be useful to seep in areas with sandy soils and retain stormwater in areas with loamy-clayey soils for evaporation purposes .The potential of the system to adapt to various conditions and requirements is limitless.

Thus, the concept of dec.RW-management differs from the conventional principles of stormwater drainage. With the decentralized system, a part of rainfall runoff is released locally to the water cycle. This can also be considered as a replicate of the natural system where water balance is respected  in contrast to conventional measures.


Decentral stormwater management measures, especially infiltration systems, swale-trench systems, as well as rainwater harvesting systems and green roofs; have become well established, in recent years, within the West German urban water management approach. The experience from numerous pilot projects has led to a substantial gain in knowledge about the construction and operation as well as the effects (Sieker, Kaiser et al. 2006).

Many measures are already implemented as per standards (DWA-A 138 2005). The positive impact of these systems on water resources and material inputs into the aquatic environment is optimal.

Legal basis

1996 saw the rise of introducing, the rainwater infiltration of newly sealed surfaces law in article §51of the State Water Act “Nordrhein-Westfalen”. Other states (e.g Baden-Württemberg, Bavaria, Berlin) have followed in subsequent years. Stormwater infiltration is now the preferred solution for new residential areas.

International developments


This trend is not only limited to Germany. Other countries (eg USA, Netherlands, UK,…) ,under the headings, "Sustainable stormwater Management", "BMP", "SUD", "lid" or "WSUD" are increasingly promoting alternative strategies for dealing with stormwater (Förster, et Thévenot al. 2004).

Applications in new and existing developpments

For new plans, a semi-natural rainwater management will be the standard procedure in the future. But the implementation for existing settlement is increasingly discussed; and is possible as shown in numerous pilot projects, for example, the Emscher catchment (Emschergenossenschaft 2003) or in the Berlin area.


  • DWA A138 (2005). DWA-Arbeitsblatt DWA-A 138: Planung, Bau und Betrieb von Anlagen zur Versickerung von Niederschlagswasser. Hennef, DWA Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall e. V.: S. 59.

  • Förster, M.,  Thévenot, D.,  Geldof, G.,  Svensson, G.,  Mikkelsen, P. S.,  Revitt, M.,  Aftias, E.,  Krejcik, J.,  Sieker, H.,  Legret, M. &  Viklander, M. (2004). "Urban stormwater source control management in European countries: DayWater project", 2004.

  • Rudolph, K.-U. and H. Balke (2000). "Wirtschaftlichkeit der naturnahen Regenwasserentsorgung." KA - Wasserwirtschaft, Abwasser, Abfall Jg. 47(Heft 3).

  • Sieker, F., Kaiser, M. & Sieker, H. (2006). Dezentrale Regenwasserbewirtschaftung im privaten, gewerblichen und kommunalen Bereich (Grundlagen und Ausführungsbeispiele). Fraunhofer IRB-Verlag, Stuttgart.

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Prof. Dr.-Ing. Heiko Sieker
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