Thames barrier - 'high wall defence' from WWZ

Thames barrier is the second largest movable flood barriers in the world. Operational since 1982, its purpose is to prevent the floodplain of all but the easternmost boroughs of Greater London from being flooded by exceptionally high tides and storm surges moving up from the North Sea. When needed, it is closed (raised) during high tide; at low tide it can be opened to enhance the river's flow towards the sea. 

London is vulnerable to flooding and from heavy tides closing in. A storm surge generated by low pressure in the Atlantic Ocean sometimes tracks eastwards past the north of Scotland and may then be driven into the shallow waters of the North Sea. The surge tide is funnelled down the North Sea which narrows towards theEnglish Channel and the Thames Estuary. If the storm surge coincides with a spring tide, dangerously high water levels can occur in the Thames Estuary. This situation combined with downstream flows in the Thames provides the triggers for flood defence operations.

Built across a 520-metre wide stretch of the river, the barrier divides the river into four 61-metre and two, approximately 30 metre navigable spans. There are also four smaller non-navigable channels between nine concrete piers and two abutments. The flood gates across the openings are circular segments in cross section, and they operate by rotating, raised to allow "underspill" to allow operators to control upstream levels and a complete 180 degree rotation for maintenance. 
All the gates are hollow and made of steel up to 40 millimetres (1.6 in) thick. The gates are filled with water when submerged and empty as they emerge from the river. The four large central gates are 20.1 metres (66 ft) high and weigh 3,700 tonnes.^[6] Four radial gates by the riverbanks, also about 30 metres (100 ft) wide, can be lowered. These gate openings, unlike the main six, are non-navigable.

Diagram explained how does the barrier work:

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This barrier also reminded me of the "high wall" has been built to protect the city resident from zombie's attaction in Israel from the film World War Z. However, it has been destroyed by host of zombie attacked all together at the same time: layer upon layer of zombie climb on to the wall and then crossed the wall to got inside the city. A whole city fall to zombie's occupation. The reason was people who inside the wall thought they all safe and celebrated all together used microphone.Zombie had been attraced by loud noices from out side the wall.

                                ALL THE SCREENSHOT FROM <WWZ>


Think back to the thames barriers which are protecting the whole city from flood by rasing the gates up. But what if one day, the flood could not be bear anymore? What if the maintenance work make a mistake? Actually, all the barriers/ defence seems so weak and horrible when their  opponent is the nature. We never know what will happend but we just try the best to do the defence job. And wish all of them can protect us from all kinds of disaster.