Although on a very local basis Euclidean geometry works just fine, we do live on a sphere which means that the distance between degrees of latitude is constant (about 111 km) BUT the distance between degrees of longitude varies with the cosine of the latitude. Continental France at its widest is about 956 kilometers and at its highest is about 889 kilometers. As we move northward from 45° to 55° the distance between a degree of longitude decreases from 79 to 71 kilometers.
A Tale of Two Cities
London and Paris having been well-covered by Charles Dickens and later Marcel Proust, we turn to Bordeaux and Le Havre. Bordeaux is the southernmost green square on our map; is on the Garonne river; and has a population of about 250,000. The metro area has over a million people as well as the four 951 Megawatt reactors at Blayais. Were you Mayor Alain Juppé, the potential damage from most Bay of Biscay and Atlantic events would be of immediate concern. An English Channel or North Sea event would likely mean future electrical shortages and increased port volume and many national difficulties.
Similarly, for Le Havre and Rouen (leftmost two green squares on the river) some Bay of Biscay events would likely cause only future challenges. Tsunamis in the English Channel – from either direction – would impact the reactors (from the left) at Flamanville (2600 MW), Penly (2660 MW), Paluel (5320 MW) and Gravelines (5706 MW). Le Havre’s population is 180,000, and it is the second busiest French port. The damage would be comparable to that due to World War II. How much damage would be sustained by the greater metropolitan area of Rouen (further southeast along the Seine) varies greatly. Even when Rouen itself is spared Mayor Valérie Fourneyron would face formidable technical and management decisions as she and other French leaders and engineers struggle to keep Paris, the City of Light, illuminated.