Severn – first, second or third?

In November 2016, the Bay of Fundy installed a tidal turbine that, in time, is designed to generate enough electricity for the whole of the Canadian Atlantic seaboard – as a first step toward a lower carbon future using the power of the highest tidal range in the world. The intervention raised an interesting question from Jon Tuttle: Does this mean the Bristol Channel now has now the highest tidal range in the world, moving up the ranks from second position? Sadly, the answer is no.

I did some investigating and received the following email reply from Todd Ehret, an oceanographer with the Center for Operational Oceanographic Products and Services:  I think what you are referring to is an “energy producing” object … something like a dam; but not nearly as restrictive — water still flows freely through a “barrage”. The existence of the barrage would not have a significant effect on the range of tides in the area. The Bay of Fundy is not going to lose its place as the largest range of tide, unless there is something built which all but completely blocks the entire bay. Such an energy barrage object would be installed in very small, narrow sections of the Bay of Fundy. On the “upstream side” of such a barrage, there **might be** small change in the tidal conditions, perhaps on the order of a few millimeters to 1 centimeter. But on the “downstream side” of the barrage, the range of tides would be unchanged, or might actually increase by a small amount (again on the mm to 1cm scale). That is part of the discussions and engineering of using tidal changes to create energy. Such constructions are intentionally designed to have limited impact on the “natural conditions” of area upstream of the construction.

Regards,
Todd Ehret

Oceanographer
User Services
Center for Operational Oceanographic Products and Services
Web: tidesandcurrents.noaa.gov

I have included two websites that back up this information. At this point in time, the Severn Estuary is recorded as third on the all-time list.
https://tidesandcurrents.noaa.gov/faq2.html
http://www.top-ten-10.com/science/geography/tidal-range.htm

Nevertheless, it is an invigorating and challenging stretch of water, never to be underestimated.  Without it, Clevedon Marine Lake just wouldn’t be the same. Happy swimming, paddling and sailing! 

Jo McCready-Fallon
October 2017