Bank protection using emergent plants against boat wash in rivers and canals

Bonham, A. (1980) Bank protection using emergent plants against boat wash in rivers and canals. Technical Report. Hydraulics Research Station.

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Abstract

Field test results are presented of the boat wash from recreational motor boats in the summer on the River Thames near Wallingford. A speed limit of two metres per second if successfully imposed would substantially eliminate boat wash that exceeded wind waves in height on this reach of the River Thames. Field test results are presented of the attenuation of the ship waves from motor boat wash in beds of:- Phragmites australis (syn. P communis) common or Norfolk reed; Schoenoplectusla custris (syn. Scirpusl acustris) common clubrush, greater rush or bulrush; Typha angustifolia, lesser or narrow leaved reed mace; and Acorus calamus, sweet flag. Under suitable conditions of depth, vegetation density, and a bed slope of one in four, two metres of width of bed of any of these species will dissipate almost two thirds of the ship wave energy. Bank protection is proposed against boat wash for gravel and mixed bed rivers and also for fen and Broadland rivers with high motor boat usage. The submerged toe protection utilises old tyres, with the advantage of fend off effect. The beds may then be shaped and re-established with mixed species of emergent river plants to give bank protection and to provide a scarce natural habitat.

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