The Thames Barrier as seen from Silvertown, London. Golden tones of the late afternoon with dramatic, cloudy skies. The Thames Barrier is the world’s second largest movable flood barrier, the first one being in Netherlands. Its purpose is to prevent flooding of London by exceptionally high tides and storm surges from the North Sea. With the concept of the rotating gates, it was built in early 1980. So far, there were over 100 flood defence closures of the barrier.