Possibilities and impacts of the sponges approach

Natural water retention in the valleys of the middle mountains of the Rhine region

Loss of resilience

Flooding is a natural phenomenon in every  river, and the basis for a rich biodiversity. So it’s not a problem, rather a blessing. Yet, this is not how most people experience it today. The reason: loss of floodplains and loss of water buffering capacity of lands and floodplains diminish the water storage capacity of river basins worldwide.  The Rhine is no exception. As a consequence water travels faster downhill and downstream than ever before. Due to this, European regions have become less resilient to extreme situations. The result is more floods, more droughts, biodiversity loss, damage to goods and property and loss of life.

Land use planners and water managers in Europe have typically relied on hard engineered structures in an attempt to protect their communities from such “natural” hazards. At the same time it is widely recognized, also by the EU, that restoration of ecosystems brings back resilience. This principle is at the core of the “sponges approach”: the (re)development of natural wetlands to temporarily store water, level off flood peaks and contribute to biodiversity. Reviving natural retention will bring us closer to a much needed robust water system, instead of moving farther away from it. And in policy terms: it will be a concrete step in building a strong Green Infrastructure in Europe.

The sponges approach

Stroming, WWF-NL, Wetlands International and the German Consultancy Udata  have recently carried out a study in which we  explored the possibilities and impacts of the sponges approach: restored floodplains and (newly developed) wetlands and peatlands – “natural sponges” , at well-chosen locations in the middle-mountains of the Rhine basin. Within this project a rapid appraisal method was developed which makes it easier than before to scan (sub)basins on their potential for natural storage. Up to 8% of the area covered by local catchments of tributaries to the Rhine in the middle mountains in Germany can potentially be used for increased storage and sponge restoration resulting in local peak reductions of 5 – 8 %. During this project  we also carried out a stakeholder analysis: German water managers at municipal, district and state level were contacted as well as some farmer organizations, NGO’s, Universities and some working groups active in the respective (sub)basins .

This project was jointly funded by WWF Netherlands, Michael Otto Stiftung (granted to Wetlands International – European Association)and the European Life- NGO funding (also granted to Wetlands International.

Previous projects

This project was also based on the knowledge gained in previous studies on this topic.

In 2004, WWF and Stroming published the vision ‘Storing Water near the source’ in which the concept of natural sponges and their potential is analysed and described.

In 2013, WWF, Stroming and Carthago published ‘Possibilities for storage? Stores of possibilities!’ The experience of the years since publication of the vision in 2004 learned which concerns and doubts to the sponges approach were most often expressed. The publication ‘Possibilities for storage’ deals with them and elaborates counter arguments regarding many of the objections.

In 2014, Stroming did a first scoping study of the costs and benefits of the sponges approach. Stroming compared the sponges approach with the Room for the River programme in the Netherlands and did a quickscan of the costs involved to reach a similar decrease of discharge using the sponges approach.

Restoration of the marshes in the valleys of the middle mountains of the Rhine basin for flood and drought risk reduction
‘The sponges approach’
Stroming BV : Els Otterman, Wim Braakhekke, Alphons van Winden
Carthago BV: Willem van Deursen
UDATA GmbH: Florian Zeitler Wetlands International: Eef Silver
WWF Netherlands: Bas Roels, Danny Schoch
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