Dumped trolleys and tyres 'ruining historic canal' / Swallowed by the sea, Pakistan's Indus delta now threatened by canals / The 'world's first city' - 5,400 years old and had 4,000 canals / Vast network of canals found underneath world's first city / Plan to construct new canals sets alarm bells in Senate / Fast-track canal work at Ambattur: Mayor to GCC / Archaeologists discover 4,000-year-old canals used to fish by predecessors of ancient Maya / Encroachments on canals to be cleared / Anger over canal restoration spending delays