Floodplain restoration along the Yorkshire Derwent
The Yorkshire Derwent at Yedingham is a heavily modified watercourse draining the eastern area of the North York Moors. The river flows through ancient lacustrine sediments of the former Lake Pickering and is characterised by a low gradient alluvial channel and wide floodplain (Figure 1). The original channel was engineered to a controlled sinuous form in the 16th Century and this persists today. An opportunity for the restoration of a 500m reach lowering the riparian zone and breaching floodbanks to reconnect palaeo-floodplain features
The hydromorphic audit revealed a number of significant issues with the watercourse and floodplain that restricted naturalisation opportunities. Suggestions include selective breaching of the floodbanks on the right bank based on surface flow pathway modelling, lowering of the land adjacent to the man channel to reconnect the riparian zone, modifying the culverted tributary to create a seepage zone across the floodplain. Lowering areas of sedimented wetland to rejuvenate the habitat and partial felling of mature trees to introduce floodplain woody material and encourage regrowth.
All features were modelled to establish the distribution of new aquatic and wetland habitat and to determine the impact on flooding at the site and upstream. The graphics from this exercise were presented to stakeholders including IDB representatives who have accepted the plans which are now being commissioned for detailed design and construction in 2016.