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| East Anglian Plain |
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| Habitat: Rivers and streams (of local significance) |
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Rivers and streams from bank top to bank top, including the open water area, fringing vegetation and exposed sediments.
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Many rivers originate in the East Anglian Plain and flow into adjacent Natural Areas, such as the Waveney on the Suffolk/Norfolk border and the Colne in Essex. Two such rivers, the Wensum and Nar in Norfolk, are Sites of Special Scientific Interest notified for their range of diverse aquatic plant communities. The rivers in the East Anglian Plain have low altitudinal sources and low gradient, with fine and/or rich substrates. Further classification divides the river types represented in the natural area into lowland rivers with minimal gradients, clay rivers, chalk and oolite rivers, and rivers with impoverished ditch floras.
Most rivers and streams in the East Anglian Plain have been modified for flood alleviation, agricultural drainage, reduction of bank erosion and/or maintaining navigation. This has been done by a variety of engineering methods, including widening, deepening, straightening and embanking. Dynamic fluvial processes and their interaction with biological systems were rarely regarded in planning these works. The result has been a massive loss in habitat. Natural bank profiles and vegetation have been lost, in-channel variation such as pools and riffles have been dug away or disrupted by changed flows, and dynamic river morphology (i.e. the natural erosion and deposition which slowly changes the course of the river) has stopped.
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