Impacts of constructing a rural cycle way on suspended sediment transport processes

This study reports on the short-term impact of constructing a rural cycle way on the suspended sediment load (SSL) of Golborne Brook, Cheshire, UK between August 2003 and February 2004. A float switch activated automatic water sampler retrieved 275 water samples during the 5 months following ground disturbance, which were analysed for their suspended sediment concentration (SSC). SSC vs. discharge (Q) rating curves established for three phases of the disturbance were combined with a 10-min Q record to estimate SSLs before, during and after the work. A three-fold increase in SSL was observed 5 m downstream of where drainage ditches created alongside the cycle way entered Golborne Brook. There is strong evidence that the SSLs decreased to near their pre-disturbance levels within 5 months. Re-growth of natural vegetation on the roadside drainage ditches cleared during the construction work along with the build up of natural deciduous organic debris dams (consisting mainly of leaves, twigs and small branches from hedgerows alongside the ditches) at the ends of the drainage ditches some 1–2 m before they discharged into Golborne Brook contributed to the reduced SSLs observed downstream. Further research into the precise role played by these deciduous organic debris dams in trapping sediment is needed.