Northern Thames Basin

The Northern Thames Basin is a National Character Area (NCA) as designated by Natural England.^[1] It is a diverse area, extending from Hertfordshire in the west to the Essex coast in the east. It is separated from the North Sea and Thames Estuary by a separate NCA, the Greater Thames Estuary. The Northern Thames Basin contains the suburbs of North London, historic towns and cities such as St Albans and Colchester, and new towns such as Welwyn Garden City, Hatfield and Basildon.

The topography is varied, with a wide plateau divided by river valleys. The prominent hills and ridges of the Bagshot Hills are notable to the northwest, and flat land is found in the south. A layer of thick clay, the London Clay, produces heavy, acidic soils. Therefore, much ancient woodland has been retained. Hertfordshire is heavily wooded in some areas as are parts of Essex. Glacial sands and gravels have resulted in nutrient-poor which support small areas of remnant lowland heathlands. There are alluvial deposits which produce well drained and fertile soils. The underlying chalk beds are a main source of recharge for the principal London Basin Chalk aquifer. There are broad valleys containing the major rivers Ver, Colne and Lea, and slightly steeper valleys containing other rivers.