Aquafragma is a portable automatic flood barrier with robust, durable modules that are quickly and easily assembled producing a hump-like foundation across the road. The flood barrier modules are positioned horizontally whilst deadweight modules secure them in place also providing smooth slopes up and down the hump. Traffic can safely pass over the hump until flood level is about to exceed the hump crest. The gate turns upright automatically just in time prior to flooding and returns back to horizontal again automatically when flood waters recede. The barrier operation, turning up and down, requires no power and no labour. It turns up due to buoyancy action and returns down due to gravity.