Non-metallic modular liquid retention structures; non-metallic flood defence structures; non-metallic barriers; non-metallic modular barriers; non-metallic flood barriers; non-metallic modular flood barriers; non-metallic temporary dam structures; non-metallic modular dam structures; non-metallic temporary and transportable structures and barriers; non-metallic temporary and transportable structures and barriers for retaining water; materials for assembling non-metallic flood defence structur...