Hannah Burke & Steven Payne

The Severn Estuary

The Severn estuary has a lot of potential for harnessing a large quantity of energy, it is one of the largest estuaries in Europe, it has: The second largest tidal range in the world of up to 14m. A peak tidal current exceeding 2m/s.

Background Information In 2008 the UK Government, Welsh Assembly Government and South West Regional Development Agency started a two year feasibility study into tidal power in the Severn Estuary. The aim was to investigate whether it would be economically and environmentally viable to harness tidal energy in the Estuary.

Environmental Protection The Severn Estuary : Assigned the status of a Special Area of Conservation in December Designated a Special Protection Area in July 1995 after it was identified as an area of national and international importance for breeding, feeding, wintering and migration of rare and vulnerable birds. Appointed a Ramsar Site in July Gained status as a Site of Special Scientific Interest. National Nature Reserve which is an area of high nature conservation value.

Species in the River Severn Salmon EelsPike Fish Species Bird Species Dunlin CurlewShort-eared Owl

Proposed Plans Several schemes have been proposed that harness the Severn Estuary’s power in different ways. Some of the proposed plans include: The Severn barrage (there have been alternative versions of the barrage proposed) Tidal lagoons (in Swansea and other available sites) In-stream tidal turbines

The Severn Barrage - Proposal 1 Plans for the Severn Barrage were originally proposed in 2006 by the Severn Tidal Power Group. The proposal aimed to build a barrage 10 miles long from Brean Down, in Somerset to Lavernock Point in Cardiff. The estimated cost of this proposal is £15billion. This proposal was rejected by the government due to environmental issues and not being economically viable.

The Severn Barrage - Proposal 2 After the rejection of the first proposal for a Severn tidal barrage, Hafren Power, a private company expressed their interest in the scheme. Hafren Power proposed plans to build an 11 mile barrage between Lavernock Point near Penarth, Vale of Glamorgan and Brean near Weston-Super-Mare. The cost of this proposal is £25 billion and is estimated to be capable of producing 5% of the UK's electricity needs. Barrage would have a lifespan of at least 120 years. Energy generated would be equal to that of 3 or4 nuclear power stations.

Environmental Impacts of the Severn Barrage proposal The use of fossil fuels to extract the materials to manufacture the barrage will release gases such as carbon dioxide and oxides of nitrogen which contribute to global climate change and acid rain. The barrage would decrease the tidal range which is currently 14 metres. This would lead to increased sedimentation in areas of reduced flow. Pollutants carried by the river may build up behind the barrage.

The barrage could help prevent flooding during high tides. Longer periods of static water could decrease turbidity and increase light penetration causing increased photosynthesis of macrophytes. This produces richer food webs. The barrage may be an obstacle to shipping and wildlife eg. migratory salmon- this problem can be overcome with the installation of a fish ladder. Environmental Impacts of the Severn Barrage proposal

In-Stream Tidal Turbines These are underwater turbines that generate electricity when the tide flows in and out. They do not require the construction of a barrage which reduces energy input, however they produce less energy. BUT Less materials are needed to manufacture the turbines therefore less emissions released from mining activities which leads to decreased enhanced greenhouse effect. Furthermore environmental impacts such as water levels, flow rates and sedimentation remain virtually unaffected.

Tidal Lagoon The Swansea tidal lagoon is estimated to cost £850 million and it will be the first of five tidal lagoons to be built. It works by generating energy when the tide passes through the turbines. Environmental Impacts: The construction of long rocky islands provide habitats for migratory birds Collected sediments would be settle and therefore reduce turbidity and increase the amount of light levels reaching macrophytes. Less environmentally damaging on the coastline as they do not span the estuary. Large numbers of tidal lagoons built together may change the height of the tide which could lead to protected areas flooding and therefore less habitat for migratory birds.

References s.biodiversity&contentid=DevXP s.biodiversity&contentid=DevXP the_severn_barrage_debate/?_ga= the_severn_barrage_debate/?_ga= Richard Genn, AQA Environmental Studies, Published in power-feasibility-study-conclusions power-feasibility-study-conclusions est_severn_barrage_s13_w4_feature.shtml est_severn_barrage_s13_w4_feature.shtml