]> 2026-04-09T04:24:56+00:00 Case study:River Valency at Boscastle 500 en Approved Excavation of bedrock Yes No No Improvement No Fish,No,Yes,No,Yes,No,Improvement Fish Yes Change in bed profile Creation of pools embayments and cascades created Environment Agency Great Britain Yes No Yes false Upstream reference reach.JPG 2006-02-21 11.15.10.jpg 2005-01-01 00.00.00-1.jpg P1010016.JPG P1010022.JPG Photo with beaches.jpg Reference reach upstream of Boscastle Flat and featureless prior to works - 2006 Breaking out the bedrock Post works Excavation of bedrock Formation of beaches post works - 2008 No 50.6899692,-4.6923239 James Environment Agency Burke Excavation of bedrock,Construction of flood wall,Change in bed profile, Creation of pools, embayments and cascades created ,,, 5978 2008-09-01Z 2454710.5 P1010022.JPG 2007-03-01Z 2454160.5 Complete Boscastle village is located in a steep sided and narrow valley through which the River Valency flows down to the harbour. In 2004 an intense storm centred over the small wooded catchment caused massive erosion of sediment and river-side trees. This,combined with high flows, inundated the village with water and debris causing extensive damage. Enlargement of the river channel offered the only viable way to reduce flood risk and improve the flood capacity and sediment conveyance of the river. The scheme aimed to avoid producing a deep geometrically uniform’channel. The channel was designed in such a way that it simulated the natural features found higher up in the undisturbed reaches of the river by engineering features into the excavated bedrock. A detailed topographical survey of the longitudinal profile of the river was an important design tool. This enabled a new, lower bed gradient to be superimposed onto the original one, giving the ‘best fit’ with the levels upstream and downstream of the reach. The natural valley slope at Boscastle is 1 in 45 and the channel bed upstream of the village has a depth of approximately 2.5m. Extending this channel depth down through the village to the harbour, the longitudinal section showed the original bed to be typically 1 metre higher. This helped to explain the loss of capacity through the village and its propensity to flood. Bed regrading to this 2.5m depth profile was therefore considered feasible (Figure 6.4.2). The design of the cross section and longitudinal profile of the lowered bed involved close study of the natural characteristics of the rock visible in the upper river and in the harbour. The rock featured strong bedding planes that typically dip from left to right bank, angled downstream at about 45°. It had vertical fracture lines as well as regular intrusions of much harder quartz. Concept drawings were provided to show how the rock was to be removed. An engineer worked closely with machine operators to obtain the desired result of the left side sloping with the dip and the right side vertical along the fractures. Both sides were zig-zagged to stay within the'character' stone retaining walls. River Valency at Boscastle river valency at boscastle No 300 North Cornwall, Seaton, Looe and Fowey South West Construction of flood wall VALENCY valency River Valency at Boscastle river valency at boscastle Atlantic salmon European eel (Anguilla anguilla) 10 - 100 km² 304 200 - 500 m VALENCY GB108049007170 The exact cost of the river restoration element of this project is unknown. The project was part of a £6.3M (€7.3M) flood risk management scheme. Flood risk management GB108049007170 VALENCY 2013-07-08T12:26:17Z 2456482.0182523 2018-02-21T11:03:22Z 2458170.9606713 River Valency at Boscastle 500 1 plainlist 5 [[Category:Case study]] [[Project title::!River Valency at Boscastle]] [[Subcatchment title::VALENCY]] River Valency at Boscastle# QUERY3325c4290ba063fef1f59f7d8b28129b