ThermoneX, a company that specializes in basements in the UK, has developed a precast flood barrier that doubles as sidewalk.
Named the Speedy Beaver, the precast slabs comprise the lid of the product and serve as the sidewalk. They are counterweighted and installed with very tight tolerances so that when swung up into place by hand they can clear the next panel, yet are small enough to seal.
To convert the slabs into a flood barrier, the pavement is unlocked and rotated by hand to form a vertical defense aided by gravity.
To learn more about this product, visit: http://www.thermonex.co.uk