Complex sentence: The River Cray is a tributary of the River Darent in southern England, rising in Priory Gardens Orpington (London Borough of Bromley), where rainwater permeates the chalk bedrock and forms a pond at the boundary between the chalk and impermeable clay.
Split into simpler sentences: The River Cray is a tributary of the River Darent in southern England. It rises in Priory Gardens in Orpington in the London Borough of Bromley, where rainwater permeates the chalk bedrock and forms a pond at the boundary between the chalk and impermeable clay.