 The scenic value of the Glaven valley is important to the tourist industry in North Norfolk.The river is one of over 200 chalk rivers in the world and one of 160 in the UK.The river has a catchment area of approximately 115 km2 and from its source falls 50 metres to the present tidal limit at Cley sluice The sub-surface geology is predominantly chalk and in parts of the lower valley the river runs over chalk beds.