The barrier was originally designed to protect London against a very high flood level (with an estimated return period of one hundred years) up to the year 2030, after which the protection would decrease, while remaining within acceptable limits. At the time of its construction, the barrier was expected to be used 2–3 times per year. By the mid-2000s it was being operated 6–7 times a year. In the 2010s, the barrier was generally closed twice a year but the average is still 6–7 due to the barrier being raised 50 times in 2013–14.