Tidal barriers are controversial. The proposal to build the Severn Barrier has long been opposed by many environmentalists, because of impacts upon wildlife and the marine environment. Many within the wider environment have proposed the construction of tidal lagoons as a more ecologically sound method of generating electricity from the huge power of the tides. This report on the tidal electric website provides a good example of the case argued by those who support lagoons but oppose tidal barriers.
Option 10 vigorously supports the construction of tidal lagoons within the River Severn (see zero emission technologies). There are also plans for small scale tidal generators.
However, thanks to the irresponsible behaviour of the worst polluters, both here and abroad, we know the world is condemned to a rapid rise in sea levels. We must protect our coastal cities, including London, against sea level rise, so we must construct some tidal barriers. But, in the process of spending vast sums to protect against flooding we propose that those barriers which are needed also generate electricity. An early decision on a future barrier for the River Thames is needed and we argue that electricity generation should be a key factor within that. Within 20 years, if the humanity has not decided to radically reduce CO2 emissions, we will face much greater sea level rise, and we will then have to look at tidal barriers to protect other UK cities, including Cardiff and Bristol on the River Severn.
Crucial to this debate is the question of the speed with which sea levels will rise. Scientists are concerned by the pace with which the Western Antarctic and the Greenland ice sheets will melt. Both have the potential to raise sea levels by around 7 metres, in total 14 - 15 metres or around 48 feet. Most scientists studying these ice sheets believe that the complete process of melting would take centuries, possibly as long as a thousand years. But, once the Greenland ice sheet has passed its 'tipping point', a global temperature increase of around 3°C, nothing can then be done to stop it melting completely. So, unless the CO2 tap is turned off very soon, we condemn the world to massive loss of land as sea levels rise.
Recent satellite studies of the Greenland ice sheet have been particularly worrying. The Director of the NASA Goddard Space Studies Institute has warned that the global sea levels could rise by as much as 6 feet within this century, as a result of the pace with which the ice is melting. This BBC online article provides more information.
Faced with a 6 feet rise in sea levels, the UK will be forced to retreat from many areas but will inevitably work to prolong the life of its cities by building barriers. London will probably be the first and, when a decision is reached as to how many towns should be protected within the Thames Estuary, a decision can be reached as to the scale of electricity which can be generated. Many politicians within Kent and Essex are seeking construction of the Shoebury to Sheerness barrier, which could generate as much electricity as two nuclear power plants.
There are very many other smaller towns around the UK which could be protected for another 100 - 200 years, if barriers are built so, if sea levels are set to rise dramatically, Option 10 demands that these barriers be used to generate electricity.