Difference between revisions of "Reduce anthropogenic flow peaks"

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(General description)
(Applicability)
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==Applicability ==
 
==Applicability ==
The construction of stormwater retention basins is recommended to prevent direct urban runoff into streams. These facilities store surface runoff in events of heavy rain and prevent flooding. Stormwater retention basins can be understood as artificial lakes or ponds (open and green or concrete). Another way to buffer runoff is an underground storage system (e.g. tanks). Constrains could rise due to the area needed to build retention basins. If possible, open and near-natural systems should be favored (MKULNV NRW). A less technical approach to mitigate surface runoff is the use of open, vegetated space within a city (has to be involved in urban planning). Open areas (e.g. parks, green areas) can be expected to prevent urban runoffs by retaining rainwater (storage and evapotranspiration). It further increases infiltration to groundwater.
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etention basins are dry between floods, fill and store water during floods, slowly drain when water levels in the receiving channel recede, and hence attenuate the runoff and reduce peak flows but have very limited effects on water quality.
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[[File:Stormwater retention basin.jpg|400px|thumbnail|dry stormwater detention basin in the Ruhr catchment, Germany (source: Bildarchiv Ruhrverband)]]
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Retention basins have a permanent pool of water (like ponds) and, except for the runoff exceeding the capacity of the basin that drains to the channel, the water is stored permanently. Besides reducing peak flows, retention basin have a larger effect on water quality through sedimentation of pollutants and uptake of nutrients by plants. However, due to the water permanently stored, they have a lower capacity and hence, have to be larger. In contrast to infiltration basins, they are usually not explicitly built for groundwater recharge (in contrast to infiltration basins) but still may increase the risk of groundwater contamination (Fischer et al. 2003).
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It is important to only reduce the peak flows and to ensure that low flows and environmental flows are maintained in receiving channels.
  
 
==Expected effect of measure on (including literature citations): ==
 
==Expected effect of measure on (including literature citations): ==

Revision as of 12:02, 22 December 2015

General description

Water quantity and the flow regime can be altered by different factors such as changes in land cover, soil structure and compacting, loss of floodplains and wetlands, and stormwater runoff from urban areas. Loss of water retention combined with accelerated runoff typically increases the frequency and magnitude of flood peaks but also reduces the availability of water to streams during the prevailing low flow (base flow) periods.

Preferably, a more natural flow regime can be restored by increasing water infiltration and retention at the catchment scale by e.g. changes in land cover and floodplain restoration (see measure Improve water retention) since this addresses both, increased peak flows and reduced base flows. An alternative local end-of-pipe solution to reduce peak flows caused by stormwater runoff are retention and detention basins, which are of special importance for small rivers where single effluents may already cause massive erosion, affect water quality, and organisms are flushed away (catastrophic drift).

Please note:

Applicability

etention basins are dry between floods, fill and store water during floods, slowly drain when water levels in the receiving channel recede, and hence attenuate the runoff and reduce peak flows but have very limited effects on water quality.

dry stormwater detention basin in the Ruhr catchment, Germany (source: Bildarchiv Ruhrverband)

Retention basins have a permanent pool of water (like ponds) and, except for the runoff exceeding the capacity of the basin that drains to the channel, the water is stored permanently. Besides reducing peak flows, retention basin have a larger effect on water quality through sedimentation of pollutants and uptake of nutrients by plants. However, due to the water permanently stored, they have a lower capacity and hence, have to be larger. In contrast to infiltration basins, they are usually not explicitly built for groundwater recharge (in contrast to infiltration basins) but still may increase the risk of groundwater contamination (Fischer et al. 2003).

It is important to only reduce the peak flows and to ensure that low flows and environmental flows are maintained in receiving channels.

Expected effect of measure on (including literature citations):

  • Decreased drift due to lower flow peaks,
  • Increased chemical condition (less pollution) which has positive effects on stream biota.

Temporal and spatial response

Not available

Pressures that can be addressed by this measure

Cost-efficiency

Not available

Case studies where this measure has been applied

Useful references

Other relevant information