Changes in the breeding bird population of a small clay river following flood alleviation works

Published source details Raven P. (1986) Changes in the breeding bird population of a small clay river following flood alleviation works. Bird Study, 33, 24-35.
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This study is summarised as evidence for the following.

	Action	Category
	Employ grazing in artificial grasslands/pastures Action Link
	Use environmentally sensitive flood management Action Link
	Remove flood defence banks to allow inundation Action Link

Employ grazing in artificial grasslands/pastures

A controlled study in 1980-1982 on the river Roding in Essex, England (Raven 1986), found that flood pasture alongside a 1.2 km stretch of the river with grazed ‘flood beams’ (see ‘Use environmentally sensitive flood management’) held a similar density of territories to an adjacent 1.8 km stretch which was not grazed (8-13 territories/km for grazed stretch vs. 6-21 territories/km for ungrazed). Riparian species (sedge warbler Acrocephalus schoenobaenus, Eurasian reed warbler A. scirpaceus and reed bunting Emberiza schoeniclus) were largely confined to the ungrazed section, whilst channel-nesting species (little grebe Tachybaptus ruficollis and common moorhen Gallinula chloropus) were at similar densities in both stretches.
Use environmentally sensitive flood management

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.
Remove flood defence banks to allow inundation

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 on the modified stretch vs three territories of two species on the channelized stretch). 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.