Stockproof fencing of the riparian corridor was carried out along a discontinuous 12 km length of Widden Brook as part of river restoration called 'Natural Sequence Farming'. In addition, 12 low structures were built in the same reach that unintentionally trapped sandy bedload. The combination of riparian revegetation and in-stream structures successfully sequestered large volumes of sand in the bed and channel margins over the last 6 years, causing a substantial reduction in downstream sand supply. A range of native and introduced species colonised recent marginal sand deposits. Casuarina cunninghamiana Miq has been particularly important in accelerating channel contraction by converting side bars into benches. Dense swards of the introduced pasture species, Pennisetum clandestinum, initiated oblique accretion of fine sand and mud onto river banks, causing channel contraction. Downstream channel response to sand sequestration included up to 1 m of bed degradation, channel contraction to less than half of the initial channel width, formation of marginal in-channel benches by degradation into the overwide pre-restoration works channel bed, reformation of a well-defined, rhythmically-spaced pool-riffle sequence and creation of a partially gravel-armoured bed surface. Sand storage starved the river immediately downstream, inducing bed erosion and size-selective transport of sand and fine gravel. Residual pool depths now store four times the volume of water that was present before the start of river restoration. Pool-riffle spacing is currently much less than the expected 4-8 channel widths because pools and riffles are being recreated.
7th International Symposium on Ecohydraulics. The 7th International Symposium on Ecohydraulics: the International Conference of Science and Information Technologies for Sustainable Management of Aquatic Ecosystems (Concepción, Chile 12-16 January, 2009)