February 18, 2014
Ecology, Environmental Design, Infrastructure
Nicholas Pearson Associates coordinated the non statutory Environmental Impact Assessment and undertook initial ecological surveys (2009) for the removal of the redundant Kentchurch weir on the River Monnow, a tributary of the Herefordshire Wye. The weir was proving a barrier to the migration of fish.
The Environmental Report proposed full removal as the most appropriate option. In 2011 the weir was removed. A tracked excavator lowered a 3m wide section down to the river bed. Once breached the flow was directed through the breach allowing the impounded area to be dewatered during the removal.
The level of sediment deposition immediately upstream of the weir was found to be significantly less than anticipated and analysis did not identify any hazardous substances. Cardiff University are continuing to monitor the rivers changing morphology.
Upstream, the right bank was eroded by approximately 5m, due not only to the weir removal but also very high flows on the river, therefore stabilisation works were required. Works included bank regarding, toe protection and tree planting. The river has been left to recolonise naturally and fish have since been recorded spawning upstream. Lowering the river level upstream also uncovered four ancestral weirs.
The River Restoration Centre website http://www.therrc.co.uk/pdata/pdfs/p1753.pd
