 The water levels in the moors and levels are controlled by a series of small narrow canals called rhynes ( known as ' <unk> ' in Avonmouth and Gloucestershire - both are pronounced ' reens ' ) . along with larger drains , gates and pumping stations . The rhynes are often used as field boundary ditches instead of hedges . Some parts are allowed to flood in winter . The area is mainly used for grazing but some peat extraction is carried out . 
