Weather & Climate Change

WPestuaryDI

Weather & Climate Change

The marine environment of the Severn Estuary is one of the most dynamic in Europe, with changes in sea level, waves and storms all playing their part in shaping this coastline. Historical records show that severe storms have caused much coastal erosion and flooding and modern research suggests such events are likely to occur again in the future. Perhaps one of the biggest threats to the Estuary is from rising sea levels which, coupled with a significant storm event, could exacerbate the effects of coastal erosion and flooding and cause significant issues for coastal planners, engineers and local communities. The Severn Estuary coastline is already considerably defended, especially around the Wentlooge and Caldicot levels and the Somerset Levels, with several small scale localised defences existing elsewhere. MORE

Meteorology and Oceanography

The Severn Estuary is commonly considered to have the second highest tidal range in the world after sites in the Bay of Fundy in Canada. This is a result of its shape and alignment. The alignment of the Bristol Channel is predominantly east-west, and that of the Estuary is north east-south west. This change in direction is enough to change the dynamics from wave-dominated in the wider Severn Sea to the west, to tidally-dominated in the upper Estuary. As a result of a combination of geology and human intervention through the draining of the Somerset Levels and coastal engineering works, the Estuary is funnel-shaped. This, together with the westward facing direction and the flattened Estuary floor, magnifies the already ‘macrotidal’ (over 6m range) tidal range at the Bristol Channel which (on a mean spring tide), approaches 12.2m at Avonmouth and 12.3m at Beachley. In the Estuary’s swiftly narrowing funnel form, the tidal flow overcomes the resistance of the Estuary bed, producing a tidal bore. MORE

Comments are closed