There is increasing interest in reclaiming tyres for use in bank-side and coastal-protection structures. However, concern has been expressed about the potential for tyres to release pollutants into the environment and to retain their long-term structural stability. This paper describes laboratory leaching tests for heavy metals from new used tyres and tyres which have been exposed to an aquatic environment for thirteen years. The results show that the limiting factor to their use could be cadmium release. Tests found evidence of the loss of ultraviolet screening agents such as carbon black, suggesting that chemical breakdown of the tyre through leaching of vulcanising chemicals is more significant in the physical breakdown of the tyre, than the reverse. Three case studies of tyre flood-protection and river-control structures are presented, which examine the ability of tyres to retain structural integrity over long periods. Based on this evidence, guidance on design principles is offered. It is concluded that tyres can be used sustainably in a river or coastal environment, subject to careful consideration of local site conditions.