Action: Use environmentally sensitive flood management
Key messagesRead our guidance on Key messages before continuing
- One of two studies, a before-and-after study from the UK, found that there were significantly more bird territories in a stretch of river with ‘flood beams’ installed, compared to a channelized river.
- A replicated site comparison study in the USA found that 13 of 20 bird species increased at sites with the restoration of river dynamics and vegetation.
Many rivers across the world have been channelized and managed, meaning that then natural dynamics (changes in water levels, flooding etc) are lost. This has destroyed habitat and can also lead to less frequent, but far more damaging floods. Using environmentally sensitive flood management may both provide habitats and reduce the damage caused by flooding.
Supporting evidence from individual studies
A controlled before-and-after study on the river Roding in Essex, England (Raven 1986), found that in 1982 there were more territories and more species of bird on a 3 km stretch of the river that was modified in 1979 to reduce flooding in the area, compared to an adjacent 500 m stretch of river that was channelized in 1974 (52 territories of nine species vs. three territories of two species). The experimental stretch had one bank excavated to create a 0.3 m high shelf (a ‘flood beam’) just above the level of the main channel. This meant that the main channel continued to carry water during dry periods (at a rate of 2 m3/s) but during heavy rains, the beam would carry water as well (at up to 40 m3/s) increasing the width and the flow capacity of the river.
A replicated site comparison trial in 1993-2003 on ten sites along the Sacramento River, California, USA (Gardali et al. 2006), found that 13 of 20 bird species were increasing on plots where both riparian vegetation and the river’s hydrological dynamics were restored. This study is discussed in detail in ‘Habitat restoration and creation’.
- Raven P. (1986) Changes in the breeding bird population of a small clay river following flood alleviation works. Bird Study, 33, 24-35
- Gardali T., Holmes A.L., Small S.L., Nur N., Geupel G.R. & Golet G.H. (2006) Abundance patterns of landbirds in restored and remnant riparian forests on the Sacramento River, California, USA. Restoration Ecology, 14, 391-403