An idle calculation I did; roughly the bridge arches here total roughly 10m wide, to a depth of 2 m, with water travelling at 1m/sec (slow walking pace - 3.6 km/hour). That means 20 cubic metres i.e. 20 tonnes of water per second = 1200 tonnes per minute = 72000 tonnes per hour (quite a large ship) = 1,728,000 tonnes per day. Makes you think.
Sean
