Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Preservation of floodplains is flood protection

27.09.2017

The silting of rivers and streams leads to problems for fish, mussels, and other aquatic organisms because their habitats disappear. However, not only intensive agriculture and erosion are destroying these habitats. Now a study conducted by researchers at the Technical University of Munich (TUM) refutes this wide-spread view. In order to save the species living in the river basin – and protect people from the threat of devastating floods – rivers need more space, diversity, and freedom.

The subject of the study was the Moosach, a tributary of the Isar and located right at the Weihenstephaner “doorstep” of the TUM. The Moosach largely flows between the Munich gravel plain and tertiary hill country in an artificial bed. Every few years the river has to be excavated to remove several thousand cubic meters of mud.


The silting of rivers and streams leads to problems for fish, mussels, and other aquatic organisms.

Photo: TUM/J. Geist


The throughflow is decisive for the bottom of a body of water and the chance to change the course of the river creates habitat.

Photo: TUM/J. Geist

The tertiary hill country, 65 million years old, is among the areas with the highest erosion rates. However, less than one percent of the erosion material remains on the ground and the siltation problem cannot be solved by reducing the erosion. This result was provided by the analysis of riverbed samples over the course of several years by Professor Karl Auerswald from the Chair of Grassland Studies and Professor Jürgen Geist from the Chair of Aquatic Systems Biology.

“The prevention of erosion alone, as water and fisheries management have long demanded, does not then help river beds,” says Professor Auerswald. Fortified and dammed as well as straightened and deepened over many decades, the rivers lack their natural flow behavior. Likewise, the floodplain landscape is lacking buffer function and interplay with the river during flooding. The Moosach diagnosis: “a channel, no longer a river” can be transferred to all rivers in Bavaria and worldwide, says the TUM professor.

The Disappearance of Natural Change

The two TUM scientists just published the results of their study in the international journal “Land Degradation & Development.” The title, “Extent and causes of siltation in a headwater stream bed: catchment soil erosion is less important than internal stream processes,” shows how important the throughflow is for the riverbed. Namely the cavities between the gravel filled with oxygen-containing water gravel constitute the primary refuge of small and micro-organisms as well as the egg-laying site for various river fish. Even a thin sediment layer suffices to seal these interstices.

“The entry of erosion material also occurs under natural conditions,” Auerswald explains. “Under natural conditions, however, the riverbed is constantly being relocated and the cavity system is cleared from the inundated floodplain by the groundwater flow.” Because rivers have been straightened and channeled, these floodplain dynamics disappear just as the natural inflow from below has greatly decreased.

Humankind initially intervened in the course of the rivers with good reason: In order to protect cities from flooding, to drain swamps, and to push back cholera and typhus, at the start of the 19th century, rivers began to be straightened and forced into canals. Thus, land was also won for further settlement. The floodplain landscapes, important for sediment retention and natural flood protection, became dysfunctional more and more. Thus, the rivers lacking in shores and natural water inflow lack the possibility of change. But it is precisely these differences that are decisive for the biodiversity of a body of water and for its wealth of species in the water and below.

Auerswald warns: “River floodplains must be off-limits”

The right measure is lacking for Auerswald: “As is so often the case, humans continue down a path that was initially correct, even if he’s already well past the goal.” In the case of local planning and construction decisions, the floodplain is “always the loser.” Auerswald advises, as he has for many years, to once again give the rivers the freedom to determine their own shape.

This means, consequently, that the river could shape its bed during renaturation measures. “Whatever floodplains are still around must absolutely be off-limits,” he says, warning against the unchecked need of the cities for land to develop – and in view of his model calculations on future flood events: “We would do well to allow the rivers to meander on their own again.”

Publication:
Karl Auerswald und Jürgen Geist: Extent and Causes of Siltation in a Headwater Stream Bed: Catchment Soil Erosion is Less Important than Internal Stream Processes, Land Degradation & Development, 6 September 2017.
DOI: 10.1002/ldr.2779
Link: http://onlinelibrary.wiley.com/doi/10.1002/ldr.2779/full

Contact:
Prof. Dr. Karl Auerswald
Technical University of Munich
Chair of Grassland Studies
Phone: Tel: 0049/8161/71-3965
Mail: karl.auerswald@mytum.de

Weitere Informationen:

https://www.tum.de/en/about-tum/news/press-releases/detail/article/34198/

Dr. Ulrich Marsch | Technische Universität München

More articles from Ecology, The Environment and Conservation:

nachricht CO2 tracking in space
25.02.2020 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

nachricht Project provides information on energy recovery from agricultural residues in Germany and China
13.02.2020 | Deutsches Biomasseforschungszentrum

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Therapies without drugs

Fraunhofer researchers are investigating the potential of microimplants to stimulate nerve cells and treat chronic conditions like asthma, diabetes, or Parkinson’s disease. Find out what makes this form of treatment so appealing and which challenges the researchers still have to master.

A study by the Robert Koch Institute has found that one in four women will suffer from weak bladders at some point in their lives. Treatments of this condition...

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

Helpful Customization or Furtive Manipulation? How Germans See Personalization of Online Services

25.02.2020 | Information Technology

CO2 tracking in space

25.02.2020 | Ecology, The Environment and Conservation

Marine Expedition Sheds Light on the Interior of the Earth

25.02.2020 | Earth Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>